Codename One Developer Guide

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Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1

1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5

1.1. Build Cloud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5

1.1.1. Why Build Servers? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6

1.1.2. How does Codename One Work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6

Lightweight Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7

Why ParparVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8

Windows Phone/UWP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8

JavaScript Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  9

Desktop and Android . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  9

1.1.3. Versions In Codename One. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  9

1.2. History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  9

1.3. Core Concepts of Mobile Programming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10

1.3.1. Density. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10

1.3.2. Touch Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  12

1.3.3. Device Fragmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13

1.3.4. Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13

App Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13

Power Drain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13

1.3.5. Sandbox and Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  14

1.4. Installing Codename One . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  14

1.5. IntelliJ/IDEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  14

1.6. NetBeans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  15

1.7. Eclipse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  16

1.8. Hello World Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  17

1.8.1. Running . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  19

1.8.2. The Source Code Of The Hello World App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  20

1.8.3. Building and Deploying On Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  24

Signing/Certificates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  25

Build and Install . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  30

1.9. Kotlin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  32

1.9.1. Hello Kotlin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  32

2. Basics: Themes, Styles, Components and Layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  37

2.1. Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  37

2.1.1. Layout Managers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  38

Terse Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  43

Flow Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  43

Box Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  45

Border Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  47

Grid Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  49

2.1.2. Table Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  50

The Full Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  52

TextMode Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  54

2.1.3. Layered Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  55

Insets and Reference Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  56

auto Insets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  57

% Insets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58

Insets, Margin, and Padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58

Component References: Linking Components together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  59

2.1.4. GridBag Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  62

2.1.5. Group Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  64

2.1.6. Mig Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  66

2.2. Themes and Styles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  66

2.2.1. Theme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  68

Native Theme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  72

2.3. GUI Builder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  76

2.3.1. Hello World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  78

NetBeans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  78

IntelliJ/IDEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  79

Eclipse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  80

Basic Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  81

Events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  84

Underlying XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  85

2.3.2. Auto-Layout Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  87

The Inset Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  87

Auto Snap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  88

Smart Insets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  88

The Widget Control Pad. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  88

Keyboard Short-Cuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  89

Sub-Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  89

The Canvas Resize Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  90

3. Theme Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  91

3.1. Understanding Codename One Themes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  91

3.2. Customizing Your Theme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  92

3.3. Customizing The Title . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  95

3.3.1. Background Priorities and Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  95

3.3.2. The Background Behavior and Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  96

3.3.3. The Color Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  105

3.3.4. Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  106

3.3.5. Padding and Margin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  106

3.3.6. Borders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  107

3.3.7. 9-Piece Image Border . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  108

Customizing The 9-Piece Border . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  111

3.3.8. Horizontal/Vertical Image Border. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  113

3.3.9. Empty Border. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  114

3.3.10. Round Border . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  114

3.3.11. Rounded Rectangle Border. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  115

3.3.12. Bevel/Etched Borders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  115

3.3.13. Derive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  116

3.3.14. Fonts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  117

Font Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  121

4. Advanced Theming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  123

4.1. Working With UIID’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  123

4.2. Theme Layering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  123

4.3. Override Resources In Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  124

4.4. Theme Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  125

4.5. Native Theming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  136

4.6. Under the Hood of the Theme Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  136

4.7. Understanding Images and Multi-Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  138

4.8. Use Millimeters for Padding/Margin and Font Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  140

4.8.1. Fractions of Millimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  140

4.9. Creating a Great Looking Side Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  141

4.10. Converting a PSD To A Theme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  145

4.10.1. Breaking Down the PSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  147

Removing the Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  149

The Camera Button. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  150

4.10.2. The Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  153

4.10.3. Styling The UI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  156

Not Quite There Yet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  158

5. CSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  159

5.1. Activating CSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  159

5.2. Supported CSS Selectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  160

5.2.1. Inheriting properties using cn1-derive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  161

5.3. Special Selectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  161

5.3.1. #Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  161

5.3.2. #Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  161

5.3.3. Default . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  163

5.4. Standard CSS Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  163

5.5. Custom Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  164

5.6. CSS Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  164

5.7. CSS Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  165

5.7.1. text-decoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  165

5.7.2. border . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  166

Round Borders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  166

5.7.3. background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  168

Background Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  168

Gradients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  168

5.7.4. cn1-background-type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  174

5.8. Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  175

5.8.1. Image DPI and Device Densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  175

5.8.2. Multi-Images vs Regular Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  176

5.8.3. Multi-Images as Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  176

5.8.4. Image Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  177

5.9. Image Recipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  178

5.9.1. Import Multiple Images In Single Selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  178

5.9.2. Loading Images from URLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  179

5.9.3. Generating 9-Piece Image Borders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  179

5.9.4. Image Backgrounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  180

Example Setting Background Image to Scale Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  181

5.10. Image Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  181

5.11. Fonts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  181

5.11.1. font-family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  182

Using TTF Fonts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  182

5.11.2. font-size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  183

5.11.3. text-decoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  183

5.11.4. Some Sample CSS Directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  184

5.12. Media Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  188

5.12.1. Compound Media Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  189

5.12.2. Order or Precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  190

5.12.3. Font Scaling Constants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  190

6. The Components of Codename One. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  193

6.1. Container . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  193

6.1.1. Composite Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  193

6.2. Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  194

6.3. Dialog. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  196

6.3.1. Styling Dialogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  197

6.3.2. Tint and Blurring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  198

6.3.3. Popup Dialog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  200

Styling The Arrow Of The Popup Dialog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  200

6.4. InteractionDialog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  201

6.5. Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  202

6.5.1. Label Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  203

6.5.2. Autosizing Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  203

6.6. TextField and TextArea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  204

6.6.1. Masking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  207

6.6.2. The Virtual Keyboard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  207

Action Button Client Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  208

Next and Done on iOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  208

6.6.3. Clearable Text Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  209

6.7. TextComponent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  209

6.7.1. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  210

6.7.2. InputComponent and PickerComponent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  211

6.7.3. Underlying Theme Constants and UIID’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  212

6.8. Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  213

6.8.1. Uppercase Buttons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  214

6.8.2. Raised Button. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  214

6.8.3. Ripple Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  215

6.9. CheckBox/RadioButton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  216

6.9.1. Toggle Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  217

6.10. ComponentGroup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  218

6.11. MultiButton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  219

6.11.1. Styling The MultiButton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  221

6.12. SpanButton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  221

6.13. SpanLabel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  221

6.14. OnOffSwitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  222

6.14.1. Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  223

6.15. InfiniteProgress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  224

6.16. InfiniteScrollAdapter and InfiniteContainer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  225

6.16.1. The InfiniteContainer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  227

6.17. List, MultiList, Renderers & Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  228

6.17.1. InfiniteContainer/InfiniteScrollAdapter vs. List/ContainerList. . . . . . . . . . . . . . . . . . . . . .  228

6.17.2. Why Isn’t List Deprecated?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  229

6.17.3. MVC In Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  229

6.17.4. Understanding MVC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  229

Why is this useful? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  230

6.17.5. Important - Lists & Layout Managers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  231

6.17.6. MultiList & DefaultListModel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  231

Going Further With the ListModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  233

6.17.7. List Cell Renderer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  235

6.17.8. Generic List Cell Renderer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  237

Custom UIID Of Entry in GenenricListCellRenderer/MultiList . . . . . . . . . . . . . . . . . . . . . . . . . .  240

Rendering Prototype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  240

6.17.9. ComboBox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  241

6.18. Slider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  242

6.19. Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  243

6.19.1. Sorting Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  249

6.20. Tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  249

6.21. ShareButton. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  252

6.22. Tabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  254

6.23. MediaManager & MediaPlayer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  256

6.24. ImageViewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  258

6.25. ScaleImageLabel & ScaleImageButton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  261

6.26. Toolbar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  262

6.26.1. Search Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  265

6.26.2. South Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  267

6.26.3. Title Animations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  267

6.27. BrowserComponent & WebBrowser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  269

6.27.1. BrowserComponent Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  271

6.27.2. NavigationCallback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  271

6.27.3. JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  272

So what was wrong with the old API? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  273

The New API. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  273

Synchronous Wrappers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  274

Multi-use Callbacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  275

Passing Parameters to Javascript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  275

Proxy Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  276

Legacy JSObject Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  277

The JavaScript Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  278

6.27.4. Cordova/PhoneGap Integration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  280

6.28. AutoCompleteTextField . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  281

6.28.1. Using Images In AutoCompleteTextField . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  283

6.29. Picker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  285

6.30. SwipeableContainer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  289

6.31. EmbeddedContainer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  290

6.32. MapComponent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  290

6.33. Chart Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  293

6.33.1. Device Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  293

6.33.2. Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  294

6.33.3. Chart Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  294

6.33.4. How to Create A Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  296

6.34. Calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  297

6.35. ToastBar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  298

6.35.1. Actions In ToastBar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  300

6.36. SignatureComponent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  301

6.37. Accordion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  301

6.38. Floating Hint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  302

6.39. Floating Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  303

6.39.1. Using Floating Button as a Badge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  304

6.40. SplitPane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  304

7. Animations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  307

7.1. Layout Reflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  307

7.2. Layout Animations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  307

7.2.1. Unlayout Animations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  311

7.2.2. Hiding & Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  312

7.2.3. Synchronicity In Animations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  312

Animation Fade and Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  313

7.2.4. Sequencing Animations Via AnimationManager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  314

Animation Manager to the Rescue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  315

7.3. Low Level Animations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  315

7.3.1. Why Not Just Write Code In Paint?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  316

7.4. Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  316

7.4.1. Replace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  317

7.4.2. Slide Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  318

7.4.3. Fade and Flip Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  320

7.4.4. Bubble Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  321

7.4.5. Morph Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  323

7.4.6. SwipeBackSupport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  323

8. The EDT - Event Dispatch Thread. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  325

8.1. What Is The EDT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  325

8.2. Call Serially (And Wait) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  326

8.2.1. callSerially On The EDT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  327

8.3. Debugging EDT Violations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  327

8.4. Invoke And Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  328

9. Monetization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  333

9.1. Google Play Ads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  333

9.2. In App Purchase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  333

9.2.1. The SKU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  333

9.2.2. Types of Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  334

9.2.3. The "Hello World" of In-App Purchase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  334

9.2.4. Making it Consumable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  338

9.2.5. Non-Renewable Subscriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  339

9.2.6. The Server-Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  340

The Receipts API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  340

9.2.7. The "Hello World" of Non-Renewable Subscriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  340

Implementing the Receipt Store . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  341

Synchronizing Receipts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  345

Expiry Dates and Subscription Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  346

Allowing the User to Purchase the Subscription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  347

9.2.8. subscribe() vs purchase() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  349

Handling Purchase Callbacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  349

9.2.9. Screenshots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  349

9.2.10. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  351

9.2.11. Auto-Renewable Subscriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  351

9.2.12. Auto-Renewable vs Non-Renewable.  Best Choice? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  352

9.2.13. Learning By Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  352

9.2.14. Building the IAP Demo Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  352

Setting up the Client Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  352

Setting up the Server Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  353

Setting up the Database. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  353

Testing the Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  354

9.2.15. Looking at the Source of the App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  357

Client Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  357

Server-Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  359

9.2.16. The CN1-IAP-Validator Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  361

9.2.17. The validateAndSaveReceipt() Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  362

9.2.18. Google Play Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  365

Creating the App in Google Play . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  365

Testing The App. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  367

Creating Google Play Receipt Validation Credentials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  367

9.2.19. iTunes Connect Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  371

Setting up In-App Products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  371

Creating Test Accounts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  371

Setting up Receipt Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  372

10. Graphics, Drawing, Images & Fonts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  373

10.1. Basics - Where & How Do I Draw Manually?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  373

10.2. Glass Pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  375

10.3. Shapes & Transforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  376

10.4. Device Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  376

10.5. A 2D Drawing App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  376

10.5.1. Implementing addPoint() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  378

10.5.2. Using Bezier Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  378

10.5.3. Detecting Platform Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  380

10.6. Transforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  380

10.6.1. Device Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  381

10.7. Example: Drawing an Analog Clock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  381

10.7.1. The AnalogClock Component. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  382

10.7.2. Setting up the Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  382

10.7.3. Drawing the Tick Marks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  383

10.7.4. Drawing the Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  385

10.7.5. Drawing the Hands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  387

10.7.6. The Final Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  390

10.7.7. Animating the Clock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  390

10.8. Starting and Stopping the Animation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  391

10.9. Shape Clipping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  391

10.10. The Coordinate System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  393

10.10.1. Relative Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  394

10.10.2. Transforms and Rotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  395

10.10.3. Event Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  398

10.11. Images. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  398

10.11.1. Loaded Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  398

10.11.2. The RGB Image’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  399

Internal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  399

RGBImage class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  399

10.11.3. EncodedImage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  400

10.11.4. MultiImage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  401

10.11.5. FontImage & Material Design Icons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  401

Material Design Icons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  402

10.11.6. Timeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  403

10.11.7. Image Masking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  403

10.11.8. URLImage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  404

Mask Adapter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  406

URLImage In Lists. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  406

11. Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  409

11.1. High Level Events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  409

11.1.1. Chain Of Events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  409

11.1.2. Action Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  409

Types Of Action Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  410

Source Of Event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  410

Event Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  410

NetworkEvent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  411

11.1.3. DataChangeListener. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  412

11.1.4. FocusListener. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  412

11.1.5. ScrollListener. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  413

11.1.6. SelectionListener . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  413

11.1.7. StyleListener . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  414

11.1.8. Event Dispatcher. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  414

11.2. Low Level Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  414

11.2.1. Low Level Event Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  415

11.2.2. Drag Event Sanitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  416

11.3. BrowserNavigationCallback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  416

12. File System, Storage, Network & Parsing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  419

12.1. Jar Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  419

12.2. Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  419

12.2.1. The Preferences API. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  422

12.3. File System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  423

12.3.1. File Paths & App Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  423

12.3.2. Storage vs. File System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  425

12.4. SQL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  426

12.5. Network Manager & Connection Request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  428

12.5.1. Threading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  430

12.5.2. Arguments, Headers & Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  430

Arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  430

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  431

Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  431

Server Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  432

Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  432

Error Stream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  433

12.5.3. GZIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  434

12.5.4. File Upload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  434

12.5.5. Parsing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  435

Parsing CSV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  435

JSON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  436

XML Parsing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  439

XPath Processing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  440

Properties Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  446

12.6. Debugging Network Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  447

12.6.1. Simpler Downloads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  447

Downloading Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  447

12.7. Rest API. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  449

12.7.1. Rest in Practice - Twilio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  449

12.8. Webservice Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  451

12.9. Connection Request Caching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  455

12.9.1. getCachedData() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  456

12.9.2. cacheUnmodified() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  456

12.9.3. purgeCache & purgeCacheDirectory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  457

12.10. Cached Data Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  457

12.11. Externalizable Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  457

12.12. UI Bindings & Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  462

12.13. Logging & Crash Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  463

12.14. Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  463

12.15. Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  465

12.15.1. Properties in Java . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  467

Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  467

Introspection & Observability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  468

12.15.2. The Cool Stuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  468

Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  469

Seamless Serialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  470

Seamless SQL Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  471

Preferences Binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  473

UI Binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  474

UI Generation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  476

13. Push Notifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  479

13.1. Understanding Push Notifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  479

13.2. Implementing Push Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  479

13.3. The Push Lifecycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  480

13.3.1. Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  480

13.3.2. Sending a Push Notification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  481

13.3.3. Receiving a Push Notification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  481

13.4. Testing Push Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  481

13.5. Push Types and Message Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  484

13.5.1. Example Push Type 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  485

13.5.2. Example Push Type 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  485

13.5.3. Example Push Type 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  486

13.5.4. Example Push Type 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  486

13.5.5. Example Push Type 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  487

13.5.6. Example Push Type 100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  487

13.5.7. Example Push Type 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  487

13.6. Rich Push Notifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  488

13.6.1. Image Attachment Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  488

13.6.2. Notification Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  490

13.7. Deploying Push-Enabled Apps to Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  493

13.7.1. The Push Bureaucracy - Android . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  493

13.7.2. The Push Bureaucracy - iOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  496

13.7.3. The Push Bureaucracy - UWP (Windows 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  498

13.7.4. The Push Bureaucracy - Javascript. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  499

13.8. Sending Push Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  500

13.8.1. Sending a Push Message From Codename One. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  501

13.8.2. Sending Push Message From A Java or Generic Server . . . . . . . . . . . . . . . . . . . . . . . . . . . .  502

Server JSON Responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  503

14. Miscellaneous Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  505

14.1. Phone Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  505

14.1.1. SMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  505

14.1.2. Dialing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  506

14.1.3. E-Mail. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  506

14.2. Contacts API. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  507

14.3. Localization & Internationalization (L10N & I18N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  510

14.3.1. Localization Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  511

14.3.2. RTL/Bidi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  512

14.4. Location - GPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  513

14.4.1. Location In The Background - Geofencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  514

14.5. Background Music Playback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  516

14.6. Capture - Photos, Video, Audio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  516

14.6.1. Capture Asynchronous API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  523

14.7. Gallery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  523

14.8. Analytics Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  524

14.8.1. Application Level Analytics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  525

14.8.2. Overriding The Analytics Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  525

14.9. Native Facebook Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  525

14.9.1. Getting Started - Web Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  525

14.9.2. IDE Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  528

14.9.3. The Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  528

14.9.4. Facebook Publish Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  529

14.10. Google Sign-In . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  530

14.10.1. iOS Setup Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  530

14.10.2. Android Setup Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  533

14.10.3. OAuth Setup (Simulator and REST API Access) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  536

Client ID, Client Secret and Redirect URL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  536

14.10.4. Javascript Setup Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  537

14.10.5. The Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  537

14.11. Lead Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  538

14.11.1. Blocking Lead Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  539

14.12. Pull To Refresh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  541

14.13. Running 3rd Party Apps Using Display’s execute. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  541

14.14. Automatic Build Hint Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  542

14.15. Easy Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  543

14.16. Mouse Cursor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  544

14.17. Working With GIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  544

14.17.1. cn1lib’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  544

14.17.2. Resource Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  545

14.17.3. Eclipse Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  545

14.17.4. IntelliJ/IDEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  546

15. Performance, Size & Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  549

15.1. Reducing Resource File Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  549

15.2. Improving Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  550

15.3. Performance Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  551

15.4. Network Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  552

15.5. Debugging Codename One Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  553

15.6. Device Testing Framework/Unit Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  553

15.7. EDT Error Handler and sendLog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  554

15.8. Kitchen Sink Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  555

15.8.1. Scroll Performance - Threads aren’t magic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  556

16. Advanced Topics/Under the Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  559

16.1. Sending Arguments To The Build Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  559

16.2. Offline Build . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  574

16.2.1. Prerequisites for iOS Builds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  574

16.2.2. Prerequisites for Android Builds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  575

16.2.3. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  575

16.2.4. Building. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  576

16.2.5. FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  577

Should I use the Offline Builder? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  577

Can I Move/Backup my Builders? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  577

Can I install the builders for all our developers? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  577

What Happens if I Cancel? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  578

When are Versions Released? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  578

Are Version Numbers Sequential? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  578

Why is this Feature Limited to Enterprise Subscribers? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  578

How Different is the Code From Cloud Builds? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  578

16.3. Android Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  578

16.3.1. Permissions Under Marshmallow (Android 6+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  579

Enabling Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  580

Permission Prompts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  580

Code Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  582

Simulating Prompts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  583

AndroidNativeUtil’s checkForPermission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  583

16.4. On Device Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  583

16.4.1. Android Studio Debugging (Easy Way) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  584

16.4.2. Android Studio Debugging the Hard Way . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  584

16.5. Native Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  585

16.5.1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  585

Use the Android Main Thread (Native EDT). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  588

Gradle Dependencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  589

16.5.2. Objective-C (iOS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  590

Using the iOS Main Thread (Native EDT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  591

Use Cocoapods For Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  592

16.5.3. Javascript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  592

JavaScript Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  594

16.5.4. Native GUI Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  595

16.5.5. Type Mapping & Rules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  596

16.5.6. Android Native Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  598

16.5.7. Native AndroidNativeUtil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  599

16.5.8. Broadcast Receiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  599

Listening & Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  602

16.5.9. Native Code Callbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  603

Accessing Callbacks from Objective-C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  604

Accessing Callbacks from Javascript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  605

Callbacks of the SMS Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  606

Asynchronous Callbacks & Threading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  607

16.6. Libraries - cn1lib . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  608

16.6.1. Why Not Use JAR?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  609

16.6.2. How To Use cn1libs? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  609

16.6.3. Creating a Simple cn1lib . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  610

16.6.4. Build Hints in cn1libs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  610

16.7. Integrating Android 3rd Party Libraries & JNI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  614

16.8. Drag & Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  615

16.9. Continuous Integration & Release Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  617

16.10. Android Lollipop ActionBar Customization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  617

16.11. Intercepting URL’s On iOS & Android . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  618

16.11.1. Passing Launch Arguments To The App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  618

16.12. Native Peer Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  619

16.12.1. Why does Codename One Need Native Widgets at all? . . . . . . . . . . . . . . . . . . . . . . . . . . .  619

16.12.2. So what’s the problems with native widgets? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  620

16.12.3. So how do we show dialogs on top of Peer Components? . . . . . . . . . . . . . . . . . . . . . . . . .  620

16.12.4. Why can’t we combine peer component scrolling and Codename One scrolling? . . .  620

16.12.5. Native Components In The First Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  620

16.13. Integrating 3rd Party Native SDKs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  620

16.13.1. Step 1 : Review the FreshDesk SDKs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  621

16.13.2. Step 2: Designing the Codename One Public API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  621

16.13.3. Step 3: The Architecture and Internal APIs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  621

Things to Notice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  623

16.13.4. Step 4: Implement the Public API and Native Interface . . . . . . . . . . . . . . . . . . . . . . . . . . .  623

Adapting Method Signatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  623

Callbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  624

Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  626

The Resulting Public API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  627

The Native Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  629

Connecting the Public API to the Native Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  631

Implementing the Glue Between Public API and Native Interface. . . . . . . . . . . . . . . . . . . . . . .  632

16.13.5. Step 5: Implementing the Native Interface in Android . . . . . . . . . . . . . . . . . . . . . . . . . . . .  633

16.13.6. Step 6: Bundling the Native SDKs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  635

The FreshDesk SDK. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  635

Dependencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  635

16.13.7. Step 7 : Injecting Android Manifest and Proguard Config . . . . . . . . . . . . . . . . . . . . . . . . .  637

Proguard Config . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  639

Troubleshooting Android Stuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  640

16.14. Part 2: Implementing the iOS Native Code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  640

16.14.1. Using the MobihelpNativeCallback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  641

16.14.2. Bundling Native iOS SDK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  641

16.14.3. Troubleshooting iOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  642

16.14.4. Adding Required Core Libraries and Frameworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  642

16.15. Part 3 : Packaging as a cn1lib . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  643

16.16. Building Your Own Layout Manager. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  643

16.16.1. Porting a Swing/AWT Layout Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  645

16.17. Port a Language to Codename One . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  645

16.17.1. What is a JVM Language? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  645

16.17.2. How Hard is it to Port a JVM Language to Codename One?. . . . . . . . . . . . . . . . . . . . . . . .  646

Step 1: Assess the Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  646

Step 2: Convert the Runtime Library into a CN1Lib . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  651

Step 3: Hello World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  652

Step 4: A More Complex Hello World. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  653

Step 5: Automation and Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  653

16.18. Update Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  655

16.18.1. How does it Work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  655

16.18.2. What isn’t Covered. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  656

17. Signing, Certificates & Provisioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  657

17.1. Common Terms In Signing & Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  657

17.1.1. What Is A Certificate? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  657

17.1.2. What Is Provisioning? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  657

17.1.3. What’s a Signing Authority? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  657

17.1.4. What is UDID? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  657

17.1.5. Should I Reuse the Same Certificate for All Apps? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  658

17.2. iOS Signing Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  658

17.2.1. Logging into the Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  658

17.2.2. Selecting Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  659

17.2.3. Decisions & Edge Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  660

17.2.4. App IDs and Provisioning Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  661

17.2.5. Installing Files Locally. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  662

17.2.6. Building Your App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  663

17.3. Advanced iOS Signing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  663

17.4. Provisioning Profile & Certificates Visual Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  664

17.4.1. iOS Code Signing Failure Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  667

17.5. Android. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  669

17.5.1. Generating an Android Certificate Manually . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  669

17.6. RIM/BlackBerry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  670

17.7. J2ME. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  670

18. Working with iOS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  671

18.1. Troubleshooting iOS Debug Build installs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  671

18.2. The iOS Screenshot/Splash Screen Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  672

18.2.1. Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  673

18.2.2. Mutable first screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  673

18.2.3. Unsupported component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  674

18.3. Launch Screen Storyboards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  674

18.3.1. Launch Storyboard vs Launch Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  674

18.4. Local Notifications on iOS and Android . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  674

18.4.1. Sending Notifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  675

Example Sending Notification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  675

18.4.2. Receiving Notifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  675

Example Receiving Notification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  676

18.4.3. Canceling Notifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  676

18.5. iOS Beta Testing (Testflight) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  677

18.6. Accessing Insecure URL’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  677

18.7. Using Cocoapods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  677

18.7.1. Including Multiple Pods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  678

18.7.2. Other Pod Related Build Hints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  678

18.7.3. Converting PodFile To Build Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  678

18.8. Including Dynamic Frameworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  679

19. Working with JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  681

19.1. Limitations of the Javascript Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  681

19.1.1. No Multithreaded Code inside Static Initializers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  681

19.2. Troubleshooting Build Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  682

19.3. ZIP, WAR, or Preview.  What’s the difference? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  683

19.4. Setting up a Proxy for Network Requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  685

19.4.1. Step 1: Setting up a Proxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  685

19.4.2. Step 2: Configuring your Application to use the Proxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  685

19.5. Using the CORS Proxy for Same Origin Requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  686

Using Apache as a Proxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  687

19.6. Customizing the Splash Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  687

19.7. Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  687

19.8. Including Third-Party Javascript Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  688

19.8.1. Libraries vs Resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  688

19.8.2. The Javascript Manifest File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  689

How to NOT generate the <script> tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  690

Library Directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  690

Including Remote Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  691

Including CSS Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  692

Embedding Variables in URLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  693

19.9. Browser Environment Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  693

19.10. Changing the Native Theme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  694

19.10.1. Example:  Using Android Theme on Android . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  695

19.11. Disabling the 'OnBeforeUnload' Handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  695

19.11.1. Example: Toggling the BeforeUnload Prompt On/Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  695

19.12. Deploying as a Progressive Web App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  696

19.12.1. Customizing the App Manifest File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  697

19.12.2. Related Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  697

19.12.3. Device/Browser Support for PWAs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  698

19.13. Playing Media and Opening Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  699

20. Working with UWP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  701

20.1. Deploying Outside of the Windows App Store (Sideloading). . . . . . . . . . . . . . . . . . . . . . . . . . . .  701

20.1.1. Side-loading to Windows 10 Mobile Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  701

Enabling Developer Mode on Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  701

Building App for UWP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  703

Installing App On Device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  703

20.1.2. Side-loading to Windows 10 Desktop Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  704

Enabling Developer Mode on PC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  704

Building the App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  705

Installing the App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  706

20.1.3. Building for the Windows Store . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  707

20.2. Debugging UWP Apps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  710

20.2.1. No Line Numbers in Stack Traces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  710

20.3. Customizing the Status Bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  712

20.4. Associating App with File Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  712

21. Working with Mac OS X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  715

21.1. Mac OS Desktop Build Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  715

21.1.1. Bundle Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  715

21.1.2. Understanding Mac Certificates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  715

21.1.3. Obtaining Certificates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  716

21.1.4. Exporting Certificates as P12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  717

21.1.5. Entitlements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  718

22. Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  719

22.1. Constant Obfuscation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  719

22.2. Storage Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  721

22.3. Disabling Screenshots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  722

22.4. Blocking Copy & Paste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  722

22.5. Blocking Jailbreak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  722

22.6. Strong Android Certificates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  723

22.6.1. The Bad News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  723

22.6.2. The Good. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  724

22.7. Certificate Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  724

22.7.1. Certificate Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  724

23. Travis CI Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  727

23.1. Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  727

23.1.1. Enabling Travis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  727

Activating/Deactivating Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  729

23.1.2. Pushing to GitHub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  730

23.1.3. Activate Repository On Travis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  731

23.1.4. Setting Environment Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  731

23.1.5. Testing Travis Script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  732

23.1.6. Writing Unit Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  733

Disabling Travis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  733

24. Working with Codename One Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  735

24.1. Checking out the Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  735

24.2. Building Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  735

24.3. Running Unit Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  735

24.4. Running iOS Unit Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  735

24.4.1. Installing npm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  736

24.4.2. Installing and Running Appium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  736

24.4.3. Running the Unit tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  736

24.4.4. Overriding the Codename One Build Server Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  736

Preface

This 

developer 

guide 

is 

automatically 

generated 

from 

the  wiki 

pages 

at

https://github.com/codenameone/CodenameOne/wiki 

[https://github.com/codenameone/CodenameOne/

wiki].

You  can  edit  any  page  within  the  wiki  pages  using  AsciiDoc.  Your  changes  might  make  it  (after

review) into the official documentation available on the web here: https://www.codenameone.com/

manual/ and available as a PDF file here: https://www.codenameone.com/files/developer-guide.pdf

[https://www.codenameone.com/files/developer-guide.pdf].

Occasionally this book is updated to the print edition available here: https://www.amazon.com/dp/

1549910035

We  also  recommend  that  you  check  out  the  full  JavaDoc  [https://www.codenameone.com/javadoc/]

reference for Codename One which is very complete.

You  can  download  the  full  Codename  One  source  code  from  the  Codename  One  git  repository

[https://github.com/codenameone/CodenameOne/]  where  you  can  also  edit  the  JavaDocs  and  submit  pull

requests to include new features into Codename One [https://www.codenameone.com/blog/how-to-use-the-

codename-one-sources.html].

1

Authors

This document includes content from multiple authors and community wiki edits. If you edit pages

within the guide feel free to add your name here alphabetized by surname:

• Shai Almog [https://github.com/codenameone/]

• Ismael Baum [https://github.com/Isborg]

• Eric Coolman [https://twitter.com/ericcoolmandev]

• Chen Fishbein [http://github.com/chen-fishbein/]

• Steve Hannah [http://github.com/shannah/]

• Matt [https://github.com/kheops37]

2

Rights & Licensing

You  may  copy/redistribute/print  this  document  without  prior  permission  from  Codename  One.

However, you may not charge for the document itself although charging for costs such as printing

is permitted.

Notice that while you can print and reproduce sections arbitrarily such changes must explicitly and

clearly 

state 

that 

this 

is  a  modified  copy  and 

link 

to 

the  original 

source  at

https://www.codenameone.com/manual/ in a clear way!

3

Conventions

This guide uses some notations to provide tips and further guidance.

In case of further information that breaks from the current tutorial flow we use a sidebar as such:

Sidebar

Dig  deeper  into  some  details  that  don’t  quite  fit  into  the  current  flow.  We  use  sidebars  for

things that are an important detour, you can skip them while reading but you might want to

come back and read them later.

Here are common conventions for highlighting notes:

 This is an important note



This is a helpful tip

 This is a general informational note, something interesting but not crucial

 This is a warning something we should pay attention to

This  convention  is  used  when  we  refer  to  a  button  or  a  widget  to  press  in  the  UI.  E.g.  press  the

button labeled Press Here.

Quotes are presented as:

This is a quote

— By Author

Bold is used for light emphasis on a specific word or two within a sentence.

4

1. Introduction

Codename  One  is  a  Write  Once  Run  Anywhere  mobile  development  platform  for  Java/Kotlin

developers. It integrates with IntelliJ/IDEA, Eclipse or NetBeans to provide seamless native mobile

development.

Codename One’s mission statement is:

Unify the complex and fragmented task of mobile device programming into

a single set of tools, APIs and services. As a result create a more manageable

approach  to  mobile  application  development  without  sacrificing  the

power/control given to developers.

This  effectively  means  bringing  that  old  "Write  Once  Run  Anywhere"  (WORA)  Java  mantra  to

mobile devices without "dumbing it down" to the lowest common denominator.

The things that make Codename One stand out from other tools in this field are:

• Write  Once  Run  Anywhere  support  with  no  special  hardware  requirements  and  100%  code

reuse

• Compiles Java/Kotlin into native code for iOS, UWP (Universal Windows Platform), Android and

even JavaScript/PWA

• Open Source and Free with commercial backing/support

• Easy to use with 100% portable Drag and Drop GUI builder

• Full access to underlying native OS capabilities using the native OS programming language (e.g.

Objective-C) without compromising portability

• Provides full control over every pixel on the screen

• Lets you use native widgets (views) and mix them with Codename One components within the

same hierarchy (heavyweight/lightweight mixing)

• Supports seamless Continuous Integration out of the box

Codename One can trace its roots to the open source LWUIT project started at Sun Microsystem in

2007 by Chen Fishbein (co-founder of Codename One). It’s a huge project that’s been under constant

development for over a decade!

1.1. Build Cloud

One  of  the  things  that  make  Codename  One  stand  out  is  the  build  cloud  approach  to  mobile

development.  iOS  native  development  requires  a  Mac  with  xcode.  Windows  native  development

requires a Windows machine. To make matters worse, Apple, Google and Microsoft make changes

to their tools on a regular basis…

This makes it hard to keep up.

When  we  develop  an  app  in  Codename  One  we  use  the  builtin  simulator  when  running  and

5

debugging. When we want to build a native app we can use the build cloud where Macs create the

native  iOS  apps  and  Windows  machines  create  the  native  Windows  apps.  This  works  seamlessly

and makes Codename One apps native as they are literally compiled by the native platform. E.g. for

iOS builds the build cloud uses Macs running xcode (the native Apple tool) to build the app.

 Codename  One  doesn’t  send  source  code  to  the  build  cloud,  only  compiled

bytecode!

Notice that Codename One also provides an option to build offline which means corporations that

have policies forbidding such cloud architectures can still use Codename One with some additional

overhead/complexity of setting up the native build tools. Since Codename One is open source some

developers  use  the  source  code  to  compile  applications  offline  but  that’s  outside  the  scope  of  this

book.

1.1.1. Why Build Servers?

The build servers allow building native iOS Apps without a Mac and native Windows apps without

a Windows machine. They remove the need to install/update complex toolchains and simplify the

process of building a native app to a right click.

E.g.: Since building native iOS applications requires a Mac OS X machine with a recent version of

xcode  Codename  One  maintains  such  machines  in  the  cloud.  When  developers  send  an  iOS  build

such  a  Mac  will  be  used  to  generate  C  source  code  using  ParparVM  [https://github.com/codenameone/

CodenameOne/tree/master/vm]  and  it  will  then  compile  the  C  source  code  using  xcode  &  sign  the

resulting binary using xcode. You can install the binary to your device or build a distribution binary

for the appstore. Since C code is generated it also means that your app will be "future proof" in a

case of changes from Apple. You can also inject Objective-C native code into the app while keeping

it 100% portable thanks to the "native interfaces" capability of Codename One.

Subscribers can receive the C source code back using the include sources feature of Codename One

and use those sources for benchmarking, debugging on devices etc.

The same is true for most other platforms. For the Android, J2ME & Blackberry the standard Java

code is executed as is.

Java  8  syntax  is  supported  thru  retrolambda  [https://github.com/orfjackal/retrolambda]  installed  on  the

Codename  One  servers.  This  is  used  to  convert  bytecode  seamlessly  down  to  Java  5  syntax  levels.

Java 5 syntax is translated to the JDK 1.3 cldc subset on J2ME/Blackberry to provide those language

capabilities and API’s across all devices. This is done using a server based bytecode processor based

on  retroweaver  and  a  great  deal  of  custom  code.  Notice  that  this  architecture  is  transparent  to

developers as the build servers abstract most of the painful differences between devices.

1.1.2. How does Codename One Work?

Codename  One  uses  a  SaaS  based  approach  so  the  information  in  this  appendix  might  (and

probably  will)  change  in  the  future  to  accommodate  improved  architectures.  I  included  this

information for reference only, you don’t need to understand this in order to follow the content of

the book…

6

Since  Android  is  already  based  on  Java,  Codename  One  is  already  native  to  Android  and  “just

works” with the Android VM (ART/Dalvik).

On  iOS,  Codename  One  built  and  open  sourced  ParparVM,  which  is  a  very  conservative  VM.

ParparVM  features  a  concurrent  (non-blocking)  GC  and  it’s  written  entirely  in  Java/C.  ParparVM

generates  C  source  code  matching  the  given  Java  bytecode.  This  effectively  means  that  an  xcode

project is generated and compiled on the build servers. It’s as if you handcoded a native app and is

thus “future proof” for changes that Apple might introduce. E.g. Apple migrated to 64bit and later

introduced  bitcode  support  to  iOS.  ParparVM  needed  no  modifications  to  comply  with  those

changes.

 Codename One translates the bytecode to C which is faster than Swift/Objective-C.

The port code that invokes iOS API’s is hand coded in Objective-C

For Windows 10 desktop and Mobile support, Codename One uses iKVM to target UWP (Universal

Windows Platform) and has open sourced the changes to the original iKVM code.

JavaScript  build  targets  use  TeaVM  to  do  the  translation  statically.  TeaVM  provides  support  for

threading  using  JavaScript  by  breaking  the  app  down  in  a  rather  elaborate  way.  To  support  the

complex  UI  Codename  One  uses  the  HTML5  Canvas  API  which  allows  absolute  flexibility  for

building applications.

For desktop builds Codename One uses javapackager, since both Macs and Windows machines are

available in the cloud the platform specific nature of javapackager is not a problem.

Lightweight Architecture

What makes Codename One stand out is the approach it takes to UI: “lightweight architecture”.

Lightweight architecture is the “not so secrete sauce” to Codename One’s portability. Essentially it

means  all  the  components/widgets  in  Codename  One  are  written  in  Java.  Thus  their  behavior  is

consistent  across  all  platforms  and  they  are  fully  customizable  from  the  developer  code  as  they

don’t rely on OS internal semantics. This allows developers to preview the application accurately in

the simulators and GUI builders.

One  of  the  big  accomplishments  in  Codename  One  is  its  unique  ability  to  embed  “heavyweight”

widgets  into  place  among  the  “lightweights”.  This  is  crucial  for  apps  such  as  Uber  where  the  cars

and  widgets  on  top  are  implemented  as  Codename  One  components  yet  below  them  we  have  the

native map component.

Codename  One  achieves  fast  performance  by  drawing  using  the  native  gaming  API’s  of  most

platforms e.g. OpenGL ES on iOS. The core technologies behind Codename One are all open source

including  most  of  the  stuff  developed  by  Codename  One  itself,  e.g.  ParparVM  but  also  the  full

library, platform ports, designer tool, device skins etc.

7

Lightweight Architecture Origin

Lightweight components date back to Smalltalk frameworks, this notion was popularized in

the  Java  world  by  Swing.  Swing  was  the  main  source  of  inspiration  to  Codename  One’s

predecessor  LWUIT.  Many  frameworks  took  this  approach  over  the  years  including  JavaFX

and most recently Ionic in the JavaScript world.

Why ParparVM

On  iOS,  Codename  One  uses  ParparVM  [https://github.com/codenameone/CodenameOne/tree/master/vm]

which  translates  Java  bytecode  to  C  code  and  boasts  a  non-blocking  GC  as  well  as  64  bit/bitcode

support.  This  VM  is  fully  open  source  in  the  Codename  One  git  repository  [https://github.com/

codenameone/CodenameOne/].  In  the  past  Codename  One  used  XMLVM  [http://www.xmlvm.org/]  to

generate native code in a very similar way but the XMLVM solution was too generic for the needs of

Codename One. ParparVM [https://github.com/codenameone/CodenameOne/tree/master/vm] boasts a unique

architecture  of  translating  code  to  C  (similarly  to  XMLVM),  because  of  that  Codename  One  is  the

only solution of its kind that can guarantee future iOS compatibility since the officially supported

iOS toolchain is always used instead of undocumented behaviors.

 XMLVM could guarantee that in theory but it is no longer maintained

The key advantages of ParparVM over other approaches are:

• Truly Native — since code is translated to C rather than directly to ARM or LLVM code the app

is "more native". It uses the official tools and approaches from Apple and can benefit from their

advancements e.g. latest bitcode changes or profiling capabilities.

• Smaller  Class  Library — ParparVM  includes  a  very  small  segment  of  the  full  JavaAPI’s

resulting  in  final  binaries  that  are  smaller  than  the  alternatives  by  orders  of  magnitude.  This

maps directly to performance and memory overhead.

• Simple and Extensible — to work with ParparVM you need a basic understanding of C. This is

crucial for the fast moving world of mobile development, as Apple changes things left and right

we need a more agile VM.

Windows Phone/UWP

In the past Codename One had 2 major Windows VM port rewrites and 3 or 4 rendering pipelines

within those ports (depends on how you would define a "rewrite").

 The old Windows Phone port was deprecated and is no longer supported, the UWP

port is the only supported Windows mobile target

Codename  One  now  targets  UWP  by  leveraging  a  modified  version  of  iKVM  [https://github.com/

shannah/cn1-ikvm-uwp] to build native Windows Universal Applications.

iKVM uses a bytecode to CLR translation process that effectively converts Java bytecode directly to

the .net equivalent. This is paired with a port of the Codename One API’s that was built for the UWP

environment.  The  UWP  port  generates  native  Windows  10  applications  that  can  support  ARM

8

Windows  devices  natively  as  well  as  desktops  etc.  These  binaries  can  be  uploaded  directly  to

Microsofts online store without special processing.

JavaScript Port

The  JavaScript  port  of  Codename  One  is  based  on  the  amazing  work  of  the  TeaVM  project

[http://teavm.org:]. The team behind TeaVM effectively built a JVM that translates Java bytecode into

JavaScript source code while maintaining threading semantics using a very imaginative approach.

The  JavaScript  port  allows  unmodified  Codename  One  applications  to  run  within  a  desktop  or

mobile  browser.  The  port  itself  is  based  on  the  HTML5  Canvas  API,  this  provides  a  pixel  perfect

implementation of the Codename One API.

 The JavaScript port is only available for Enterprise grade subscribers of Codename

One

Desktop and Android

The  other  ports  of  Codename  One  use  the  VM’s  available  on  the  host  machines/environments  to

execute  the  runtime.  Retrolambda  [https://github.com/orfjackal/retrolambda]  is  used  to  provide  Java  8

language features in a portable way.

The Android port uses the native Android tools including the gradle build environment in the latest

versions.

The  desktop  port  creates  a  standard  JavaSE  application  which  is  packaged  with  the  JRE  and  an

installer.

 The Desktop port is only available to pro grade subscribers of Codename One

1.1.3. Versions In Codename One

One  of  the  confusing  things  about  Codename  One  is  the  versions.  Since  Codename  One  is  a  SaaS

product versioning isn’t as simple as a 2.x or 3.x moniker. However, to conform to this convention

Codename One does make versioned releases which contribute to the general confusion.

When a version of Codename One is released the version number refers to the libraries at the time

of  the  release.  These  libraries  are  then  frozen  and  are  made  available  to  developers  who  use  the

Versioned  Builds 

[https://www.codenameone.com/how-do-i---get-repeatable-builds-build-against-a-consistent-

version-of-codename-one-use-the-versioning-feature.html] feature. The plugin, which includes the designer

as well as all development that is unrelated to versioned builds continues with its regular updates

immediately  after  release.  The  same  is  true  for  the  build  servers  that  move  directly  to  their

standard update cycle.

1.2. History

9

Figure 1. LWUIT App Screenshot circa 2007

Codename  One  was  started  by  Chen  Fishbein  and  Shai  Almog  who  authored  the  Open  Source

LWUIT  project  at  Sun  Microsystems  (circa  2007).  The  LWUIT  project  aimed  to  solve  the

fragmentation within J2ME/Blackberry devices by creating a higher standard of user interface than

the  common  baseline  at  the  time.  LWUIT  received  critical  acclaim  and  traction  within  multiple

industries  but  was  limited  by  the  declining  feature  phone  market.  It  was  forked  by  several

companies  including  Nokia.  It  was  used  as  the  base  standard  for  DTV  in  Brazil.  Another  fork  has

brought  a  LWUIT  into  high  end  cars  from  Toyota  and  other  companies.  This  fork  later  adapted

Codename One as well.

In 2012 Shai and Chen formed Codename One as they left Oracle. The project has taken many of the

basic  concepts  developed  within  the  LWUIT  project  and  adapted  them  to  the  smartphone  world

which is still experiencing similar issues to the device fragmentation of the old J2ME phones.

1.3. Core Concepts of Mobile Programming

Before  we  proceed  I’d  like  to  explain  some  universal  core  concepts  of  mobile  programming  that

might not be intuitive. These are universal concepts that apply to mobile programming regardless

of the tools you are using.

You  can  skip  this  section  if  you  feel  you  are  familiar  enough  with  the  core  problems/issues  in

mobile app development.

1.3.1. Density

Density is also known as DPI (Dots Per Inch) or PPI (pixels or points per inch). Density is confusing,

unintuitive  and  might  collide  with  common  sense.  E.g.  an  iPhone  7  plus  has  a  resolution  of
1080x1920  pixels  and  a  PPI  of  401  for  a  5  inch  screen.  On  the  other  hand  an  iPad  4  has  1536x2048
pixels with a PPI of 264 on a 9.7 inch screen… Smaller devices can have higher resolutions!

As the following figure shows, if a Pixel 2 XL had pixels the size of an iPad it would have been twice

the size of that iPad. While in reality it’s nearly half the height of the iPad!

10

Figure 2. Device Density vs. Resolution

Differences  in  density  can  be  extreme.  A  second  generation  iPad  has  132  PPI,  where  modern

phones  have  PPI  that  crosses  the  600  mark.  Low  resolution  images  on  high  PPI  devices  will  look

either  small  or  pixelated.  High  resolution  images  on  low  PPI  devices  will  look  huge,  overscaled

(artifacts) and will consume too much memory.

11

Figure 3. How the Same Image Looks in Different Devices

The exact same image will look different on each device, sometimes to a comical effect. One of the

solutions for this problem is multi-images. All OS’s support the ability to define different images for

various densities. I will discuss multi-images later in Chapter 2.

This  also  highlights  the  need  for  working  with  measurements  other  than  pixels.  Codename  One

supports millimeters (or dips) as a unit of measurement. This is highly convenient and is a better

representation of size when dealing with mobile devices.

But  there  is  a  bigger  conceptual  issue  involved.  We  need  to  build  a  UI  that  adapts  to  the  wide

differences in form factors. We might have fewer pixels on an iPad but because of its physical size

we  would  expect  the  app  to  cram  more  information  into  that  space  so  the  app  won’t  feel  like  a

blown up phone application. There are multiple strategies to address that but one of the first steps

is in the layout managers.

I’ll discuss the layout managers in depth in Chapter 2 but the core concept is that they decide where

a UI element is placed based on generic logic. That way the user interface can adapt automatically

to the huge variance in display size and density.

1.3.2. Touch Interface

The  fact  that  mobile  devices  use  a  touch  interface  today  isn’t  news…  But  the  implications  of  that

aren’t immediately obvious to some developers.

UI  elements  need  to  be  finger  sized  and  heavily  spaced.  Otherwise  we  risk  the  “fat  finger”  effect.

12

That means spacing should be in millimeters and not in pixels due to device density.

Scrolling  poses  another  challenge  in  touch  based  interfaces.  In  desktop  applications  it’s  very

common  to  nest  scrollable  items.  However,  in  touch  interfaces  the  scrolling  gesture  doesn’t  allow

such nuance. Furthermore, scrolling on both the horizontal and vertical axis (side scrolling) can be

very inconvenient in touch based interfaces.

1.3.3. Device Fragmentation

Some developers single out this wide range of resolutions and densities as “device fragmentation”.

While it does contribute to development complexity for the most part it isn’t a difficult problem to

overcome.

Densities aren’t the cause of device fragmentation. Device fragmentation is caused by multiple OS

versions with different behaviors. This is very obvious on Android and for the most part relates to

the  slow  rollout  of  Android  vendor  versions  compared  to  Googles  rollout.  E.g.  7  months  after  the

Android 8 (Oreo) release in 2018 it was still available on 1.1% of the devices. The damning statistic

is that 12% of the devices in mid 2018 run Android 4.4 Kitkat released in 2013!

This makes QA difficult as the disparity between these versions is pretty big. These numbers will be

out  of  date  by  the  time  you  read  this  but  the  core  problem  remains.  It’s  hard  to  get  all  device

manufacturers  on  the  same  page  so  this  problem  will  probably  remain  in  the  foreseeable  future

despite everything.

1.3.4. Performance

Besides the obvious need for performance and smooth animation within a mobile app there are a

couple of performance related issues that might not be intuitive to new developers: size and power.

App Size

Apps are installed and managed via stores. This poses some restrictions about what an app can do.

But  it  also  creates  a  huge  opportunity.  Stores  manage  automatic  update  and  to  some  degree  the

marketing/monetization of the app.

A  good  mobile  app  is  updated  once  a  month  and  sometimes  even  once  a  week.  Since  the  app

downloads automatically from the store this can be a huge benefit:

• Existing users are reminded of the app and get new features instantly

• New users notice the app featured on a “what’s new” list

If  an  app  is  big  it  might  not  update  over  a  cellular  network  connection.  Google  and  Apple  have

restrictions on automatic updates over cellular networks to preserve battery life and data plans. A

large  app  might  negatively  impact  users  perception  of  the  app  and  trigger  uninstalls  e.g.  when  a

phone is low on available space.

Power Drain

Desktop developers rarely think about power usage within their apps. In mobile development this

is a crucial concept. Modern device OS’s have tools that highlight misbehaving applications and this

13

can lead to bad reviews.

Code that loops forever while waiting for input will block the CPU from sleeping and slowly drain

the battery.

Worse. Mobile OS’s kill applications that drain the battery. If the app is draining the battery and is

minimized (e.g. during an incoming call) the app could be killed. This will impact app performance

and usability.

1.3.5. Sandbox and Permissions

Apps installed on the device are “sandboxed” to a specific area so they won’t harm the device or its

functionality. The filesystem of mobile applications is restricted so one application can’t access the

files of another application. Things that most developers take for granted on the desktop such as a

“file picker” or accessing the image folder don’t work on devices!

This means that when your application works on a file it belongs only to your application. In order

to share the file with a different application you need to ask the operating system to do that for you.

Furthermore, some features require a “permission” prompt and in some cases require special flags

in system files. Apps need to request permission to use sensitive capabilities e.g. Camera, Contacts

etc. 

Historically  Android  developers  just  declared  required  permissions  for  an  app  and  the  user  was

prompted  with  permissions  during  install.  Android  6  adopted  the  approach  used  by  iOS  of

prompting the user for permission when accessing a feature.

This  means  that  in  runtime  a  user  might  revoke  a  permission.  A  good  example  in  the  case  of  an

Uber  app  is  the  location  permission.  If  a  user  revokes  that  permission  the  app  might  lose  its

location.

1.4. Installing Codename One

 The minimum JDK for Codename One is JDK 8

 The  following  screenshots  are  from  Mac  OS  but  the  process  should  work  exactly

the same on Windows and Linux

1.5. IntelliJ/IDEA

Codename One recommends IntelliJ/IDEA 2016 or newer.

 Codename  One  doesn’t  support  Android  Studio!  You  can  use  IntelliJ/IDEA

community edition instead

14

Figure 4. IntelliJ Installation Instructions

1.6. NetBeans

NetBeans  install  is  pretty  simple  although  the  default  “plugin  center”  for  NetBeans  is  notoriously

unreliable.  That’s  why  we 

recommend  using 

the  Codename  One  plugin 

center:

https://www.codenameone.com/files/netbeans/updates.xml

15

Figure 5. NetBeans Installation Instructions



Make  sure  you  are  using  a  NetBeans  version  that  includes  Java  support,  don’t

download a version for Ruby/PHP or J2ME and make sure the IDE runs on top of

JDK 8

1.7. Eclipse

Codename One supports Eclipse Neon 2 or newer. There are a few pitfalls that can happen with an

Eclipse install specifically when other JVM versions are installed on your machine.

 If you are new to Java, Eclipse might be intimidating. It’s a very powerful IDE but

its configuration is rough

Make sure your JAVA_HOME environment variable points at JDK 8 and that the path to the JDK 8 bin
directory  is  first  in  the  PATH  statement.  If  all  else  fails  edit  the  eclipse.ini  file  to  force  Eclipse  to
use your JDK 8 install. See this site for help with editing the eclipse.ini file: https://wiki.eclipse.org/
Eclipse.ini

16

Figure 6. Eclipse Installation Instructions

 In order to run the app in Eclipse make sure to select the .launch file in Eclipse

1.8. Hello World Application

Before we get to the code there are few important things we need to go over with the new project

wizard.

We  need  to  create  a  new  project.  We  need  to  pick  a  project  name  and  I’ll  leave  that  up  to  you
although it’s hard to go wrong with HelloWorld. The following four values are important:

• App Name - This is the name of the app and the main class, it’s important to get this right as it’s

hard to change this value later

• Package Name - It’s crucial you get this value right. Besides the difficulty of changing this after

the fact, once an app is submitted to iTunes/Google Play with a specific package name this can’t

be changed! See the sidebar "Picking a Package Name".

• Theme - There are various types of builtin themes in Codename One, for simplicity I pick Native

as it’s a clean slate starting point

• Template  -  There  are  several  builtin  app  templates  that  demonstrate  various  features,  for

simplicity I always pick Bare Bones which includes the bare minimum

17

Figure 7. The New App Wizard

18

Picking a Package Name

Apple, Google and Microsoft identify applications based on their package names. If you use a

domain  that  you  don’t  own  it’s  possible  that  someone  else  will  use  that  domain  and  collide
with you. In fact some developers left the default com.mycompany domain in place all the way
into production in some cases.

This can cause difficulties when submitting to Apple, Google or Microsoft. Submitting to one

of them is no guarantee of success when submitting to another.

To come up with the right package name use a reverse domain notation. So if my website is
goodstuff.co.uk my package name should start with uk.co.goodstuff. I highly recommend the
following guidelines for package names:

• Lower Case - some OS’s are case sensitive and handling a mistake in case is painful. The

Java convention is lower case and I would recommend sticking to that although it isn’t a

requirement

• Avoid Dash and Underscore - You can’t use a dash character (-) for a package name in
Java.  Underscore  (_)  doesn’t  work  for  iOS.  If  you  want  more  than  one  word  just  use  a
deeper package e.g.: com.mydomain.deeper.meaningful.name

• Obey  Java  Rules  -  A  package  name  can’t  start  with  a  number  so  you  can’t  use

com.mydomain.1sler. You should avoid using Java keywords like this, if etc.

• Avoid Top Level - instead of using uk.co.goodstuff use uk.co.goodstuff.myapp. That would

allow you to have more than one app on a domain

1.8.1. Running

We can run the HelloWorld application by pressing the Play or Run button in the IDE for NetBeans or
IntelliJ. In Eclipse we first need to select the simulator .launch file and then press run. When we do
that the Codename One simulator launches. You can use the menu of the simulator to control and

inspect details related to the device. You can rotate it, determine it’s location in the world, monitor

networking calls etc.

With  the  Skins  menu  you  can  download  device  skins  to  see  how  your  app  will  look  on  different
devices.



Some  skins  are  bigger  than  the  screen  size,  uncheck  the  Scrollable  flag  in  the
Simulator menu to handle them more effectively

Debug works just like Run by pressing the IDE’s debug button. It allows us to launch the simulator in
debug mode where we can set breakpoints, inspect variables etc.

19

Figure 8. HelloWorld Running on the Simulator with an iPhone X Skin

Simulator vs. Emulator

Codename  One  ships  with  a  simulator  similarly  to  the  iOS  toolchain  which  also  has  a

simulator. Android ships with an emulator. Emulators go the extra mile. They create a virtual

machine that’s compatible with the device CPU and then boot the full mobile OS within that

environment. This provides an accurate runtime environment but is painfully slow.

Simulators  rely  on  the  fact  that  OS’s  are  similar  and  so  they  leave  the  low  level  details  in

place  and  just  map  the  API  behavior.  Since  Codename  One  relies  on  Java  it  can  start

simulating  on  top  of  the  virtual  machine  on  the  desktop.  That  provides  several  advantages

including  fast  development  cycles  and  full  support  for  all  the  development  tools/debuggers

you can use on the desktop.

Emulators make sense for developers who want to build OS level services e.g. screensavers or

low level services. Standard applications are better served by simulators.

1.8.2. The Source Code Of The Hello World App

After  clicking  finish  in  the  new  project  wizard  we  have  a  HelloWorld  project  with  a  few  default
settings. I’ll break the class down to small pieces and explain each piece starting with the enclosing

class:

Listing 1. HelloWorld Class

public class HelloWorld { ①
    private Form current; ②
    private Resources theme; ③

    // ... class methods ...
}

① This  is  the  main  class,  it’s  the  entry  point  to  the  app,  notice  it  doesn’t  have  a  main  method  but

rather callback which we will discuss soon

② Forms  are  the  “top  level”  UI  element  in  Codename  One.  Only  one  Form  is  shown  at  a  time  and

everything you see on the screen is a child of that Form

③ Every  app  has  a  theme,  it  determines  how  everything  within  the  application  looks  e.g.  colors,

fonts etc.

20

Next  let’s  discuss  the  first  lifecycle  method  init(Object).  I  discuss  the  lifecycle  in  depth  in  the
Application Lifecycle Sidebar.

Listing 2. HelloWorld init(Object)

public void init(Object context) { ①
    updateNetworkThreadCount(2); ②
    theme = UIManager.initFirstTheme("/theme"); ③
    Toolbar.setGlobalToolbar(true); ④
    Log.bindCrashProtection(true); ⑤
    addNetworkErrorListener(err -> { ⑥
        err.consume(); ⑦
        if(err.getError() != null) { ⑧
            Log.e(err.getError());
        }
        Log.sendLogAsync(); ⑨
        Dialog.show("Connection Error", ⑩
            "There was a networking error in the connection to " +
            err.getConnectionRequest().getUrl(), "OK", null);
    });
}

① init is the first of the four lifecycle methods. It’s responsible for initialization of variables and

values

② By default Codename One has one thread that performs all the networking, we set the default to

two which gives better performance

③ The theme determines the appearance of the application. We’ll discuss this in the next chapter

④ This enables the Toolbar API by default, it allows finer control over the title bar area

⑤ Crash protection automatically sends device crash logs through the cloud

⑥ In  case  of  a  network  error  the  code  in  this  block  would  run,  you  can  customize  it  to  handle

networking errors effectively

⑦ consume() swallows the event so it doesn’t trigger other alerts, it generally means “we got this”

⑧ Not all errors include an exception, if we have an exception we can log it with this code

⑨ This will email the log from the device to you if you have a pro subscription

⑩ This shows an error dialog to the user, in production you might want to remove that code

init(Object)  works  as  a  constructor  to  some  degree. We  recommend  avoiding  the  constructor  for
the main class and placing logic in the init method instead. This isn’t crucial but we recommend it

since the constructor might happen too early in the application lifecycle.

In  a  cold  start  init(Object)  is  invoked  followed  by  the  start()  method.  However,  start()  can  be
invoked more than once if an app is minimized and restored, see the sidebar Application Lifecycle:

21

Listing 3. HelloWorld start()

public void start() {
    if(current != null){ ①
        current.show(); ②
        return;
    }
    Form hi = new Form("Hi World", BoxLayout.y()); ③
    hi.add(new Label("Hi World")); ④
    hi.show(); ⑤
}

① If  the  app  was  minimized  we  usually  don’t  want  to  do  much,  just  show  the  last  Form  of  the

application

② current is a Form which is the top most visual element. We can only have one Form showing and

we enforce that by using the show() method

③ We  create  a  new  simple  Form  instance.  It  has  the  title  “Hello  World”  and  arranges  elements

vertically (on the Y axis)

④ We  add  another  Label  below  the  title,  see  figure  [TitleAndLabelImage].  We  will  discuss

component hierarchy later

⑤ The show() method places the Form on the screen. Only one Form can be shown at a time

Figure 9. Title and Label in the UI

There  are  some  complex  ideas  within  this  short  snippet  which  I’ll  address  later  in  this  chapter
when talking about layout. The gist of it is that we create and show a Form. Form is the top level UI
element, it takes over the whole screen. We can add UI elements to that Form object, in this case the
Label.  We  use  the  BoxLayout  to  arrange  the  elements  within  the  Form  from  top  to  the  bottom
vertically.

22

Application Lifecycle

A few years ago Romain Guy (a senior Google Android engineer) was on stage at the Google
IO conference. He asked for a show of hands of people who understand the Activity lifecycle
(Activity  is  similar  to  a  Codename  One  main  class).  He  then  proceeded  to  jokingly  call  the
audience members who lifted their hands “liars” claiming that after all his years in Google he

still doesn’t understand it…

Lifecycle  seems  simple  on  the  surface  but  hides  a  lot  of  nuance.  Android’s  lifecycle  is

ridiculously  complex.  Codename  One  tries  to  simplify  this  and  also  make  it  portable.

Sometimes complexity leaks out and the nuances can be difficult to deal with.

Simply explained an application has three states:

• Foreground  -  it’s  running  and  in  the  foreground  which  means  the  user  can  physically

interact with the app

• Suspended  -  the  app  isn’t  in  the  foreground,  it’s  either  paused  or  has  a  background

process running

• Not Running - the app was never launched, was killed or crashed

The lifecycle is the process of transitioning between these 3 states and the callbacks invoked

when such a transition occurs. The first time we launch the app we start from a “Cold Start”

(Not  Running  State)  but  on  subsequent  launches  the  app  is  usually  started  from  the  "Warm

Start" (Suspended State).

Figure 10. Codename One Application Lifecycle

Codename One has four standard callback methods in the lifecycle API:

• init(Object) - is invoked when the app is first launched from a Not Running state.

23

• start() - is invoked for two separate cases. After start() is finished the app transitions to

the Foreground state.

◦ Following init(Object) in case of a cold start. Cold start refers to starting the app from

a Not Running state.

◦ When the app is restored from Suspended state. In this case init(Object) isn’t invoked

• stop()  -  is  invoked  when  the  app  is  minimized  e.g.  when  switching  to  a  different  app.

After stop() is finished the app transitions to the Suspended state.

• destroy() - is invoked when the app is destroyed e.g. killed by a user in the task manager.
After destroy() is finished the app is no longer running hence it’s in the Not Running state.

 destroy() is optional there is no guarantee that it will be invoked. It should

be used only as a last resort

Now that we have a general sense of the lifecycle lets look at the last two lifecycle methods:

Listing 4. HelloWorld stop() and destroy()

public void stop() { ①
    current = getCurrentForm(); ②
    if(current instanceof Dialog) { ③
        ((Dialog)current).dispose();
        current = getCurrentForm();
    }
}

public void destroy() { ④
}

① stop() is invoked when the app is minimized or a different app is opened

② As the app is stopped we save the current Form so we can restore it back in start() if the app is

restored

③ Dialog  is  a  bit  of  a  special  case  restoring  a  Dialog  might  block  the  proper  flow  of  application

execution so we dispose them and then get the parent Form

④ destroy()  is  a  very  special  case.  Under  normal  circumstances  you  shouldn’t  write  code  in

destroy(). stop() should work for most cases

That’s it. Hopefully you have a general sense of the code. It’s time to run on the device.

1.8.3. Building and Deploying On Devices

24

Figure 11. Codename One Settings

You  can  use  the  project  settings  to  configure  almost  anything.  Specifically,  the  application  title,

application version, application icon etc. are all found in the right click menu of your IDE.

Just right click your Codename One project icon in any IDE, select Codename One → Codename One

Settings.

There  are  many  options  within  this  UI  that  control  almost  every  aspect  of  the  application  from

signing to basic settings.

Signing/Certificates

All of the modern mobile platforms require signed applications but they all take radically different

approaches when implementing it.

Signing is a process that marks your final application for the device with a special value. This value

(signature) is a value that only you can generate based on the content of the application and your

certificate.  Effectively  it  guarantees  the  app  came  from  you.  This  blocks  a  3rd  party  from  signing

their apps and posing as you to the appstore or to the user. It’s a crucial security layer.

A  certificate  is  the  tool  we  use  for  signing.  Think  of  it  as  a  mathematical  rubber  stamp  that

generates a different value each time. Unlike a rubber stamp a signature can’t be forged!

Signing on Android

 Backup your Android certificate and save its password!

If you lose your Android certificate you will not be able to update your app

Android  uses  a  self  signed  certificate  approach.  You  can  just  generate  a  certificate  by  describing

who you are and picking a password!

Anyone can do that. However, once a certificate is published it can’t be replaced…

If this wasn’t the case someone else could potentially push an “upgrade” to your app. Once an app is

submitted with a certificate to Google Play this app can’t be updated with any other certificate.

With that in mind generating an Android certificate is trivial.

 The following chart illustrates a process that’s identical on all IDE’s

25

Figure 12. Process of Certificate Generation for Android



Your certificate will generate into the file Keychain.ks in your home directory

Make  sure  to  back  that  up  and  the  password  as  losing  these  can  have  dire

consequences

Should I Use a Different Certificate for Each App?

In  theory  yes.  In  practice  it’s  a  pain…  Keeping  multiple  certificates  and  managing  them  is  a

pain so we often just use one.

The  drawback  of  this  approach  occurs  when  you  are  building  an  app  for  someone  else  or

want to sell the app. Giving away your certificate is akin to giving away your house keys. So it

makes sense to have separate certificates for each app.

Signing and Provisioning iOS

Code signing for iOS relies on Apple as the certificate authority. This is something that doesn’t exist

on  Android.  iOS  also  requires  provisioning  as  part  of  the  certificate  process  and  completely

separates the process for development/release.

But first let’s start with the good news:

• Losing  an  iOS  certificate  is  no  big  deal  -  in  fact  we  revoke  them  often  with  no  impact  on

shipping apps

26

• Codename One has a wizard that hides most of the pain related to iOS signing

In iOS Apple issues the certificates for your applications. That way the certificate is trusted by Apple

and is assigned to your Apple iOS developer account. There is one important caveat: You need an

iOS Developer Account and Apple charges a 99USD Annual fee for that.



The 99USD price and requirement have been around since the introduction of the

iOS  developer  program  for  roughly  10  years  at  the  time  of  this  writing.  It  might

change at some point though

Apple  also  requires  a  “provisioning  profile”  which  is  a  special  file  bound  to  your  certificate  and

app. This file describes some details about the app to the iOS installation process. One of the details

it includes during development is the list of permitted devices.

Figure 13. The Four Files Required for iOS Signing and Provisioning

We need 4 files for signing. Two certificates and two provisioning profiles:

27

1. Production — The production certificate/provisioning pair is used for builds that are uploaded

to iTunes

2. Development — The  development  certificate/provisioning 

is  used 

to 

install  on  your

development devices

The certificate wizard automatically creates these 4 files and configures them for you.

Figure 14. Using the iOS Certificate Wizard Steps 1 and 2

Figure 15. Using the iOS Certificate Wizard Steps 3 and 4

28

Figure 16. Using the iOS Certificate Wizard Steps 5 and 6



If you have more than one project you should use the same iOS P12 certificate files

in  all  the  projects  and  just  regenerate  the  provisioning.  In  this  situation  the

certificate wizard asks you if you want to revoke the existing certificate which you

shouldn’t revoke in such a case. You can update the provisioning profile in Apple’s

iOS developer website.

One important aspect of provisioning on iOS is the device list in the provisioning step. Apple only

allows  you  to  install  the  app  on  100  devices  during  development.  This  blocks  developers  from

skipping  the  appstore  altogether.  It’s  important  you  list  the  correct  UDID  for  the  device  in  the  list

otherwise install will fail.

 There  are  several  apps  and  tools  that  offer  the  UDID  of  the  device,  they  aren’t

necessarily reliable and might give a fake number!

29

Figure 17. Get the UDID of a Device



You can right click the UDID and select copy to copy it

The simplest and most reliable process for getting a UDID is via iTunes. I’ve used other approaches

in the past that worked but this approach is guaranteed.



Ad  hoc  provisioning  allows  1000  beta  testers  for  your  application  but  it’s  a  more

complex process that we won’t discuss here although it’s supported by Codename

One

Build and Install

Before  we  continue  with  the  build  we  should  sign  up  at  https://www.codenameone.com/build-

server.html  where  you  can  soon  follow  the  progress  of  your  builds.  You  need  a  Codename  One

account in order to build for the device.

Now  that  we  have  certificates  the  process  of  device  builds  is  literally  a  right  click  away  for  both

OS’s. We can right click the project and select Codename One  → Send iOS Debug Build  or Codename

One → Send Android Build.

30

Figure 18. Right click menu options for sending device builds

 The first time you send a build you will be prompted for the email and password

you provided when signing up for Codename One

Once you send a build you should see the results in the build server page:

Figure 19. Build Results



On  iOS  make  sure  you  use  Safari  when  installing,  as  3rd  party  browsers  might

have issues

Once you go through those steps you should have the HelloWorld app running on your device. This

process is non-trivial when starting so if you run into difficulties don’t despair and seek help at the

discussion 

forum 

(https://www.codenameone.com/discussion-forum.html)  or  stack  overflow

(https://stackoverflow/tags/codenameone/).  Once  you  go  through  signing  and  installation,  it

becomes easier.



You  can  also  install  the  application  either  by  emailing  the  install  link  to  your

account (using the e-mail Link button)

You can also download the binaries in order to upload them to the appstores.

31

1.9. Kotlin

Codename One started before Kotlin became public. Kotlin has since shown itself as an interesting

option  for  developers  especially  within  the  Android  community. With  that  in  mind  we  decided  to

integrate support for Kotlin into Codename One.

To use Kotlin with Codename One you will need the following:

• You need to use IntelliJ/IDEA - Currently only the IDEA version of the Codename One plugin has

Kotlin support

• You  need  to  install  the  Kotlin  support  libraries  from  the  extension  manager  tool  in  Codename

One Preferences

• Don’t  use  the  project  conversion  tools  or  accept  the  warning  that  the  project  isn’t  a  Kotlin

project. We do our own build process

• Warnings  and  errors  aren’t  listed  correctly  and  a  build  that  claimed  to  have  2  errors  actually

passed…

• This will increase your jar size by roughly 730kb which might make it harder for free tier users

You  can  install  the  Kotlin  libraries  which  are  required  for  compilation  by  using  the  extension

manager.

In the right click menu select Codename One → Codename One Preferences.

Select  Extensions  type  in  kotlin  and  install.  Then  right  click  the  project  select  Codename One  →
Refresh Libs.

1.9.1. Hello Kotlin

Due  to  the  way  Kotlin  works  you  can  just  create  a  regular  Java  project  and  convert  sources  to

Kotlin. You can mix Java and Kotlin code without a problem and Codename One would "just work".

The hello world Java source file looks like this (removed some comments and whitespace):

32

public class MyApplication {
    private Form current;
    private Resources theme;

    public void init(Object context) {
        theme = UIManager.initFirstTheme("/theme");
        Toolbar.setGlobalToolbar(true);
        Log.bindCrashProtection(true);
    }

    public void start() {
        if(current != null){
            current.show();
            return;
        }
        Form hi = new Form("Hi World", BoxLayout.y());
        hi.add(new Label("Hi World"));
        hi.show();
    }

    public void stop() {
        current = getCurrentForm();
        if(current instanceof Dialog) {
            ((Dialog)current).dispose();
            current = getCurrentForm();
        }
    }

    public void destroy() {
    }
}

When  you  select  that  file  and  select  the  menu  option  Code  →  Convert Java file to Kotlin File  you

should get this:

33

class MyApplication {
    private var current: Form? = null
    private var theme: Resources? = null

    fun init(context: Any) {
        theme = UIManager.initFirstTheme("/theme")
        Toolbar.setGlobalToolbar(true)
        Log.bindCrashProtection(true)
    }

    fun start() {
        if (current != null) {
            current!!.show()
            return
        }
        val hi = Form("Hi World", BoxLayout.y())
        hi.add(Label("Hi World"))
        hi.show()
    }

    fun stop() {
        current = getCurrentForm()
        if (current is Dialog) {
            (current as Dialog).dispose()
            current = getCurrentForm()
        }
    }

    fun destroy() {
    }
}

That’s pretty familiar. The problem is that there are two bugs in the automatic conversion… That is

the code for Kotlin behaves differently from standard Java.

The  first  problem  is  that  Kotlin  classes  are  final  unless  declared  otherwise  so  we  need  to  add  the

open keyword before the class declaration as such:

open class MyApplication

This is essential as the build server will fail with weird errors related to instanceof.

 This only applies to the main class of the project, other classes in Codename One

can remain final

The second problem is that arguments are non-null by default. The init method might have a null
argument. So this fails with an exception. The solution is to add a question mark to the end of the
call: fun init(context: Any?).

34

So the full working sample is:

open class MyApplication {
    private var current: Form? = null
    private var theme: Resources? = null
    fun init(context: Any?) {
        theme = UIManager.initFirstTheme("/theme")
        Toolbar.setGlobalToolbar(true)
        Log.bindCrashProtection(true)
    }

    fun start() {
        if (current != null) {
            current!!.show()
            return
        }
        val hi = Form("Hi World", BoxLayout.y())
        hi.add(Label("Hi World"))
        hi.show()
    }

    fun stop() {
        current = getCurrentForm()
        if (current is Dialog) {
            (current as Dialog).dispose()
            current = getCurrentForm()
        }
    }

    fun destroy() {
    }
}

Once  all  of  that  is  in  place  Kotlin  should  just  work.  This  should  be  possible  for  additional  JVM

languages in the future.

35

36

2. Basics: Themes, Styles, Components and
Layouts

Let’s  start  with  a  brief  overview  of  the  ideas  within  Codename  One.  We’ll  dig  deeper  into  these

ideas as we move forward.

2.1. Components

Every  button,  label  or  element  you  see  on  the  screen  in  a  Codename  One  application  is  a

Component  [https://www.codenameone.com/javadoc/com/codename1/ui/Component.html].  This  is  a  highly

simplified version of this class hierarchy:

Figure 20. The Core Component Class Hierarchy

The  Form  [https://www.codenameone.com/javadoc/com/codename1/ui/Form.html]  is  a  special  case  Component.
It’s the root component that you can show to the user. Container is a Component type that can hold
other components within it. This lets us create elaborate hierarchies by nesting Container instances.

Figure 21. Component UML

37

A Codename One application is effectively a series of forms, only one Form can be shown at a time.
The Form includes everything we see on the screen. Under the hood the Form is comprised of a few
separate pieces:

Figure 22. Structure of a Form

• Content Pane - this is literally the body of the Form. When we add a Component into the Form it goes

into the content pane. Notice that Content Pane is scrollable by default on the Y axis!

• Title Area - we can’t add directly into this area. The title area is managed by the Toolbar class.
Toolbar is a special component that resides in the top portion of the form and abstracts the title
design. The title area is broken down into two parts:

◦ Title of the Form and its commands (the buttons on the right/left of the title)

◦ Status Bar - on iOS the area on the top includes a special space so the notch, battery, clock

etc. can fit. Without this the battery indicator/clock or notch would be on top of the title

Now  that  we  understand  this  let’s  look  at  the  new  project  we  created  and  open  the  Java  file
TodoApp.java. In it we should see the lines that setup the UI in the start() method:

2.1.1. Layout Managers

A  layout  manager  is  an  algorithm  that  decides  the  size  and  location  of  the  components  within  a
Container. Every Container has a layout manager associated with it. The default layout manager is
FlowLayout.

To understand layouts we need to understand a basic concept about Component. Each component has
a  “preferred  size”.  This  is  the  size  in  which  a  component  “wants”  to  appear.  E.g.  for  a  Label  the
preferred size will be the exact size that fits the label text, icon and padding of the component.

38

Understanding Preferred Size

[https://www.codenameone.com/javadoc/com/codename1/ui/Component.html]  class
The  Component 
contains many useful methods. One of the most important ones is calcPreferredSize() which
is invoked to recalculate the size a component “wants” when something changes



By  default  Codename  One  invokes  the  getPreferredSize()  method  and  not
calcPreferredSize() directly.
getPreferredSize() invokes calcPreferredSize() and caches the value

The preferred size is decided by the component based on internal constraints such as the font

size, border sizes, padding etc.

When a layout manager positions and sizes the component, it MIGHT take the preferred size

into account. Notice that it MIGHT ignore it entirely!

E.g.  FlowLayout 

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/FlowLayout.html]

always 

gives 

components 

their 

exact 

preferred 

size, 

yet 

BorderLayout

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/BorderLayout.html] resizes the center

component by default (and the other components are resized on one of their axis).

You can define a group of components to have the same preferred width or height by using
the setSameWidth and setSameHeight methods e.g.:

Listing 5. setSameWidth/Height

Component.setSameWidth(cmp1, cmp2, cmp3, cmp4);
Component.setSameHeight(cmp5, cmp6, cmp7);

Codename One has a setPreferredSize method that allows developers to explicitly request the
size  of  the  component.  However,  this  caused  quite  a  lot  of  problems.  E.g.  the  preferred  size

should change with device orientation or similar operations. The API also triggered frequent

inadvertent  hardcoding  of  UI  values  such  as  forcing  pixel  sizes  for  components.  As  a  result

the method was deprecated.

We recommend developers use setSameWidth, setSameHeight when sizing alignment is needed.
setHidden  when  hiding 
last  resort  we  recommend  overriding
calcPreferredSize.

is  needed.  As  a 

A  layout  manager  places  a  component  based  on  its  own  logic  and  the  preferred  size  (sometimes
referred  to  as  “natural  size”).  A  FlowLayout  will  just  traverse  the  components  based  on  the  order
they were added and size/place them one after the other. When it reaches the end of the row it will

go to the new row.

39

Use FlowLayout Only for Simple Things



FlowLayout is great for simple things but has issues when components change their
sizes dynamically (like a text field). In those cases it can make bad decisions about

line breaks and take up too much space

Figure 23. Layout Manager Primer Part I

Figure 24. Layout Manager Primer Part II

Scrolling  doesn’t  work  well  for  all  types  of  layouts  as  the  positioning  algorithm  within  the  layout
might  break.  Scrolling  on  the  Y  axis  works  great  for  BoxLayout  Y  which  is  why  I  picked  it  for  the
TodoForm:

Table 1. Scrolling in Layout Managers

Layout

Flow Layout

Border Layout

Box Layout Y

Box Layout X

Grid Layout

LayeredLayout

40

Scrollable

Possible on Y axis only

Scrolling is blocked

Scrollable only on the Y axis

Scrollable only on the X axis

Scrollable

Not scrollable (usually)

Nesting Scrollable Containers

Only  one  element  can  be  scrollable  within  the  hierarchy,  otherwise  if  you  drag  your  finger
over the Form Codename One won’t know which element you are trying to scroll. By default
form’s  content  pane  is  scrollable  on  the  Y  axis  unless  you  explicitly  disable  it  (setting  the
layout to BorderLayout implicitly disables scrolling).

It’s important to notice that it’s OK to have non-scrollable layouts, e.g. BorderLayout, as items
within  a  scrollable  container  type.  E.g.  in  the  TodoApp  we  added  TodoItem  which  uses
BorderLayout into a scrollable BoxLayout Form.

Layouts can be divided into two distinct groups:

• Constraint  Based  -  BorderLayout  (and  a  few  others  such  as  GridBagLayout,  MigLayout  and

TableLayout)

• Regular - All of the other layout managers

When we add a Component to a Container with a regular layout we do so with a simple add method:

Listing 6. Adding to a Regular Container

Container cnt = new Container(BoxLayout.y());
cnt.add(new Label("Just Added"));

This works great for regular layouts but might not for constraint based layouts. A constraint based
layout accepts another argument. E.g. BorderLayout needs a location for the Component:

Listing 7. Adding to a Regular Container

cnt.add(NORTH, new Label("Just Added"));

This  line  assumes  you  have  an  import  static  com.codename1.ui.CN.*;  in  the  top  of  the  file.  In
BorderLayout (which is a constraint based layout) placing an item in the NORTH places it in the top of
the Container.



The CN class is a class that contains multiple static helper methods and functions.
It’s specifically designed for static import in this way to help keep our code terse

41

Static Global Context

The  CN  class  is  a  thin  wrapper  around  features  in  Display,  NetworkManager,  Storage,
FileSystemStorage etc. It also adds common methods and constants from several other classes
so Codename One code feels more terse e.g. we can do:

import static com.codename1.ui.CN.*;



That’s  optional,  if  you  don’t  like  static  imports  you  can  just  write  CN.  for
every element

From that point on you can write code that looks like this:

callSerially(() -> runThisOnTheEDT());

Instead of:

Display.getInstance().callSerially(() -> runThisOnTheEDT());

The same applies for most network manager calls e.g.:

addToQueue(myConnectionRequest);

Instead of:

NetworkManager.getInstance().addToQueue(myConnectionRequest);

Some  things  were  changed  so  we  won’t  have  too  many  conflicts  e.g.  Log.p  or  Log.e  would
have been problematic so we now have:

log("my log message");
log(myException);

Instead  of  Display.getInstance().getCurrent()  we  now  have  getCurrentForm()  since
getCurrent()  is  too  generic.  For  most  methods  you  should  just  be  able  to  remove  the
NetworkManager or Display access and it should "just work".

The motivation for this is three fold:

• Terse code

• Small performance gain

42

• Cleaner API without some of the baggage in Display or NetworkManager

Some of our samples in this guide might rely on that static import being in place. This helps

us keep the code terse and readable in the code listings.

Terse Syntax

Almost every layout allows us to add a component using several variants of the add method:

Listing 8. Versions of add

Container cnt = new Container(BoxLayout.y());
cnt.add(new Label("Just Added")); ①
cnt.addAll(new Label("Adding Multiple"), ②
    new Label("Second One"));

cnt.add(new Label("Chaining")). ③
    add(new Label("Value"));

① Regular add

② addAll accepts several components and adds them in a batch

③ add returns the parent Container instance so we can chain calls like that

In the race to make code “tighter” we can make this even shorter. Almost all layout managers have

their own custom terse syntax style e.g.:

Listing 9. Terse Syntax

Container boxY = BoxLayout.encloseY(cmp1, cmp2); ①
Container boxX = BoxLayout.encloseX(cmp3, cmp4);
Container flowCenter = FlowLayout. ②
    encloseCenter(cmp5, cmp6);

① Most layouts have a version of enclose to encapsulate components within

② FlowLayout has variants that support aligning the components on various axis

To  sum  this  up,  we  can  use  layout  managers  and  nesting  to  create  elaborate  UI’s  that  implicitly

adapt to different screen sizes and device orientation.

Flow Layout

43

Figure 25. Flow Layout

Flow 

layout 

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/FlowLayout.html] 

lets 

the

components “flow” horizontally and break a line when reaching the edge of the container. It’s the

default layout manager for containers. Because it’s so flexible it’s also problematic as it can result in

incorrect  preferred  size  values  for  the  parent  Container  [https://www.codenameone.com/javadoc/com/

codename1/ui/Container.html].  This  can  create  a  reflow  issue,  as  a  result  we  recommend  using  flow

layout only for trivial cases. Avoid it for things such as text input etc. As the size of the text input

can vary in runtime.

Form hi = new Form("Flow Layout", new FlowLayout());
hi.add(new Label("First")).
    add(new Label("Second")).
    add(new Label("Third")).
    add(new Label("Fourth")).
    add(new Label("Fifth"));
hi.show();

Flow layout also supports terse syntax shorthand such as:

Container flowLayout = FlowLayout.encloseIn(
        new Label("First"),
        new Label("Second"),
        new Label("Third"),
        new Label("Fourth"),
        new Label("Fifth")));

Flow  layout  can  be  aligned  to  the  left  (the  default),  to  the  center,  or  to  the  right.  It  can  also  be

vertically aligned to the top (the default), middle (center), or bottom.

44

Figure 26. Flow layout aligned to the center

Figure 27. Flow layout aligned to the right

Figure 28. Flow layout aligned to the center horizontally & the middle vertically

Components within the flow layout get their natural preferred size by default and are not stretched

in any axis.



Box Layout

The  natural  sizing  behavior  is  often  used  to  prevent  other  layout  managers  from

stretching  components.  E.g.  if  we  have  a  border  layout  element  in  the  south  and

we  want  it  to  keep  its  natural  size  instead  of  adding  the  element  to  the  south
parent.add(BorderLayout.SOUTH,

directly 
FlowLayout.encloseCenter(dontGrowThisComponent)).

using 

wrap 

can 

we 

it 

BoxLayout 
places
elements in a row (X_AXIS) or column (Y_AXIS) according to box orientation. Box is a very simple and

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/BoxLayout.html] 

45

predictable layout that serves as the "workhorse" of component lists in Codename One.

You can create a box layout Y using something like this:

Form hi = new Form("Box Y Layout", new BoxLayout(BoxLayout.Y_AXIS));
hi.add(new Label("First")).
    add(new Label("Second")).
    add(new Label("Third")).
    add(new Label("Fourth")).
    add(new Label("Fifth"));

Which results in this

Figure 29. BoxLayout Y

Box layout also supports a shorter terse notation which we use here to demonstrate the X axis box.

Container box = BoxLayout.encloseX(new Label("First"),
        new Label("Second"),
        new Label("Third"),
        new Label("Fourth"),
        new Label("Fifth")));

Figure 30. BoxLayout X

The  box  layout  keeps  the  preferred  size  of  its  destination  orientation  and  scales  elements  on  the
other axis. Specifically X_AXIS will keep the preferred width of the component while growing all the
components  vertically  to  match  in  size.  Its  Y_AXIS  counterpart  keeps  the  preferred  height  while

46

growing the components horizontally.

This behavior is very useful since it allows elements to align as they would all have the same size.

In  some  cases  the  growing  behavior  in  the  X  axis  is  undesired,  for  these  cases  we  can  use  the
X_AXIS_NO_GROW variant.

Figure 31. BoxLayout X_AXIS_NO_GROW

FlowLayout vs. BoxLayout.X_AXIS



When  applicable  we  recommend  BoxLayout  over  FlowLayout  as  it  acts  more
consistently  in  all  situations.  Another  advantage  of  BoxLayout  is  the  fact  that  it
grows and thus aligns nicely

Border Layout

Figure 32. Border Layout

Border  layout  [https://www.codenameone.com/javadoc/com/codename1/ui/layouts/BorderLayout.html]  is  quite
unique. BorderLayout is a constraint-based layout that can place up to five components in one of the
five positions: NORTH, SOUTH, EAST, WEST or CENTER.

Form hi = new Form("Border Layout", new BorderLayout());
hi.add(BorderLayout.CENTER, new Label("Center")).
    add(BorderLayout.SOUTH, new Label("South")).
    add(BorderLayout.NORTH, new Label("North")).
    add(BorderLayout.EAST, new Label("East")).
    add(BorderLayout.WEST, new Label("West"));
hi.show();



The Constraints are Included in the CN class

You can use the static import of the CN class and then the syntax can be add(SOUTH,
new Label("South"))

47

The  layout  always  stretches  the  NORTH/SOUTH  components  on  the  X-axis  to  completely  fill  the
container and the EAST/WEST components on the Y-axis. The center component is stretched to fill the
remaining area by default. However, the setCenterBehavior allows us to manipulate the behavior of
the center component so it is placed in the center without stretching.

E.g.:

Form hi = new Form("Border Layout", new BorderLayout());
((BorderLayout)hi.getLayout()).setCenterBehavior(BorderLayout.CENTER_BEHAVIOR_CENTER);
hi.add(BorderLayout.CENTER, new Label("Center")).
    add(BorderLayout.SOUTH, new Label("South")).
    add(BorderLayout.NORTH, new Label("North")).
    add(BorderLayout.EAST, new Label("East")).
    add(BorderLayout.WEST, new Label("West"));
hi.show();

Results in:

Figure 33. Border Layout with CENTER_BEHAVIOR_CENTER



Scrolling is Disabled in Border Layout

Because of its scaling behavior scrolling a border layout makes no sense. Container
implicitly blocks scrolling on a border layout, but it can scroll its parents/children

In the case of RTL the EAST and WEST values are implicitly reversed as shown in this image:

Figure 34. Border Layout in RTL mode

RTL and Bidi

RTL  (Right  To  Left)  or  Bidi  (bi-directional)  are  common  terms  used  for  languages  such  as

Hebrew, Arabic etc. These languages are written from the right to left direction hence all the

UI needs to be “reversed”. Bidi denotes the fact that while the language is written from right

to left, the numbers are still written in the other direction hence two directions…

48

Preferred Size Still Matters



The preferred size of the center component doesn’t matter in border layout but the
preferred size of the sides is. E.g. If you place an very large component in the SOUTH
it will take up the entire screen and won’t leave room for anything

Grid Layout

GridLayout 

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/GridLayout.html]  accepts  a

predefined  grid  (rows/columns)  and  grants  all  components  within  it  equal  size  based  on  the

dimensions of the largest components.



The  main  use  case  for  this  layout  is  a  grid  of  icons  e.g.  like  one  would  see  in  the

iPhone home screen

If  the  number  of  rows  *  columns  is  smaller  than  the  number  of  components  added  a  new  row  is
implicitly added to the grid. However, if the number of components is smaller than available cells

(won’t fill the last row) blank spaces will be left in place.

In this example we can see that a 2x2 grid is used to add 5 elements, this results in an additional

row that’s implicitly added turning the grid to a 3x2 grid implicitly and leaving one blank cell.

Form hi = new Form("Grid Layout 2x2", new GridLayout(2, 2));
hi.add(new Label("First")).
    add(new Label("Second")).
    add(new Label("Third")).
    add(new Label("Fourth")).
    add(new Label("Fifth"));

Figure 35. Grid Layout 2x2

When we use a 2x4 size ratio we would see elements getting cropped as we do here. The grid layout

uses the grid size first and doesn’t pay too much attention to the preferred size of the components it

holds.

49

Figure 36. Grid Layout 2x4

Grid  also  has  an  autoFit  attribute  that  can  be  used  to  automatically  calculate  the  column  count

based on available space and preferred width. This is really useful for working with UI’s where the

device orientation might change.

There is also a terse syntax for working with a grid that has two versions, one that uses the "auto

fit"  option  and  another  that  accepts  the  number  of  columns.  Here’s  a  sample  of  the  terse  syntax

coupled with auto fit followed by screenshots of the same code in two orientations:

GridLayout.encloseIn(new Label("First"),
    new Label("Second"),
    new Label("Third"),
    new Label("Fourth"),
    new Label("Fifth")));

Figure 37. Grid Layout autofit portrait

Figure 38. Grid Layout autofit landscape

2.1.2. Table Layout

The  TableLayout  [https://www.codenameone.com/javadoc/com/codename1/ui/table/TableLayout.html]  is  a  very

elaborate  constraint  based  layout  manager  that  can  arrange  elements  in  rows/columns  while

50

defining constraints to control complex behavior such as spanning, alignment/weight etc.

Note the Different Package for TableLayout



The  TableLayout  is  in  the  com.codename1.ui.table  package  and  not  in  the  layouts
package.
This  is  due  to  the  fact  that  TableLayout  was  originally  designed  for  the  Table
[https://www.codenameone.com/javadoc/com/codename1/ui/table/Table.html] class.

Despite being constraint based the TableLayout isn’t strict about constraints and will implicitly add a
constraint  when  one  is  missing.  This  is  unlike  the  BorderLayout  which  will  throw  an  exception  in
this case.

 Unlike GridLayout TableLayout won’t implicitly add a row if the row/column count

is incorrect

Form hi = new Form("Table Layout 2x2", new TableLayout(2, 2));
hi.add(new Label("First")).
    add(new Label("Second")).
    add(new Label("Third")).
    add(new Label("Fourth")).
    add(new Label("Fifth"));
hi.show();

Figure 39. 2x2 TableLayout with 5 elements, notice that the last element is missing

TableLayout  supports  the  ability  to  grow  the  last  column  which  can  be  enabled  using  the
setGrowHorizontally  method.  You  can  also  use  a  shortened  terse  syntax  to  construct  a  TableLayout
however since the TableLayout is a constraint based layout you won’t be able to utilize its full power
with this syntax.

The default usage of the encloseIn method below uses the setGrowHorizontally flag.

Container tl = TableLayout.encloseIn(2, new Label("First"),
                new Label("Second"),
                new Label("Third"),
                new Label("Fourth"),
                new Label("Fifth")));

51

Figure 40. TableLayout.encloseIn() with default behavior of growing the last column

The Full Potential

TableLayout is a beast, to truly appreciate it we need to use the constraint syntax which allows us to
span, align and set width/height for the rows and columns.

TableLayout  works  with  a  Constraint  [https://www.codenameone.com/javadoc/com/codename1/ui/table/
TableLayout.Constraint.html]  instance  that  can  communicate  our  intentions  into  the  layout  manager.

Such constraints can include more than one attribute e.g. span and height.

 TableLayout constraints can’t be reused for more than one component

The constraint class supports the following attributes

Table 2. Constraint Properties

column

row

width

height

spanHorizontal

spanVertical

horizontalAlign

verticalAlign

The column for the table cell. This defaults to -1

which will just place the component in the next

available cell

Similar to column, defaults to -1 as well

The column width in percentages, -1 will use the

preferred size. -2 for width will take up the rest

of the available space

Similar to width but doesn’t support the -2 value

The cells that should be occupied horizontally

defaults to 1 and can’t exceed the column count -

current offset.

Similar to spanHorizontal with the same

limitations

The horizontal alignment of the content within

the cell, defaults to the special case -1 value to
take up all the cell space can be either -1,
Component.LEFT, Component.RIGHT or
Component.CENTER

Similar to horizontalAlign can be one of -1,
Component.TOP, Component.BOTTOM or
Component.CENTER



You only need to set width/height to one cell in a column/row

The table layout constraint sample tries to demonstrate some of the unique things you can do with

52

constraints.

TableLayout tl = new TableLayout(2, 3); ①
Form hi = new Form("Table Layout Cons", tl);
hi.setScrollable(false); ②
hi.add(tl.createConstraint(). ③
            widthPercentage(20),
                new Label("AAA")).

        add(tl.createConstraint(). ④
            horizontalSpan(2).
            heightPercentage(80).
            verticalAlign(Component.CENTER).
            horizontalAlign(Component.CENTER),
                new Label("Span H")).

        add(new Label("BBB")).

        add(tl.createConstraint().
            widthPercentage(60).
            heightPercentage(20),
                new Label("CCC")).

        add(tl.createConstraint().
            widthPercentage(20),
                new Label("DDD"));

① We need the TableLayout instance to create constraints. A constraint must be created for every

component and must be used with the same layout as the parent container

② To  get  the  look  in  the  screenshot  we  need  to  turn  scrolling  off  so  the  height  constraint  doesn’t
take up available height. Otherwise it will miscalculate available height due to scrolling. You can
scroll a TableLayout but sizing will be different

③ We create the constraint and instantly apply width to it. This is a shorthand syntax for the code

block below

④ We can chain constraint creation using a call like this so multiple constraints apply to a single
cell. Notice that we don’t span and set width on the same axis (horizontal span + width), doing

something like that would create confusing behavior

Here is the full code mentioned in item 3:

TableLayout.Constraint cn = tl.createConstraint();
cn.setWidthPercentage(20);
hi.add(cn, new Label("AAA")).

53

Figure 41. TableLayout constraints can be used to create very elaborate UI’s

TextMode Layout

TextModeLayout  is  a  unique  layout  manager.  It  acts  like  TableLayout  on  Android  and  like
BoxLayout.Y_AXIS in other platforms. Internally it delegates to one of these two layout managers so
in a sense it doesn’t have as much functionality of its own.

E.g. this is a sample usage of TextModeLayout:

TextModeLayout tl = new TextModeLayout(3, 2);
Form f = new Form("Pixel Perfect", tl);
TextComponent title = new TextComponent().label("Title");
TextComponent price = new TextComponent().label("Price");
TextComponent location = new TextComponent().label("Location");
TextComponent description = new TextComponent().label("Description").multiline(true);

f.add(tl.createConstraint().horizontalSpan(2), title);
f.add(tl.createConstraint().widthPercentage(30), price);
f.add(tl.createConstraint().widthPercentage(70), location);
f.add(tl.createConstraint().horizontalSpan(2), description);
f.setEditOnShow(title.getField());
f.show();

Figure 42. TextModeLayout on iOS

Figure 43. TextModeLayout on Android with the same code

As you can see from the code and samples above there is a lot going on under the hood. On Android
we want a layout that’s similar to TableLayout so we can “pack” the entries. On iOS we want a box

54

layout Y type of layout but we also want the labels/text to align properly…

The  TextModeLayout  isn’t  really  a  layout  as  much  as  it  is  a  delegate.  When  running  in  the  Android
mode  (which  we  refer  to  as  the  “on  top”  mode)  the  layout  is  almost  an  exact  synonym  of
TableLayout and in fact delegates to an underlying TableLayout. In fact there is a public final table
instance within the layout that you can refer to directly…

There is one small difference between the TextModeLayout and the underlying TableLayout and that’s
our choice to default to align entries to TOP with this mode.



Aligning  to  TOP  is  important  for  error  handling  for  TextComponent  in  Android
otherwise the entries “jump”

When  working  in  the  non-android  environment  we  use  a  BoxLayout  on  the  Y  axis  as  the  delegate.
There’s one thing we do here that’s different from a default box layout: grouping. Grouping allows
the labels to align by setting them to the same width, internally it invokes Component.setSameWidth().
Since  text  components  hide  the  labels  there  is  a  special  group  method  there  that  can  be  used.
However, this is implicit with the TextModeLayout which is pretty cool.

TextModeLayout  was  created  specifically  for  the  TextComponent  and  InputComponent  so  check  out  the
section about them in the components chapter.

2.1.3. Layered Layout

When  used  without  constraints, 

the  LayeredLayout  [https://www.codenameone.com/javadoc/com/

codename1/ui/layouts/LayeredLayout.html]  places  the  components  in  order  one  on  top  of  the  other  and

sizes them all to the size of the largest component. This is useful when trying to create an overlay

on top of an existing component. E.g. an “x” button to allow removing the component.

Figure 44. The X on this button was placed there using the layered layout code below

The  code  to  generate  this  UI  is  slightly  complex  and  contains  very  few  relevant  pieces.  The  only

truly relevant piece is this block:

hi.add(LayeredLayout.encloseIn(settingsLabel,
        FlowLayout.encloseRight(close)));

We are doing three distinct things here:

55

1. We are adding a layered layout to the form

2. We  are  creating  a  layered  layout  and  placing  two  components  within.  This  would  be  the

equivalent of just creating a LayeredLayout Container and invoking add twice

3. We use FlowLayout to position the X close button in the right position



When  used  without  constraints,  the  layered  layout  sizes  all  components  to  the

exact  same  size  one  on  top  of  the  other.  It  usually  requires  that  we  use  another

container within; in order to position the components correctly

This is the full source of the example for completeness:

Form hi = new Form("Layered Layout");
int w = Math.min(Display.getInstance().getDisplayWidth(), Display.getInstance().getDisplayHeight());
Button settingsLabel = new Button("");
Style settingsStyle = settingsLabel.getAllStyles();
settingsStyle.setFgColor(0xff);
settingsStyle.setBorder(null);
settingsStyle.setBgColor(0xff00);
settingsStyle.setBgTransparency(255);
settingsStyle.setFont(settingsLabel.getUnselectedStyle().getFont().derive(w / 3, Font.STYLE_PLAIN));
FontImage.setMaterialIcon(settingsLabel, FontImage.MATERIAL_SETTINGS);
Button close = new Button("");
close.setUIID("Container");
close.getAllStyles().setFgColor(0xff0000);
FontImage.setMaterialIcon(close, FontImage.MATERIAL_CLOSE);
hi.add(LayeredLayout.encloseIn(settingsLabel,
        FlowLayout.encloseRight(close)));

Forms  have  a  built  in  layered  layout  that  you  can  access  via  getLayeredPane(),  this  allows  you  to
overlay elements on top of the content pane.

The 

layered  pane 

is  used 

internally  by 

components 

such  as 

InteractionDialog

[https://www.codenameone.com/javadoc/com/codename1/components/InteractionDialog.html], 

AutoComplete

[https://www.codenameone.com/javadoc/com/codename1/ui/AutoCompleteTextField.html] etc.



Codename One also includes a GlassPane that resides on top of the layered pane.

Its  useful  if  you  just  want  to  "draw"  on  top  of  elements  but  is  harder  to  use  than

layered pane

Insets and Reference Components

As of Codename One 3.7, LayeredLayout [https://www.codenameone.com/javadoc/com/codename1/ui/layouts/

LayeredLayout.html] 

supports 

insets 

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/

LayeredLayout.LayeredLayoutConstraint.Inset.html] for its children. This effectively allows you to position

child  components  precisely  where  you  want  them,  relative  to  their  container  or  siblings.  This

functionality forms the under-pinnings of the GUI Builder’s Auto-Layout mode.

As an example, suppose you wanted to position a button in the lower right corner of its container.

This  can  be  achieved  with  LayeredLayout  [https://www.codenameone.com/javadoc/com/codename1/ui/

56

layouts/LayeredLayout.html] as follows:

Container cnt = new Container(new LayeredLayout());
Button btn = new Button("Submit");
LayeredLayout ll = (LayeredLayout)cnt.getLayout();
cnt.add(btn);
ll.setInsets(btn, "auto 0 0 auto");

The result is:

The only thing new here is this line:

ll.setInsets(btn, "auto 0 0 auto");

This is called after btn has already been added to the container. It says that we want its insets to be
"auto" on the top and left, and 0 on the right and bottom. This insets string follows the CSS notation
of  top  right  bottom  left  (i.e.  start  on  top  and  go  clockwise),  and  the  values  of  each  inset  may  be
provided in pixels (px), millimetres (mm), percent (%), or the special "auto" value. Like CSS, you can

also specify the insets using a 1, 2, or 3 values. E.g.

1. "1mm" - Sets 1mm insets on all sides.

2. "1mm 2mm" - Sets 1mm insets on top and bottom; 2mm on left and right.

3. "1mm 10% 2mm" - Sets 1mm on top, 10% on left and right, and 2mm on bottom.

4. "1mm 2mm 1px 50%" - Sets 1mm on top, 2mm on right, 1px on bottom, and 50% on left.

auto Insets

The  special  "auto"  inset  indicates  that  it  is  a  flexible  inset.  If  all  insets  are  set  to  "auto",  then  the

component will be centered both horizontally and vertically inside its "bounding box".



The  "inset  bounding  box"  is  the  containing  box  from  which  a  component’s  insets

are  measured.  If  the  component’s  insets  are  not  linked  to  any  other  components,

then  its  inset  bounding  box  will  be  the  inner  bounds  (i.e.  taking  padding  into

account) of the component’s parent container.

If one inset is fixed (i.e. defined in px, mm, or %), and the opposite inset is "auto", then the "auto"

57

inset  will  simply  allow  the  component  to  be  its  preferred  size.  So  if  you  want  to  position  a

component to be centered vertically, and 5mm from the left edge, you could do:

ll.setInsets(btn, "auto auto auto 5mm");

Resulting in:

Figure 45. Button vertically centered 5mm from left edge

Move it to the right edge with:

ll.setInsets(btn, "auto 5mm auto auto");

% Insets

Percent (%) insets are calculated with respect to the inset bounding box. A 50% inset is measured as

50% of the length of the bounding box on the inset’s axis. E.g. A 50% inset on top would be 50% of

the  height  of  the  inset  bounding  box.  A  50%  inset  on  the  right  would  be  50%  of  the  width  of  the

inset bounding box.

Insets, Margin, and Padding

A  component’s  position  in  a  layered  layout  is  determined  as  follows:  (Assume  that  cmp  is  the
component that we are positioning, and cnt is the container (In pseudo-code):

x = cnt.paddingLeft + cmp.calculatedInsetLeft + cmp.marginLeft
y = cnt.paddingTop + cmp.calculatedInsetTop + cmp.marginTop
w = cnt.width - cnt.verticalScroll.width - cnt.paddingRight - cmp.calculatedInsetRight - cmp.marginRight - x
h = cnt.height - cnt.horizontalScroll.height - cnt.paddingBottom - cmp.calculatedInsetBottom - cmp.marginBottom - y



The  calculatedInsetXXX  values  here  will  be  the  same  as  the  corresponding
provided inset if the inset has no reference component. If it does have a reference

component, then the calculated inset will depend on the position of the reference

component.

If no inset is specified, then it is assumed to be 0. This ensures compatibility with designs that were

created before layered layout supported insets.

58

Component References: Linking Components together

If  all  you  need  to  do  is  position  a  component  relative  to  its  parent  container’s  bounds,  then  mere

insets provide you with sufficient vocabulary to achieve this. But most UIs are more complex than

this and require another concept: reference components. In many cases you will want to position a

component relative to another child of the same container. This is also supported.

For example, suppose I want to place a text field in the center of the form (both horizontally and

vertically),  and  have  a  button  placed  beside  it  to  the  right.  Positioning  the  text  field  is  trivial
(setInset(textField,  "auto")),  but  there  is  no  inset  that  we  can  provide  that  would  position  the
button  to  the  right  of  the  text  field.  To  accomplish  our  goal,  we  need  to  set  the  text  field  as  a

reference component of the button’s left inset - so that the button’s left inset is "linked" to the text

field. Here is the syntax:

Container cnt = new Container(new LayeredLayout());
LayeredLayout ll = (LayeredLayout)cnt.getLayout();
Button btn = new Button("Submit");
TextField tf = new TextField();
cnt.add(tf).add(btn);
ll.setInsets(tf, "auto")
  .setInsets(btn, "auto auto auto 0")
  .setReferenceComponentLeft(btn, tf, 1f);

This would result in:

Figure 46. Button’s left inset linked to text field

The two active lines here are the last two:

  .setInsets(btn, "auto auto auto 0") ①
  .setReferenceComponentLeft(btn, tf, 1f); ②

① Sets the left inset on btn to 0.

② Links btn’s left inset to `tf so that it is measured from the text field. The third parameter (
1.0) is the reference position. This will generally either be 0 (meaning the reference point is the
left edge of the text field), or 1 (meaning the reference point is the right edge of the text field). In

59

this case we set a reference position of 1.0 because we want the button to be aligned to the text
field’s right edge.

The  reference  position  is  defined  as  the  distance,  expressed  as  a  fraction  of  the

reference  component’s  length  on  the  inset’s  axis,  between  the  reference

component’s leading (outer) edge and the point from which the inset is measured.



A reference position of 0 means that the inset is measured from the leading edge of

the reference component. A value of 1.0 means that the inset is measured from the

trailing  edge  of  the  reference  component.  A  value  of  0.5  means  that  the  inset  is

measured  from  the  center  of  the  reference  component.  Etc…  Any  floating  point

value can be used. The designer currently only makes use of 0 and 1.

The definition above may make reference components and reference position seem more complex

than it is. Some examples:

1. For a top inset:

a. referencePosition  ==  0  ⇒  the  inset  is  measured  from  the  top  edge  of  the  reference

component.

b. referencePosition  ==  1  ⇒  the  inset  is  measured  from  the  bottom  edge  of  the  reference

component.

2. For a bottom inset:

a. referencePosition  ==  0  ⇒  the  inset  is  measured  from  the  bottom  edge  of  the  reference

component.

b. referencePosition  ==  1  ⇒  the  inset  is  measured  from  the  top  edge  of  the  reference

component.

3. For a left inset:

a. referencePosition  ==  0  ⇒  the  inset  is  measured  from  the  left  edge  of  the  reference

component.

b. referencePosition  ==  1  ⇒  the  inset  is  measured  from  the  right  edge  of  the  reference

component.

4. For a right inset:

a. referencePosition  ==  0  ⇒  the  inset  is  measured  from  the  right  edge  of  the  reference

component.

b. referencePosition  ==  1  ⇒  the  inset  is  measured  from  the  left  edge  of  the  reference

component.

60

Layers In Codename One

Codename  One  allows  placing  components  one  on  top  of  the  other  and  we  commonly  use
layered layout to do that. The form class has a builtin Container that resides in a layer on top
of the content pane of the form.

When  you  add  an  element  to  a  form  it  implicitly  goes  into  the  content  pane.  However,  you
can use getLayeredPane() and add any Component there. Such a Component will appear above the
content pane. Notice that this layer resides below the title area (on the Y axis) and won’t draw

on top of that.

When  Codename  One  introduced  the  layered  pane  it  was  instantly  useful.  However,  its

popularity caused conflicts. Two separate pieces of code using the layered pane could easily
collide with one another. Codename One solved it with getLayeredPane(Class c, boolean top).
This  method  allocates  a  layer  for  a  specific  class  within  the  layered  pane.  This  way  if  two
different  classes  use  this  method  instead  of  the  getLayeredPane()  method  they  won’t  collide.
Each  will  get  its  own  container  in  a  layered  layout  within  the  layered  pane  seamlessly.  The
top flag indicates whether we want the layer to be the top most or bottom most layer within
the  layered  pane  (assuming  it  wasn’t  created  already).  This  allows  you  to  place  a  layer  that

can appear above or below the already installed layers.

We only make use of the layered pane in this book but there are two additional layers on top

of it. The form layered pane is identical to the layered pane but spans the entire height of the
Form (including the title area). As a result the form layered pane is slower as it needs to handle
some special cases to support this functionality.

The glass pane is the top most layer, unlike the layered pane it’s purely a graphical layer. You
can only draw on the glass pane with a Painter instance and a Graphics object. You can’t add
components into that layer.

Figure 47. The Layered Pane

61

2.1.4. GridBag Layout

GridBagLayout 

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/GridBagLayout.html]  was

introduced  to  simplify  the  process  of  porting  existing  Swing/AWT  code  with  a  more  familiar  API.

The  API  for  this  layout  is  problematic  as  it  was  designed  for  AWT/Swing  where  styles  were

unavailable. As a result it has its own insets API instead of using elements such as padding/margin.

Our  recommendation  is  to  use  Table  which  is  just  as  powerful  but  has  better  Codename  One

integration.

To  demonstrate  GridBagLayout  we  ported  the  sample  from  the  Java  tutorial  [http://docs.oracle.com/
javase/tutorial/uiswing/layout/gridbag.html] to Codename One.

62

Button button;
hi.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
//natural height, maximum width
c.fill = GridBagConstraints.HORIZONTAL;
button = new Button("Button 1");
c.weightx = 0.5;
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx = 0;
c.gridy = 0;
hi.addComponent(c, button);

button = new Button("Button 2");
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 0.5;
c.gridx = 1;
c.gridy = 0;
hi.addComponent(c, button);

button = new Button("Button 3");
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 0.5;
c.gridx = 2;
c.gridy = 0;
hi.addComponent(c, button);

button = new Button("Long-Named Button 4");
c.fill = GridBagConstraints.HORIZONTAL;
c.ipady = 40;      //make this component tall
c.weightx = 0.0;
c.gridwidth = 3;
c.gridx = 0;
c.gridy = 1;
hi.addComponent(c, button);

button = new Button("5");
c.fill = GridBagConstraints.HORIZONTAL;
c.ipady = 0;       //reset to default
c.weighty = 1.0;   //request any extra vertical space
c.anchor = GridBagConstraints.PAGE_END; //bottom of space
c.insets = new Insets(10,0,0,0);  //top padding
c.gridx = 1;       //aligned with button 2
c.gridwidth = 2;   //2 columns wide
c.gridy = 2;       //third row
hi.addComponent(c, button);

Notice that because of the way gridbag works we didn’t provide any terse syntax API for it although

it should be possible.

63

Figure 48. GridbagLayout sample from the Java tutorial running on Codename One

2.1.5. Group Layout

GroupLayout [https://www.codenameone.com/javadoc/com/codename1/ui/layouts/GroupLayout.html] is a layout

that would be familiar to the users of the NetBeans GUI builder (Matisse) [https://netbeans.org/features/

java/swing.html]. Its a layout manager that’s really hard to use for manual coding but is powerful for
some elaborate use cases. Although MiGLayout and LayeredLayout might be superior options.

It  was  originally  added  during  the  LWUIT  days  as  part  of  an  internal  attempt  to  port  Matisse  to

LWUIT.  It’s  still  useful  to  this  day  as  developers  copy  and  paste  Matisse  code  into  Codename  One

and produce very elaborate layouts with drag and drop.

Since the layout is based on an older version of GroupLayout some things need to be adapted in the
code or you should use the special "compatibility" library for Matisse to get better interaction. We

also recommend tweaking Matisse to use import statements instead of full package names, that way
if you use Label just changing the awt import to a Codename One import will make it use work for
Codenmae One’s Label.

Unlike any other layout manager GroupLayout adds the components into the container instead of the
standard API. This works nicely for GUI builder code but as you can see from this sample it doesn’t

make the code very readable:

Form hi = new Form("GroupLayout");

Label label1 = new Label();
Label label2 = new Label();
Label label3 = new Label();
Label label4 = new Label();
Label label5 = new Label();
Label label6 = new Label();
Label label7 = new Label();

label1.setText("label1");

label2.setText("label2");

label3.setText("label3");

label4.setText("label4");

label5.setText("label5");

label6.setText("label6");

label7.setText("label7");

GroupLayout layout = new GroupLayout(hi.getContentPane());
hi.setLayout(layout);
layout.setHorizontalGroup(
    layout.createParallelGroup(GroupLayout.LEADING)

64

    .add(layout.createSequentialGroup()
        .addContainerGap()
        .add(layout.createParallelGroup(GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .add(label1, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(LayoutStyle.RELATED)
                .add(layout.createParallelGroup(GroupLayout.LEADING)
                    .add(label4, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .add(label3, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .add(label2, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)))
            .add(label5, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
            .add(layout.createSequentialGroup()
                .add(label6, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(LayoutStyle.RELATED)
                .add(label7, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)))
        .addContainerGap(296, Short.MAX_VALUE))
);
layout.setVerticalGroup(
    layout.createParallelGroup(GroupLayout.LEADING)
    .add(layout.createSequentialGroup()
        .addContainerGap()
        .add(layout.createParallelGroup(GroupLayout.TRAILING)
            .add(label2, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
            .add(label1, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
        .addPreferredGap(LayoutStyle.RELATED)
        .add(label3, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(LayoutStyle.RELATED)
        .add(label4, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(LayoutStyle.RELATED)
        .add(label5, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(LayoutStyle.RELATED)
        .add(layout.createParallelGroup(GroupLayout.LEADING)
            .add(label6, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
            .add(label7, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
        .addContainerGap(150, Short.MAX_VALUE))
);

Figure 49. GroupLayout Matisse generated UI running in Codename One

If you are porting newer Matisse code there are simple changes you can do:

• Change addComponent to add

• Change addGroup to add

• Remove references to ComponentPlacement and reference LayoutStyle directly

65

2.1.6. Mig Layout

MigLayout 

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/mig/MigLayout.html] 

is 

a

popular cross platform layout manager that was ported to Codename One from Swing.

 MiG is still considered experimental so proceed with caution!

The API was deprecated to serve as a warning of its experimental status.

The  best  reference 

for  MiG  would  probably  be 

its  quick  start  guide 

(PDF 

link)

[http://www.miglayout.com/QuickStart.pdf]. As a reference we ported one of the samples from that PDF to

Codename One:

Form hi = new Form("MigLayout", new MigLayout("fillx,insets 0"));

hi.add(new Label("First")).
    add("span 2 2", new Label("Second")).  // The component will span 2x2 cells.
    add("wrap", new Label("Third")).      // Wrap to next row
    add(new Label("Forth")).
    add("wrap", new Label("Fifth")).    // Note that it "jumps over" the occupied cells.
    add(new Label("Sixth")).
    add(new Label("Seventh"));
hi.show();

Figure 50. MiG layout sample ported to Codename One

It should be reasonably easy to port MiG code but you should notice the following:

• MiG  handles  a  lot  of  the  spacing/padding/margin  issues  that  are  missing  in  Swing/AWT.  With

Codename One styles we have the padding and margin which are probably a better way to do a

lot of the things that MiG does

• The add method in Codename One can be changed as shown in the sample above.

• The constraint argument for Coedname One add calls appears before the Component instance.

2.2. Themes and Styles

Next we need to introduce you to 3 important terms in Codename One: Theme, Style and UIID.

Themes  are  very  similar  conceptually  to  CSS,  in  fact  they  can  be  created  with  CSS  syntax  as  we’ll

66

discuss  soon.  The  various  Codename  One  ports  ship  with  a  native  theme  representing  the

appearance of the native OS UI elements. Every Codename One application has its own theme that

derives the native theme and overrides behavior within it.

If the native theme has a button defined, we can override properties of that button in our theme.

This  allows  us  to  customize  the  look  while  retaining  some  native  appearances.  This  works  by

merging the themes to one big theme where our application theme overrides the definitions of the

native theme. This is pretty similar to the cascading aspect of CSS if you are familiar with that.

Themes  consist  of  a  set  of  UIID  definitions.  Every  component  in  Codename  One  has  a  UIID

associated  with  it.  UIID  stands  for  User  Interface  Identifier.  This  UIID  connects  the  theme  to  a

specific  component.  A  UIID  maps  to  CSS  classes  if  you  are  familiar  with  that  concept.  However,

Codename  One  doesn’t  support  the  complex  CSS  selector  syntax  options  as  those  can  impact

runtime performance.

E.g. see this code where:

Listing 10. setUIID on TextField

nameText.setUIID("Label");

This is a text field component (user input field) but it will look like a Label.

Effectively we told the text field that it should use the UIID of Label when it’s drawing itself. It’s very
common to do tricks like that in Codename One. E.g. button.setUIID("Label") would make a button
appear like a label and allow us to track clicks on a “Label”.

The  UIID’s  translate  the  theme  elements  into  a  set  of  Style  objects.  These  Style  objects  get  their
initial values from the theme but can be further manipulated after the fact. So if I want to make the

text field’s foreground color red I could use this code:

Listing 11. setUIID on TextField

nameText.getAllStyles().setFgColor(0xff0000);

The color is in hexadecimal RRGGBB format so 0xff00 would be green and 0xff0000 would be red.

getAllStyles() returns a Style object but why do we need “all” styles?

Each component can have one of 4 states and each state has a Style object. This means we can have
4 style objects per Component:

• Unselected — used  when  a  component  isn’t  touched  and  doesn’t  have  focus.  You  can  get  that

object with getUnselectedStyle().

• Selected — used when a component is touched or if focus is drawn for non-touch devices. You

can get that object with getSelectedStyle().

• Pressed — used when a component is pressed. Notice it’s only applicable to buttons and button

subclasses usually. You can get that object with getPressedStyle().

67

• Disabled — used  when  a  component 

is  disabled.  You  can  get 

that  object  with

getDisabledStyle().

The  getAllStyles()  method  returns  a  special  case  Style  object  that  lets  you  set  the  values  of  all  4
styles from one class so the code before would be equivalent to invoking all 4 setFgColor methods.
However, getAllStyles() only works for setting properties not for getting them!

Don’t use getStyle() for manipulation



getStyle()  returns  the  current  Style  object  which  means  it  will  behave
inconsistently.  The  paint  method  uses  getStyle()  as  it  draws  the  current  state  of
the  Component  but  other  code  should  avoid  that  method.  Use  the  specific  methods
getPressedStyle(),
instead: 
getDisabledStyle() and getAllStyles()

getUnselectedStyle(), 

getSelectedStyle(), 

As  you  can  see,  it’s  a  bit  of  a  hassle  to  change  styles  from  code  which  is  why  the  theme  is  so

appealing.

2.2.1. Theme

A theme allows the designer to define the styles externally via a set of UIID’s (User Interface ID’s),

the themes are created via the Codename One Designer tool and allow developers to separate the

look of the component from the application logic.



You can customize the theme using CSS which we’ll discuss a bit later

The theme is stored in the theme.res file in the src root of the project. We load the theme file using
this line of code in the init(Object) method in the main class of the application:

Listing 12. Theme Loading Code

theme = UIManager.initFirstTheme("/theme");

This  code  is  shorthand  for  resource  file  loading  and  for  the  installation  of  theme.  You  could

technically  have  more  than  one  theme  in  a  resource  file  at  which  point  you  could  use
initNamedTheme()  instead.  The  resource  file  is  a  special  file  format  that  includes  inside  it  several
features:

• Themes

• Images

• Localization Bundles

• Data files

It also includes some legacy features such as the old GUI builder.

 We’re mentioning the legacy GUI builder for reference only we won’t discuss the

old GUI builders in this guide

68

We can open the designer tool by double clicking the res file. The UI can be a bit overwhelming at

first so I’ll try to walk slowly through the steps.

Figure 51. Codename One Designer Feature Map



If you end up using CSS this section isn’t crucial but it’s worth browsing through as

using the designer tool helps in tracking CSS issues

There are two crucial features in this tool: theming and images.

Figure 52. Add a New Image

You will notice there is more than one type of image. We’ll discuss multi-images later.

69

Now  we  can  go  back  to  the  theme  view  in  the  designer  tool  and  press  the  Add  button  in  the
Unselected  tab.  Notice  we  have  tabs  for  every  state  of  Style  as  well  as  a  special  tabl  for  theme
constants that we will discuss later.

Figure 53. The Add Button

After pressing that button we should see something that looks like this:

Figure 54. Add the Theme Entry for the Toolbar



Don’t forget to press the save button in the designer after making changes

There are several other options in the add theme entry dialog. Lets go over them and review what

we should do for each tab in this UI:

70

Figure 55. The Rest of the Add Theme Entry Dialog - Part I

71

Figure 56. The Rest of the Add Theme Entry Dialog - Part II

We’ll cover these options in-depth in the theming chapters.

Native Theme

By  default  Codename  One  applications  are  created  with  a  theme  that  derives  from  the  builtin  OS

native  theme.  You  can  add  additional  themes  into  the  resource  file  by  pressing  the  Add A New

Theme button. You can also create multiple themes and ship them with your app or download them

dynamically.

You can create a theme from scratch or customize one of the Codename one themes to any look you

desire.



To preview the look of your theme in the various platforms use the  Native Theme

menu option in the designer

Figure 57. The native theme menu option

72

You can easily create deep customizations that span across all themes by adding a UIID or changing

an  existing  UIID.  E.g.  looking  at  the  getting  started  application  that  ships  with  the  plugin  you  will

notice a green button. This button is defined using the "GetStarted" UIID which is defined within the

designer as:

• A green background

• White foreground

• A thin medium sized font

• Center aligned text

• A small amount of spacing between the text and the edges

To achieve the colors we define them in the color tab.



We  define  the  transparency  to  255  which  means  the  background  will  be  a  solid

green  color.  This  is  important  since  the  native  OS’s  might  vary  with  the  default

value for background transparency so this should be defined explicitly

Figure 58. The Color tab for the get started button theme settings

The  alignment  of  the  text  is  pretty  simple,  notice  that  the  alignment  style  attribute  applies  to  text

and doesn’t apply to other elements. To align other elements we use layout manager logic.

73

Figure 59. The alignment tab for the get started button theme settings

Padding can be expressed in pixels, millimeters (approximate) or percentages of the screen size.



We recommend using millimeters for all measurements to keep the code portable

for various device DPI’s.

74

Figure 60. The padding tab for the get started button theme settings

The font uses native OS light font but has a fallback for older OS’s that don’t support truetype fonts.

The  "True  Type"  font  will  be  applicable  for  most  modern  OS’s.  In  the  case  of  the  "native:"  fonts

Android devices will use  Roboto whereas iOS devices will use  Helvetica Neue. You can supply your

own TTF and work with that.

 Since  Codename  One  cannot  legally  ship  Helvetica Neue  fonts  the  simulator  will

fallback to Roboto on PC’s.



At the time of this writing the desktop/simulator version of the Roboto font doesn’t

support  many  common  character  sets  (languages).  This  will  have  no  effect  on  an

Android device where thenative font works properly.

75

Figure 61. The font tab for the get started button theme settings

2.3. GUI Builder

The  GUI  builder  allows  us  to  arrange  components  visually  within  a  UI  using  drag  and  drop,

property  sheets  etc.  With  the  GUI  builder  we  can  create  elaborate,  rich  UI’s  without  writing  the

layout code.

76

Why two GUI Builders?

The original old GUI builder has its roots in our work at Sun Microsystems, it was developed

directly into the designer tool and stores it’s data as part of the resource file. When creating

an application for the old GUI builder you must define it as a "visual application" which will

make it use the old GUI builder.

The roots of this GUI builder are pretty old. When we initially built it we still had to support

feature phones with 2mb of RAM and the iPad wasn’t announced yet. Due to that we picked

an  architecture  that  made  sense  for  those  phones  with  a  greater  focus  on  navigation  and

resource  usage.  Newer  mobile  applications  are  rivaling  desktop  applications  in  complexity

and in those situations the old GUI builder doesn’t make as much sense

The  old  GUI  builder  is  in  the  designer  tool,  it’s  a  Swing  application  that  includes  the  theme

design etc.
It generates a Statemachine class that contains all the main user GUI interaction code.

The new GUI builder is a standalone application that you launch from the right click menu by

selecting a form as explained below. Here are screenshots of both to help you differentiate:

Figure 62. The old GUI builder

Figure 63. The same UI in the new GUI builder

As of version 3.7, the new GUI Builder also supports an auto layout mode which allows you to

freely position and resize components on a canvas. This mode is now the default for new GUI

forms, and it always uses LayeredLayout as the root layout manager.

77

Figure 64. The new GUI builder in auto-layout mode

2.3.1. Hello World

Creating a hello world app in the new GUI builder is actually pretty trivial, you need to start with a

regular handcoded application. Not a GUI builder application as it refers to the old GUI builder!

This is the exact same hello world application we created before…

Following  are  the  instructions  for  creating  a  form  and  launching  the  GUI  builder.  While  they  are

similar there are minor IDE differences. Usage of the GUI builder is identical in all IDE’s as the GUI

builder is a separate application.

NetBeans

In NetBeans you need to follow these 4 steps:

Figure 65. Right click the package select  New  →  Other

78

Figure 66. In the Codename One section select the GUI builder form

Figure 67. Type in the name of the form and click finish, you can change the type to be a Container or Dialog

Figure 68. Launch the GUI builder thru the right click menu on the newly created file

IntelliJ/IDEA

In IntelliJ you need to follow these 3 steps:

Figure 69. Right click the package select  New  → Codename One AutoLayout Form (or Dialog/Container)

79

Figure 70. Type in a name for the new form

Figure 71. Launch the GUI builder thru the right click menu on the newly created file

Eclipse

In Eclipse you need to follow these 4 steps:

Figure 72. Right click the package select  New  →  Other

Figure 73. In the Codename One section select the GUI builder option

80

Figure 74. Type in the name of the form and click finish, you can change the type to be a Container or Dialog

Figure 75. Launch the GUI builder thru the right click menu on the newly created file

Basic Usage

Notice  that  the  UI  of  the  new  GUIBuilder  might  change  in  various  ways  but  the  basic  concepts

should remain the same.

The  GUI  builder  is  controlled  via  it’s  main  toolbar,  notice  that  your  changes  will  only  be  applied

when you click the Save button on the right:

Figure 76. The features of the left toolbar

81

Figure 77. The features of the right toolbar

The main UI includes four important parts:

• Main Form — This is where we place the components of the UI we are building

• Component Tree — This is a logical representation of the component hierarchy within the  Main

Form. It’s often easier to pick a component from the tree rather than the form itself

• Property Inspector — When we select an element in the tree or form we can see its details here.

We can then edit the various details of the component in this area

• Palette — Components can be dragged from the palette to the Main Form and placed in the UI

Figure 78. The four parts of the GUI builder

We’ll start by selecting the Component Palette and dragging a button into the UI:

82

Figure 79. You can drag any component you want from the palette to the main UI

By  default  the  auto-layout  mode  of  the  GUI  builder  uses  layered  layout  to  position  components.
Sides  can  be  bound  to  a  component  or  to  the  Form.  We  then  use  distance  units  to  determine  the
binding  behavior.  The  GUI  builder  tries  to  be  "smart"  and  guesses  your  intention  as  you  drag  the

components along.

When you select the component you placed you can edit the properties of that component:

Figure 80. Properties allow you to customize everything about a component

There are five property sheets per component:

• Basic Settings — These include the basic configuration for a component e.g. name, icon, text etc.

• Advanced Settings — These include features that aren’t as common such as icon gap, mask etc.

• Events — By  clicking  a  button  in  this  tab  a  method  will  be  added  to  the  source  file  with  a

callback matching your component name. This will let you bind an event to a button, text field

etc.

• Layout — You can determine the layout of the parent Container here. For auto-layout this should

stay as layered layout, however you can nest other layout types in here

• Style Customization — This  isn’t  a  theme,  if  you  want  to  customize  the  style  of  a  specific

component you can do that through this UI. The theme works on a more global/reusable level

and this is designed for a specific component only

For  things  like  setting  the  text  on  the  component  we  can  use  a  convenient  "long  click"  on  the

83

component to edit the text in place as such:

Figure 81. Use the long click to edit the text "in place"

Events

When  a  component  supports  broadcasting  events  you  can  bind  such  events  by  selecting  it,  then

selecting the events tab and clicking the button matching the event type

Figure 82. The events tab is listed below supported event types can be bound above

Once an event is bound the IDE will open to the event code e.g.:

public void onButton_1ActionEvent(com.codename1.ui.events.ActionEvent ev) {
}



Some  IDE’s  only  generate  the  project  source  code  after  you  explicitly  build  the

project so if your code needs to access variables etc. try building first

Within  the  code  you  can  access  all  the  GUI  components  you  defined  with  the  gui_  prefix  e.g.
Button_1 from the UI is represented as:

84

private com.codename1.ui.Button gui_Button_1 = new com.codename1.ui.Button();

Underlying XML

Saving  the  project  generates  an  XML  file  representing  the  UI  into  the  res  directory  in  the  project,
the GUI file is created in a matching hierarchy in the project under the res/guibuilder directory:

Figure 83. The java and GUI files in the hierarchy

 If you refactor (rename or move) the java file it’s connection with the GUI file will

break. You need to move/rename both

You can edit the GUI file directly but changes won’t map into the GUI builder unless you reopen it.

These files should be under version control as they are the main files that change. The GUI builder

file for the button and label code looks like this:

<?xml version="1.0" encoding="UTF-8"?>

<component type="Form" layout="FlowLayout" flowLayoutFillRows="false" flowLayoutAlign="1"
flowLayoutValign="0"  title="My new title" name="MyForm">
  <component type="Button" text="Button" name="Button_1" actionEvent="true">
  </component>
  <component type="Label" text="Hi World" name="Label_1">
  </component>
</component>

This format is relatively simple and is roughly the same format used by the old GUI builder which

makes  the  migration  to  the  new  GUI  builder  possible.  This  file  triggers  the  following  Java  source

file:

package com.mycompany.myapp;

/**
 * GUI builder created Form

85

 *
 * @author shai
 */
public class MyForm extends com.codename1.ui.Form {

    public MyForm() {
        this(com.codename1.ui.util.Resources.getGlobalResources());
    }

    public MyForm(com.codename1.ui.util.Resources resourceObjectInstance) {
        initGuiBuilderComponents(resourceObjectInstance);
    }

//-- DON'T EDIT BELOW THIS LINE!!!
    private com.codename1.ui.Label gui_Label_1 = new com.codename1.ui.Label();
    private com.codename1.ui.Button gui_Button_1 = new com.codename1.ui.Button();

// <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void guiBuilderBindComponentListeners() {
        EventCallbackClass callback = new EventCallbackClass();
        gui_Button_1.addActionListener(callback);
    }

    class EventCallbackClass implements com.codename1.ui.events.ActionListener,
com.codename1.ui.events.DataChangedListener {
        private com.codename1.ui.Component cmp;
        public EventCallbackClass(com.codename1.ui.Component cmp) {
            this.cmp = cmp;
        }

        public EventCallbackClass() {
        }

        public void actionPerformed(com.codename1.ui.events.ActionEvent ev) {
            com.codename1.ui.Component sourceComponent = ev.getComponent();
            if(sourceComponent.getParent().getLeadParent() != null) {
                sourceComponent = sourceComponent.getParent().getLeadParent();
            }

            if(sourceComponent == gui_Button_1) {
                onButton_1ActionEvent(ev);
            }
        }

        public void dataChanged(int type, int index) {
        }
    }
    private void initGuiBuilderComponents(com.codename1.ui.util.Resources resourceObjectInstance) {
        guiBuilderBindComponentListeners();
        setLayout(new com.codename1.ui.layouts.FlowLayout());
        setTitle("My new title");
        setName("MyForm");
        addComponent(gui_Label_1);
        addComponent(gui_Button_1);
        gui_Label_1.setText("Hi World");
        gui_Label_1.setName("Label_1");
        gui_Button_1.setText("Click Me");
        gui_Button_1.setName("Button_1");
    }// </editor-fold>

//-- DON'T EDIT ABOVE THIS LINE!!!
    public void onButton_1ActionEvent(com.codename1.ui.events.ActionEvent ev) {
    }

}

86

 Don’t touch the code within the DON’T EDIT comments…

The GUI builder uses the "magic comments" approach where code is generated into those areas to

match the XML defined in the GUI builder. Various IDE’s generate that code at different times. Some

will  generate  it  when  you  run  the  app  while  others  will  generate  it  as  you  save  the  GUI  in  the

builder.

You can write code freely within the class both by using the event mechanism, by writing code in

the constructors or thru overriding functionality in the base class.

2.3.2. Auto-Layout Mode

As of version 3.7, new forms created with the GUI Builder will use auto-layout mode. In this mode

you  can  move  and  resize  your  components  exactly  as  you  see  fit.  You  aren’t  constrained  to  the

positions dictated by the form’s layout manager.



All forms designed in auto-layout mode use LayeredLayout

Auto-Layout  Mode  is  built  upon  the  inset  support  in  LayeredLayout.  Component

positioning uses insets and reference components, not absolute positioning

As  an  example,  let’s  drag  a  button  onto  a  blank  form  and  see  what  happens.  The  button  will  be

"selected" initially after adding, it so you’ll see its outline, and resize handles for adjusting its size

and position. You’ll also see four floating labels (above, below, to the left, and to the right) that show

the corresponding side’s inset values and allow you to adjust them.

Figure 84. A button selected on the canvas in auto-layout mode.  You can drag it to reposition it, or resize it

using the resize handles.

Press the mouse inside the bounds of the button and drag it around to reposition it. You will notice

that the inset labels change to reflect the new inset values. If you drag the button close to the edge

of  the  form,  the  corresponding  inset  value  will  change  to  millimetres.  If  you  move  farther  away

from the edge, it will change to percentage values.

The Inset Control

Let’s take a closer look at the inset control (the inset controls are the black buttons that appear to

the top, bottom, left, and right of the selected component).

Figure 85. The inset control allows you to change the inset size and units, toggle it between fixed and

flexible, and link it to another component.

Each control has three sections:

1. The  inset  value  drop-down  menu.  This  shows  the  current  value  of  the  inset  (e.g.  0mm,  25%,

87

auto, etc…). If you click on this, it will open a menu that will allow you to change the units. If the

inset  is  currently  in  millimetres,  it  will  have  options  for  pixels,  and  percent.  If  the  inset  is  in

percent, it will have options for pixels and millimetres. Etc.. It also includes a text field to enter

a an inset value explicitly.

2.

3.

The "Link" Button 

 - If the inset is linked to a reference component, then this button will

be highlighted "blue", and hovering over it will highlight the reference component in the UI so

that  you  can  clearly  see  which  component  it  is  linked  to.  Clicking  on  this  button  will  open  a

dialog that will allow you to "break" this link. You can drag this button over any component in

the form to "link".

The  "Lock"  Button" 

  -  This  button  allows  you  to  toggle  the  inset  between  "flexible"  (i.e.

auto) and "fixed" (i.e. millimetres or percent).

Auto Snap

Notice the "auto-snap" checkbox that appears in the top-right corner of the designer.

Figure 86. Auto-snap checkbox

Auto-snap does exactly what it sounds like: It automatically snaps two components together when

you  drag  them  near  each  other.  This  is  handy  for  linking  components  together  without  having  to

explicitly  link  them  (using  the  "link"  button).  This  feature  is  turned  on  by  default.  If  auto-snap  is

turned  off,  you  can  still  initiate  a  "snap"  by  holding  down  the  ALT/Option  key  on  your  keyboard

during the drag.

Smart Insets

Beside the "auto-snap" checkbox is another checkbox named "Smart Insets".

Figure 87. Smart insets checkbox

Smart Inset uses some heuristics during a drag to try to determine how the insets should be linked.

Currently the heuristics are quite basic (it tries to link to the nearest neighbor component in most

cases), but we will be working on improving this for future releases. This feature is turned off by

default while it is still being refined. The goal is to improve this to the point where it always makes

the  correct  link  choices  -  at  which  time  you  will  be  able  to  use  the  designer  without  having  any

knowledge of insets or reference components.

The Widget Control Pad

88

Figure 88. Widget control pad

When a component is selected, you should see a black floating panel appear in the lower right of

the screen.

This is the widget control pad, and it provides an alternative view of the component’s links. It also

provides  a  useful  list  of  incoming  links  (i.e.  components  that  "depend  on"  this  component’s

positioning).  In  some  cases,  you  may  want  to  disconnect  incoming  links  so  that  you  can  drag  the

component without affecting the position of dependent components.

This control pad also includes game-pad-like controls (up, down, left, right), that allow you to "tab"

the  component  to  the  next  guide  in  that  direction.  Tab  positions  exist  at  component  edges  in  the

form. This is useful for aligning components with each other.

Keyboard Short-Cuts

1. Arrow Keys - Use the up/down/left/right arrow keys to nudge the currently selected component

a little bit at a time. This is a convenient way to move the component to a position that is more

precise than can easily be achieved with a mouse drag.

2. Arrow Keys + SHIFT - Hold down the SHIFT key while pressing an arrow key and it will "tab"

the  component  to  the  next  tab  marker.  The  form  has  implicit  tab  markers  at  the  edge  of  each

component on the form.

3. ALT/Option Key + Click or Drag - Holding down the option/alt key while clicking or dragging a

component will resulting in "snapping" behaviour even if auto-snap is turned off.

Sub-Containers

In  some  cases,  you  may  need  to  add  sub-containers  to  your  form  to  aid  in  grouping  your

components together. You can drag a container onto your form using the "Container" palette item

(under "Core Components"). The default layout the subcontainer will be LayeredLayout so that you

are  able  to  position  components  within  the  sub-container  with  precision,  just  like  on  the  root

container.

You  can  also  change  the  layout  of  subcontainers  to  another  classical  layout  manager  (e.g.  grid

layout, box layout, etc..) and drag components directly into it just as you did with the old designer.

This is very useful if parts of your form lend themselves. As an example, let’s drag a container onto

the  canvas  that  uses  BoxLayout  Y.  (You  can  find  this  under  the  "Containers"  section  of  the

component palette).

Drag the button (that was previously on the form) over that container, and you should see a drop-

zone become highlighted.

89

Figure 89. Dropping container on child container with box layout y

You  can  drop  the  button  directly  there.  You  can  As  you  drag  more  components  into  the  sub-

container, you’ll see them automatically laid out vertically.

Figure 90. Box Layout Y dropping 2nd child

The Canvas Resize Tool

When  designing  a  UI  with  the  new  designer  it  is  very  important  that  you  periodically  test  the

form’s "resizing" behavior so that you know how it will behave on different devices. Components

may appear to be positioned correctly when the canvas is one size, but become out of whack when

the  container  is  resized.  After  nearly  every  manipulation  you  perform,  it  is  good  practice  to  drag

the canvas resize tool (the button in the lower right corner of the designer) smaller and bigger so

you can see how the positions are changed. If things grow out of whack, you may need to toggle an

inset  between  fixed  and  auto,  or  add  a  link  between  some  of  the  components  so  that  the  resizing

behavior matches your expectations.

90

3. Theme Basics

This chapter covers the creation of a simple hello world style theme and its visual customization. It

uses the Codename One Designer tool to demonstrate basic concepts in theme creation such as 9-

piece  borders,  selectors  and  style  types. We  would  recommend  reviewing  this  even  if  you  end  up

using CSS.

3.1. Understanding Codename One Themes

Codename One themes are pluggable CSS like elements that allow developers to determine/switch

the  look  of  the  application  in  runtime.  A  theme  can  be  installed  via  the  UIManager  class

[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/UIManager.html]  and  themes  can  be  layered

one on top of the other (like CSS). A theme can be generated from CSS as well, we’ll cover this (and

the supported CSS syntax) soon.

By  default,  Codename  One  themes  derive  the  native  operating  system  themes,  although  this

behavior is entirely optional.

A  theme 

initializes  the  Style  [https://www.codenameone.com/javadoc/com/codename1/ui/plaf/Style.html]

objects,  which  are  then  used  by  the  components  to  render  themselves  or  by  the  LookAndFeel

[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/LookAndFeel.html]  and  DefaultLookAndFeel

[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/DefaultLookAndFeel.html]  classes  to  create  the

appearance of the application.

Codename  One 

themes  have  some  built-in  defaults.  E.g.  borders 

for  buttons  and

padding/margin/opacity  for  various  components.  These  are  a  set  of  “common  sense”  defaults  that

can be overridden within the theme.

Codename One themes are effectively a set of UIID’s mapped to a Style [https://www.codenameone.com/

javadoc/com/codename1/ui/plaf/Style.html] object. Codename One applications always have a theme, you

can modify it to suit your needs and you can add multiple themes within the main resource file.

You  can  also  add  multiple  resource  files  to  a  project  and  work  with  them.  In  code  a  theme  is

initialized using this code in your main class:

private Resources theme;

public void init(Object context) {
    theme = UIManager.initFirstTheme("/theme");
}

The  initFirstTheme  method  is  a  helper  method  that  hides  some  try/catch  logic  as  well  as  some
verbosity. This could be expressed as:

91

try {
    theme = Resources.openLayered("/theme");
    UIManager.getInstance().setThemeProps(theme.getTheme(theme.getThemeResourceNames()[0]));
} catch(IOException e){
    e.printStackTrace();
}

3.2. Customizing Your Theme

We can launch the designer tool by double clicking on the theme.res file found in typical Codename
One applications. In the left side you can see the section picker and within it the Theme section.

Figure 91. The theme area in the designer

When you select the theme you will see the theme default view.

92

Figure 92. Theme default view

There are several interesting things to notice here the preview section allows us to instantly see the

changes we make to the theme data.

Figure 93. Theme preview section

The theme state tabs and constant tabs allow us to pass between the various editing modes for the

theme and also add theme constants.

We discussed styles before, you can pick the right style mode through the tabs.

93

Figure 94. You can use these tabs to add the various types of styles and theme constants

The most important section is the style section. It allows us to add/edit/remove style UIID’s.

Notice the  Default Style section, it allows us to customize global defaults for the styles. Use it with

caution as changes here can have wide implications.

Figure 95. The theme selection area allows us to add, edit and delete entries. Notice the default style entry

which is a unique special case

When we add an entry to the style we can just type the desired UIID into the box at the top of the

dialog. We can also pick a UIID from the combo box but that might not include all potential options.



You can use the Component Inspector tool in the simulator to locate a component

and its UIID in a specific Form [https://www.codenameone.com/javadoc/com/codename1/ui/

Form.html]

Figure 96. When pressing the Add/Edit entry we can edit a specific style entry UIID

When we add/edit an entry an important piece of the puzzle is the  Derive check box that appears

next  to  all  of  the  UIID  entries.  All  styles  derive  from  the  base  style  and  usually  from  the  native

94

theme defaults, so when this flag is checked the defaults will be used.

When  you  uncheck  that  checkbox  the  fields  below  it  become  editable  and  you  can  override  the

default behavior. To restore the default just recheck that flag.



A common oddity for developers is that when they press  Add and don’t derive any

entry nothing is actually added. The entries in the theme are essentially key/value

pairs so when you don’t add anything there are no keys so the entry doesn’t show

up

3.3. Customizing The Title

The title is a great target for customization since it includes a few interesting "complexities".

The Title is surrounded by a TitleArea container that encloses it, above the title you will also see
the StatusBar UIID that prevents the status details from drawing on top of the title text.

Figure 97. Title Area UIID’s



The StatusBar UIID is a special case that is only there on iOS. In iOS the application
needs  to  render  the  section  under  the  status  bar  (which  isn’t  the  case  for  other
OS’s) and the StatusBar UIID was added so developers can ignore that behavior.

3.3.1. Background Priorities and Types

A slightly confusing aspects of styles in Codename One is the priorities of backgrounds. When you

define  a  specific  type  of  background  it  will  override  prior  definitions,  this  even  applies  to

inheritance.

E.g. if the theme defined a border for the Button UIID (a very common case) if you will try to define
the background image or the background color of Button those will be ignored!



The solution is to derive the border and select the Empty border type

The order for UIID settings for background is as follows:

1. Border  -  if  the  component  has  a  border  it  can  override  everything.  Image  borders  always

override all background settings you might have.

2. Image or gradient - an image or gradient background overrides background color/transparency

settings.

3. Background Color/Transparency - If transparency is larger than 0 then this takes effect.

95

3.3.2. The Background Behavior and Image

Lets start in the first page of the style entry, we’ll customize the background behavior for the Title
UIID and demonstrate/explain some of the behaviors.

The pictures below demonstrate the different types of background image behaviors.

Figure 98. IMAGE_SCALED scales the image without preserving aspect ratio to fit the exact size of the

component

Figure 99. IMAGE_SCALED_FILL scales the image while preserving aspect ratio so it fills the entire space of

the component

96



Aspect ratio is the ratio between the width and the height of the image. E.g. if the
image  is  100x50  pixels  and  we  want  the  width  to  be  200  pixels  preserving  the
aspect ratio will require the height to also double to 200x100.
We highly recommend preserving the aspect ratio to keep images more "natural".

Figure 100. IMAGE_SCALED_FIT scales the image while preserving aspect ratio so it fits within the

component

Figure 101. IMAGE_TILE_BOTH tiles the image on both axis of the component

97

Figure 102. IMAGE_TILE_VERTICAL_ALIGN_LEFT tiles the image on the left side of the component

Figure 103. IMAGE_TILE_VERTICAL_ALIGN_CENTER tiles the image in the middle of the component

98

Figure 104. IMAGE_TILE_VERTICAL_ALIGN_RIGHT tiles the image on the right side of the component

Figure 105. IMAGE_TILE_HORIZONTAL_ALIGN_TOP tiles the image on the top of the component

99

Figure 106. IMAGE_TILE_HORIZONTAL_ALIGN_CENTER tiles the image in the middle of the component

Figure 107. IMAGE_TILE_HORIZONTAL_ALIGN_BOTTOM tiles the image to the bottom of the component

100

Figure 108. IMAGE_ALIGNED_TOP places the image centered at the top part of the component

Figure 109. IMAGE_ALIGNED_BOTTOM places the image centered at the bottom part of the component

101

Figure 110. IMAGE_ALIGNED_LEFT places the image centered at the left part of the component

Figure 111. IMAGE_ALIGNED_RIGHT places the image centered at the right part of the component

102

Figure 112. IMAGE_ALIGNED_TOP_LEFT places the image at the top left corner

Figure 113. IMAGE_ALIGNED_TOP_RIGHT places the image at the top right corner

103

Figure 114. IMAGE_ALIGNED_BOTTOM_LEFT places the image at the bottom left corner

Figure 115. IMAGE_ALIGNED_BOTTOM_RIGHT places the image at the bottom right corner

104

Figure 116. IMAGE_ALIGNED_CENTER places the image in the middle of the component

3.3.3. The Color Settings

The color settings are much simpler than the background behavior. As explained above the priority

for color is at the bottom so if you have a border, image or gradient defined the background color

settings will be ignored.

Figure 117. Add theme entry color settings

There are three color settings:

• Foreground  color  is  the  RRGGBB  color  that  sets  the  style  foreground  color  normally  used  to

draw the text of the component. You can use the color picker button on the side to pick a color

• Background same as foreground only determines the background color of the component

• Transparency  represents  the  opacity  of  the  component  background  as  a  value  between  0

(transparent) and 255 (opaque)

105



Setting the background will have no effect unless transparency is higher than 0. If

you don’t explicitly define this it might have a different value based on the native

theme

3.3.4. Alignment

Not  all  component  types  support  alignment  and  even  when  they  do  they  don’t  support  it  for  all

elements.  E.g.  a  Label  [https://www.codenameone.com/javadoc/com/codename1/ui/Label.html]  and 

its

subclasses support alignment but will only apply it to the text and not the icon.

Notice  that  Container  [https://www.codenameone.com/javadoc/com/codename1/ui/Container.html]  doesn’t

support alignment. You should use the layout manager to tune component positioning.

Figure 118. Alignment of the text within some component types



Aligning text components to anything other than the default alignment might be a

problem if they are editable. The native editing capabilities might collide with the

alignment behavior.

 Bidi/RtL layout reverses the alignment value so left becomes right and visa versa

3.3.5. Padding and Margin

Padding  and  margin  are  concepts  derived  from  the  CSS  box  model.  They  are  slightly  different  in

Codename One, where the border spacing is part of the padding, but other than that they are pretty

similar:

106

Figure 119. Padding and Margin/Box Model

In the diagram, we can see the component represented in yellow occupying its preferred size. The

padding portion in gray effectively increases the components size. The margin is the space between

components, it allows us to keep whitespace between multiple components. Margin is represented

in red in the diagram.

The  theme  allows  us  to  customize  the  padding/margin,  and  specify  them  for  all  4  sides  of  a

component. They can be specified in pixels, millimeters/dips, or screen percentage:

Figure 120. Padding tab



We recommend using millimeters for all spacing to make it look good for all device

densities. Percentages make sense only in very extreme cases

3.3.6. Borders

Borders are a big subject in their own right, the UI for their creation is also a bit confusing:

107

Figure 121. Border entry in the theme

3.3.7. 9-Piece Image Border

A common border type is the 9-piece image border, to facilitate that border type we have a special

Image Border Wizard.

A 9 piece image border is a common convention in UI theming that divides a border into 9 pieces 4

representing corners, 4 representing the sides and one representing the middle.



Android  uses  a  common  variation  on  the  9-piece  border:  9-patch.  The  main

difference between the 9-piece border and 9-patch is that 9-piece borders tile the

sides/center whereas 9-patch scales them

9-piece  image  borders  work  better  than  background  images  for  many  use  cases  where  the

background needs to "grow/shrink" extensively and might need to change aspect ratio.

They  don’t  work  well  in  cases  where  the  image  is  asymmetric  on  both  axis.  E.g.  a  radial  gradient

image. 9-piece images in general don’t work very well with complex gradients.

The image border wizard simplifies the process of generating a 9-piece image border using a 3 stage

process.

108

Figure 122. Stage 1: create or pick an image from an existing PNG file that we will convert to a 9-piece

image



Use an image that’s designed for a high DPI device

For  your  convenience  you  can  create  a  rudimentary  image  with  the  create  image  stage  but  for  a

professional looking application you would usually want to use a design by a professional designer.

109

Figure 123. Stage 2: Cutting the image and adapting it to the DPI’s

The second stage is probably the hardest and most important one in this wizard!

You  can  change  the  values  of  the  top/bottom/left/right  spinners  to  move  the  position  of  the  guide

lines  that  indicate  the  various  9  pieces.  The  image  shows  the  correct  cut  for  this  image  type  with

special attention to the following:

• The left/right position is high enough to fit in the rounded corners in their entirety. Notice that

we didn’t just leave 1 pixel as that performs badly, we want to leave as much space as possible!

• The  top  and  bottom  lines  have  exactly  one  pixel  between  them.  This  is  to  avoid  breaking  the

gradient. E.g. if we set the lines further apart we will end up with this:

Figure 124. This is why it’s important to keep the lines close when a gradient is involved, notice the tiling

effect…

Figure 125. When the lines are close together the gradient effect grows more effectively

• The  elements  on  the  right  hand  side  include  the  Generate Multi Image  options.  Here  you  can

indicate the density of the source image you are using (e.g. if its for iPhone 5 class device pick

Very High). You can then select in the checkboxes below the densities that should be generated

automatically  for  you.  This  allows  fine  detail  on  the  border  to  be  maintained  in  the  various

high/low resolution devices.

We go into a lot of details about multi images in the advanced theming section.



110

Figure 126. Stage 3: Styles to which the border is applied

The  last  page  indicates  the  styles  to  which  the  wizard  will  apply  the  border.  Under  normal  usage

you don’t really need to touch this as its properly filled out.

You can define the same border for multiple UIIDs from here though.

Border Minimum Size

A  common  oddity  when  using  the  image  borders  is  the  fact  that  even  when  padding  is

removed the component might take a larger size than the height of the text within it.

The reason for that is the border. Because of the way borders are implemented they can’t be

drawn  to  be  smaller  than  the  sum  of  their  corners.  E.g.  the  minimum  height  of  a  border

would be the height of the bottom corner + the height of the top corner. The minimum width

would be the width of the left + right corners.

This  is  coded  into  the  common  preferred  size  methods  in  Codename  One  and  components

generally don’t shrink below the size of the image border even if padding is 0.

Customizing The 9-Piece Border

Normally  we  can  just  use  the  9-piece  border  wizard  but  we  can  also  customize  the  border  by

pressing the "…" button on the border section in the theme.

111

Figure 127. Press this to customize borders

The UI for the 9-piece border we created above looks like this.

Figure 128. 9-piece border in edit mode

You can pick the image represented by every section in the border from the combo boxes. They are

organized in the same way the border is with the 9-pieces placed in the same position they would

occupy when the border is rendered.

112

 Notice that the other elements in the UI are disabled when the image border type

is selected.

3 Image Mode

The 9-piece border has a (rarely used) special case: 3 image mode. In this mode a developer

can  specify  the  top  left  corner,  the  top  image  and  the  center  image  to  produce  a  9  piece

border. The corner and top piece are then rotated dynamically to produce a standard 9-piece

border on the device.

This  is  useful  for  reducing  application  code  size  but  isn’t  used  often  as  it  requires  a  more

symetric UI.

 Don’t  confuse  the  3-image  mode  for  the  9-piece  border  with  the

horizontal/vertical image border below

3.3.8. Horizontal/Vertical Image Border

The  9-piece  border  is  the  workhorse  of  borders  in  Codename  One,  however  there  are  some  edge

cases of UI elements that should grow on one axis and not on another. A perfect example of this is

the  iOS  6  style  back  button.  If  we  tried  to  cut  it  into  a  9-piece  border  the  arrow  effect  would  be

broken.

Figure 129. Horizontal image border is commonly used for UI’s that can’t grow vertically e.g. the iOS 6 style

back button

113

The  horizontal  and  vertical  image  borders  accept  3  images  of  their  respective  AXIS  and  build  the

border  by  placing  one  image  on  each  side  and  tiling  the  center  image  between  them.  E.g.  A

horizontal border will never grow vertically.



In RTL/Bidi  [1] modes the borders flip automatically to show the reverse direction.
An iOS style back button will point to the right in such languages.

3.3.9. Empty Border

Empty borders enforce the removal of a border. This is important if you would like to block a base

style from having a border.

E.g.  Buttons  have  borders  by  default. 

If  you  would 

like 

to 

create  a  Button

[https://www.codenameone.com/javadoc/com/codename1/ui/Button.html]  that  is  strictly  of  solid  color  you

could just define the border to be empty and then use the solid color as you see fit.

 There is a null border which is often confused with an empty border. You should

use empty border and not null border

3.3.10. Round Border

Circles and completely round border sides are problematic for multi-resolutions. You need to draw

them dynamically and can’t use image borders which can’t be tiled/cut to fit round designs (due to

physical constraints of the round shape).

We designed the RoundBorder to enable two distinct types of borders:

• Circular borders - e.g. Android floating action

• Rectangles with round (not rounded) sides

Round  Border  is  a  bit  confusing  since  we  already  support  a  rounded  border  type.  The  rounded

border type is a rectangle with rounded corners whereas the round border has completely round

sides or appears as a circle.

To make matters worse the round border has a ridiculous number of features/configurations that

would  have  made  the  already  cluttered  UI  darn  near  impossible  to  navigate.  To  simplify  this  we

split the UI into 3 tabs for standard borders, image borders and round border.

114

Figure 130. Round Border

3.3.11. Rounded Rectangle Border

The RoundRectBorder was developed based on the RoundBorder and has similar features. It produces a
rounded rectangle UI.



Don’t confuse the Rounded Rectangle border with the deprecated Rounded border…

It’s a pretty simple border type akin to the RoundBorder.

Figure 131. Rounded Rectangle Border

3.3.12. Bevel/Etched Borders

We generally recommend avoiding bevel/etched border types as they aren’t as efficient and look a

bit dated in todays applications. We cover them here mostly for completeness.

115

Figure 132. Bevel border

Figure 133. Etched border

3.3.13. Derive

Derive allows us to inherit the behavior of a UIID and extend it with some customization.

E.g. Lets say we created a component that’s supposed to look like a title, we could do something like:

cmp.setUIID("Title");

But  title  might  sometimes  be  aligned  to  the  left  (based  on  theme)  and  we  always  want  our

component to be center aligned. However, we don’t want that to affect the actual titles in the app…

To solve this we can define a MyTitle UIID and derive the Title UIID. Then just customize that one
attribute.

Figure 134. Derive title

116

Issues With Derive

Style inheritance is a problematic topic in every tool that supports such behavior. Codename

One styles start from a global default then have a system default applied and on top of that

have the native OS default applied to them.

At  that  point  a  developer  can  define  the  style  after  all  of  the  user  settings  are  in  place.

Normally this works reasonably well, but there are some edge cases where inheriting a style

can fail.

When  you  override  an  existing  style  such  as  Button  and  choose  to  derive  from  Button  in  a
different  selection  mode  or  even  a  different  component  altogether  such  as  Label  you  might
trigger a recursion effect where a theme setting in the base theme depends on something in a

base triggering an infinite loop.

To avoid this always inherit only from UIID’s you defined e.g. MyButton.

3.3.14. Fonts

Codename One currently supports 3 font types:

• System fonts — these are very simplistic builtin fonts. They work on all platforms and come in

one of 3 sizes. However, they are ubiquitous and work in every platform in all languages.

• TTF files — you can just place a TTF file in the src directory of the project and it will appear in

the True Type combo box.

• Native fonts — these aren’t supported on all platforms but generally they allow you to use a set

of platform native good looking fonts. E.g. on Android the devices Roboto font will be used and

on iOS San Francisco or Helvetica Neue will be used. This is the recommended font type we

suggest for most use cases!

 If  you  use  a  TTF  file  MAKE  SURE  not  to  delete  the  file  when  there  MIGHT  be  a

reference to it. This can cause hard to track down issues!



Notice  that  a  TTF  file  must  have  the  ".ttf"  extension,  otherwise  the  build  server

won’t be able to recognize the file as a font and set it up accordingly (devices need

fonts to be defined in very specific ways). Once you do that, you can use the font

from code or from the theme

117

Figure 135. Font Theme Entry

 System fonts are always defined even if you use a TTF or native font. If the native

font/TTF is unavailable in a specific platform the system font will be used instead.

You  can  size  native/TTF  fonts  either  via  pixels,  millimeters  or  based  on  the  size  of  the  equivalent

system fonts:

1. System font size - the truetype font will have the same size as a small, medium or large system

font. This allows the developer to size the font based on the device DPI

2. Millimeter size - allows sizing the font in a more DPI aware size

3. Pixels - useful for some unique cases, but highly problematic in multi-DPI scenarios

 You  should  notice  that  font  sizing  is  very  inconsistent  between  platforms  we

recommend using millimeters for sizing

You can load a truetype font from code using:

if(Font.isTrueTypeFileSupported()) {
    Font myFont = Font.createTrueTypeFont(fontName, fontFileName);
    myFont = myFont.derive(sizeInPixels, Font.STYLE_PLAIN);
    // do something with the font
}

Notice that, in code, only pixel sizes are supported, so it’s up to you to decide how to convert that.
We  recommend  using  millimeters  with  the  convertToPixels  method.  You  also  need  to  derive  the
font with the proper size, unless you want a 0 sized font which isn’t very useful.

The font name is the difficult bit, iOS requires the name of the font in order to load the font. This

font name doesn’t always correlate to the file name making this task rather "tricky". The actual font

name is sometimes viewable within a font viewer. It isn’t always intuitive, so be sure to test that on

the device to make sure you got it right.

118



due  to  copyright  restrictions  we  cannot  distribute  Helvetica  and  thus  can’t

simulate it. In the simulator you will see Roboto and not the device font unless you

are running on a Mac

The code below demonstrates all the major fonts available in Codename One with the handlee ttf

file posing as a standin for arbitrary TTF:

private Label createForFont(Font fnt, String s) {
  Label l = new Label(s);
  l.getUnselectedStyle().setFont(fnt);
  return l;
}

public void showForm() {
  GridLayout gr = new GridLayout(5);
  gr.setAutoFit(true);
  Form hi = new Form("Fonts", gr);

  int fontSize = Display.getInstance().convertToPixels(3);

  // requires Handlee-Regular.ttf in the src folder root!
  Font ttfFont = Font.createTrueTypeFont("Handlee", "Handlee-Regular.ttf").
                      derive(fontSize, Font.STYLE_PLAIN);

  Font smallPlainSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_SMALL);
  Font mediumPlainSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_MEDIUM);
  Font largePlainSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_LARGE);
  Font smallBoldSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_BOLD, Font.SIZE_SMALL);
  Font mediumBoldSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_BOLD, Font.SIZE_MEDIUM);
  Font largeBoldSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_BOLD, Font.SIZE_LARGE);
  Font smallItalicSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_ITALIC, Font.SIZE_SMALL);
  Font mediumItalicSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_ITALIC, Font.SIZE_MEDIUM);
  Font largeItalicSystemFont = Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_ITALIC, Font.SIZE_LARGE);

  Font smallPlainMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_PLAIN, Font.SIZE_SMALL);
  Font mediumPlainMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_PLAIN, Font.SIZE_MEDIUM);
  Font largePlainMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_PLAIN, Font.SIZE_LARGE);
  Font smallBoldMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_BOLD, Font.SIZE_SMALL);
  Font mediumBoldMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_BOLD, Font.SIZE_MEDIUM);
  Font largeBoldMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_BOLD, Font.SIZE_LARGE);
  Font smallItalicMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_ITALIC, Font.SIZE_SMALL);
  Font mediumItalicMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_ITALIC, Font.SIZE_MEDIUM);
  Font largeItalicMonospaceFont = Font.createSystemFont(Font.FACE_MONOSPACE, Font.STYLE_ITALIC, Font.SIZE_LARGE);

  Font smallPlainProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_PLAIN, Font.SIZE_SMALL);
  Font mediumPlainProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_PLAIN, Font.SIZE_MEDIUM);
  Font largePlainProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_PLAIN, Font.SIZE_LARGE);
  Font smallBoldProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_BOLD, Font.SIZE_SMALL);
  Font mediumBoldProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_BOLD, Font.SIZE_MEDIUM);
  Font largeBoldProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_BOLD, Font.SIZE_LARGE);
  Font smallItalicProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_ITALIC, Font.SIZE_SMALL);
  Font mediumItalicProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_ITALIC, Font.SIZE_MEDIUM);
  Font largeItalicProportionalFont = Font.createSystemFont(Font.FACE_PROPORTIONAL, Font.STYLE_ITALIC, Font.SIZE_LARGE);

  String[] nativeFontTypes = {
      "native:MainThin", "native:MainLight",
      "native:MainRegular", "native:MainBold",
      "native:MainBlack", "native:ItalicThin",
      "native:ItalicLight", "native:ItalicRegular",
      "native:ItalicBold", "native:ItalicBlack"};

  for(String s : nativeFontTypes) {
      Font tt  = Font.createTrueTypeFont(s, s).derive(fontSize, Font.STYLE_PLAIN);

119

      hi.add(createForFont(tt, s));
  }

  hi.add(createForFont(ttfFont, "Handlee TTF Font")).
          add(createForFont(smallPlainSystemFont, "smallPlainSystemFont")).
          add(createForFont(mediumPlainSystemFont, "mediumPlainSystemFont")).
          add(createForFont(largePlainSystemFont, "largePlainSystemFont")).
          add(createForFont(smallBoldSystemFont, "smallBoldSystemFont")).
          add(createForFont(mediumBoldSystemFont, "mediumBoldSystemFont")).
          add(createForFont(largeBoldSystemFont, "largeBoldSystemFont")).
          add(createForFont(smallPlainSystemFont, "smallItalicSystemFont")).
          add(createForFont(mediumItalicSystemFont, "mediumItalicSystemFont")).
          add(createForFont(largeItalicSystemFont, "largeItalicSystemFont")).

          add(createForFont(smallPlainMonospaceFont, "smallPlainMonospaceFont")).
          add(createForFont(mediumPlainMonospaceFont, "mediumPlainMonospaceFont")).
          add(createForFont(largePlainMonospaceFont, "largePlainMonospaceFont")).
          add(createForFont(smallBoldMonospaceFont, "smallBoldMonospaceFont")).
          add(createForFont(mediumBoldMonospaceFont, "mediumBoldMonospaceFont")).
          add(createForFont(largeBoldMonospaceFont, "largeBoldMonospaceFont")).
          add(createForFont(smallItalicMonospaceFont, "smallItalicMonospaceFont")).
          add(createForFont(mediumItalicMonospaceFont, "mediumItalicMonospaceFont")).
          add(createForFont(largeItalicMonospaceFont, "largeItalicMonospaceFont")).

          add(createForFont(smallPlainProportionalFont, "smallPlainProportionalFont")).
          add(createForFont(mediumPlainProportionalFont, "mediumPlainProportionalFont")).
          add(createForFont(largePlainProportionalFont, "largePlainProportionalFont")).
          add(createForFont(smallBoldProportionalFont, "smallBoldProportionalFont")).
          add(createForFont(mediumBoldProportionalFont, "mediumBoldProportionalFont")).
          add(createForFont(largeBoldProportionalFont, "largeBoldProportionalFont")).
          add(createForFont(smallItalicProportionalFont, "smallItalicProportionalFont")).
          add(createForFont(mediumItalicProportionalFont, "mediumItalicProportionalFont")).
          add(createForFont(largeItalicProportionalFont, "largeItalicProportionalFont"));

  hi.show();
}

Figure 136. The fonts running on the ipad simulator on a Mac, notice that this will look different on a PC

120

Figure 137. The same demo running on a OnePlus One device with Android 5.1

Font Effects

You can define an effect to be applied to a specific font, specifically:

• Underline

• Strike thru

• 3d text raised/lowered

• 3d shadow north

The "3d" effects effectively just draw the text twice, with a sligh offest and two different colors to

create a "3d" feel.

All of the effects are relatively simple and performant.

[1] Languages that are written from right to left such as Hebrew, Arabic etc.

121

122

4. Advanced Theming

Before we go into CSS there are a few advanced theme concepts. Notice this still applies to CSS as

features such as theme constants are used there as well…

4.1. Working With UIID’s

UIID’s (User Interface IDentifier) are unique qualifiers given to UI components that associate a set
of theme definitions with a specific set of components. E.g. we can associate the Button UIID with a
component and then define the look for the Button in the theme.

One of the biggest advantages with UIID’s is the ability to change the UIID of a component. E.g. to

create a multiline label, one can use something like:

TextArea t = …;
t.setUIID("Label");
t.setEditable(false);



This 

is 

pretty  much 

how 

components 

such 

as 

SpanLabel

[https://www.codenameone.com/javadoc/com/codename1/components/SpanLabel.html] 

are

implemented internally

UIID’s  can  be  customized  via  the  GUI  builder  and  allow  for  powerful  customization  of  individual

components.

 The class name of the component is commonly the same as the UIID, but they are

in essence separate entities

4.2. Theme Layering

There are two use cases in which you would want to use layering:

• You want a slightly different theme in one platform

• You want the ability to customize your theme for a specific use case, e.g. let a user select larger

fonts

This  is  actually  pretty  easy  to  do  and  doesn’t  require  re-doing  the  entire  theme.  You  can  do

something very similar to the cascading effect of CSS where a theme is applied "on top" of another

theme. To do that just add a new theme using the Add Theme button.

 Make sure to remove the includeNativeBool constant in the new theme!

In  the  new  theme  define  the  changes  e.g.  if  you  just  want  a  larger  default  font  define  only  that

property for all the relevant UIID’s and ignore all other properties!

For a non-gui builder app the theme loading looks like this by default:

123

theme = UIManager.initFirstTheme("/theme");

You should fix it to look like this:

theme = UIManager.initNamedTheme("/theme", "Theme");

 This  assumes  the  name  of  your  main  theme  is  "Theme"  (not  the  layer  theme  you

just added).

The original code relies on the theme being in the 0 position in the theme name array which might

not be the case!

When you want to add the theme layer use:

UIManager.getInstance().addThemeProps(theme.getTheme("NameOfLayerTheme"));

The addThemeProps call will layer the secondary theme on top of the primary "Theme" and keep the
original UIID’s defined in the "Theme" intact.

If you apply theme changes to a running application you can use Form’s `refreshTheme() to update
the UI instantly and provide visual feedback for the theme changes.

4.3. Override Resources In Platform

When we want to adapt the look of an application to different OS conventions one of the common

requirements is to use different icons. Sometimes we want to change behavior based on device type

e.g. have a different UI structure for a Tablet.

Codename One allows you to override a resource for a specific platform when doing this you can

redefine a resource differently for that specific platform and also add platform specific resources.

Figure 138. Override resources for specific platform

Overriden resources take precedence over embedded resources thus allowing us to change the look
or even behavior (when overriding a GUI builder element) for a specific platform/OS.

124

 Overriding  the  theme  is  dangerous  as  a  theme  has  external  dependencies  (e.g.

image borders). The solution is to use theme layering and override the layer!

To override select the platform where overriding is applicable

Figure 139. Override for platform, allows us to override the checked resources and replace them with

another resource

You  can  then  click  the  green  checkbox  to  define  that  this  resource  is  specific  to  this  platform.  All

resources  added  when  the  platform  is  selected  will  only  apply  to  the  selected  platform.  If  you

change your mind and are no longer interested in a particular override just delete it in the override

mode and it will no longer be overridden.

4.4. Theme Constants

The  Codename  One  Designer  has  a  tab  for  creating  constants  which  can  be  used  to  add  global

values  of  various  types  and  behavior  hints  to  Codename  One  and  its  components.  Constants  are

always  strings.  There  are  some  conventions  that  allow  the  UI  to  adapt  to  input  types  e.g.  if  a

constant  ends  with  the  word  Bool  it  is  treated  as  a  boolean  (true/false)  value.  Such  a  value  will
display as a checkbox. Similarly an Int suffix will display a numeric picker and an Image suffix will
show a combo box to pick an image.

 The  combo  box  in  the  designer  for  adding  a  theme  constant  is  editable,  you  can

just type in any value you want!

To  use  a  constant  one  can  use  the  UIManager  [https://www.codenameone.com/javadoc/com/codename1/ui/

plaf/UIManager.html]'s methods to get the appropriate constant type specifically:

• getThemeConstant

• isThemeConstant

• getThemeImageConstant

Internally,  Codename  One  has  several  built  in  constants  and  the  list  is  constantly  growing.  As  we

add  features  to  Codename  One,  we  try  to  keep  this  list  up  to  date  but  the  very  nature  of  theme

constants is "adhoc" and some might not make it here.

Table 3. Theme Constants

Constant

alwaysTensileBool

Description/Argument

Enables tensile drag even when there is no

scrolling in the container (only for scrollable

containers)

backGestureThresholdInt

The threshold for the back gesture in the

SwipeBackSupport [https://www.codenameone.com/

javadoc/com/codename1/ui/util/SwipeBackSupport.html]

class, defaults to 5

125

Constant

backUsesTitleBool

buttonRippleBool

capsButtonTextBool

capsButtonUiids

Description/Argument

Indicates to the GUI builder that the back

command should use the title of the previous

form and not just the word "Back"

true to activate the material design ripple effect
on the buttons. This effect draws a growing

circle from the point of touch onwards. This is
false by default except for Android where it
defaults to true. This is equivalent to
setButtonRippleEffectDefault(bool) in the Button
class

true to activate the caps text mode in the
buttons. When activated setText on Button and
all the constructors will invoke upcase() on all
the strings effectively making the application
buttons use uppercase exclusively. This is false
by default except for Android where it defaults
to true. It’s equivalent to
Button.setCapsTextDefault(boolean) and can be
tuned to an individual Component via
Component.setRippleEffect(boolean)

A list of the UIID’s that should be capitalized by

default (in supported platforms) other than the
Button and RaisedButton which are already
capitalized. This list can be separated by spaces

or commas e.g.
capsButtonUiids=UpcaseButton,OtherCustomButton

defaultCommandImage

Image to give a command with no icon

dialogButtonCommandsBool

Place commands in the dialogs as buttons

dialogBlurRadiusInt

dialogPosition

Sets the default Gaussian blur radius for the

background of the dialogs. The default value is

-1 indicating no blur

Place the dialog in an arbitrary border layout

position (e.g. North, South, Center, etc.)

centeredPopupBool

Popup of the combo box will appear in the

center of the screen

changeTabOnFocusBool

Useful for feature phones, allows changing the

tab when the focus changes immediately,

without pressing a key

checkBoxCheckDisImage

CheckBox image to use instead of Codename

One drawing it on its own

checkBoxCheckedImage

CheckBox image to use instead of Codename

One drawing it on its own

126

Constant

Description/Argument

checkBoxOppositeSideBool

Indicates the check box should be drawn on the

opposite side to the text and not next to the text

checkBoxUncheckDisImage

CheckBox image to use instead of Codename

One drawing it on its own

checkBoxUncheckedImage

CheckBox image to use instead of Codename

One drawing it on its own

comboImage

Combo image to use instead of Codename One

commandBehavior

drawing it on its own

Deprecated: Don’t use this constant as it conflicts
with the Toolbar. Indicates how commands
should act, as a touch menu, native menu etc.

Possible values: SoftKey, Touch, Bar, Title, Right,

Native

ComponentGroupBool

Enables component group, which allows

components to be logically grouped together, so

the UIID’s of components would be modified

based on their group placement. This allows for

some unique styling effects where the first/last

elements have different styles from the rest of

the elements. It’s disabled by default, thus

leaving its usage up to the designer

dialogTransitionIn

Default transition for dialog

dialogTransitionInImage

Default transition Image

dialogTransitionOut

defaultCommandImage

[https://www.codenameone.com/javadoc/com/

codename1/ui/Image.html] for dialog, causes a

Timeline [https://www.codenameone.com/javadoc/com/

codename1/ui/animations/Timeline.html] transition

effect

Default transition for dialog

An image to place on a command if none is

defined, only applies to touch commands

defaultEmblemImage

The emblem painted on the side of the

multibutton, by default this is an arrow on some

platforms

dialogTransitionOutImage

Default transition Image

[https://www.codenameone.com/javadoc/com/

codename1/ui/Image.html] for dialog, causes a

Timeline [https://www.codenameone.com/javadoc/com/

codename1/ui/animations/Timeline.html] transition

effect

disabledColor

Color to use when disabling entries by default

127

Constant

Description/Argument

dlgButtonCommandUIID

The UIID used for dialog button commands

dlgCommandButtonSizeInt

Minimum size to give to command buttons in

the dialog

dlgCommandGridBool

Places the dialog commands in a grid for

dlgInvisibleButtons

dlgSlideDirection

dlgSlideInDirBool

dlgSlideOutDirBool

uniform sizes

Includes an RRGGBB color for the line

separating dialog buttons, as is the case with

Android 4 and iOS 7 buttons in dialogs

Slide hints

Slide hints

Slide hints

drawMapPointerBool

Indicates whether a pointer should appear in

the center of the map component

fadeScrollBarBool

Boolean indicating if the scrollbar should fade

fadeScrollEdgeBool

fadeScrollEdgeInt

firstCharRTLBool

noTextModeBool

fixedSelectionInt

when there is inactivity

Places a fade effect at the edges of the screen to

indicate that it’s possible to scroll until we reach

the edge (common on Android)

Amount of pixels to fade out at the edge

Indicates to the GenericListCellRenderer

[https://www.codenameone.com/javadoc/com/

codename1/ui/list/GenericListCellRenderer.html] that it

should determine RTL status based on the first

character in the sentence

Indicates that the on/off switch in iOS shouldn’t

draw text on top of the switch, which is the case

for iOS 7+ but not for prior versions

Number corresponding to the fixed selection

constants in List [https://www.codenameone.com/

javadoc/com/codename1/ui/List.html]

formTransitionIn

Default transition for form

formTransitionInImage

Default transition Image

[https://www.codenameone.com/javadoc/com/

codename1/ui/Image.html] for form, causes a

Timeline [https://www.codenameone.com/javadoc/com/

codename1/ui/animations/Timeline.html] transition

effect

formTransitionOut

Default transition for form

128

Constant

Description/Argument

formTransitionOutImage

Default transition Image

[https://www.codenameone.com/javadoc/com/

codename1/ui/Image.html] for form, causes a

Timeline [https://www.codenameone.com/javadoc/com/

codename1/ui/animations/Timeline.html] transition

effect

globalToobarBool

Indicates that the Toolbar API should be on/off

hasRaisedButtonBool

by default for all forms

Is true in platforms where the theme has the
RaisedButton UIID defined. This is currently only
true in the native Android theme to allow some

material design guidelines

hideBackCommandBool

Hides the back command from the side menu

hideEmptyTitleBool

when possible

Indicates that a title with no content should be

hidden even if the border for the title occupies

space

hideLeftSideMenuBool

Hides the side menu icon that appears on the

left side of the UI

ignorListFocusBool

Hide the focus component of the list when the

infiniteImage

includeNativeBool

labelGap

listItemGapInt

list doesn’t have focus

The image used by the infinite progress

component, the component will rotate it as

needed

True to derive from the platform native theme,

false to create a blank theme that only uses the

basic defaults

Positive floating point value representing the

default gap value between the label text and the

icon in millimeters

Built-in item gap in the list, this defaults to 2,

which predated padding/margin in Codename

One

listLongPressBool

Indicates whether a list should handle long press

events, defaults to true

mapTileLoadingImage

An image to preview while loading the

MapComponent [https://www.codenameone.com/

javadoc/com/codename1/maps/MapComponent.html]

tile

129

Constant

mapTileLoadingText

Description/Argument

The text of the tiles in the MapComponent

[https://www.codenameone.com/javadoc/com/

codename1/maps/MapComponent.html] during

loading, defaults to "Loading…"

mapZoomButtonsBool

Indicates whether buttons should be drawn on

mediaBackImage

mediaFwdImage

mediaPauseImage

mediaPlayImage

the map component

Media icon used by the media player class

Media icon used by the media player class

Media icon used by the media player class

Media icon used by the media player class

menuButtonBottomBool

When set to true this flag aligns the menu button

menuButtonTopBool

menuHeightPercent

menuImage

menuImageSize

menuPrefSizeBool

menuSlideDirection

menuSlideInDirBool

menuSlideOutDirBool

menuTransitionIn

to the bottom portion of the title. Defaults to

false

When set to true this flag aligns the menu button

to the top portion of the title. Defaults to false

Allows positioning and sizing the menu

The three dot menu image used in Android and

the Toolbar [https://www.codenameone.com/javadoc/

com/codename1/ui/Toolbar.html] to show additional

command entries

The size in millimeters (floating point value) of

the generated side menu image, this is only used

if you don’t supply a custom image. The default

value is 4.5.

Allows positioning and sizing the menu

Defines menu entrance effect

Defines menu entrance effect

Defines menu entrance effect

Defines menu entrance effect

menuTransitionInImage

Defines menu entrance effect

menuTransitionOut

Defines menu exit effect

menuTransitionOutImage

Defines menu entrance effect

menuWidthPercent

minimizeOnBackBool

130

Allows positioning and sizing the menu

Indicates whether the form should minimize the

entire application when the physical back

button is pressed (if available) and no command

is defined as the back command. Defaults to true

Constant

onOffIOSModeBool

Description/Argument

Indicates whether the on/off switch should use

the iOS or Android mode

otherPopupRendererBool

Indicates that a separate renderer UIID/instance

PackTouchMenuBool

paintsTitleBarBool

should be used to the list within the combo box

popup

Enables preferred sized packing of the touch

menu (true by default), when set to false this

allows manually determining the touch menu

size using percentages

Indicates that the StatusBar UIID should be

added to the top of the form to space down the

title area, as is the case on iOS 7+ where the

status bar is painted on top of the UI

popupCancelBodyBool

Indicates that a cancel button should appear

PopupDialogArrowBool

within the combo box popup

Indicates whether the popup dialog has an

arrow, notice that this constant will change if

you change UIID of the popup dialog

PopupDialogArrowBottomImage

Image of the popup dialog arrow, notice that this

constant will change if you change UIID of the

popup dialog

PopupDialogArrowTopImage

Image of the popup dialog arrow, notice that this

constant will change if you change UIID of the

popup dialog

PopupDialogArrowLeftImage

Image of the popup dialog arrow, notice that this

constant will change if you change UIID of the

popup dialog

PopupDialogArrowRightImage

Image of the popup dialog arrow, notice that this

constant will change if you change UIID of the

popup dialog

popupNoTitleAddPaddingInt

Adds padding to a popup when no title is present

popupTitleBool

Indicates that a title should appear within the

pullToRefreshImage

pureTouchBool

radioOppositeSideBool

combo box popup

The arrow image used to draw the pullToRefresh
animation

Indicates the pure touch mode

Indicates the radio button should be drawn on

the opposite side to the text and not next to the

text

radioSelectedDisImage

Radio button image

131

Constant

radioSelectedImage

radioUnselectedDisImage

radioUnselectedImage

radioSelectedDisFocusImage

radioSelectedFocusImage

Description/Argument

Radio button image

Radio button image

Radio button image

Radio button image

Radio button image

radioUnselectedDisFocusImage

Radio button image

radioUnselectedFocusImage

Radio button image

releaseRadiusInt

Indicates the distance from the button with

dragging, in which the button should be

released, defaults to 0

rendererShowsNumbersBool

Indicates whether renderers should render the

entry number

reverseSoftButtonsBool

Swaps the softbutton positions

rightSideMenuImage

Same as sideMenuImage only for the right side,

optional and defaults to sideMenuImage

rightSideMenuPressImage

Same as sideMenuPressImage only for the right

scrollVisibleBool

side, optional and defaults to

sideMenuPressImage

true/false default is platform dependent.
Toggles whether the scroll bar is visible

showBackCommandOnTitleBool

Used by the Toolbar [https://www.codenameone.com/

javadoc/com/codename1/ui/Toolbar.html] API to

indicate whether the back button should appear

on the title

shrinkPopupTitleBool

Indicates the title of the popup should be set to 0

if it’s missing

sideMenuAnimSpeedInt

The speed at which a sidemenu moves defaults

to 300 milliseconds

sideMenuFoldedSwipeBool

Indicates the side menu could be opened via

swiping

sideMenuImage

The image representing the side menu, three

lines (Hamburger menu)

sideMenuPressImage

Optional pressed version of the sideMenuImage

sideMenuScrollVisibleBool

Indicates whether the scroll bar on the side

menu should be visible or not, defaults to

hidden

sideMenuShadowBool

Indicates whether the shadow for the side menu

should be drawn

132

Constant

Description/Argument

sideMenuShadowImage

The image used when drawing the shadow (a

default is used if this isn’t supplied)

sideMenuSizeTabPortraitInt

The size of the side menu when expanded in a

tablet in portrait mode

sideMenuSizePortraitInt

The size of the side menu when expanded in a

phone in portrait mode

sideMenuSizeTabLandscapeInt

The size of the side menu when expanded in a

tablet in landscape mode

sideMenuSizeLandscapeInt

The size of the side menu when expanded in a

phone in landscape mode

sideMenuTensileDragBool

Enables/disables the tensile drag behavior

sideSwipeActivationInt

sideSwipeSensitiveInt

slideDirection

slideInDirBool

slideOutDirBool

sliderThumbImage

snapGridBool

statusBarScrollsUpBool

within the opened side menu

Indicates the threshold in the side menu bar at

which a swipe should trigger activation, defaults

to 15 (percent)

Indicates the region of the screen that is

sensitive to side swipe in the side menu bar,

defaults to 10 (percent)

Default slide transition settings

Default slide transition settings

Default slide transition settings

The thumb image that can appear on the sliders

Snap to grid toggle

Indicates that a tap on the status bar should

scroll up the UI, only relevant in OS’s where

paintsTitleBarBool is true

switchButtonPadInt

Indicates the padding in the on/off switch,

defaults to 16

switchMaskImage

Indicates the mask image used in iOS mode to

draw on top of the switch

switchOnImage

Indicates the on image used in iOS mode to draw

the on/off switch

switchOffImage

Indicates the off image used in iOS mode to

draw the on/off switch

TabEnableAutoImageBool

Indicates images should be filled by default for

TabSelectedImage

tabs

Default selected image for tabs (if

TabEnableAutoImageBool=true)

133

Constant

TabUnselectedImage

tabPlacementInt

tabsSlideSpeedInt

Description/Argument

Default unselected image for tabs (if

TabEnableAutoImageBool=true)

The placement of the tabs in the Tabs

[https://www.codenameone.com/javadoc/com/

codename1/ui/Tabs.html] component: TOP = 0, LEFT

= 1, BOTTOM = 2, RIGHT = 3

The time of the animation that occurs (in

milliseconds) between between releasing a

swiped tab and reaching the next tab. Currently

defaults to 200

tabsFillRowsBool

Indicates if the tabs should fill the row using

tabsGridBool

tabsOnTopBool

flow layout

Indicates whether tabs should use a grid layout

thus forcing all tabs to have identical sizes

Indicates the tabs should be drawn on top of

their content in a layered UI, this allows a tab to

intrude into the content of the tabs

textCmpVAlignInt

The vertical alignment of the text component:

TOP = 0, CENTER = 4, BOTTOM = 2

textComponentErrorColor

A hex RGB color which defaults to null in which

case this has no effect. When defined this will

change the color of the border and label to the

given color to match the material design styling.

This implements the red border underline in

cases of error and the label text color change

Toggles the on top mode which makes things

look like they do on Android. This defaults to

true on Android and false on other OS’s. This

can also be manipulated via the
onTopMode(boolean) method in InputComponent
however the layout will only use the theme

constant

toggles the animation mode which again can be
manipulated by a method in InputComponent. If
you want to keep the UI static without the

floating hint effect set this to false. Notice this

defaults to true only on Android

textComponentOnTopBool

textComponentAnimBool

134

Constant

Description/Argument

textComponentFieldUIID

sets the UIID of the text field to something other
than TextField this is useful for platforms such
as iOS where the look of the text field is different

within the text component. This allows us to

make the background of the text field
transparent when it’s within the TextComponent
and make it different from the regular text field

textFieldCursorColorInt

The color of the cursor as an integer (not hex)

tickerSpeedInt

tintColor

The speed of label/button etc. (in milliseconds)

The aarrggbb hex color to tint the screen when a

dialog is shown

topMenuSizeTabPortraitInt

The size of the side menu when expanded and

topMenuSizePortraitInt

attached to the top in a tablet in portrait mode

The size of the side menu when expanded and

attached to the top in a phone in portrait mode

topMenuSizeTabLandscapeInt

The size of the side menu when expanded and

attached to the top in a tablet in landscape mode

topMenuSizeLandscapeInt

The size of the side menu when expanded and

attached to the top in a phone in landscape

mode

touchCommandFillBool

Indicates how the touch menu should layout the

commands within

touchCommandFlowBool

Indicates how the touch menu should layout the

transitionSpeedInt

treeFolderImage

commands within

Indicates the default speed for transitions

Picture of a folder for the Tree

[https://www.codenameone.com/javadoc/com/

codename1/ui/tree/Tree.html] class

treeFolderOpenImage

Picture of a folder expanded for the Tree class

treeNodeImage

tensileDragBool

Picture of a file node for the Tree class

Indicates that tensile drag should be

enabled/disabled. This is usually set by platform

themes

135

Dynamic Theme Swapping & Theme Constants

Once  a  theme  constant  is  set  by  a  theme,  it  isn’t  removed  on  a  refresh  when  replacing  the

theme.

E.g. if one would set the comboImage constant to a specific value in theme A and then switch to
theme B, that doesn’t define the comboImage, the original theme A comboImage might remain!

The  reason  for  this  is  simple:  when  extracting  the  constant  values,  components  keep  the

values  in  cache  locally  and  just  don’t  track  the  change  in  value.  Furthermore,  since  the

components allow manually setting values, it’s impractical for them to track whether a value

was set by a constant or explicitly by the user.

The  solution  for  this  is  to  either  manually  reset  undesired  values  before  replacing  a  theme

(e.g.  for  the  case,  above  by  calling  the  default  look  and  feel  method  for  setting  the  combo

image with a null value), or defining a constant value to replace the existing value.

4.5. Native Theming

Codename  One  uses  a  theme  constant  called  includeNativeBool,  when  that  constant  is  set  to  true
Codename  One  starts  by  loading  the  native  theme  first  and  then  applying  all  the  theme  settings.

This  effectively  means  your  theme  "derives"  the  style  of  the  native  theme  first,  similar  to  the

cascading effect of CSS. Internally this is exactly what the theme layering section covered.

By avoiding this flag you can create themes that look EXACTLY the same on all platforms.



If  you  avoid  the  native  theming  you  might  be  on  your  own.  A  few  small  device

oddities such as the iOS status bar are abstracted by native theming. Without it you

will need to do everything from scratch

You can simulate different OS platforms by using the native theme menu option

Figure 140. The native theme menu option

Developers  can  pick  the  platform  of  their  liking  and  see  how  the  theme  will  appear  in  that

particular platform by selecting it and having the preview update on the fly.

4.6. Under the Hood of the Theme Engine

To truly understand a theme we need to understand what it is. Internally a theme is just a Hashtable
key/value pair between UIID based keys and their respective values. E.g. the key:

136

Button.fgColor=ffffff

Will  set  the  foreground  color  of  the  Button  [https://www.codenameone.com/javadoc/com/codename1/ui/

Button.html] UIID to white.

When 

a  Codename  One  Component 

[https://www.codenameone.com/javadoc/com/codename1/ui/

Component.html]  is  instantiated  it  requests  a  Style  [https://www.codenameone.com/javadoc/com/codename1/

ui/plaf/Style.html] object from the UIManager [https://www.codenameone.com/javadoc/com/codename1/ui/plaf/
UIManager.html] class. The Style object is based on the settings within the theme and can be modified
thru code or by using the theme.

We  can  replace  the  theme  dynamically  in  runtime  and  refresh  the  styles  assigned  to  the  various

components  using 

the 

refreshTheme() 

[https://www.codenameone.com/javadoc/com/codename1/ui/

Component.html#refreshTheme--] method.



It’s  a  common  mistake  to  invoke  refreshTheme()  without  actually  changing  the
theme.  We  see  developers  doing  it  when  all  they  need  is  a  repaint()  or
revalidate(). Since refreshTheme() is very expensive we recommend that you don’t
use it unless you really need to…

A theme Hashtable key is comprised of:

[UIID.][type#]attribute

The  UIID,  corresponds  to  the  component’s  UIID  e.g.  Button,  CheckBox  [https://www.codenameone.com/
javadoc/com/codename1/ui/CheckBox.html]  etc.  It  is  optional  and  may  be  omitted  to  address  the  global

default style.

The  type  is  omitted  for  the  default  unselected  type,  and  may  be  one  of  sel  (selected  type),  dis

(disabled type) or press (pressed type). The attribute should be one of:

• derive - the value for this attribute should be a string representing the base component.

• bgColor - represents the background color for the component, if applicable, in a web hex string

format RRGGBB e.g. ff0000 for red.

• fgColor - represents the foreground color, if applicable.

• border - an instance of the border class, used to display the border for the component.

• bgImage - an Image [https://www.codenameone.com/javadoc/com/codename1/ui/Image.html] object used in

the background of a component.

• transparency  -  a  String  containing  a  number  between  0-255  representing  the  alpha  value  for

the background. This only applies to the bgColor.

• margin  -  the  margin  of  the  component  as  a  String  containing  4  comma  separated  numbers  for

top,bottom,left,right.

• padding - the padding of the component, it has an identical format to the margin attribute.

• font - A Font [https://www.codenameone.com/javadoc/com/codename1/ui/Font.html] object instance.

• alignment  -  an  Integer  object  containing  the  LEFT/RIGHT/CENTER  constant  values  defined  in

137

Component.

• textDecoration  -  an  Integer  value  containing  one  of  the  TEXT_DECORATION_*  constant  values

defined in Style.

• backgroundType - a Byte object containing one of the constants for the background type defined in
Style [https://www.codenameone.com/javadoc/com/codename1/ui/plaf/Style.html] under BACKGROUND_*.

• backgroundGradient  -  contains  an  Object  array  containing  2  integers  for  the  colors  of  the
gradient.  If  the  gradient  is  radial  it  contains  3  floating  points  defining  the  x,  y  &  size  of  the

gradient.

So to set the foreground color of a selected button to red, a theme will define a property like:

Button.sel#fgColor=ff0000

This information is mostly useful for understanding how things work within Codename One, but it

can also be useful in runtime.

E.g. to increase the size of all fonts in the application, we can do something like:

Hashtable h = new Hashtable();
h.put("font", largeFont);
UIManager.getInstance().addThemeProps(h);
Display.getInstance().getCurrent().refreshTheme();

4.7. Understanding Images and Multi-Images



This  section  provides  a  very  high  level  overview  of  images.  We  dive  deeper  into

the  various  types  of  images  in  the  graphics  section  [https://www.codenameone.com/

manual/graphics.html#deep-into-images-section].

When working with a theme, we often use images for borders or backgrounds. We also use images

within the GUI for various purposes and most such images will be extracted from the resource file.

Adding a standard JPEG/PNG image to the resource file is straight forward, and the resulting image

can  be  viewed  within  the  images  section.  However,  due  to  the  wide  difference  between  device

types,  an  image  that  would  be  appropriate  in  size  for  an  iPhone  3gs  would  not  be  appropriate  in

size for a Nexus device or an iPhone 4 (but perhaps, surprisingly, it will be just right for iPad 1 and

iPad 2).

The  density  of  the  devices  varies  significantly  and  Codename  One  tries  to  simplify  the  process  by

unifying  everything  into  one  set  of  values  to  indicate  density.  For  simplicity’s  sake,  density  is

sometimes  expressed  in  terms  of  pixels,  however  it  is  mapped  internally  to  actual  screen

measurements where possible.

A multi-image is an image that has multiple varieties for different densities, and thus looks sharp in

all  the  densities.  Since  scaling  on  the  device  can’t  interpolate  the  data  (due  to  performance

considerations), significant scaling on the device becomes impractical. However, a multi-image will

just provide the “right” resolution image for the given device type.

138

From  the  programming  perspective  this  is  mostly  seamless,  a  developer  just  accesses  one  image

and has no ability to access the images in the different resolutions. Within the designer, however,

we  can  explicitly  define  images  for  multiple  resolutions  and  perform  high  quality  scaling  so  the

“right” image is available.

We can use two basic methods to add a multi-image: quick add and standard add.

Both methods rely on understanding the source resolution of the image, e.g. if you have an icon that

you expect to be 128x128 pixels on iPhone 4, 102x102 on nexus one and 64x64 on iPhone 3gs. You

can  provide  the  source  image  as  the  128  pixel  image  and  just  perform  a  quick  add  option  while

picking the Very High density option.

This  will  indicate  to  the  algorithm  that  your  source  image  is  designed  for  the  "very  high"  density

and it will scale for the rest of the densities accordingly.



This relies on the common use case of asking your designer to design for one high

end device (e.g. iPhone X) then you can take the resources and add them as "HD"

resources. They will automatically adapt to the lower resolutions

Alternatively, you can use the standard add multi-image dialog and set it like this:

Notice that we selected the square image option, essentially eliminating the height option. Setting

values to 0 prevents the system from generating a multi-image entry for that resolution, which will

mean a device in that category will fall on the closest alternative.

The percentage value will change the entire column, and it means the percentage of the screen. E.g.

We  know  the  icon  is  128  for  the  very  high  resolution,  we  can  just  move  the  percentage  until  we

reach something close to 128 in the “Very High” row and the other rows will represent a size that

should be pretty close in terms of physical size to the 128 figure.

At  runtime,  you  can  always  find  the  host  device’s  approximate  pixel  density  using  the
Display.getDeviceDensity() method. This will return one of:

Table 4. Densities

139

Constant

Display.DENSITY_VERY_LOW

Display.DENSITY_LOW

Display.DENSITY_MEDIUM

Display.DENSITY_HIGH

Display.DENSITY_VERY_HIGH

Display.DENSITY_HD

Display.DENSITY_560

Density.DENSITY_2HD

Density.DENSITY_4K

Density

~ 88 ppi

~ 120 ppi

~ 160 ppi

~ 240 ppi

~ 320 ppi

~ 540 ppi

~ 750 ppi

~ 1000 ppi

~ 1250ppi

Example Device

Android ldpi devices

iPhone 3GS, iPad, Android mdpi

devices

Android hdpi devices

iPhone 4, iPad Air 2, Android

xhdpi devices

iPhone 6+, Android xxhdpi

devices

Android xxxhdpi devices

4.8. Use Millimeters for Padding/Margin and Font Sizes

When  configuring  your  styles,  you  should  almost  never  use  "Pixels"  as  the  unit  for  padding,

margins,  font  size,  and  border  thickness  because  the  results  will  be  inconsistent  on  different

densities. Instead, you should use millimeters for all non-zero units of measurement.

As we now understand the complexities of DPI it should be clear why this is important.

4.8.1. Fractions of Millimeters

Sometimes  millimeters  don’t  give  you  enough  precision  for  what  you  want  to  do.  Currently  the

designer only allows you to specify integer values for most units. However, you can achieve more
precise results when working directly in Java. The Display.convertToPixels() method will allow you
to convert millimeters (or DIPS) to pixels. It also only takes an integer input, but you can use it to

obtain a multiplier that you can then use to convert any millimeter value you want into pixels.

E.g.

double pixelsPerMM = ((double)Display.getInstance().convertToPixels(10, true)) / 10.0;

And now you can set the padding on an element to 1.5mm. E.g.

myButton.getAllStyles().setPaddingUnit(Style.UNIT_TYPE_PIXELS);
int pixels = (int)(1.5 * pixelsPerMM);
myButton.getAllStyles().setPadding(pixels, pixels, pixels, pixels);

140

4.9. Creating a Great Looking Side Menu

Figure 141. Side Menu final result

A side menu is a crucial piece of an elegant application. We’ll explain how one creates a simple side

menu  that’s  elegant,  portable  and  easy  to  build.  This  is  a  good  "starting  point"  side  menu  from

which you can build more elaborate designs.

To  get  this  result  we  will  start  from  a  native  theme  and  a  bare  bones  application  to  keep  things

simple.

The code for the side menu is this:

141

Form hi = new Form("Hi World");

Toolbar tb = hi.getToolbar();
Image icon = theme.getImage("icon.png"); ①
Container topBar = BorderLayout.east(new Label(icon));
topBar.add(BorderLayout.SOUTH, new Label("Cool App Tagline...", "SidemenuTagline")); ②
topBar.setUIID("SideCommand");
tb.addComponentToSideMenu(topBar);

tb.addMaterialCommandToSideMenu("Home", FontImage.MATERIAL_HOME, e -> {}); ③
tb.addMaterialCommandToSideMenu("Website", FontImage.MATERIAL_WEB, e -> {});
tb.addMaterialCommandToSideMenu("Settings", FontImage.MATERIAL_SETTINGS, e -> {});
tb.addMaterialCommandToSideMenu("About", FontImage.MATERIAL_INFO, e -> {});

hi.addComponent(new Label("Hi World"));
hi.show();

① This is the icon which was used in lieu of a logo it appears in the top right of the side menu

② This is the top bar containing the tagline and the icon it’s styled as if it’s a command but you can

put anything here e.g. an image etc.

③ The commands are added as usual to the side menu with no styling or functionality, the entire

look is determined by the theme

Next we’ll open the designer tool to style the UI

Figure 142. Open the side menu so we will get the right values in the combo box on add

Now when we press  Add the side menu entries will appear in the combo box (you can type them

but this is more convenient). We’ll start with the SideNavigationPanel style:

Figure 143. The SideNavigationPanel has an opaque white background

The  SideCommand style is a bit more elaborate, we start with a white foreground and an opaque

bluish/purple color:

142

Figure 144. The SideCommand has a white foreground and opaque bluish background

We’ll set padding to 3 millimeters which gives everything a good feel and spacing. This is important

for finger touch sensitivity.

Figure 145. Padding is 3mm so it will feel spacious and touch friendly

We’ll set margin to 0 except for the bottom one pixel which will leave a nice white line by showing

off the background. This means the commands will have a space between them and the white style

we gave to the SideNavigationPanel will appear thru that space.

Figure 146. Margin is 0 except for a thin line below each command

Setting the border to empty is crucial!

The iOS version of the side command inherits a border style so we must "remove" it by defining a

different border in this case an empty border. Since borders take precedence over color this would

have prevented the color changes we made from appearing.

Figure 147. Border must be defined as Empty

143

Next we need to pick a good looking font and make sure it’s large enough. We use millimeters size it

correctly for all OS’s and override the derived text decoration which has a value in the iOS native

theme so it can impact the final look.

Figure 148. Pick a good looking font for the side command

Next we need to move to the selected tab and add a new side command entry that derives from the

unselected  version.  We’ll  pick  a  new  color  that’s  slightly  deeper  and  will  make  the  selected  style

appear selected. We’ll also copy and paste this selected style to the pressed style.

Figure 149. Selected & Pressed SideCommand

Figure 150. Color for the Selected/Pressed SideCommand

The  SidemenuTagline  is  just  a  SideCommand  style  that  was  slightly  adapted.  We’ll  remove  the

padding and margin because the whole section is wrapped in a side command and we don’t want

double padding. We’ll leave 1mm padding at the top for a bit of spacing from the logo.

Figure 151. Padding of the SidemenuTagline

We’ll also update the font to a smaller size and italic styling so it will feel like a tagline.

144

Figure 152. Font for the SideMenuTagline is slightly smaller and italic

The last change for the theme is for the  StatusBarSideMenu UIID which is a spacing on the top of

the  sidemenu.  This  spacing  is  there  for  iOS  devices  which  render  the  clock/battery/reception

symbols on top of the app. We’ll set the padding to 0.

Figure 153. StatusBarSideMenu padding for the top of the side menu

Finally, we’ll add the icon image (or a logo if you have it) into the theme as a multi image so we can

use  it  within  the  side  menu  as  a  good  looking  logo.  A  relatively  large  icon  image  works  as  a  2HD

multi-image but you can use many strategies to get a fitting image for this spot.



Rounded  images  work  well  here,  you  can  round  images  dynamically  using

masking

These steps produce the UI above as a side menu, they might seem like a long set of steps but each

step  is  pretty  simple  as  you  walk  thru  each  one.  This  does  show  off  the  versatility  and  power  of

Codename One as a change to one step can create a radically different UI design.

4.10. Converting a PSD To A Theme

Codename  One  provides  extensive  support  for  designing  beautiful  user  interfaces,  but  it  isn’t

necessarily  obvious  to  new  developers  how  to  achieve  their  desired  results.  A  common  workflow

for app design includes a PSD file with mock-ups of the UI, created by a professional designer.



PSD  is  the  Adobe  Photoshop  file  format,  it’s  the  most  common  format  for  UI

designs in the industry

For  this  tutorial  we  adapt  a  very  slick  looking  sign-up  form  found  online  and  convert  it  to  a

Codename One component that can be used inside an application.

The process we followed was:

1. Find the PSD design we want to use: this PSD file [http://freebiesbug.com/psd-freebies/iphone-6-ui-kit/]

created  by  Adrian  Chiran 

[https://dribbble.com/adrianchiran] 

(we  mirrored 

it  here

[https://www.codenameone.com/files/iOS_UI-Kit.psd] in case it goes offline):

145

Figure 154. Sign Up form Design

2. Re-create the general structure and layout of the design in a Codename One Form using nested
components and layout managers. Here is a break-down of how we structured the component
hierarchy in the Form:

Figure 155. Component hierarchy and layouts

3. Extract the images we needed using Photoshop - this process is often referred to as "cutting"

4. Extract the fonts, colors, and styles we needed to reproduce the design in Codename One

5. Import images into the Codename one project, and define theme styles so that our components

match the look of the original design

Here is a screenshot of the resulting component running inside the Codename One simulator:

146

Figure 156. Resulting app in the Codename One simulator

4.10.1. Breaking Down the PSD

Open the PSD you are interested in using Photoshop.



You might be missing fonts in your system so you can either install them or ignore

that.  Keep  in  mind  that  some  fonts  might  not  be  redistributable  with  your

application

In this PSD we want only one of the screen designs so initially we want to remove everything that

isn’t related so we can get our bearings more effectively:

• Select the drag tool (the top left tool)

• In the toolbar for the tool (top bar area) check the Auto Select mode

• Select the  Layer Mode for auto selection (in some cases group would actually be better so feel

free to experiment)

• Click on the portion in the PSD that you are interested in

You should end up with something like this where a layer is selected in the layers window:

147

Figure 157. Selecting a layer from the region you are interested in

Scroll up the hierarchy a bit and uncheck/recheck the eye icon on the left until you locate the right

element layer.

Figure 158. Selecting a layer from the region you are interested in

Right click the layer and select Convert To Smart Object.

 The right click menu will present different options when you click different areas

of the layer, clicking on the left area of the layer works

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Figure 159. In the right click menu option select "Convert To Smart Object"

Once  the  layer  hierarchy  is  a  smart  object  you  can  just  double  click  it  which  will  open  the  sub

hierarchy in a new tab and you now only have the pieces of the image you care about.

Figure 160. Double clicking the smart object allows us to edit only the form we need

Removing the Noise

The first thing we need to do is remove from the image all of the things that we don’t really need.

The status bar area on the top is redundant as if is a part of the phones UI. We can select it using the

select tool and click the eye icon next to the layer to hide it.

Normally we’d want to have the back arrow but thanks to the material design icons that are a part

of Codename One we don’t need that icon so we can hide that too.

We don’t need the "Sign Up" or "Done" strings in the title either but before removing them we’d like

to know the font that is used.

149

To discover that I can click them to select the layer then switch to the text tool:

Figure 161. The text tool allows us to inspect the font used

Then I can double click the text area layer to find out the font in the top of the UI like this:

Figure 162. The Done toolbar entry uses SourceSansPro Regular



Notice  that  I  don’t  actually  need  to  have  the  font  installed  in  this  case  I  don’t

(hence the square brackets)

Also notice that the color of the font is accessible in that toolbar, by clicking the color element we

get this dialog which shows the color value to be f73267, this is something we will use later

Figure 163. The color dialog lists the hex color at the bottom, we can paste that directly to the designer tool

We can now hide both text layers so they won’t pose a problem later.

The Camera Button

The  camera  button  includes  an  icon  and  the  button  background  itself.  You  can  just  use  that  as  a

single image and be done with it, but for the purpose of this tutorial I will take the harder route of

separating this into a button background and a foreground image.

When  you  click  on  the  camera  icon  you  will  notice  that  the  camera  icon  is  comprised  of  two

separate layers: the camera and the "x" symbol above it. We can select both layers using  ctrl-click

(command click on the Mac) and convert both to a smart object together using the same method as

before:

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Figure 164. The camera smart object

Since the image is used as an icon we want it to be completely square which isn’t the situation here!

This is important as a non-square image can trigger misalignment when dealing with icons and the

background. So we need to use the  Image →  Canvas Size menu and set the values to be the same

(the higher value of the two).

Figure 165. The canvas size dialog for the camera.png file

We  can  now  use  File  →  Export  and  save  the  first  image  resource  we  will  need  into  a  temporary

directory. Make sure to save a PNG file to preserve quality and transparency!



Use File → Export and never use File → Save As . The latter can produce a huge size

difference as it retains image meta-data

For convenience we’ll refer to the file as camera.png when we need it later.

Figure 166. The camera icon image

We can follow the exact same procedure with the parent button layer (the white portion) which we
can convert to a smart object and export camera-button.png.

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Figure 167. The camera button image set to a gray background so it will be visible

Now we can hide both of these elements and proceed to get the background image for the title.

Here  the  "smart  object  trick"  won’t  work…  There  is  an  effects  layer  in  place  and  the  smart  object

will  provide  us  with  the  real  underlying  image  instead  of  the  look  we  actually  want.  However,

solving this is trivial now that we hid all of the elements on top of the image!

We need to switch to the rectangular select tool:

Figure 168. The select tool and the clean image we want to select

Now drag the select tool to select the image don’t cross into the white pixels below the image. You

can use the zoom value and set it to a very high value to get the selection right.

When the selection is right click  Edit →  Copy Merged. Normally  Copy would only copy a specific

layer but in this case we want to copy what we see on the screen!

Now click  File →  New it should have the  Presets set to  Clipboard which means the newly created

image is based on what we just copied (that is seriously great UX). Just accept that dialog and paste

(Ctrl-V or Command-V).

You  can  now  save  the  image,  since  it’s  just  a  background  using  JPEG  is  totally  acceptable  in  this
case. We named it background.jpg.

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Figure 169. The background image

The last thing we need is the colors used in the UI. We can use the "eye drop" tool in a high zoom
level to discover the colors of various elements e.g. the text color is 4d606f and the separator color is
f5f5f5:

Figure 170. The eye drop tool can be pointed at an area of the image to get the color in that region

4.10.2. The Code

While  that  was  verbose  it  was  relatively  simple.  We’ll  create  a  simple  barebones  manual

application with the native theme.

 The reason for this is to avoid "noise", if we use a more elaborate theme it would

have some existing settings. This can make the tutorial harder to follow

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Figure 171. Simple bare bones app settings

Once the project is created double click the theme.res file and within the designer select  Images →
Quick Add Multi Images. Select the 3 images we created above: background.jpg, camera.png & camera-
button.png. Leave the default setting on Very High and press OK.

Then save the resource file so we can use these images from code.

Here  is  the  source  code  we  used  to  work  with  the  UI  above  there  are  comments  within  the  code

explaining some of the logic:

private Label createSeparator() {
    Label sep = new Label();
    sep.setUIID("Separator");
    // the separator line  is implemented in the theme using padding and background color, by default labels
    // are hidden when they have no content, this method disables that behavior
    sep.setShowEvenIfBlank(true);
    return sep;
}

public void start() {
    if(current != null){
        current.show();
        return;
    }
    // The toolbar uses the layered mode so it resides on top of the background image, the theme makes
    // it transparent so we will see the image below it, we use border layout to place the background image on
    // top and the "Get started" button in the south
    Form psdTutorial = new Form("Signup", new BorderLayout());
    Toolbar tb = new Toolbar(true);
    psdTutorial.setToolbar(tb);

    // we create 4mm material arrow images for the back button and the Get started button

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    Style iconStyle = psdTutorial.getUIManager().getComponentStyle("Title");
    FontImage leftArrow = FontImage.createMaterial(FontImage.MATERIAL_ARROW_BACK, iconStyle, 4);
    FontImage rightArrow = FontImage.createMaterial(FontImage.MATERIAL_ARROW_FORWARD, iconStyle, 4);

    // we place the back and done commands in the toolbar, we need to change UIID of the "Done" command
    // so we can color it in Red
    tb.addCommandToLeftBar("", leftArrow, (e) -> Log.p("Back pressed"));
    Command doneCommand = tb.addCommandToRightBar("Done", null, (e) -> Log.p("Done pressed"));
    tb.findCommandComponent(doneCommand).setUIID("RedCommand");

    // The camera button is comprised of 3 pieces. A label containing the image and the transparent button
    // with the camera icon on top. This is all wrapped in the title container where the title background image
    // is placed using the theme. We chose to use a Label rather than a background using the cameraLayer so
    // the label will preserve the original size of the image without scaling it and take up the space it needs
    Button cameraButton = new Button(theme.getImage("camera.png"));
    Container cameraLayer = LayeredLayout.encloseIn(
            new Label(theme.getImage("camera-button.png")),
            cameraButton);
    cameraButton.setUIID("CameraButton");
    Container titleContainer = Container.encloseIn(
            new BorderLayout(BorderLayout.CENTER_BEHAVIOR_CENTER),
            cameraLayer, BorderLayout.CENTER);
    titleContainer.setUIID("TitleContainer");

    TextField firstName = new TextField("", "First Name");
    TextField lastName = new TextField("", "Last Name");
    TextField email = new TextField("", "Email Address", 20, TextField.EMAILADDR);
    TextField password = new TextField("", "Choose a Password", 20, TextField.PASSWORD);
    TextField phone = new TextField("", "Phone Number", 20, TextField.PHONENUMBER);
    Label phonePrefix = new Label("+1");
    phonePrefix.setUIID("TextField");

    // The phone and full name have vertical separators, we use two table layouts to arrange them correctly
    // so the vertical separator will be in the right place
    TableLayout fullNameLayout = new TableLayout(1, 3);
    Container fullName = new Container(fullNameLayout);
    fullName.add(fullNameLayout.createConstraint().widthPercentage(49), firstName).
        add(fullNameLayout.createConstraint().widthPercentage(1), createSeparator()).
        add(fullNameLayout.createConstraint().widthPercentage(50), lastName);
    Container fullPhone = TableLayout.encloseIn(3, phonePrefix, createSeparator(), phone);

    // The button in the south portion needs the arrow icon to be on the right side so we place the text on the left
    Button southButton = new Button("Get started", rightArrow);
    southButton.setTextPosition(Component.LEFT);
    southButton.setUIID("SouthButton");

    // we add the components and the separators the center portion contains all of the elements in a box
    // Y container which we allow to scroll. BorderLayout Containers implicitly disable scrolling
    Container by = BoxLayout.encloseY(
                    fullName,
                    createSeparator(),
                    email,
                    createSeparator(),
                    password,
                    createSeparator(),
                    fullPhone,
                    createSeparator()
            );
    by.setScrollableY(true);
    psdTutorial.add(BorderLayout.NORTH, titleContainer).
            add(BorderLayout.SOUTH, southButton).
            add(BorderLayout.CENTER, by);

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    psdTutorial.show();
}

4.10.3. Styling The UI

So the code above is most of the work but we still need to put everything together using the theme.

This is what we have so far:

Figure 172. Before applying the changes to the theme this is what we have

Figure 173. This is what we are aiming at with no additional code changes

This looks like a major set of changes but it requires exactly 10 UIID definitions to get to this look!

Open the designer and select the theme. Press the  Add button and type in  TitleContainer. Uncheck

derive  for  the  background  and  select  IMAGE_SCALED_FILL  for  the  Type  and  the  background.jpg

image.

Define the padding as:

• Left - 3 millimeter

• Right - 3 millimeter

• Top - 8 millimeter

• Bottom - 2 millimeter

This will allow enough space for the title. Define margin as 0 on all sides. Then press OK.

Add the "Title" UIID. In the  Color tab define the foreground as ffffff define transparency as 0 (fully
transparent  so  we  will  see  the  TitleContainer).  Define  padding  as  1  millimeter  on  all  sides  and

156

margin as 0 on all sides.

In the Border tab press the … button and select [Empty].

In the  Font tab select the  True Type as  native:MainThin. Select the  True Type Size as millimeters
and set the value to 3.5.

Press OK to save the changes.

Copy  the  Title  UIID  and  paste  it,  change  the  name  to  "TitleCommand"  and  press  OK  to  save  the
changes.

Copy the Title UIID again and paste it, change the name to "RedCommand". In the  Color tab set the
foreground color to f73267. In the Font tab set the  True Type to native:MainLight and set the size to
3. Press OK to save the changes.

Add the "TitleArea" UIID. In the  Color tab define transparency as 0 (fully transparent so we will see
the TitleContainer). Define padding and margin as 0 on all sides.
In the Border tab press the … button and select [Empty]. Press OK to save the changes.

Add  the  "TextField"  UIID.  In  the  Color  tab  define  transparency  as  255  (fully  opaque)  and  the
background  as  ffffff  (white).  Define  padding  as  2  millimeter  on  all  sides  and  margin  as  0  on  all
sides.

In  the  Border  tab  press  the  …  button  and  select  [Empty].  In  the  Font  tab  set  the  True Type  to

native:MainLight and set the size to 2. Press OK to save the changes.

Copy the TextField UIID again and paste it, change the name to "TextHint". In the  Color tab set the
foreground color to 4d606f. Press OK to save the changes.

Add  the  "SouthButton"  UIID.  In  the  Color  tab  define  transparency  as  255  (fully  opaque)  and  the
background as f73267 (red) and the foreground as ffffff (white). Define Alignment as Center.

Define padding as:

• Left - 1 millimeter

• right - 1 millimeter

• top - 2 millimeters

• bottom - 2 millimeters

Define margin as 0 on all sides. In the Font tab set the True Type  to native:MainThin and set the size

to 3. Press OK to save the changes.

Add the "CameraButton" UIID. In the  Color tab define transparency as 0 (fully transparent). Define
Alignment as Center.

Define padding as:

• Left - 1 millimeter

• right - 1 millimeter

• top - 3 millimeters

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• bottom - 1 millimeter

 This helps spacing away from the title

Define margin as 1 millimeter on all sides. Press OK to save the changes.

You can now save the theme and the app should look like the final result!

Not Quite There Yet

There is one last piece that you would notice if you actually try to run this code. When pressing the

buttons/text  fields  you  would  see  their  look  change  completely  due  to  the  different  styles  for

focus/press behavior.

You can derive the regular styles from the selected/pressed styles but one of the simplest ways is to
just  copy  &  paste  the  styles  to  the  pressed/selected  tabs.  We  can  copy  CameraButton,  RedCommand,
SouthButton  &  TextField  to  the  selected  state.  Then  copy  CameraButton,  RedCommand  &  SouthButton  to
the pressed state to get the complete app running!

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5. CSS

In this chapter we’ll discuss theming with CSS in Codename One.



CSS Changes Don’t Require a Recompile

You can change the CSS values while the simulator is running and the changes will

reflect in the simulator within a few seconds

5.1. Activating CSS

Codename  One  applications  always  use  the  resource  file.  The  CSS  support  compiles  a  file  in  CSS

syntax to a Codename One resource file and adds it to the application. In runtime the CSS no longer

exists and the file acts like a regular theme file.

To enable CSS support in Codename One you need to flip a switch in Codename One Settings.

Figure 174. The CSS Option in Codename One Settings Part I

159

Figure 175. The CSS Option in Codename One Settings Part II

Once  enabled  your  theme.res  file  will  regenerate  from  a  CSS  file  that  resides  under  the  css
directory.  Changes  you  make  to  the  CSS  file  will  instantly  update  the  simulator  as  you  save.

However,  there  are  some  limits  to  this  live  update  so  in  some  cases  a  simulator  restart  would  be

necessary.

5.2. Supported CSS Selectors

Since Codename One stylesheets are meant to be used with Codename One component hierarchies

instead of XML/HTML documents, selectors work a little differently.

1. All selectors (with some specific exceptions discussed below) are interpreted as UIIDs.

2. Only 4 predefined CSS classes are supported:

◦ .pressed — Targets the component when in "Pressed" state.

◦ .selected — Targets the component when in "Selected" state.

◦ .unselected — Targets the component when in "Unselected" state.

◦ .disabled — Targets the component when in "Disabled" state.

If no class is specified, then the selector targets "all" states of the given component.

The following are a few possible selectors you can include in your stylesheet.

1. Button — Defines styles for the "Button" UIID.

160

2. Button.pressed — Defines styles for the "Button" UIID’s "pressed" state.

3. Button, TextField, Form — Defines styles for the "Button", "TextField", and "Form" UIIDs.

The  following  example  creates  a  simple  button  with  a  border,  and  text  aligned  center.  By  default

the  button  will  have  a  transparent  background,  but  when  it  is  pressed,  it  will  have  a  gray

background:

Button {
    text-align: center;
    border: 1pt solid gray;
    background-color: transparent;
}

Button.pressed {
    background-color: gray;
}

5.2.1. Inheriting properties using cn1-derive

The  following  example  defines  a  custom  Button  style  named  "MyButton"  that  inherits  all  of  the

styles of Button but changes the background color to blue.

MyButton {
   cn1-derive: Button;
   background-color: blue;
}

5.3. Special Selectors

5.3.1. #Device

The #Device selector allows you to define which device resolutions this CSS file should target. Mutli-
images  generated  from  this  style-sheet  will  only  be  include  variants  for  device  resolutions  in  the
range  (min-resolution,  max-resolution)  as  defined  in  this  section.  By  default  all  resolutions  are
generated.

#Device {
    min-resolution: 120dpi;
    max-resolution: 480dpi;
    resolution: 480dpi;
}

5.3.2. #Constants

The #Constants selector allows you to specify theme constants.

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e.g.

#Constants {
    PopupDialogArrowBool: false;
    calTitleDayStyleBool: true;
    calTransitionVertBool: false;
    calendarLeftImage: "calendar-arrow-left.png";
    calendarRightImage: "calendar-arrow-right.png";
    centeredPopupBool: false;
    checkBoxCheckDisFocusImage: "Check-Box_Normal.png";
    checkBoxCheckedFocusImage: "Check-Box_Press.png";
    checkBoxCheckedImage: "Check-Box_Press.png";
    checkBoxOppositeSideBool: true;
    checkBoxUncheckedFocusImage: "Check-Box_Normal.png";
    checkBoxUncheckedImage: "Check-Box_Normal.png";
    comboImage: "combo.png";
    commandBehavior: "Side";
    dialogTransitionIn: "fade";
    dialogTransitionOut: "fade";
    dlgButtonCommandUIID: "DialogButton";
    dlgCommandGridBool: true;
    dlgInvisibleButtons: #1a1a1a;
    formTransitionIn: "empty";
    formTransitionOut: "slide";
    includeNativeBool: true;
    menuImage: "of_menu.png";
    noTextModeBool: true;
    onOffIOSModeBool: true;
    otherPopupRendererBool: false;
    pureTouchBool: true;
    radioSelectedFocusImage: "Radio_btn_Press.png";
    radioSelectedImage: "Radio_btn_Press.png";
    radioUnselectedFocusImage: "Radio_btn_Normal.png";
    radioUnselectedImage: "Radio_btn_Normal.png";
    sideMenuImage: "menu.png";
    switchMaskImage: "switch-mask-3.png";
    switchOffImage: "switch-off-3.png";
    switchOnImage: "switch-on-3.png";
    tabPlacementInt: 0;
    backIconImage: "Back-icon.png";
    articleSourceIconImage: "Source-icon.png";
    articleDateIconImage: "Date-icon.png";
    articleArrowRightImage: "Arrow-right.png";
    articleShareIconImage: "Share-icon.png";
    articleBookmarkIconImage: "Bookmark-icon.png";
    articleTextIconImage: "Text-icon.png";
    articleCommentsIconImage: "Comments-icon.png";
    newsIconImage: "News-icon.png";
    channelsIconImage: "Channels-icon.png";
    bookmarksIconImage: "Bookmarks-icon.png";

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    overviewIconImage: "Overview-icon.png";
    calendarIconImage: "Calendar-icon.png";
    timelineIconImage: "Timeline-icon.png";
    profileIconImage: "Profile-icon.png";
    widgetsIconImage: "Widgets-icon.png";
    settingsIconImage: "Settings-icon.png";
    SubmitIconImage: "Submit-icon.png";
    SubmitIconDarkImage: "SubmitButtonLight-icon.png";

}

In the above example, the constants referring to an image name as a string requires that the image

exists in one of the following locations:

• res/<cssfilename>/<imageName>

• ../res/<cssfilename>/<imageName>

• ../../res/<cssfilename>/<imageName>

or that it has been defined as a background image in some selector in this CSS file.

5.3.3. Default

The  Default  selector  is  special  in  that  it  will  set  properties  on  the  theme’s  "default"  element.  The
default element is a special UIID in Codename One from which all other UIIDs in the same theme

are derived. This is a good place to set things like default fonts or background-colors.

5.4. Standard CSS Properties

• padding (and variants)

• margin (and variants)

• border (and variants)

• border-radius

• background (Usage below)

• background-color

• background-repeat

• background-image

• border-image

• border-image-slice

• font (Usage is covered in the following font section)

• font-family (Usage is covered in the following font section)

• font-style (Usage is covered in the following font section)

• font-size (Usage is covered in the following font section)

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• @font-face (Usage is covered in the following font section)

• color

• text-align

• text-decoration(Usage below)

• opacity

• box-shadow

• width (only used for generating background-images and borders)

• height (only used for generating background-images and borders)

5.5. Custom Properties

• cn1-source-dpi — Used to specify source DPI for multi-image generation of background images.
Accepted values: 0 (Not multi-image), 120 (Low res), 160 (Medium Res), 320 (Very High Res), 480
(HD), Higher than 480 (2HD)

• cn1-background-type — Used to explicitly specify the background-type that should be used for the

class.

• cn1-9patch — Used  to  explicitly  specify  the  slices  used  when  generating  9-piece  borders.

Deprecated - Use border-image and border-image-slice for 9-piece borders.

• cn1-derive — Used to specify that this UIID should derive from an existing UIID.

5.6. CSS Variables

As of CodenameOne 7.0, you can use variables in your CSS file via the var() CSS function. E.g.

var(--header-color, blue);

The var() function can only be used inside property values. I.e. You cannot use it in property names
or selectors.

Syntax:

var(<custom-property-name>, <declaration-value>?)

The <custom-property-name> must begin with two dashes (--).

The <declaration-value> is the fallback value that will be used if the variable hasn’t been defined in
the CSS file. The fallback value may include commas.

Examples

164

Listing 13. Example defining and using a CSS variable

#Constants {
    --main-bg-color: red;
}

MyContainer {
    background-color: var(--main-bg-color);
}

Listing 14. Example using a fallback value

#Constants {
    --main-bg-color: red;
}

MyContainer {
    background-color: var(--main-bg-color, blue);
}

See  the  MDN  docs  [https://developer.mozilla.org/en-US/docs/Web/CSS/var]  for  more  details  about  the  CSS

variable spec.

5.7. CSS Properties

This section isn’t as comprehensive as it should be due to the breadth of CSS.

5.7.1. text-decoration

underline

overline

line-through

none

cn1-3d

cn1-3d-lowered

Underlines text. E.g. text-decoration: underline;

Overlines text. E.g. text-decoration: overline;

Strikes through text. E.g. text-decoration: line-
through;

No text decoration. E.g. text-decoration: none;

3D 

text. 

E.g. 

text-decoraton: 

cn1-3d;

3D  lowered  text.  E.g.  text-decoration:  cn1-3d-
lowered;

cn1-3d-shadow-north

3D text with north shadow. E.g. text-decoration:
cn1-3d-shadow-north;

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For other CSS font settings see the Fonts section [Fonts]

5.7.2. border

This  library  supports  the  border  property  [https://developer.mozilla.org/en-US/docs/Web/CSS/border]  and

most  of  its  variants  (e.g.  border-width  [https://developer.mozilla.org/en-US/docs/Web/CSS/border-width],

border-style 

[https://developer.mozilla.org/en-US/docs/Web/CSS/border-style], 

and 

border-color

[https://developer.mozilla.org/en-US/docs/Web/CSS/border-color].  It  will  try  to  use  native  Codename  One

styles for generating borders if possible. If the border definition is too complex, it will fall-back to

generating  a  9-piece  image  border  at  compile-time.  This  has  the  effect  of  making  the  resulting

resource file larger, but will produce good runtime performance, and a look that is faithful to the

provided CSS.

The algorithm used to determine whether to use a native border or to generate a 9-piece image, is

complex,  but  the  following  guidelines  may  help  you  if  you  wish  to  design  borders  that  can  be

rendered natively in CN1:

• Non-pixel units border-width. (Except with the cn1-round-border and cn1-pill-border styles)

• Using the border-radius directive.

• Using box-shadow (Except when using cn1-round-border or cn1-pill-border styles)

• Using a background gradient in combination with a border or any kind

• Using a different border-width, border-style, or border-color for different sides of the border

• Using a filter



You  can  open  the  resulting  theme  file  in  the  designer  and  inspect  it  to  see  if  an

image was generated

Generating  the  image  triggers  slower  CSS  compilation  and  a  larger  binary  so  we  generally

recommend tuning the CSS so it avoids this fallback.

Round Borders

Rounded borders can be achieved in a few different ways. The easiest methods are:

• The  cn1-round-border  style.  This  will  render  a  circular  round  border  in  the  background

natively. I.e. this doesn’t require generation of an image border

• The  cn1-pill-border  style.  This  will  render  a  pill-shaped  border  in  the  background  natively.

This also doesn’t require generation of an image border

• The  border-radius  property.  This  will  round  the  corners  of  the  border.  If  the  style  can  be
achieved using the RoundRectBorder in CodenameOne, then it will use that border. If not, this will
cause the style to be generated as an image border

Examples using cn1-round-border

166

RoundBorder {
    border: 1px #3399ff  cn1-round-border;
    text-align:center;
    margin:2mm;
    padding:3mm;
}

RoundBorderFilled {
    background: cn1-round-border;
    background-color: #ccc;
    text-align:center;
    margin:2mm;
    padding:3mm;
}

Examples using cn1-pill-border

PillBorder {
    border: 1pt #3399ff cn1-pill-border;
    text-align:center;
}

PillBorderFilled {
    background: cn1-pill-border;
    background-color: #3399ff;
    color:white;
    text-align:center;
}

Examples using border-radius

RoundRectLabel {
    background-color: red;
    border-radius: 2mm;
}

cn1-pill-border  and  cn1-round-border  don’t  support  the  standard  CSS  box-shadow  property.  This  is
because the box-shadow property parameters don’t map nicely onto the shadow parameters for the
Codename  One  RoundBorder  class.  To  get  shadows  on  the  cn1-pill-border,  you  should  use  one  or
more of the following CSS properties:

• cn1-box-shadow-spread — Accepts  values  in  any  scalar  unit  (e.g.  px,  mm,  cm,  etc…).  This  maps
directly  to  the  border’s  shadowSpread  [https://www.codenameone.com/javadoc/com/codename1/ui/plaf/

RoundBorder.html#shadowSpread-int-boolean-] property.

• cn1-box-shadow-h — Accepts  values  in  real  values  or  integers  (not  a  scalar  unit).  This  maps
[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/

the  border’s  shadowX 

directly 

to 

167

RoundBorder.html#shadowX-float-] property.

• cn1-box-shadow-v — Accepts  values  in  real  values  or  integers  (not  a  scalar  unit).  This  maps
[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/

the  border’s  shadowY 

directly 

to 

RoundBorder.html#shadowY-float-] property.

• cn1-box-shadow-blur — Scalar 

value. 

Maps 

to 

the 

border’s 

shadowBlur

[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/RoundBorder.html#shadowBlur-float-]

property.

• cn1-box-shadow-color — The shadow color

Currently  using  the  regular  CSS  box-shadow  in  conjunction  with  border-radius  will  cause  a  9-piece
border  to  be  generated  rather  than  mapping  to  the  RoundRectBorder.  If,  however,  you  use  the  cn1-
box-* properties for the shadow instead, it will use the RoundRectBorder — assuming that no other
styles are specified that trigger an image border to be generated.

5.7.3. background

The background property supports most standard CSS values [https://developer.mozilla.org/en-US/docs/Web/
CSS/background] for setting the background color, or background image.



9-piece  Image  borders  always  take  precedence  over  background  settings  in

Codename  One.  If  your  background  directive  seems  to  have  no  effect,  it  is  likely

because  the  theme  has  specified  a  9-piece  image  border  for  the  UIID.  You  can
disable the image border using a directive like border: none

Background Images

See Images [Images]

Gradients

Both  the  linear-gradient  and  radial-gradient  CSS  functions  are  fully  supported  by  this  library.  If
Codename One is capable of rendering the gradient natively then the theme resource file generated

will  only  include  encoded  parameters  for  the  gradients.  If  the  gradient  is  not  supported  by

Codename  One,  then  the  module  will  fall  back  to  an  image  background  which  it  generates  at

compile-time.  It  is  generally  preferable  to  try  to  stick  to  gradients  that  Codename  One  supports

natively.  This  will  result  in  a  smaller  theme  resource  file  since  it  doesn’t  need  to  generate  any

images for the gradient.

Natively Supported linear-gradient Syntax

In order for a linear gradient to be natively supported by Codename One, the following properties

must be met:

1. The gradient function has exactly two color stops, and these colors have the same opacity.

2. The gradient is either perfectly horizontal or perfectly vertical. (e.g Direction can be 0deg, 90deg,

180deg, or 270deg.

Examples

168

MyContainer {
   background: linear-gradient(0deg, #ccc, #666);
}

Figure 176. Native linear gradient 0 degrees

MyContainer {
    background: linear-gradient(to top, #ccc, #666);
}

Figure 177. Native linear gradient to top

169

MyContainer {
    background: linear-gradient(90deg, #ccc, #666);
}

Figure 178. Native linear gradient 90deg

MyContainer {
    background: linear-gradient(to left, #ccc, #666);
}

Figure 179. Native linear gradient to left

Unsupported linear-gradient syntax

The  following  are  some  examples  of  linear  gradients  that  aren’t  supported  natively  by  Codename

170

One, and will result in a background image to be generated at compile-time:

MyComponent {
    background: linear-gradient(45deg, #eaeaea, #666666);
}

Figure 180. 45deg gradient rendered at compile-time — uses background image

The  above  example  is  not  supported  natively  because  the  gradient  direction  is  45  degrees.

Codename One only supports 0, 90, 180, and 270 degrees natively. Therefore this would result in a

background image being generated at compile-time with the appropriate gradient.

MyComponent {
    background: linear-gradient(90deg, rgba(255, 0, 0, 0.6), blue);
}

171

Figure 181. Linear gradient with different alpha

The  above  linear-gradient  is  not  supported  natively  because  the  stop  colors  have  different

transparencies. The first color has an opacity of 0.5, and the second as an opacity of 1.0 (implicitly).

Therefore, this would result in the gradient being generated as an image at compile-time.

Natively Supported radial-gradient Syntax

The following syntax is supported natively for radial gradients. Other syntaxes are also supported

by  the  CSS  library,  but  they  will  use  compile-time  image  generation  for  the  gradients  rather  than

generating them at runtime.

background: radial-gradient(circle [closest-side] [at <position>], <color stop>, <color stop>)

• <position> — The position using either offset keywords or percentages.

• <color stop> — Either a color alone, or a color followed by a percentage. 0% indicates that color
begins  at  center  of  the  circle.  100%  indicates  that  the  color  begins  at  the  closest  edge  of  the

bounding box. Higher/lower values (>0%) will shift the color further or closer to circle’s center.

If  the  first  color  stop  is  set  to  a  non-zero  value,  the  gradient  cannot  be  rendered  natively  by

Codename One, and an image of the gradient will instead be generated at compile-time.

More complex gradients are supported by this library, but they will be generated at compile-time.
For  more  information  about  the  radial-gradient  CSS  function  see  its  MDN  Wiki  page
[https://developer.mozilla.org/en-US/docs/Web/CSS/radial-gradient].

Examples

MyContainer {
    background: radial-gradient(circle, gray, white);
}

172

Figure 182. Radial gradient 0 to 100

MyContainer {
    background: radial-gradient(circle, gray, white 200%);
}

Figure 183. Radial gradient 0 to 200

MyContainer {
    background: radial-gradient(circle at left, gray, white);
}

173

Figure 184. Radial gradient at left

MyContainer {
    background: radial-gradient(circle at right, gray, white);
}

Figure 185. Radial gradient at right

5.7.4. cn1-background-type

It also supports some special Codename One values, which are identifiers with a "cn1-" prefix. The

following  special  values  are  available.  They  map  to  the  standard  Codename  One  values  we

discussed in the theming chapter:

• cn1-image-scaled

• cn1-image-scaled-fill

• cn1-image-scaled-fit

• cn1-image-tile-both

• cn1-image-tile-valign-left

• cn1-image-tile-valign-center

174

• cn1-image-tile-valign-right

• cn1-image-tile-halign-top

• cn1-image-tile-halign-center

• cn1-image-tile-halign-bottom

• cn1-image-align-bottom

• cn1-image-align-left

• cn1-image-align-right

• cn1-image-align-center

• cn1-image-align-top-left

• cn1-image-align-top-right

• cn1-image-align-bottom-left

• cn1-image-align-bottom-right

• cn1-image-border

• cn1-none

• cn1-round-border

• cn1-pill-border

5.8. Images

Images  are  supported  as  both  "inputs"  of  the  stylesheet,  and  as  outputs  to  the  compiled  resource
file.  "Input"  images  are  usually  specified  via  the  background-image  property  in  a  selector.  "Output"
images are always saved as multi-images inside the resource file.

5.8.1. Image DPI and Device Densities

In order to appropriately size the image, the CSS compiler needs to know what the source density of

the image is. E.g. if an image is 160x160 pixels with a source density of 160dpi (i.e. medium density -

or the same as an iPhone 3G), then the resulting multi-image will be sized at 160x160 for medium

density devices and 320x320 on very high density devices (e.g. iPhone 4S Retina) - which will result

in the same perceived size to the user of 1x1 inch.

However  if  the  image  has  a  source  density  of  320dpi,  then  the  resulting  multi-image  would  be

80x80 pixels on medium density devices and 160x160 pixels on very high density devices.

Some images have this density information embedded in the image itself so that the CSS processor

will  know  how  to  resize  the  image  properly.  However,  it  is  usually  better  to  explicitly  document
your intentions by including the cn1-source-dpi property as follows:

175

SomeStyle {
    background-image: url(images/my-image.png);
    cn1-source-dpi: 160;
}

cn1-source-dpi  values  are  meant  to  fall  into  threshold  ranges.  Values  less  than  or
equal to 120, are interpreted as low density. 121 - 160 are medium density (iPhone



3GS). 161 - 320, very high density (iPhone 4S). 321 - 480 == HD. 481 and higher ==

2HD.  In  general,  you  should  try  to  use  images  that  are  one  of  these  DPIs  exactly:

160,  320,  or  480,  then  images  will  be  scaled  up  or  down  to  the  other  densities

accordingly.

5.8.2. Multi-Images vs Regular Images

By default all images are imported as multi-images. If you want to import an image as a "regular"
image, you can simply set cn1-source-dpi to 0. E.g.

SomeStyle {
    background-image: url(images/my-image.png);
    cn1-source-dpi: 0;
}

5.8.3. Multi-Images as Inputs

If  you  have  already  generated  images  in  all  of  the  appropriate  sizes  for  all  densities,  you  can

provide them in the same file structure used by the Codename One XML resource files: The image

path is a directory that contains images named after the density that they are intended to be used

for. The possible names include:

• verylow.png

• low.png

• medium.png

• high.png

• veryhigh.png

• 560.png

• hd.png

• 2hd.png

• 4k.png

E.g. Given the CSS directives:

176

MyStyle {
    background-image: url(images/mymultiimage.png);
}

The files would look like:

css/
 +--- mycssfile.css
 +--- images/
       +--- mymultiimage.png/
             +--- verylow.png
             +--- low.png
             +--- medium.png
              ... etc...

 Multi-image inputs are only supported for local URLs. You cannot use remote (e.g.

http://) urls with multi-image inputs

5.8.4. Image Constants

Theme constants can be images. The convention is to suffix the constant name with "Image" so that
it will be treated as an image. In addition to the standard url() notation for specifying a constant
image, you can provide a simple string name of the image, and the CSS processor will try to find an

image by that name specified as a background image for one of the styles. If it cannot find one, it

will look inside a special directory named "res" (located in the same directory as the CSS stylesheet),

inside which it will look for a directory named the same as the stylesheet, inside which it will look

for  a  directory  with  the  specified  multi-image.  This  directory  structure  is  the  same  as  used  for

Codename One’s XML resources directory.

E.g. In the CSS file "mycssfile.css":

radioSelectedFocusImage: "Radio_btn_Press.png";

Will  look  for  a  directory  located  at  res/mycssfile.css/Radio_btn_Press.png/  with  the  following
images:

• verylow.png

• low.png

• medium.png

• high.png

• veryhigh.png

• 560.png

• hd.png

177

• 2hd.png

• 4k.png

It will then create a multi-image from these images and include them in the resource file.

5.9. Image Recipes

5.9.1. Import Multiple Images In Single Selector

It is quite useful to be able to embed images inside the resource file that is generated from the CSS
stylesheet so that you can access the images using the Resources.getImage() method in your app and
set it as an icon on a button or label. In this case, it is easier to simply create a dummy style that you

don’t intend to use and include multiple images in the background-image property like so:

Images {
    background-image: url(images/NowLogo.png),
        url(images/Username-icon.png),
        url(images/Password-icon.png),
        url(images/Name-icon.png),
        url(images/Email-icon.png),
        url(images/SeaIce.png),
        url(images/Back-icon.png),
        url(images/Source-icon.png),
        url(images/Date-icon.png),
        url(images/Arrow-right.png),
        url(images/Share-icon.png),
        url(images/Text-icon.png),
        url(images/Comments-icon.png),
        url(images/RedPlanet.png),
        url(images/News-icon.png),
        url(images/Channels-icon.png),
        url(images/Bookmarks-icon.png),
        url(images/Overview-icon.png),
        url(images/Calendar-icon.png),
        url(images/Timeline-icon.png),
        url(images/Profile-icon.png),
        url(images/Widgets-icon.png),
        url(images/Settings-icon.png),
        url(images/Bookmark-icon.png);
}

Then in Java, I might do something like:

Resources theme = Resources.openLayered("/theme.css.res");

Label bookmark = new Label(theme.getImage("Bookmark-icon.png"));

178

5.9.2. Loading Images from URLs

You can also load images from remote URLs. E.g.

Images {
    background-image: url(http://solutions.weblite.ca/logo.png);
}

5.9.3. Generating 9-Piece Image Borders

9-Piece image borders can be created using the image-border and image-border-slice properties.

E.g.

NinePiece {
    border-image:url('dashbg_landscape.png');
}

In  the  above  example  we  omitted  the  border-image-slice  property,  so  it  defaults  to  "40%",  which
means that the image is sliced 40% from the top, 40% from the bottom, 40% from the left, and 40%

from the right.

If you want more specific "slice" points, you can add the border-image-slice property. E.g.

179

NinePiece {
    border-image:url('dashbg_landscape.png');
    border-image-slice:10% 49%;  /*vertical horizontal*/
}

NinePiece2 {
    border-image:url('dashbg_landscape.png');
    border-image-slice:10% 49% 20%;  /*top horizontal bottom*/
}

NinePiece3 {
    border-image:url('dashbg_landscape.png');
    border-image-slice:10% 30% 40% 20%;  /*top right bottom left*/
}

NinePiece4 {
    border-image:url('dashbg_landscape.png');
    border-image-slice:10%;  /*all*/
}

5.9.4. Image Backgrounds

Component  backgrounds  in  Codename  One  are  a  common  source  of  confusion  for  newcomers

because there are 3 different properties that can be used to define what a component’s background

looks like, and they have priorities:

1. Background Color - You can specify an RGB color to be used as the background for a component.

2. Background Image - You can specify an image to be used as the background for a component.

Codename  One  includes  settings  to  define  how  the  image  is  treated,  e.g.  scale/fill,  tile,  etc.  If  a

background image is specified, it will override the background color setting - unless the image

has transparent regions.

3. Image  Border  -  You  can  define  a  9-piece  image  border  which  will  effectively  cover  the  entire

background of the component. If an image border is specified, it will override the background

image of the component.

A common scenario that I run into is trying to set the background color of a component and see no

change  when  I  preview  my  form  because  the  style  had  an  image  background  defined  -  which

overrides my background color change.

The  potential  for  confusion  is  mitigated  somewhat,  but  still  exists  when  using  CSS.  You  can  make
your  intentions  explicit  by  adding  the  cn1-background-type  property  to  your  style.  Possible  values
include:

• cn1-image-scaled

• cn1-image-scaled-fill

• cn1-image-scaled-fit

• cn1-image-tile-both

180

• cn1-image-tile-valign-left

• cn1-image-tile-valign-center

• cn1-image-tile-valign-right

• cn1-image-tile-halign-top

• cn1-image-tile-halign-center

• cn1-image-tile-halign-bottom

• cn1-image-align-bottom

• cn1-image-align-left

• cn1-image-align-right

• cn1-image-align-center

• cn1-image-align-top-left

• cn1-image-align-top-right

• cn1-image-align-bottom-left

• cn1-image-align-bottom-right

• cn1-image-border

• cn1-none

• none

Example Setting Background Image to Scale Fill

MyContainer {
    background-image: url(myimage.png);
    cn1-background-type: cn1-image-scaled-fill;
}

5.10. Image Compression

CN1 resource files support both PNG and JPEG images, but PNG is the default. Multi-images that are

generated by the CSS compiler will be PNG if they include alpha transparency, and JPEG otherwise.

This is to try to reduce the file size as much as possible while not sacrificing quality.

5.11. Fonts

This 

library 

supports 

the 

font 

[https://developer.mozilla.org/en/docs/Web/CSS/font], 

font-size

[https://developer.mozilla.org/en/docs/Web/CSS/font-size],  font-family  [https://developer.mozilla.org/en/docs/Web/

CSS/font-family], 

font-style 

[https://developer.mozilla.org/en/docs/Web/CSS/font-style], 

font-weight

[https://developer.mozilla.org/en/docs/Web/CSS/font-weight],  and  text-decoration  [https://developer.mozilla.org/

en/docs/Web/CSS/text-decoration]  properties,  as  well  at  the  @font-face  [https://developer.mozilla.org/en/docs/

Web/CSS/@font-face] CSS "at" rule for including TTF/OTF fonts.

181

5.11.1. font-family

By  default,  CN1’s  native  fonts  [https://www.codenameone.com/blog/good-looking-by-default-native-fonts-

simulator-detection-more.html] are used. The appropriate native font is selected for the provided font-

weight and font-style properties. You can also explicitly specify the native font you wish to use in
the font-family property. E.g.

SideCommand {
    font-family:  "native:MainThin";
}

If you omit the font-family directive altogether, it will use native:MainRegular. The following native
fonts are available:

1. native:MainThin

2. native:MainLight

3. native:MainRegular

4. native:MainBold

5. native:MainBlack

6. native:ItalicThin

7. native:ItalicLight

8. native:ItalicRegular

9. native:ItalicBold

10. native:ItalicBlack

Using TTF Fonts

If you want to use a font other than the built-in fonts, you’ll need to define the font using the @font-
face rule. E.g.

@font-face {
    font-family: "Montserrat";
    src: url(res/Montserrat-Regular.ttf);
}

Then you’ll be able to reference the font using the specified font-family in any CSS element. E.g.

MyLabel {
    font-family: "Montserrat";
}

The @font-face directive’s src property will accept both local and remote URLs. E.g.

182

@font-face {
    font-family: "MyFont";
    src: url(http://example.com/path/to/myfont.ttf);
}

In this case, it will download the myfont.ttf file to the same directory as the CSS file. From then on
it  will  use  that  locally  downloaded  version  of  the  font  so  that  it  doesn’t  have  to  make  a  network

request for each build.

Fonts are automatically copied to the project’s "src" directory when the CSS file is compiled so that

they will be distributed with the app and available at runtime.

Github URLs

Fonts hosted on GitHub are accessible using a special github: protocol to make it easier to reference
such fonts. E.g. the following directive includes the "FontAwesome" font directly from Github

@font-face {
    font-family: "FontAwesome";
    src: url(github://FontAwesome/Font-Awesome/blob/master/fonts/fontawesome-webfont.ttf);
}

 Apparently FontAwesome has removed its public repositories from Github so this

URL no longer works.

5.11.2. font-size

It  is  best  practice  to  size  your  fonts  using  millimetres  (mm)  (or  another  "real-world"  measurement
unit  such  as  inches  (in),  centimetres  (cm).  This  will  allow  the  font  to  be  sized  appropriate  for  all
display densities. If you specify size in pixels (px), it will treat it the same as if you sized it in points
(pt), where 1pt == 1/72 inches (one seventy-second of an inch).

If  you  size  your  font  in  percentage  units  (e.g.  150%)  it  will  set  the  font  size  relative  to  the  medium
font  size  of  the  platform.  This  is  different  than  the  standard  behaviour  of  a  web  browser,  which

would size it relative to the parent element’s font size.

You can use system fonts, true type fonts, and native fonts in your CSS stylesheet. True Type fonts
need  to  be  defined  in  a  @font-face  directive  before  they  can  be  referenced.  True-type  fonts  and
native fonts have the advantage that you can specify their sizes in generic terms (e.g. small, medium,
large) and in more specific units such as millimeters (mm) or pixels (px).

5.11.3. text-decoration

See  the  text-decoration  section  [Supported-Properties#text-decoration]  in  the  "Supported  Properties"

page.

183

5.11.4. Some Sample CSS Directives

@font-face {
    font-family: "Montserrat";
    src: url(res/Montserrat-Regular.ttf);
}

@font-face {
    font-family: "Montserrat-Bold";
    src: url(res/Montserrat-Bold.ttf);
}

@font-face {
    font-family: "FontAwesome";
    src: url(github://FontAwesome/Font-Awesome/blob/master/fonts/fontawesome-webfont.ttf);
}

PlainText0p5mm {
    font-size: 0.5mm;
}

PlainText1mm {
    font-size: 1mm;
}

PlainText2mm {
    font-size: 2mm;
}

PlainText5mm {
    font-size: 5mm;
}

PlainText10mm {
    font-size: 10mm;
}

PlainText50mm {
    font-size: 50mm;
}

PlainTextSmall {
    font-size: small;
}

PlainTextMedium {
    font-size: medium;
}

PlainTextLarge {
    font-size: large;
}

184

PlainText3pt {
    font-size: 3pt;
}

PlainText6pt {
    font-size: 6pt;
}

PlainText12pt {
    font-size: 12pt;
}

PlainText20pt {
    font-size: 20pt;
}

PlainText36pt {
    font-size: 36pt;
}

BoldText {
    font-weight: bold;
}

BoldText1mm {
    font-weight: bold;
    font-size: 1mm;
}

BoldText2mm {
    font-weight: bold;
    font-size: 2mm;
}

BoldText3mm {
    font-weight: bold;
    font-size: 3mm;
}

BoldText5mm {
    font-weight: bold;
    font-size: 5mm;
}

ItalicText {
    font-style: italic;
}

ItalicText3mm {
    font-style: italic;
    font-size: 3mm;
}

185

ItalicBoldText {
    font-style: italic;
    font-weight: bold;
}

PlainTextUnderline {
    text-decoration: underline;
}

BoldTextUnderline {
    text-decoration: underline;
    font-weight: bold;
}

ItalicTextUnderline {
    text-decoration: underline;
    font-style: italic;
}

PlainText3d {
    text-decoration: cn1-3d;
    color:white;
    background-color: #3399ff
}

BoldText3d {
    text-decoration: cn1-3d;
    font-weight: bold;
    color:white;
    background-color: #3399ff;
}

ItalicText3d {
    text-decoration: cn1-3d;
    font-style: italic;
    color:white;
    background-color: #3399ff;
}

PlainText3dLowered {
    text-decoration: cn1-3d-lowered;
    color:black;
    background-color: #3399ff;
}

BoldText3dLowered {
    text-decoration: cn1-3d-lowered;
    font-weight: bold;
    color:black;
    background-color: #3399ff;
}

186

ItalicText3dLowered {
    text-decoration: cn1-3d-lowered;
    font-style: italic;
    color:black;
    background-color: #3399ff;
}

PlainText3dShadow {
    text-decoration: cn1-3d-shadow-north;
    color:white;
    background-color: #3399ff;
}

BoldText3dShadow {
    text-decoration: cn1-3d-shadow-north;
    font-weight: bold;
    color:white;
    background-color: #3399ff;
}

ItalicText3dShadow {
    text-decoration: cn1-3d-shadow-north;
    font-style: italic;
    color:white;
    background-color: #3399ff;
}

MainThin {

    font-size: 200%;
    background: radial-gradient(circle at top left, yellow, blue 100%);
}

MainRegular0001 {
    font-family: "native:MainRegular";
    /*background: cn1-pill-border;
    background-color: red;*/
    color: blue;
    border: 1px cn1-pill-border blue;
    /*box-shadow: 1mm 1mm 0 2mm rgba(0,0,0,1.0);*/
    padding: 2mm;
}

MainRegular0001.pressed {
    font-family: "native:MainRegular";
    background: cn1-pill-border blue;
    /*background-color: red;*/
    color: white;
    border: 1px solid white;
    /*box-shadow: 1mm 1mm 0 2mm rgba(0,0,0,1.0);*/
    padding: 2mm;
}

187

Heading {
    font-size: 4mm;
    font-family: "Montserrat-Bold";
    color: black;
    padding: 2mm;
    text-align: center;
}

XMLVIewIcon {
    font-family: "FontAwesome";
}

5.12. Media Queries

You  can  use  media  queries  to  target  styles  to  specific  platforms,  devices,  and  device  densities.

Currently the following media queries are supported:

1. platform-xxx - Target a specific platform. E.g. platform-and, platform-ios, platform-mac, platform-

win.

2. density-xxx - Target a specific device density. E.g. density-very-low, density-low, density-medium,

density-high, density-very-high, density-hd, density-2hd, and density-560.

3. device-xxx - Target a specific device type. E.g. device-desktop, device-tablet, device-phone.

Listing 15. Example: Different font colors on Android and iOS.  On Android, labels will appear green.  On

iOS, they will appear red.  On all other platforms, they will appear black.

Label {
    color: black;
}

@media platform-and {
    Label {
        color: green;
    }
}

@media platform-ios {
    Label {
        color: red;
    }
}

188

Listing 16. Example: Different font colors based on device density.  On lower densities, labels will be green.

On higher densities, labels will be red.

Label {
    color: black;
}

@media density-very-low, density-low, density-medium, density-high {
    Label {
        color: green;
    }
}

@media density-very-high, density-h2, density-2hd, density-560 {
    Label {
        color: red;
    }
}

Listing 17. Example: Different label colors based on device type.

Label {
    color: black;
}

@media device-desktop {
    Label {
        color: green;
    }
}

@media device-tablet, device-phone {
    Label {
        color: red;
    }
}

When  deploying  your  app  using  the  Javascript  port,  it  will  use  a  platform  name



derived  from  the  "UserAgent"  string  in  the  browser,  rather  than  the  result  of
Display.getPlatformName(),  which  is  used  for  other  ports.  When  running  on
Android, then, the platform will be "and". When running on iOS, the platform will

be "ios". Etc…

5.12.1. Compound Media Queries

You can combine multiple media queries together, separated by a comma. Queries of the same type

are  "OR"ed  together.  Queries  of  different  types  are  "AND"ed  together.  For  example  if  you  have  a
media  query  that  specifies  two  different  device  densities  (e.g.  density-low  and  density-high)  the

189

query will match both devices with low density and high density. However, if the query specifies a
device density and a platform (e.g. density-low and platform-and), then it will only match a device if
it matches the platform and the density.

Listing 18. Example: Targeting styles to only Android devices with high density

@media platform-and, density-high {
    ....
}

Listing 19. Example: Targeting styles to iOS devices with high or low density

@media platform-ios, density-high, density-low {
    ....
}

Listing 20. Example: Targeting only Mac Desktop.

@media device-desktop, platform-mac {
    ....
}

5.12.2. Order or Precedence

The  order  of  precendence  when  applying  styles  differs  slightly  from  the  way  styles  would  be

applied in standard CSS. The order of precendence is as follows:

1. Styles defined inside @media blocks will always take precendence over styles defined outside of

@media blocks.

2. @media  blocks  with  more  query  matches  will  take  precendence  over  blocks  with  fewer  query
matches. E.g. A media block matching density, platform, and device will take precendence over

a block that only matches the density and platform.

3. If  the  same  style  is  defined  in  two  media  blocks  which  contain  the  same  number  of  query
matches,  then  the  order  precedence  is  platform,  device,  density  in  decreasing  order.  I.e.  the
block that matches on platform will take precedence over the block that matches on density.

4. If the same style is defined in two media blocks with identical query matches, then the order of

precedence is undefined.

5.12.3. Font Scaling Constants

In  some  cases  you  may  find  that  fonts  are  coming  out  too  large  or  too  small  across  the  board  on

certain types of devices. You can use standard media queries to customize font sizes, but you can
also  use  font-scaling  constants  to  scale  font  sizes  for  the  entires  stylesheet  based  on  platform,
device, and/or density. In some cases you may find this approach easier.

For example, consider the following simple stylesheet that defines a font size of 2mm on labels:

190

Label {
    font-size: 3mm;
}

During testing, perhaps you find that, on desktop, the fonts are a little bit too small. In this case, you

can apply a font-scale constant that only applies to the desktop.

#Constants {
    device-desktop-font-scale: "1.5";
}

Label {
    font-size: 3mm;
}

Now, on most devices the Label style will have 3mm fonts. But on desktop, it will have 4.5mm fonts.

The above would be roughly equivalent to:

Label {
    font-size: 3mm;
}

@media device-desktop {
    Label {
        font-size: 4.5mm;
    }
}

Listing 21. Example: Font-scaling based on device, platform, and density

#Constants {
    device-phone-font-scale: "1.5";
    device-tablet-font-scale: "1.2";
    device-desktop-font-scale: "1.4";
    platform-ios-font-scale: "0.9";
    density-low-font-scale: "1.2";
    platform-ios-density-low-font-scale: "1.3";
}



All matching font-scale constants will be applied to the styles. If you define 3 font-
scale  constants  that  all  match  the  current  runtime  environment,  they  will  all  be

applied. E.g. If there are 3 matching font-scale constants with "2.0", "3.0", and "4.0",

then fonts will be scaled by 2*3*4=24!

191

192

6. The Components of Codename One

This chapter covers the components of Codename One. Not all components are covered, but it tries

to go deeper than the JavaDocs [https://www.codenameone.com/javadoc/].

6.1. Container

The  Codename  One  container  is  a  base  class  for  many  high  level  components;  a  container  is  a

component that can contain other components.

Every  component  has  a  parent  container  that  can  be  null  if  it  isn’t  within  a  container  at  the

moment or is a top-level container. A container can have many children.

Figure 186. Component-Container relationship expressed as UML

Components  are  arranged  in  containers  using  layout  managers  which  are  algorithms  that

determine the arrangement of components within the container.

You can read more about layout managers in the basics section [https://www.codenameone.com/manual/

basics.html#component-container-hierarchy].

6.1.1. Composite Components

Codename  One  components  share  a  very  generic  hierarchy  of 

inheritance  e.g.  Button

[https://www.codenameone.com/javadoc/com/codename1/ui/Button.html] 

derives 

from 

Label

[https://www.codenameone.com/javadoc/com/codename1/ui/Label.html] and thus receives all its abilities.

However, 

some 

components 

are 

composites 

and 

derive 

from 

the 

Container

[https://www.codenameone.com/javadoc/com/codename1/ui/Container.html]  class.  E.g. 

the  MultiButton

[https://www.codenameone.com/javadoc/com/codename1/components/MultiButton.html]  is  a  composite  button
that  derives  from  Container  but  acts/looks  like  a  Button.  Normally  this  is  pretty  seamless  for  the
developer, with a few things to keep in mind.

• You  should  not  use  the  Container  derived  methods  on  such  a  composite  component  (e.g.  add

/remove etc.).

• You can’t cast it to the type that it relates to e.g. you can’t cast MultiButton to Button.

• Events  might  be  more  nuanced.  E.g. 

if  you 

rely  on  ActionEvent.getSource()

[https://www.codenameone.com/javadoc/com/codename1/ui/events/ActionEvent.html#getSource--] 

or

ActionEvent.getComponent() 

[https://www.codenameone.com/javadoc/com/codename1/ui/events/

ActionEvent.html#getComponent--] notice that they might not behave the way you would expect. For
a  MultiButton  they  will  return  the  underlying  Button.  To  workaround  this  we  have
[https://www.codenameone.com/javadoc/com/codename1/ui/events/
ActionEvent.getActualComponent() 

193

ActionEvent.html#getActualComponent--].

Lead Component

Codename  One  has  a  rather  unique  feature  for  creating  composite  components:  "lead
components". This feature effectively allows components like MultiButton to act as if they are
a single component while really being comprised of multiple components.

Lead components work by setting a single component within as the "leader" it determines the
style state for all the components in the hierarchy so if we have a Container that is lead by a
Button  the  button  will  determine  if  the  selected/pressed  state  is  returned  for  the  entire
container hierarchy.

This creates a case where a single Component has multiple nested UIID’s e.g. `MultiButton has
UIID’s  such  as  `MultiLine1  that  can  be  customized  via  API’s  such  as  setUIIDLine1
[https://www.codenameone.com/javadoc/com/codename1/components/MultiButton.html#setUIIDLine1-

java.lang.String-].

The  lead  component  also  handles  the  events  from  a  single  source  so  clicking  in  one  of  the
other components within the hierarchy will send the event to the leading Button resulting in
action events that behave "oddly" (hence the need for getActualComponent);

You  can  learn  more  about  lead  components  in  here  [https://www.codenameone.com/manual/misc-

features.html#lead-component-section].

6.2. Form

Form  [https://www.codenameone.com/javadoc/com/codename1/ui/Form.html]  is  the  top-level  container  of
Codename One, Form derives from Container and is the element we “show”. Only one form can be
visible at any given time. We can get the currently visible Form using the code:

Form currentForm = Display.getInstance().getCurrent();

A  form  is  a  unique  container  in  the  sense  that  it  has  a  title,  a  content  area  and  optionally  a
menu/menu  bar  area.  When  invoking  methods  such  as  add/remove  on  a  form,  you  are  in  fact
invoking something that maps to this:

myForm.getContentPane().add(...);

Form  is  in  effect  just  a  Container  [https://www.codenameone.com/javadoc/com/codename1/ui/Container.html]
that has a border layout, its north section is occupied by the title area and its south section by the

optional menu bar. The center (which stretches) is the content pane. The content pane is where you

place all your components.

194

Figure 187. Form layout graphic

You can see that every Form has space allocated for the title area. If you don’t set the title it won’t
show up (its size will be zero), but it will still be there. The same isn’t always true for the case of the

menu bar, which can vary significantly. Effectively, the section that matters is the content pane, so

the  form  tries  to  do  the  “right  thing”  by  pretending  to  be  the  content  pane.  However,  this  isn’t
always  seamless  and  sometimes  code  needs  to  just  invoke  getContentPane()  in  order  to  work
directly with the container.



A  good  example  for  such  a  case  is  with  layout  animations.  Animating  the  form

might  not  produce  the  right  results.  When  in  doubt  its  pretty  easy  to  just  use
getContentPane instead of working with the Form directly.

As you can see from the graphic, Form has two layers that reside on top of the content pane/title. The
first is the layered pane which allows you to place "always on top" components. The layered pane
added implicitly when you invoke getLayeredPane().

 You still need to place components using layout managers in order to get them to

appear in the right place when using the layered pane.

The second layer is the glass pane which allows you to draw arbitrary things on top of everything.

The order in the image is indeed accurate:

1. ContentPane is lowest

2. LayeredPane is second

3. GlassPane is painted last



Its  important  to  notice  that  a  layered  pane  is  on  top  of  the  ContentPane  only  and
doesn’t stretch to the title. A GlassPane usually stretches all the way but only with a
"lightweight" title area e.g. the Toolbar API [https://www.codenameone.com/javadoc/com/

codename1/ui/Toolbar.html].

The GlassPane allows developers to overlay UI on top of existing UI and paint as they see fit. This is
useful for things that provide notification but don’t want to intrude with application functionality.

In earlier versions of Codename One (pre-3.6), LayeredPane & GlassPane didn’t work
with "native" peer components such as media, browser, native maps etc, because



peer components were always rendered "in front" of the Codename One UI canvas.

However, current versions now allow for proper layering of peer components and

light-weight  components  so  that  LayeredPane  and  GlassPane  can  be  used

seamlessly with peer components.

195

6.3. Dialog

A Dialog [https://www.codenameone.com/javadoc/com/codename1/ui/Dialog.html] is a special kind of Form that
can  occupy  only  a  portion  of  the  screen,  it  also  has  the  additional  functionality  of  the  modal  show
method.

When showing a dialog we have two basic options: modeless and modal:

• Modal  dialogs  (the  default)  block  the  current  EDT  thread  until  the  dialog  is  dismissed  (to

understand how they do it, read about invokeAndBlock).
Modal  dialogs  are  an  extremely  useful  way  to  prompt  the  user  since  the  code  can  assume  the

user responded in the next line of execution. This promotes a linear & intuitive way of writing

code.

• Modless dialogs return immediately so a call to show such a dialog can’t assume anything in the

next  line  of  execution.  This  is  useful  for  features  such  as  progress  indicators  where  we  aren’t

waiting for user input.

E.g. a modal dialog can be expressed as such:

if(Dialog.show("Click Yes Or No", "Select one", "Yes", "No")) {
    // user clicked yes
} else {
    // user clicked no
}

Notice  that  during  the  show  call  above  the  execution  of  the  next  line  was  "paused"  until  we  got  a
response from the user and once the response was returned we could proceed directly.



All usage of Dialog must be within the Event Dispatch Thread (the default thread of
Codename One). This is especially true for modal dialogs. The Dialog class knows
how to "block the EDT" without blocking it.

To learn more about invokeAndBlock which is the workhorse behind the modal dialog functionality
check out the EDT section [https://www.codenameone.com/manual/edt.html].

The Dialog class contains multiple static helper methods to quickly show user notifications, but also
allows  a  developer  to  create  a  Dialog  instance,  add  information  to  its  content  pane  and  show  the
dialog.



Dialogs contain a ContentPane just like Form.

When  showing  a  dialog  in  this  way,  you  can  either  ask  Codename  One  to  position  the  dialog  in  a

specific  general  location  (taken  from  the  BorderLayout  [https://www.codenameone.com/javadoc/com/

codename1/ui/layouts/BorderLayout.html]  concept  for  locations)  or  position  it  by  spacing  it  (in  pixels)

from the 4 edges of the screen.

E.g. you could do something like this to show a simple modal Dialog:

196

Dialog d = new Dialog("Title");
d.setLayout(new BorderLayout());
d.add(BorderLayout.CENTER, new SpanLabel("Dialog Body", "DialogBody"));
d.showPacked(BorderLayout.SOUTH, true);

Figure 188. Custom modal Dialog in the south position



You  can  turn  the  code  above  to  a  modless  Dialog  by  flipping  the  boolean  true
argument to false.

We can position a Dialog absolutely by determining the space from the edges e.g. with this code we
can occupy the bottom portion of the screen:

Dialog d = new Dialog("Title");
d.setLayout(new BorderLayout());
d.add(BorderLayout.CENTER, new SpanLabel("Dialog Body", "DialogBody"));
d.show(hi.getHeight() / 2, 0, 0, 0);

Figure 189. Custom Dialog positioned absolutely

 hi is the name of the parent Form in the sample above.

6.3.1. Styling Dialogs

It’s  important  to  style  a  Dialog  using  getDialogStyle()  [https://www.codenameone.com/javadoc/com/
[https://www.codenameone.com/javadoc/com/
codename1/ui/Dialog.html#getDialogStyle--]  or 

setDialogUIID 

197

codename1/ui/Dialog.html#setDialogUIID-java.lang.String-]  methods  rather  than  styling  the  dialog  object

directly.

The reason for this is that the Dialog is really a Form that takes up the whole screen. The Form that is
visible behind the Dialog is rendered as a screenshot. So customizing the actual UIID of the Dialog
won’t produce the desired results.

6.3.2. Tint and Blurring

By default a Dialog uses a platform specific tint color when it is showing e.g. notice the background
in the image below is tinted:

Form hi = new Form("Tint Dialog", new BoxLayout(BoxLayout.Y_AXIS));
Button showDialog = new Button("Tint");
showDialog.addActionListener((e) -> Dialog.show("Tint", "Is On....", "OK", null));
hi.add(showDialog);
hi.show();

Figure 190. Dialog with tinted background

The tint color can be manipulated on the parent form, you can set it to any AARRGGBB value to set
any color using the setTintColor method. Notice that this is invoked on the parent form and not on
the Dialog!

 This is an AARRGGBB value and not an RRGGBB value! This means that 0 will be

transparent.

You can also manipulate this default value globally using the theme constant tintColor. The sample
below tints the background in green:

Form hi = new Form("Tint Dialog", new BoxLayout(BoxLayout.Y_AXIS));
hi.setTintColor(0x7700ff00);
Button showDialog = new Button("Tint");
showDialog.addActionListener((e) -> Dialog.show("Tint", "Is On....", "OK", null));
hi.add(showDialog);
hi.show();

198

Figure 191. Dialog with green tinted background

We can apply Gaussian blur to the background of a dialog to highlight the foreground further and
produce  a  very  attractive  effect.  We  can  use  the  setDefaultBlurBackgroundRadius  to  apply  this
globally, we can use the theme constant dialogBlurRadiusInt to do the same or we can do this on a
per Dialog basis using setBlurBackgroundRadius.



Not  all  device  types  support  blur  you  can  test  if  your  device  supports  it  using
Display.getInstnace().isGaussianBlurSupported().  If  blur  isn’t  supported  the  blur
setting will be ignored.

Form hi = new Form("Blur Dialog", new BoxLayout(BoxLayout.Y_AXIS));
Dialog.setDefaultBlurBackgroundRadius(8);
Button showDialog = new Button("Blur");
showDialog.addActionListener((e) -> Dialog.show("Blur", "Is On....", "OK", null));
hi.add(showDialog);
hi.show();

Figure 192. The blur effect coupled with the OS default tint

It might be a bit hard to notice the blur effect with the tinting so here is the same code with tinting

disabled:

hi.setTintColor(0);

199

Figure 193. The blur effect is more pronounced when the tint is disabled

6.3.3. Popup Dialog

A popup dialog is a common mobile paradigm showing a Dialog that points at a specific component.
It’s just a standard Dialog that is shown in a unique way:

Dialog d = new Dialog("Title");
d.setLayout(new BorderLayout());
d.add(BorderLayout.CENTER, new SpanLabel("Dialog Body", "DialogBody"));
d.showPopupDialog(showDialog);

Figure 194. Popup Dialog

The  popup  dialog  accepts  a  Component  [https://www.codenameone.com/javadoc/com/codename1/ui/

Component.html]  or  Rectangle  [https://www.codenameone.com/javadoc/com/codename1/ui/geom/Rectangle.html]

to point at and handles the rest.

Styling The Arrow Of The Popup Dialog

When  Codename  One  was  young  we  needed  a  popup  arrow  implementation  but  our  low  level

graphics API was pretty basic. As a workaround we created a version of the 9-piece image border

that supported pointing arrows at a component.

Today  Codename  One  supports  pointing  an  arrow  from  the  RoundRectBorder  class.  This  is  implicit
for  the  PopupDialog  UI.  This  allows  for  better  customization  of  the  border  (color  etc.)  and  it  looks
better on newer displays. It also works on all OSs. Right now only the iOS theme has the old image

border approach.

200

 This will change with a future update where all OS’s will align and iOS will use the

lightweight popup too



You  can  make  all  OS’s  act  the  same  way  by  overriding  the  PopupDialog  UIID  and
defining its style to RoundRectBorder

The new RoundRectBorder support works by setting the track component property on border. When
that’s done the border implicitly points to the right location.

If  you  still  need  deeper  customization  of  the  arrow  you  can  still  use  the  old  9-piece  border

functionality illustrated below.

Legacy 9-Piece Border Arrow

One of the harder aspects of a popup dialog is the construction of the theme elements required for

arrow  styling.  To  get  that  sort  of  behavior  you  will  need  a  custom  image  border  and  4  arrows

pointing in each direction that will be overlaid with the border.



The sizes of the arrow images should be similarly proportioned and fit within the

image borders whitespace. The block image of the dialog should have empty pixels

in  the  sides  to  reserve  space  for  the  arrow.  E.g.  if  the  arrows  are  all  32x32  pixels
then the PopupDialog image should have 32 pixels of transparent pixels around it.

You will need to define the following theme constants for the arrow to work:

PopupDialogArrowBool=true
PopupDialogArrowTopImage=arrow up image
PopupDialogArrowBottomImage=arrow down image
PopupDialogArrowLeftImage=arrow left image
PopupDialogArrowRightImage=arrow right image

Then style the PopupDialog UIID with the image for the Dialog itself.

6.4. InteractionDialog

Dialogs in Codename One can be modal or modeless, the former blocks the calling thread and the

latter does not. However, there is another definition to those terms: A modal dialog blocks access to

the rest of the UI while a modeless dialog "floats" on top of the UI.

In  that  sense,  all  dialogs  in  Codename  One  are  modal;  they  block  the  parent  form  since  they  are

effectively 

just 

forms 

that  show 

the  "parent" 

in 

their  background. 

InteractionDialog

[https://www.codenameone.com/javadoc/com/codename1/components/InteractionDialog.html]  has  an  API  that  is

very  similar  to  the  Dialog  [https://www.codenameone.com/javadoc/com/codename1/ui/Dialog.html]  API  but,

unlike dialog, it never blocks anything. Neither the calling thread nor the UI.

201



InteractionDialog  isn’t  a  Dialog  since  it  doesn’t  share  the  same  inheritance
hierarchy. However, it acts and "feels" like a Dialog despite the fact that it’s just a
Container in the LayeredPane.

InteractionDialog  is  really  just  a  container  that  is  positioned  within  the  layered  pane.  Notice  that
because of that design, you can have only one such dialog at the moment and, if you add something

else to the layered pane, you might run into trouble.

Using the interaction dialog is pretty trivial and very similar to dialog:

InteractionDialog dlg = new InteractionDialog("Hello");
dlg.setLayout(new BorderLayout());
dlg.add(BorderLayout.CENTER, new Label("Hello Dialog"));
Button close = new Button("Close");
close.addActionListener((ee) -> dlg.dispose());
dlg.addComponent(BorderLayout.SOUTH, close);
Dimension pre = dlg.getContentPane().getPreferredSize();
dlg.show(0, 0, Display.getInstance().getDisplayWidth() - (pre.getWidth() + pre.getWidth() / 6), 0);

Figure 195. Interaction Dialog

This will show the dialog on the right hand side of the screen, which is pretty useful for a floating in

place dialog.



The  InteractionDialog  can  only  be  shown  at  absolute  or  popup  locations.  This  is
inherent to its use case which is "non-blocking". When using this component you

need to be very aware of its location.

6.5. Label

Label [https://www.codenameone.com/javadoc/com/codename1/ui/Label.html] represents a text, icon or both.
Label is also the base class of Button which in turn is the base class for RadioButton & CheckBox. Thus
the functionality of the Label class extends to all of these components.

Label text can be positioned in one of 4 locations as such:

202

Label left = new Label("Left", icon);
left.setTextPosition(Component.LEFT);
Label right = new Label("Right", icon);
right.setTextPosition(Component.RIGHT);
Label bottom = new Label("Bottom", icon);
bottom.setTextPosition(Component.BOTTOM);
Label top = new Label("Top", icon);
top.setTextPosition(Component.TOP);
hi.add(left).add(right).add(bottom).add(top);

Figure 196. Label positions

Label allows only a single line of text, line breaking is a very expensive operation on mobile devices
[2] and so the Label class doesn’t support it.



SpanLabel  supports  multiple  lines  with  a  single  label,  notice  that  it  does  carry  a

performance penalty for this functionality.

Labels  support  tickering  and  the  ability  to  end  with  “…”  if  there  isn’t  enough  space  to  render  the

label.  Developers  can  determine  the  placement  of  the  label  relatively  to  its  icon  in  quite  a  few

powerful ways.

6.5.1. Label Gap

The  gap  between  the  label  text  &  the  icon  defaults  to  2  pixels  due  to  legacy  settings.  The  setGap
method of Label accepts a gap size in pixels.

Two pixels is low for most cases & it’s hard to customize for each Label.

You  can  use  the  theme  constant  labelGap  which  is  a  floating  point  value  you  can  specify  in
millimeters that will allow you to determine the default gap for a label. You can also customize this
manually using the method Label.setDefaultGap(int) which determines the default gap in pixels.

6.5.2. Autosizing Labels

One of the common requests we received over the years is a way to let text "fit" into the allocated

space  so  the  font  will  match  almost  exactly  the  width  available.  In  some  designs  this  is  very

important  but  it’s  also  very  tricky.  Measuring  the  width  of  a  String  is  a  surprisingly  expensive

203

operation  on  some  OS’s.  Unfortunately,  there  is  no  other  way  other  than  trial  &  error  to  find  the

"best size".

Still despite the fact that something is "slow" we might still want to use it for some cases, this isn’t

something  you  should  use  in  a  renderer,  infinite  scroll  etc.  and  we  recommend  minimizing  the

usage of this feature as much as possible.

This  feature  is  only  applicable  to  Label  and  its  subclasses  (e.g.  Button),  with  components  such  as
TextArea (e.g. SpanButton) the choice between shrinking and line break would require some complex
logic.

To activate this feature just use setAutoSizeMode(true) e.g.:

Form hi = new Form("AutoSize", BoxLayout.y());

Label a = new Label("Short Text");
a.setAutoSizeMode(true);
Label b = new Label("Much Longer Text than the previous line...");
b.setAutoSizeMode(true);
Label c = new Label("MUCH MUCH MUCH Much Longer Text than the previous line by a pretty big margin...");
c.setAutoSizeMode(true);

Label a1 = new Button("Short Text");
a1.setAutoSizeMode(true);
Label b1 = new Button("Much Longer Text than the previous line...");
b1.setAutoSizeMode(true);
Label c1 = new Button("MUCH MUCH MUCH Much Longer Text than the previous line by a pretty big margin...");
c1.setAutoSizeMode(true);
hi.addAll(a, b, c, a1, b1, c1);

hi.show();

Figure 197. Automatically sizes the fonts of the buttons/labels based on text and available space

6.6. TextField and TextArea

The  TextField  [https://www.codenameone.com/javadoc/com/codename1/ui/TextField.html]  class  derives  from

the  TextArea  [https://www.codenameone.com/javadoc/com/codename1/ui/TextArea.html]  class,  and  both  are

used for text input in Codename One.

TextArea defaults to multi-line input and TextField defaults to single line input but both can be used

204

in both cases. The main differences between TextField and TextArea are:

• Blinking cursor is rendered on TextField only

• DataChangeListener 

[https://www.codenameone.com/javadoc/com/codename1/ui/events/
DataChangedListener.html] is only available in TextField. This is crucial for character by character
input event tracking

• Done 

listener  [https://www.codenameone.com/javadoc/com/codename1/ui/TextField.html#setDoneListener-

com.codename1.ui.events.ActionListener-] is only available in the TextField

• Different UIID



The semantic difference between TextField & TextArea dates back to the ancestor
of  Codename  One:  LWUIT.  Feature  phones  don’t  have  “proper”  in-place  editing
capabilities & thus TextField was introduced to allow such input.

Because  it  lacks  the  blinking  cursor  capability  TextArea  is  often  used  as  a  multi-line  label  and  is
used internally in SpanLabel, SpanButton etc.



A  common  use  case  is  to  have  an  important  text  component  in  edit  mode
immediately as we enter a Form. Codename One forms support this exact use case
thru  the  Form.setEditOnShow(TextArea)  [https://www.codenameone.com/javadoc/com/

codename1/ui/Form.html#setEditOnShow-com.codename1.ui.TextArea-] method.

TextField & TextArea support constraints for various types of input such as NUMERIC, EMAIL, URL, etc.
Those usually affect the virtual keyboard used, but might not limit input in some platforms. E.g. on
iOS even with NUMERIC constraint you would still be able to input characters.



If you need to prevent specific types of input check out the validation section.

The following sample shows off simple text field usage:

205

TableLayout tl;
int spanButton = 2;
if(Display.getInstance().isTablet()) {
    tl = new TableLayout(7, 2);
} else {
    tl = new TableLayout(14, 1);
    spanButton = 1;
}
tl.setGrowHorizontally(true);
hi.setLayout(tl);

TextField firstName = new TextField("", "First Name", 20, TextArea.ANY);
TextField surname = new TextField("", "Surname", 20, TextArea.ANY);
TextField email = new TextField("", "E-Mail", 20, TextArea.EMAILADDR);
TextField url = new TextField("", "URL", 20, TextArea.URL);
TextField phone = new TextField("", "Phone", 20, TextArea.PHONENUMBER);

TextField num1 = new TextField("", "1234", 4, TextArea.NUMERIC);
TextField num2 = new TextField("", "1234", 4, TextArea.NUMERIC);
TextField num3 = new TextField("", "1234", 4, TextArea.NUMERIC);
TextField num4 = new TextField("", "1234", 4, TextArea.NUMERIC);

Button submit = new Button("Submit");
TableLayout.Constraint cn = tl.createConstraint();
cn.setHorizontalSpan(spanButton);
cn.setHorizontalAlign(Component.RIGHT);
hi.add("First Name").add(firstName).
        add("Surname").add(surname).
        add("E-Mail").add(email).
        add("URL").add(url).
        add("Phone").add(phone).
        add("Credit Card").
                add(GridLayout.encloseIn(4, num1, num2, num3, num4)).
        add(cn, submit);

Figure 198. Simple text component sample



The  Toolbar  section  contains  a  very  elaborate  TextField  search  sample  with
DataChangeListener and rather unique styling.

206

6.6.1. Masking

A  common  use  case  when  working  with  text  components  is  the  ability  to  "mask"  input  e.g.  in  the

credit card number above we would want 4 digits for each text field and don’t want the user to tap

Next 3 times.

Masking allows us to accept partial input in one field and implicitly move to the next, this can be

used to all types of complex input thanks to the text component API. E.g with the code above we can

mask the credit card input so the cursor jumps to the next field implicitly using this code:

automoveToNext(num1, num2);
automoveToNext(num2, num3);
automoveToNext(num3, num4);

Then implement the method automoveToNext as:

private void automoveToNext(final TextField current, final TextField next) {
    current.addDataChangedListener((type, index) -> {
        if(current.getText().length() == 5) {
            current.stopEditing();
            current.setText(val.substring(0, 4));
            next.setText(val.substring(4));
            next.startEditingAsync();
        }
    });
}

Notice we can invoke stopEditing(Runnable) where we receive a callback as editing is stopped.

6.6.2. The Virtual Keyboard

A  common  misconception  for  developers  is  assuming  the  virtual  keyboard  represents  "keys".  E.g.

developers often override the "keyEvent" callbacks which are invoked for physical keyboard typing

and expect those to occur with a virtual keyboard.

This  isn’t  the  case  since  a  virtual  keyboard  is  a  very  different  beast.  With  a  virtual  keyboard

characters typed might produce a completely different output due to autocorrect. Some keyboards

don’t  even  have  "keys"  in  the  traditional  sense  or  don’t  type  them  in  the  traditional  sense  (e.g.

swiping).





The constraint property for the TextField/TextArea is crucial for a virtual keyboard.

When working with a virtual keyboard it’s important that the parent Container for
the TextField/TextArea is scrollable. Otherwise the component won’t be reachable
or the UI might be distorted when the keyboard appears.

207

Action Button Client Property

By  default,  the  virtual  keyboard  on  Android  has  a  "Done"  button,  you  can  customize  it  to  be  a

search icon, a send icon, or a go icon using a hint such as this:

searchTextField.putClientProperty("searchField", Boolean.TRUE);
sendTextField.putClientProperty("sendButton", Boolean.TRUE);
goTextField.putClientProperty("goButton", Boolean.TRUE);

This will adapt the icon for the action on the keys.

Next and Done on iOS

We try to hide a lot of the platform differences in Codename One, input is very different between

OS’s.  A  common  reliance  is  the  ability  to  send  the  "Done"  event  when  the  user  presses  the  Done

button.  Unfortunately  this  button  doesn’t  always  exist  e.g.  if  there  is  an  Enter  button  (due  to

multiline input) or if there is a Next button in that place.

To make the behavior more uniform we slightly customized the iOS keyboard as such:

Figure 199. Next virtual keyboard with toolbar

Figure 200. Done virtual keyboard without toolbar

 This works with 3rd party keyboards too…

However, this behavior might not be desired so to block that we can do:

tf.putClientProperty("iosHideToolbar", Boolean.TRUE);

This will hide the toolbar for that given field.



You  can  customize  the  color  of  the  Done  button  in  the  toolbar  by  setting  the
ios.doneButtonColor display property. E.g. To change the color to red, you could do
Display.getInstance().setProperty("ios.doneButtonColor",
String.valueOf(0xff0000)). @since 5.0

208

6.6.3. Clearable Text Field

iOS has a convention where an X can be placed after the text field to clear it. Some Android apps

have it but there is no native support for that as of this writing.

You can wrap a TextField with a clearable wrapper to get this effect on all platforms. E.g. replace
this:

cnt.add(myTextField);

With this:

cnt.add(ClearableTextField.wrap(myTextField));

You can also specify the size of the clear icon if you wish. This is technically just a Container with
the text field style and a button to clear the text at the edge.

6.7. TextComponent

When building input forms we sometimes want to adapt to the native OS behavior and create a UI
that’s a bit more distinct to the native OS. TextField and TextArea are very low level, you can create
an Android style UI with such components but it might look out of place in iOS.

E.g. this is how most of us would expect the UI to look on iOS and Android respectively:

Figure 201. Text Input on iOS

Figure 202. Text Input on Android

Doing  this  with  text  fields  is  possible  but  would  require  code  that  looks  a  bit  different  and  jumps
through  hoops.  TextComponent  allows  this  exact  UI  without  forcing  developers  to  write  OS  specific
code:

209

TextModeLayout tl = new TextModeLayout(3, 2);
Form f = new Form("Pixel Perfect", tl);
TextComponent title = new TextComponent().label("Title");
TextComponent price = new TextComponent().label("Price");
TextComponent location = new TextComponent().label("Location");
TextComponent description = new TextComponent().label("Description").multiline(true);

f.add(tl.createConstraint().horizontalSpan(2), title);
f.add(tl.createConstraint().widthPercentage(30), price);
f.add(tl.createConstraint().widthPercentage(70), location);
f.add(tl.createConstraint().horizontalSpan(2), description);
f.setEditOnShow(title.getField());
f.show();



This code uses the TextModeLayout which is discussed in the layouts section

The text component uses a builder approach to set various values e.g.:

TextComponent t = new TextComponent().
    text("This appears in the text field").
    hint("This is the hint").
    label("This is the label").
    multiline(true);

The  code  is  pretty  self  explanatory  and  more  convenient  than  typical  setters/getters.  It

automatically handles the floating hint style of animation when running on Android.

6.7.1. Error Handling

The validator class supports text component and it should "just work". But the cool thing is that it

uses the material design convention for error handling!

So if we add to the sample above a Validator:

Validator val = new Validator();
val.addConstraint(title, new LengthConstraint(2));
val.addConstraint(price, new NumericConstraint(true));

You would see something that looks like this on Android:

210

Figure 203. Error handling when the text is blank

Figure 204. Error handling when there is some input (notice red title label)

Figure 205. On iOS the situation hasn’t changed much yet

The underlying system is the errorMessage method which you can chain like the other methods on
TextComponent as such:

TextComponent tc = new TextComponent().
    label("Input Required").
    errorMessage("Input is essential in this field");

6.7.2. InputComponent and PickerComponent

To keep the code common and generic we use the InputComponent abstract base class and derive the
other classes from that. PickerComponent is currently the only other option.

A picker can work with our existing sample using code like this:

211

TextModeLayout tl = new TextModeLayout(3, 2);
Form f = new Form("Pixel Perfect", tl);
TextComponent title = new TextComponent().label("Title");
TextComponent price = new TextComponent().label("Price");
TextComponent location = new TextComponent().label("Location");
PickerComponent date = PickerComponent.createDate(new Date()).label("Date");
TextComponent description = new TextComponent().label("Description").multiline(true);
Validator val = new Validator();
val.addConstraint(title, new LengthConstraint(2));
val.addConstraint(price, new NumericConstraint(true));
f.add(tl.createConstraint().widthPercentage(60), title);
f.add(tl.createConstraint().widthPercentage(40), date);
f.add(location);
f.add(price);
f.add(tl.createConstraint().horizontalSpan(2), description);
f.setEditOnShow(title.getField());
f.show();

This produces the following which looks pretty standard:

Figure 206. Picker component taking place in iOS

Figure 207. And in Android

The one tiny thing you should notice with the PickerComponent is that we don’t construct the picker
component  using  new  PickerComponent(). 
such  as
PickerComponent.createDate(new Date()). The reason for that is that we have many types of pickers
and it wouldn’t make sense to have one constructor.

Instead  we  use  create  methods 

6.7.3. Underlying Theme Constants and UIID’s

These varying looks are implemented via a combination of layouts, theme constants and UIID’s. The
most important UIID’s are: TextComponent, FloatingHint & TextHint.

212

There are several theme constants related that can manipulate some pieces of this functionality:

• textComponentErrorColor a hex RGB color which defaults to null in which case this has no effect.
When defined this will change the color of the border and label to the given color to match the

material  design  styling.  This  implements  the  red  border  underline  in  cases  of  error  and  the

label text color change

• textComponentOnTopBool  toggles  the  on  top  mode  which  makes  things  look  like  they  do  on
Android. This defaults to true on Android and false on other OS’s. This can also be manipulated
via the onTopMode(boolean) method in InputComponent however the layout will only use the theme
constant

• textComponentAnimBool  toggles  the  animation  mode  which  again  can  be  manipulated  by  a
method  in  InputComponent.  If  you  want  to  keep  the  UI  static  without  the  floating  hint  effect  set
this to false. Notice this defaults to true only on Android

• textComponentFieldUIID  sets  the  UIID  of  the  text  field  to  something  other  than  TextField  this  is
useful  for  platforms  such  as  iOS  where  the  look  of  the  text  field  is  different  within  the  text

component. This allows us to make the background of the text field transparent when it’s within
the TextComponent and make it different from the regular text field

6.8. Button

Button [https://www.codenameone.com/javadoc/com/codename1/ui/Button.html] is a subclass of Label and as a
result it inherits all of its functionality, specifically icon placement, tickering, etc.

Button adds to the mix some additional states such as a pressed UIID state and pressed icon.

 There are additional icon states in Button such as rollover and disabled icon.

Button also exposes some functionality for subclasses specifically the setToggle method call which
has no meaning when invoked on a Button but has a lot of implications for CheckBox & RadioButton.

Button  event  handling  can  be  performed  via  an  ActionListener  [https://www.codenameone.com/javadoc/
com/codename1/ui/events/ActionListener.html] or via a Command [https://www.codenameone.com/javadoc/com/

codename1/ui/Command.html].

 Changes in a Command won’t be reflected into the Button after the command was set

to the Button.

Here is a trivial hello world style Button:

Form hi = new Form("Button");
Button b = new Button("My Button");
hi.add(b);
b.addActionListener((e) -> Log.p("Clicked"));

213

Figure 208. Simple button in the iOS styling, notice iOS doesn’t have borders on buttons…

Such a button can be styled to look like a link using code like this or simply by making these settings
in the theme and using code such as btn.setUIID("Hyperlink").

Form hi = new Form("Button");
Button b = new Button("Link Button");
b.getAllStyles().setBorder(Border.createEmpty());
b.getAllStyles().setTextDecoration(Style.TEXT_DECORATION_UNDERLINE);
hi.add(b);
b.addActionListener((e) -> Log.p("Clicked"));

Figure 209. Button styled to look like a link

6.8.1. Uppercase Buttons

Buttons on Android’s material design UI use upper case styling which isn’t the case for iOS. To solve
this  we  have  the  method  setCapsText(boolean)  in  Button  which  has  the  corresponding  isCapsText,
isCapsTextDefault & setCapsTextDefault(boolean). This is pretty core to Codename One so to prevent
this from impacting everything unless you explicitly invoke setCapsText(boolean) the default value
of true will only apply when the UIID is Button, RaisedButton or for the builtin Dialog buttons.

We also have a theme constant: capsButtonTextBool. This constant controls caps text behavior from
the theme and is set to true in the Android native theme.

6.8.2. Raised Button

Raised  button  is  a  style  of  button  that’s  available  on  Android  and  used  to  highlight  an  important

action within a form. To confirm with the material design UI guidelines you might want to leverage

a raised button UI element on Android but use a regular button everywhere else.

First we need to know whether a raised button exists in the theme. So on Android this will return

true but on other OS’s it will return false. A potential future update might make another platform

true based on UI guidelines in other OS’s.

For  this  purpose  we’ve  got  the  theme  constant  hasRaisedButtonBool  which  will  return  true  on
Android but will be false elsewhere. You can use it like this:

214

if(UIManager.getInstance().isThemeConstant("hasRaisedButtonBool", false)) {
    // that means we can use a raised button
}

To enable this we have the RaisedButton UIID that derives from Button and will act like it except for
the places where hasRaisedButtonBool is true in which case it will look like this:

Figure 210. Raised and flat button in simulator

Notice that you can easily customize the colors of these buttons now since the border respects user

colors…

In this case I just set the background color to purple and the foreground to white:

Figure 211. Purple raised button

Form f = new Form("Pixel Perfect", BoxLayout.y());
Button b = new Button("Raised Button", "RaisedButton");
Button r = new Button("Flat Button");
f.add(b);
f.add(r);
f.show();

6.8.3. Ripple Effect

The  ripple  effect  in  material  design  highlights  the  location  of  the  finger  and  grows  as  a  circle  to

occupy the full area of the component as the user presses the button.

We have the ability to perform a ripple effect by darkening the touched area and growing that in a

quick animation.

Ripple effect can be applied to any component but we currently only have it turned on for buttons

on Android which also applies to things like title commands, side menu elements etc. This might not

apply at this moment to lead components like multi-buttons but that might change in the future.

Component has a property to enable the ripple effect setRippleEffect(boolean) and the corresponding
isRippleEffect(). You can turn it on or off individually in the component level. However, Button has
static setButtonRippleEffectDefault(boolean) and isButtonRippleEffectDefault(). These allow us to
define the default behavior for all the buttons and that can be configured via the theme constant
buttonRippleBool which is currently on by default on the native Android theme.

215

6.9. CheckBox/RadioButton

CheckBox 

[https://www.codenameone.com/javadoc/com/codename1/ui/CheckBox.html]  & 

RadioButton

[https://www.codenameone.com/javadoc/com/codename1/ui/RadioButton.html]  are  subclasses  of  button  that

allow for either a toggle state or exclusive selection state.

Both CheckBox & RadioButton have a selected state that allows us to determine their selection.



RadioButton  doesn’t  allow  us  to  "deselect"  it,  the  only  way  to  "deselect"  a
RadioButton is by selecting another RadioButton.

The  CheckBox  can  be  added  to  a  Container  like  any  other  Component  but  the  RadioButton  must  be
associated with a ButtonGroup otherwise if we have more than one set of RadioButton’s in the form
we might have an issue.

Notice  in  the  sample  below  that  we  associate  all  the  radio  buttons  with  a  group  but  don’t  do

anything  with  the  group  as  the  radio  buttons  keep  the  reference  internally.  We  also  show  the

opposite side functionality and icon behavior:

CheckBox cb1 = new CheckBox("CheckBox No Icon");
cb1.setSelected(true);
CheckBox cb2 = new CheckBox("CheckBox With Icon", icon);
CheckBox cb3 = new CheckBox("CheckBox Opposite True", icon);
CheckBox cb4 = new CheckBox("CheckBox Opposite False", icon);
cb3.setOppositeSide(true);
cb4.setOppositeSide(false);
RadioButton rb1 = new RadioButton("Radio 1");
RadioButton rb2 = new RadioButton("Radio 2");
RadioButton rb3 = new RadioButton("Radio 3", icon);
new ButtonGroup(rb1, rb2, rb3);
rb2.setSelected(true);
hi.add(cb1).add(cb2).add(cb3).add(cb4).add(rb1).add(rb2).add(rb3);

Figure 212. RadioButton & CheckBox usage

Both of these components can be displayed as toggle buttons (see the toggle button section below),

or just use the default check mark/filled circle appearance based on the type/OS.

216

6.9.1. Toggle Button

A toggle button is a button that is pressed and stays pressed. When a toggle button is pressed again

it’s released from the pressed state. Hence the button has a selected state to indicate if it’s pressed
or not exactly like the CheckBox/RadioButton components in Codename One.

To  turn  any  CheckBox  or  RadioButton  to  a  toggle  button  just  use  the  setToggle(true)  method.
Alternatively you can use the static createToggle method on both CheckBox and RadioButton to create
a toggle button directly.

 Invoking setToggle(true) implicitly converts the UIID to ToggleButton unless it was

changed by the user from its original default value.

We can easily convert the sample above to use toggle buttons as such:

CheckBox cb1 = CheckBox.createToggle("CheckBox No Icon");
cb1.setSelected(true);
CheckBox cb2 = CheckBox.createToggle("CheckBox With Icon", icon);
CheckBox cb3 = CheckBox.createToggle("CheckBox Opposite True", icon);
CheckBox cb4 = CheckBox.createToggle("CheckBox Opposite False", icon);
cb3.setOppositeSide(true);
cb4.setOppositeSide(false);
ButtonGroup bg = new ButtonGroup();
RadioButton rb1 = RadioButton.createToggle("Radio 1", bg);
RadioButton rb2 = RadioButton.createToggle("Radio 2", bg);
RadioButton rb3 = RadioButton.createToggle("Radio 3", icon, bg);
rb2.setSelected(true);
hi.add(cb1).add(cb2).add(cb3).add(cb4).add(rb1).add(rb2).add(rb3);

Figure 213. Toggle button converted sample

That’s  half  the  story  though,  to  get  the  full  effect  of  some  cool  toggle  button  UI’s  we  can  use  a

ComponentGroup 

[https://www.codenameone.com/javadoc/com/codename1/ui/ComponentGroup.html].  This

allows us to create a button bar effect with the toggle buttons.

E.g.  lets  enclose  the  CheckBox  components  in  a  vertical  ComponentGroup  and  the  RadioButton’s  in  a
horizontal group. We can do this by changing the last line of the code above as such:

217

hi.add(ComponentGroup.enclose(cb1, cb2, cb3, cb4)).
        add(ComponentGroup.encloseHorizontal(rb1, rb2, rb3));

Figure 214. Toggle button converted sample wrapped in ComponentGroup

6.10. ComponentGroup

ComponentGroup 

[https://www.codenameone.com/javadoc/com/codename1/ui/ComponentGroup.html] 

is  a

special  container  that  can  be  either  horizontal  or  vertical  (BoxLayout  [https://www.codenameone.com/
javadoc/com/codename1/ui/layouts/BoxLayout.html] X_AXIS or Y_AXIS respectively).

ComponentGroup  "restyles"  the  elements  within  the  group  to  have  a  UIID  that  allows  us  to  create  a
"round border" effect that groups elements together.

The  following  code  adds  4  component  groups  to  a  Container  to  demonstrate  the  various  UIID
changes:

hi.add("Three Labels").
        add(ComponentGroup.enclose(new Label("GroupElementFirst UIID"), new Label("GroupElement UIID"), new
Label("GroupElementLast UIID"))).
        add("One Label").
        add(ComponentGroup.enclose(new Label("GroupElementOnly UIID"))).
        add("Three Buttons").
        add(ComponentGroup.enclose(new Button("ButtonGroupFirst UIID"), new Button("ButtonGroup UIID"), new
Button("ButtonGroupLast UIID"))).
        add("One Button").
        add(ComponentGroup.enclose(new Button("ButtonGroupOnly UIID")));

218

Figure 215. ComponentGroup adapts the UIID’s of the components added so we can style them

Notice the following about the code above and the resulting image:

• Buttons have a different UIID than other element types. Their styling is slightly different in such

UI’s so you need to pay attention to that.

• When an element is placed alone within a ComponentGroup its a special case UIID.



By  default,  ComponentGroup  does  nothing.  You  need  to  explicitly  activate  it  in  the
theme  by  setting  a  theme  property  to  true.  Specifically  you  need  to  set
ComponentGroupBool to true for ComponentGroup to do something otherwise its just a
box  layout  container!  The  ComponentGroupBool  flag  is  true  by  default  in  the  iOS
native theme.

When  ComponentGroupBool  is  set  to  true,  the  component  group  will  modify  the  styles  of  all
components placed within it to match the element UIID given to it (GroupElement by default) with

special caveats to the first/last/only elements. E.g.

1. If I have one element within a component group it will have the UIID: GroupElementOnly

2. If  I  have  two  elements  within  a  component  group  they  will  have  the  UIID’s  GroupElementFirst,

GroupElementLast

3. If I have three elements within a component group they will have the UIID’s GroupElementFirst,

GroupElement, GroupElementLast

4. If I have four elements within a component group they will have the UIID’s GroupElementFirst,

GroupElement, GroupElement, GroupElementLast

This allows you to define special styles for the edges.

You can customize the UIID set by the component group by calling setElementUIID in the component
group e.g. setElementUIID("ToggleButton") for three elements result in the following UIID’s:

ToggleButtonFirst, ToggleButton, ToggleButtonLast

6.11. MultiButton

MultiButton 

[https://www.codenameone.com/javadoc/com/codename1/components/MultiButton.html] 

is 

a

219

composite 

component 

(lead 

component) 

that 

acts 

like 

a 

versatile 

Button

[https://www.codenameone.com/javadoc/com/codename1/ui/Button.html].  It  supports  up  to  4  lines  of  text  (it

doesn’t automatically wrap the text), an emblem (usually navigational arrow, or check box) and an

icon.

MultiButton can be used as a button, a CheckBox or a RadioButton for creating rich UI’s.

 The MultiButton was inspired by the aesthetics of the UITableView iOS component.

A  common  source  of  confusion  in  the  MultiButton  is  the  difference  between  the  icon  and  the
emblem,  since  both  may  have  an  icon  image  associated  with  them.  The  icon  is  an  image

representing the entry while the emblem is an optional visual representation of the action that will

be  undertaken  when  the  element  is  pressed.  Both  may  be  used  simultaneously  or  individually  of

one another.

MultiButton twoLinesNoIcon = new MultiButton("MultiButton");
twoLinesNoIcon.setTextLine2("Line 2");
MultiButton oneLineIconEmblem = new MultiButton("Icon + Emblem");
oneLineIconEmblem.setIcon(icon);
oneLineIconEmblem.setEmblem(emblem);
MultiButton twoLinesIconEmblem = new MultiButton("Icon + Emblem");
twoLinesIconEmblem.setIcon(icon);
twoLinesIconEmblem.setEmblem(emblem);
twoLinesIconEmblem.setTextLine2("Line 2");

MultiButton twoLinesIconEmblemHorizontal = new MultiButton("Icon + Emblem");
twoLinesIconEmblemHorizontal.setIcon(icon);
twoLinesIconEmblemHorizontal.setEmblem(emblem);
twoLinesIconEmblemHorizontal.setTextLine2("Line 2 Horizontal");
twoLinesIconEmblemHorizontal.setHorizontalLayout(true);

MultiButton twoLinesIconCheckBox = new MultiButton("CheckBox");
twoLinesIconCheckBox.setIcon(icon);
twoLinesIconCheckBox.setCheckBox(true);
twoLinesIconCheckBox.setTextLine2("Line 2");

MultiButton fourLinesIcon = new MultiButton("With Icon");
fourLinesIcon.setIcon(icon);
fourLinesIcon.setTextLine2("Line 2");
fourLinesIcon.setTextLine3("Line 3");
fourLinesIcon.setTextLine4("Line 4");

hi.add(oneLineIconEmblem).
        add(twoLinesNoIcon).
        add(twoLinesIconEmblem).
        add(twoLinesIconEmblemHorizontal).
        add(twoLinesIconCheckBox).
        add(fourLinesIcon);

220

Figure 216. Multiple usage scenarios for the MultiButton

6.11.1. Styling The MultiButton

Since the MultiButton is a composite component setting its UIID will only impact the top level UI.

To  customize  everything  you  need  to  customize  the  UIID’s  for  MultiLine1,  MultiLine2,  MultiLine3,
MultiLine4 & Emblem.

You  can  customize  the  individual  UIID’s  thru  the  API  directly  using  the  setIconUIID,  setUIIDLine1,
setUIIDLine2, setUIIDLine3, setUIIDLine4 & setEmblemUIID.

6.12. SpanButton

[https://www.codenameone.com/javadoc/com/codename1/components/SpanButton.html] 

SpanButton 
a
composite component (lead component) that looks/acts like a Button but can break lines rather than
crop them when the text is very long.

is 

Unlike the MultiButton it uses the TextArea internally to break lines seamlessly. The SpanButton is far
simpler than the MultiButton and as a result isn’t as configurable.

SpanButton sb = new SpanButton("SpanButton is a composite component (lead component) that looks/acts like a Button but
can break lines rather than crop them when the text is very long.");
sb.setIcon(icon);
hi.add(sb);

Figure 217. The SpanButton Component



SpanButton  is  slower  than  both  Button  and  MultiButton.  We  recommend  using  it
only when there is a genuine need for its functionality.

6.13. SpanLabel

SpanLabel 

[https://www.codenameone.com/javadoc/com/codename1/components/SpanLabel.html] 

is 

a

composite  component  (lead  component)  that  looks/acts  like  a  Label  [https://www.codenameone.com/

221

javadoc/com/codename1/ui/Label.html] but can break lines rather than crop them when the text is very

long.

SpanLabel  uses  the  TextArea  internally  to  break  lines  seamlessly  and  so  doesn’t  provide  all  the
elaborate configuration options of Label.

One of the features of label that moved into SpanLabel to some extent is the ability to position the
icon.  However,  unlike  a  Label  the  icon  position  is  determined  by  the  layout  manager  of  the
composite so setIconPosition accepts a BorderLayout constraint.

SpanLabel d = new SpanLabel("Default SpanLabel that can seamlessly line break when the text is really long.");
d.setIcon(icon);
SpanLabel l = new SpanLabel("NORTH Positioned Icon SpanLabel that can seamlessly line break when the text is really
long.");
l.setIcon(icon);
l.setIconPosition(BorderLayout.NORTH);
SpanLabel r = new SpanLabel("SOUTH Positioned Icon SpanLabel that can seamlessly line break when the text is really
long.");
r.setIcon(icon);
r.setIconPosition(BorderLayout.SOUTH);
SpanLabel c = new SpanLabel("EAST Positioned Icon SpanLabel that can seamlessly line break when the text is really
long.");
c.setIcon(icon);
c.setIconPosition(BorderLayout.EAST);
hi.add(d).add(l).add(r).add(c);

Figure 218. The SpanLabel Component



SpanLabel  is  significantly  slower  than  Label.  We  recommend  using  it  only  when
there is a genuine need for its functionality.

6.14. OnOffSwitch

The  OnOffSwitch 

[https://www.codenameone.com/javadoc/com/codename1/components/OnOffSwitch.html]

allows you to write an application where the user can swipe a switch between two states (on/off).

This  is  a  common  UI  paradigm  in  Android  and  iOS,  although  it’s  implemented  in  a  radically

different way in both platforms.

This is a rather elaborate component because of its very unique design on iOS, but we we’re able to

accommodate  most  of  the  small  behaviors  of  the  component  into  our  version,  and  it  seamlessly

adapts between the Android style and the iOS style.

222

The image below was generated based on the default use of the OnOffSwitch:

OnOffSwitch onOff = new OnOffSwitch();
hi.add(onOff);

Figure 219. The OnOffSwitch component as it appears on/off on iOS (top) and on Android (bottom)

As you can understand the difference between the way iOS and Android render this component has

triggered  two  very  different 

implementations  within  a  single  component.  The  Android

implementation just uses standard buttons and is the default for non-iOS platforms.



You  can  force  the  Android  or  iOS  mode  by  using  the  theme  constant
onOffIOSModeBool.

6.14.1. Validation

Validation  is  an  inherent  part  of  text  input,  and  the  Validator  [https://www.codenameone.com/javadoc/

com/codename1/ui/validation/Validator.html]  class  allows  just  that.  You  can  enable  validation  thru  the
Validator class to add constraints for a specific component. It’s also possible to define components
that  would  be  enabled/disabled  based  on  validation  state  and  the  way  in  which  validation  errors
are  rendered  (change  the  components  UIID,  paint  an  emblem  on  top,  etc.).  A  Constraint
interface  that
[https://www.codenameone.com/javadoc/com/codename1/ui/validation/Constraint.html] 

is  an 

represents validation requirements. You can define a constraint in Java or use some of the builtin

constraints  such  as  LengthConstraint  [https://www.codenameone.com/javadoc/com/codename1/ui/validation/

LengthConstraint.html],  RegexConstraint  [https://www.codenameone.com/javadoc/com/codename1/ui/validation/

RegexConstraint.html], etc.

This sample below continues from the place where the TextField sample above stopped by adding

validation to that code.

223

Validator v = new Validator();
v.addConstraint(firstName, new LengthConstraint(2)).
        addConstraint(surname, new LengthConstraint(2)).
        addConstraint(url, RegexConstraint.validURL()).
        addConstraint(email, RegexConstraint.validEmail()).
        addConstraint(phone, new RegexConstraint(phoneRegex, "Must be valid phone number")).
        addConstraint(num1, new LengthConstraint(4)).
        addConstraint(num2, new LengthConstraint(4)).
        addConstraint(num3, new LengthConstraint(4)).
        addConstraint(num4, new LengthConstraint(4));

v.addSubmitButtons(submit);

Figure 220. Validation & Regular Expressions

6.15. InfiniteProgress

The 

InfiniteProgress 

[https://www.codenameone.com/javadoc/com/codename1/components/

InfiniteProgress.html] indicator spins an image infinitely to indicate that a background process is still

working.



This style of animation is often nicknamed "washing machine" as it spins endlessly.

InfiniteProgress  can  be  used  in  one  of  two  ways  either  by  embedding  the  component  into  the  UI
thru something like this:

myContainer.add(new InfiniteProgress());

InfiniteProgress  can  also  appear  over  the  entire  screen,  thus  blocking  all  input.  This  tints  the
background while the infinite progress rotates:

Dialog ip = new InfiniteProgress().showInifiniteBlocking();

// do some long operation here using invokeAndBlock or do something in a separate thread and callback later
// when you are done just call

ip.dispose();

224

Figure 221. Infinite progress

The image used in the InfiniteProgress animation is defined by the native theme. You can override
that definition either by defining the theme constant infiniteImage or by invoking the setAnimation
[https://www.codenameone.com/javadoc/com/codename1/components/InfiniteProgress.html#setAnimation-

com.codename1.ui.Image-] method.

 Despite  the  name  of  the  method  setAnimation  expects  a  static  image  that  will  be

rotated internally. Don’t use an animated image.

6.16. InfiniteScrollAdapter and InfiniteContainer

InfiniteScrollAdapter 

[https://www.codenameone.com/javadoc/com/codename1/components/

InfiniteScrollAdapter.html]  &  InfiniteContainer  [https://www.codenameone.com/javadoc/com/codename1/ui/
InfiniteContainer.html] allow us to create a scrolling effect that "never" ends with the typical Container
/Component paradigm.

The  motivation  behind  these  classes  is  simple,  say  we  have  a  lot  of  data  to  fetch  from  storage  or

from the internet. We can fetch the data in batches and show progress indication while we do this.

Infinite  scroll  fetches  the  next  batch  of  data  dynamically  as  we  reach  the  end  of  the  Container.
InfiniteScrollAdapter  &  InfiniteContainer  represent  two  similar  ways  to  accomplish  that  task
relatively easily.

Let start by exploring how we can achieve this UI that fetches data from a webservice:

Figure 222. InfiniteScrollAdapter demo code fetching property cross data

The first step is creating the webservice call, we won’t go into too much detail here as webservices

& IO are discussed later in the guide:

225

int pageNumber = 1;
java.util.List<Map<String, Object>> fetchPropertyData(String text) {
    try {
        ConnectionRequest r = new ConnectionRequest();
        r.setPost(false);
        r.setUrl("http://api.nestoria.co.uk/api");
        r.addArgument("pretty", "0");
        r.addArgument("action", "search_listings");
        r.addArgument("encoding", "json");
        r.addArgument("listing_type", "buy");
        r.addArgument("page", "" + pageNumber);
        pageNumber++;
        r.addArgument("country", "uk");
        r.addArgument("place_name", text);
        NetworkManager.getInstance().addToQueueAndWait(r);
        Map<String,Object> result = new JSONParser().parseJSON(new InputStreamReader(new
ByteArrayInputStream(r.getResponseData()), "UTF-8"));
        Map<String, Object> response = (Map<String, Object>)result.get("response");
        return (java.util.List<Map<String, Object>>)response.get("listings");
    } catch(Exception err) {
        Log.e(err);
        return null;
    }
}



The demo code here doesn’t do any error handling! This is a very bad practice and

it is taken here to keep the code short and readable. Proper error handling is used

in the Property Cross demo.

The  fetchPropertyData  is  a  very  simplistic  tool  that  just  fetches  the  next  page  of  listings  for  the
nestoria  webservice.  Notice  that  this  method  is  synchronous  and  will  block  the  calling  thread

(legally) until the network operation completes.

Now that we have a webservice lets proceed to create the UI. Check out the code annotations below:

226

Form hi = new Form("InfiniteScrollAdapter", new BoxLayout(BoxLayout.Y_AXIS));

Style s = UIManager.getInstance().getComponentStyle("MultiLine1");
FontImage p = FontImage.createMaterial(FontImage.MATERIAL_PORTRAIT, s);
EncodedImage placeholder = EncodedImage.createFromImage(p.scaled(p.getWidth() * 3, p.getHeight() * 3), false); ①

InfiniteScrollAdapter.createInfiniteScroll(hi.getContentPane(), () -> { ②
    java.util.List<Map<String, Object>> data = fetchPropertyData("Leeds"); ③
    MultiButton[] cmps = new MultiButton[data.size()];
    for(int iter = 0 ; iter < cmps.length ; iter++) {
        Map<String, Object> currentListing = data.get(iter);
        if(currentListing == null) { ④
            InfiniteScrollAdapter.addMoreComponents(hi.getContentPane(), new Component[0], false);
            return;
        }
        String thumb_url = (String)currentListing.get("thumb_url");
        String guid = (String)currentListing.get("guid");
        String summary = (String)currentListing.get("summary");
        cmps[iter] = new MultiButton(summary);
        cmps[iter].setIcon(URLImage.createToStorage(placeholder, guid, thumb_url));
    }
    InfiniteScrollAdapter.addMoreComponents(hi.getContentPane(), cmps, true); ⑤
}, true); ⑥

① Placeholder  is  essential  for  the  URLImage  [https://www.codenameone.com/javadoc/com/codename1/ui/

URLImage.html] class which we will discuss at a different place.

② The InfiniteScrollAdapter accepts a runnable which is invoked every time we reach the edge of

the scrolling. We used a closure instead of the typical run() method override.

③ This is a blocking call, after the method completes we’ll have all the data we need. Notice that

this method doesn’t block the EDT illegally.

④ If  there  is  no  more  data  we  call  the  addMoreComponents  method  with  a  false  argument.  This

indicates that there is no additional data to fetch.

⑤ Here we add the actual components to the end of the form. Notice that we must not invoke the
add/remove method of Container. Those might conflict with the work of the InfiniteScrollAdapter.

⑥ We  pass  true  to  indicate  that  the  data  isn’t  "prefilled"  so  the  method  should  be  invoked

immediately when the Form is first shown

 Do not violate the EDT in the callback. It is invoked on the event dispatch thread

and it is crucial

6.16.1. The InfiniteContainer

InfiniteContainer 
[https://www.codenameone.com/javadoc/com/codename1/ui/InfiniteContainer.html]  was
introduced to simplify and remove some of the boilerplate of the InfiniteScrollAdapter. It takes a
more traditional approach of inheriting the Container class to provide its functionality.

Unlike the InfiniteScrollAdapter the InfiniteContainer accepts an index and amount to fetch. This
is useful for tracking your position but also important since the InfiniteContainer also implements
Pull To Refresh as part of its functionality.

Converting the code above to an InfiniteContainer is pretty simple we just moved all the code into

227

the callback fetchComponents method and returned the array of Component’s as a response.

Unlike  the  InfiniteScrollAdapter  we  can’t  use  the  ContentPane  directly  so  we  have  to  use  a
BorderLayout and place the InfiniteContainer there:

Form hi = new Form("InfiniteContainer", new BorderLayout());

Style s = UIManager.getInstance().getComponentStyle("MultiLine1");
FontImage p = FontImage.createMaterial(FontImage.MATERIAL_PORTRAIT, s);
EncodedImage placeholder = EncodedImage.createFromImage(p.scaled(p.getWidth() * 3, p.getHeight() * 3), false);

InfiniteContainer ic = new InfiniteContainer() {
    @Override
    public Component[] fetchComponents(int index, int amount) {
        java.util.List<Map<String, Object>> data = fetchPropertyData("Leeds");
        MultiButton[] cmps = new MultiButton[data.size()];
        for(int iter = 0 ; iter < cmps.length ; iter++) {
            Map<String, Object> currentListing = data.get(iter);
            if(currentListing == null) {
                return null;
            }
            String thumb_url = (String)currentListing.get("thumb_url");
            String guid = (String)currentListing.get("guid");
            String summary = (String)currentListing.get("summary");
            cmps[iter] = new MultiButton(summary);
            cmps[iter].setIcon(URLImage.createToStorage(placeholder, guid, thumb_url));
        }
        return cmps;
    }
};
hi.add(BorderLayout.CENTER, ic);

6.17. List, MultiList, Renderers & Models

6.17.1. InfiniteContainer/InfiniteScrollAdapter vs. List/ContainerList

Our recommendation is to always go with Container, InfiniteContainer or InfiniteScrollAdapter.

We  recommend  avoiding  List  or  its  subclasses/related  classes  specifically  ContainerList  &
MultiList.

 We  recommend  replacing  ComboBox  with  Picker  but  that’s  a  completely  different

discussion.

A  Container  with  ~5000  nested  containers  within  it  can  perform  on  par  with  a  List  and  probably
exceed its performance when used correctly.

Larger sets of data are rarely manageable on phones or tablets so the benefits for lists are dubious.

In terms of API we found that even experienced developers experienced a great deal of pain when

wrangling the Swing styled lists and their stateless approach.

Since  animation,  swiping  and  other  capabilities  that  are  so  common  in  mobile  are  so  hard  to

228

accomplish with lists we see no actual reason to use them.

6.17.2. Why Isn’t List Deprecated?

We  deprecated  ContainerList  which  performs  really  badly  and  has  some  inherent  complexity
issues. List has some unique use cases and is still used all over Codename One.

MultiList is a reasonable version of List that is far easier to use without most of the pains related to
renderer configuration.

There are cases where using List or MultiList is justified, they are just rarer than usual hence our
recommendation.

6.17.3. MVC In Lists

A  Codename  One  List  [https://www.codenameone.com/javadoc/com/codename1/ui/List.html]  doesn’t  contain

components, but rather arbitrary data; this seems odd at first but makes sense. If you want a list to

contain components, just use a Container.

The  advantage  of  using  a  List  in  this  way  is  that  we  can  display  it  in  many  ways  (e.g.  fixed  focus
positions, horizontally, etc.), and that we can have more than a million entries without performance

overhead.  We  can  also  do  some  pretty  nifty  things,  like  filtering  the  list  on  the  fly  or  fetching  it

dynamically from the Internet as the user scrolls down the list. To achieve these things the list uses

two  interfaces:  ListModel  [https://www.codenameone.com/javadoc/com/codename1/ui/list/ListModel.html]  and

ListCellRenderer. 

List 

[https://www.codenameone.com/javadoc/com/codename1/ui/List.html]  model

represents  the  data;  its  responsibility  is  to  return  the  arbitrary  object  within  the  list  at  a  given

offset. Its second responsibility is to notify the list when the data changes, so the list can refresh.



Think of the model as an array of objects that can notify you when it changes.

The  list  renderer  is  like  a  rubber  stamp  that  knows  how  to  draw  an  object  from  the  model,  it’s

called many times per entry in an animated list and must be very fast. Unlike standard Codename

One components, it is only used to draw the entry in the model and is immediately discarded, hence

it  has  no  memory  overhead,  but  if  it  takes  too  long  to  process  a  model  value  it  can  be  a  big

bottleneck!



Think of the render as a translation layer that takes the "data" from the model and

translates it to a visual representation.

This  is  all  very  generic,  but  a  bit  too  much  for  most,  doing  a  list  "properly"  requires  some

understanding. The main source of confusion for developers is the stateless nature of the list and

the transfer of state to the model (e.g. a checkbox list needs to listen to action events on the list and

update  the  model,  in  order  for  the  renderer  to  display  that  state).  Once  you  understand  that  it’s

easy.

6.17.4. Understanding MVC

Let’s recap, what is MVC:

229

• Model  -  Represents  the  data  for  the  component  (list),  the  model  can  tell  us  exactly  how  many

items  are  in  it  and  which  item  resides  at  a  given  offset  within  the  model.  This  differs  from  a
simple Vector (or array), since all access to the model is controlled (the interface is simpler), and
unlike a Vector/Array, the model can notify us of changes that occur within it.

• View - The view draws the content of the model. It is a "dumb" layer that has no notion of what

is  displayed  and  only  knows  how  to  draw.  It  tracks  changes  in  the  model  (the  model  sends

events) and redraws itself when it changes.

• Controller - The controller accepts user input and performs changes to the model, which in turn

cause the view to refresh.

Figure 223. Typical MVC Diagram [3]

Codename  One’s  List  [https://www.codenameone.com/javadoc/com/codename1/ui/List.html]  component  uses
the MVC paradigm in its implementation. List itself is the  Controller (with a bit of the  View mixed
in). The ListCellRenderer [https://www.codenameone.com/javadoc/com/codename1/ui/list/ListCellRenderer.html]

interface is the rest of the View and the ListModel [https://www.codenameone.com/javadoc/com/codename1/

ui/list/ListModel.html] is (you guessed it by now) the Model.

When the list is painted, it iterates over the visible elements in the model and asks the model for

the data, it then draws them using the renderer. Notice that because of this both the model and the

renderer must be REALLY fast and that’s hard.

Why is this useful?

Since the model is a lightweight interface, it can be implemented by you and replaced in runtime if

so desired, this allows several use cases:

1. A  list  can  contain  thousands  of  entries  but  only  load  the  portion  visible  to  the  user.  Since  the

model will only be queried for the elements that are visible to the user, it won’t need to load the

large data set into memory until the user starts scrolling down (at which point other elements

may be offloaded from memory).

2. A  list  can  cache  efficiently.  E.g.  a  list  can  mirror  data  from  the  server  into  local  RAM  without

actually  downloading  all  the  data.  Data  can  also  be  mirrored  from  storage  for  better

performance and discarded for better memory utilization.

3. The  is  no  need  for  state  copying.  Since  renderers  allow  us  to  display  any  object  type,  the  list

model 

interface  can  be 

implemented  by 

the  application’s  data 

structures 

(e.g.

persistence/network  engine),  which  would  return  internal  application  data  structures  saving

you  the  need  of  copying  application  state  into  a  list  specific  data  structure.  Note  that  this

230

advantage only applies with a custom renderer which is pretty difficult to get right.

4. Using  the  proxy  pattern  we  can  layer  logic  such  as  filtering,  sorting,  caching,  etc.  on  top  of

existing models without changing the model source code.

5. We  can  reuse  generic  models  for  several  views,  e.g.  a  model  that  fetches  data  from  the  server

can  be  initialized  with  different  arguments,  to  fetch  different  data  for  different  views.  View

objects in different Forms can display the same model instance in different view instances, thus

they would update automatically when we change one global model.

Most  of  these  use  cases  work  best  for  lists  that  grow  to  a  larger  size,  or  represent  complex  data,

which is what the list object is designed to do.

6.17.5. Important - Lists & Layout Managers

Usually when working with lists, you want the list to handle the scrolling (otherwise it will perform

badly).  This  means  you  should  place  the  list  in  a  non-scrollable  container  (no  parent  can  be

scrollable), notice that the content pane is scrollable by default, so you should disable that.

It 

is  also  recommended  to  place  the 

list 

in  the  CENTER 

location  of  a  BorderLayout

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/BorderLayout.html]  to  produce  the  most

effective results. e.g.:

form.setScrollable(false);
form.setLayout(new BorderLayout());
form.add(BorderLayout.CENTER, myList);

6.17.6. MultiList & DefaultListModel

So  after  this  long  start  lets  show  the  first  sample  of  creating  a  list  using  the  MultiList

[https://www.codenameone.com/javadoc/com/codename1/ui/list/MultiList.html].

The MultiList is a preconfigured list that contains a ready made renderer with defaults that make
sense  for  the  most  common  use  cases.  It  still  retains  most  of  the  power  available  to  the  List
component  but  reduces  the  complexity  of  one  of  the  hardest  things  to  grasp  for  most  developers:

rendering.

The  full  power  of  the  ListModel  is  still  available  and  allows  you  to  create  a  million  entry  list  with
just a few lines of code. However the objects that the model returns should always be in the form of
Map objects and not an arbitrary object like the standard List allows.

Here is a simple example of a MultiList containing a highly popular subject matter:

231

Form hi = new Form("MultiList", new BorderLayout());

ArrayList<Map<String, Object>> data = new ArrayList<>();

data.add(createListEntry("A Game of Thrones", "1996"));
data.add(createListEntry("A Clash Of Kings", "1998"));
data.add(createListEntry("A Storm Of Swords", "2000"));
data.add(createListEntry("A Feast For Crows", "2005"));
data.add(createListEntry("A Dance With Dragons", "2011"));
data.add(createListEntry("The Winds of Winter", "2016 (please, please, please)"));
data.add(createListEntry("A Dream of Spring", "Ugh"));

DefaultListModel<Map<String, Object>> model = new DefaultListModel<>(data);
MultiList ml = new MultiList(model);
hi.add(BorderLayout.CENTER, ml);

Figure 224. Basic usage of the MultiList & DefaultListModel]

createListEntry is relatively trivial:

private Map<String, Object> createListEntry(String name, String date) {
    Map<String, Object> entry = new HashMap<>();
    entry.put("Line1", name);
    entry.put("Line2", date);
    return entry;
}

There  is  one  major  piece  missing  here  and  that  is  the  cover  images  for  the  books.  A  simple

approach would be to just place the image objects into the entries using the "icon" property as such:

private Map<String, Object> createListEntry(String name, String date, Image cover) {
    Map<String, Object> entry = new HashMap<>();
    entry.put("Line1", name);
    entry.put("Line2", date);
    entry.put("icon", cover);
    return entry;
}

232

Figure 225. With cover images in place



Since  the  MultiList  uses  the  GenericListCellRenderer  internally  we  can  use
to
URLImage 

[https://www.codenameone.com/javadoc/com/codename1/ui/URLImage.html] 

dynamically fetch the data. This is discussed in the graphics section of this guide.

Going Further With the ListModel

Lets assume that GRRM [http://www.georgerrmartin.com/] was really prolific and wrote 1 million books.

The  default  list  model  won’t  make  much  sense  in  that  case  but  we  would  still  be  able  to  render

everything in a list model.

We’ll fake it a bit but notice that 1M components won’t be created even if we somehow scroll all the

way down…

The ListModel [https://www.codenameone.com/javadoc/com/codename1/ui/list/ListModel.html] interface can be

implemented by anyone in this case we just did a really stupid simple implementation:

class GRMMModel implements ListModel<Map<String,Object>> {
    @Override
    public Map<String, Object> getItemAt(int index) {
        int idx = index % 7;
        switch(idx) {
            case 0:
                return createListEntry("A Game of Thrones " + index, "1996");
            case 1:
                return createListEntry("A Clash Of Kings " + index, "1998");
            case 2:
                return createListEntry("A Storm Of Swords " + index, "2000");
            case 3:
                return createListEntry("A Feast For Crows " + index, "2005");
            case 4:
                return createListEntry("A Dance With Dragons " + index, "2011");
            case 5:
                return createListEntry("The Winds of Winter " + index, "2016 (please, please, please)");
            default:
                return createListEntry("A Dream of Spring " + index, "Ugh");
        }
    }

    @Override
    public int getSize() {
        return 1000000;

233

    }

    @Override
    public int getSelectedIndex() {
        return 0;
    }

    @Override
    public void setSelectedIndex(int index) {
    }

    @Override
    public void addDataChangedListener(DataChangedListener l) {
    }

    @Override
    public void removeDataChangedListener(DataChangedListener l) {
    }

    @Override
    public void addSelectionListener(SelectionListener l) {
    }

    @Override
    public void removeSelectionListener(SelectionListener l) {
    }

    @Override
    public void addItem(Map<String, Object> item) {
    }

    @Override
    public void removeItem(int index) {
    }
}

We can now replace the existing model by removing all the model related logic and changing the

constructor call as such:

MultiList ml = new MultiList(new GRMMModel());

Figure 226. It took ages to scroll this far… This goes to a million…

234

6.17.7. List Cell Renderer

The Renderer is a simple interface with 2 methods:

public interface ListCellRenderer {
   //This method is called by the List for each item, when the List paints itself.
   public Component getListCellRendererComponent(List list, Object value, int index, boolean isSelected);

   //This method returns the List animated focus which is animated when list selection changes
   public Component getListFocusComponent(List list);
}

The most simple/naive implementation may choose to implement the renderer as follows:

public Component getListCellRendererComponent(List list, Object value, int index, boolean isSelected){
     return new Label(value.toString());
}

public Component getListFocusComponent(List list){
     return null;
}

This will compile and work, but won’t give you much, notice that you won’t see the List selection
move  on  the  List,  this  is  just  because  the  renderer  returns  a  Label  [https://www.codenameone.com/

javadoc/com/codename1/ui/Label.html] with the same style regardless if it’s selected or not.

Now Let’s try to make it a bit more useful.

public Component getListCellRendererComponent(List list, Object value, int index, boolean isSelected){
      Label l = new Label(value.toString());
if (isSelected) {
             l.setFocus(true);
             l.getAllStyles().setBgTransparency(100);
         } else {
             l.setFocus(false);
             l.getAllStyles().setBgTransparency(0);
        }
        return l;
}   public Component getListFocusComponent(List list){
      return null;
}

In this renderer we set the Label.setFocus(true) if it’s selected, calling to this method doesn’t really
give the focus to the Label, it simply renders the label as selected.

Then  we 
transparency, and 0 for full transparency if not selected.

invoke  Label.getAllStyles().setBgTransparency(100) 

to  give 

the  selection  semi

That is still not very efficient because we create a new Label each time the method is invoked.

To make the code tighter, keep a reference to the Component or extend it as DefaultListCellRenderer

235

[https://www.codenameone.com/javadoc/com/codename1/ui/list/DefaultListCellRenderer.html] does.

class MyRenderer extends Label implements ListCellRenderer {
    public Component getListCellRendererComponent(List list, Object value, int index, boolean isSelected){
        setText(value.toString());
        if (isSelected) {
            setFocus(true);
            getAllStyles().setBgTransparency(100);
        } else {
            setFocus(false);
            getAllStyles().setBgTransparency(0);
        }
        return this;
        }
    }
}

Now Let’s have a look at a more advanced Renderer.

class ContactsRenderer extends Container implements ListCellRenderer {

 private Label name = new Label("");
 private Label email = new Label("");
 private Label pic = new Label("");

 private Label focus = new Label("");

 public ContactsRenderer() {
     setLayout(new BorderLayout());
     addComponent(BorderLayout.WEST, pic);
     Container cnt = new Container(new BoxLayout(BoxLayout.Y_AXIS));
     name.getAllStyles().setBgTransparency(0);
     name.getAllStyles().setFont(Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_BOLD, Font.SIZE_MEDIUM));
     email.getAllStyles().setBgTransparency(0);
     cnt.addComponent(name);
     cnt.addComponent(email);
     addComponent(BorderLayout.CENTER, cnt);

     focus.getStyle().setBgTransparency(100);
 }

 public Component getListCellRendererComponent(List list, Object value, int index, boolean isSelected) {

     Contact person = (Contact) value;
     name.setText(person.getName());
     email.setText(person.getEmail());
     pic.setIcon(person.getPic());
     return this;
 }

 public Component getListFocusComponent(List list) {
     return focus;
 }
}

In  this  renderer  we  want  to  render  a  Contact  object  to  the  Screen,  we  build  the  Component  in  the

236

constructor and in the getListCellRendererComponent we simply update the Labels' texts according
to the Contact object.

Notice that in this renderer we return a focus Label with semi transparency, as mentioned before,
the focus component can be modified within this method.

For example, I can modify the focus Component to have an icon.

focus.getAllStyles().setBgTransparency(100);
try {
    focus.setIcon(Image.createImage("/duke.png"));
    focus.setAlignment(Component.RIGHT);
} catch (IOException ex) {
    ex.printStackTrace();
}

6.17.8. Generic List Cell Renderer

As  part  of  the  GUI  builder  work,  we  needed  a  way  to  customize  rendering  for  a  List,  but  the

renderer/model  approach  seemed  impossible  to  adapt  to  a  GUI  builder  (it  seems  the  Swing  GUI
builders  had  a  similar  issue).  Our  solution  was  to  introduce  the  GenericListCellRenderer,  which
while introducing limitations and implementation requirements still manages to make life easier,

both in the GUI builder and outside of it.

[https://www.codenameone.com/javadoc/com/codename1/ui/list/
GenericListCellRenderer 
GenericListCellRenderer.html]  is  a  renderer  designed  to  be  as  simple  to  use  as  a  Component-Container
hierarchy, we effectively crammed most of the common renderer use cases into one class. To enable
that, we need to know the content of the objects within the model, so the GenericListCellRenderer
assumes the model contains only Map objects. Since Maps can contain arbitrary data the list model is
still  quite  generic  and  allows  storing  application  specific  data.  Furthermore  a  Map  can  still  be
derived and extended to provide domain specific business logic.

The GenericListCellRenderer accepts two container instances (more later on why at least two, and
not  one),  which  it  maps  to  individual  Map  entries  within  the  model,  by  finding  the  appropriate
components within the given container hierarchy. Components are mapped to the Map entries based
on the name property of the component (getName/setName) and the key/value within the Map, e.g.:

For a model that contains a Map entry like this:

"Foo": "Bar"
"X": "Y"
"Not": "Applicable"
"Number": Integer(1)

A  renderer  will  loop  over  the  component  hierarchy  in  the  container,  searching  for  components

whose name matches Foo, X, Not, and Number, and assigning the appropriate value to them.

237

You  can  also  use  image  objects  as  values,  and  they  will  be  assigned  to  labels  as



expected.  However,  you  can’t  assign  both  an  image  and  a  text  to  a  single  label,

since the key will be taken. That isn’t a big problem, since two labels can be used

quite easily in such a renderer.

To  make  matters  even  more  attractive  the  renderer  seamlessly  supports  list  tickering  when

appropriate,  and  if  a  CheckBox  [https://www.codenameone.com/javadoc/com/codename1/ui/CheckBox.html]
appears within the renderer, it will toggle a boolean flag within the Map seamlessly.

One issue that crops up with this approach is that, if a value is missing from the Map, it is treated as
empty and the component is reset.

This can pose an issue if we hardcode an image or text within the renderer and we don’t want them
replaced (e.g. an arrow graphic on a Label within the renderer). The solution for this is to name the
component with Fixed in the end of the name, e.g. HardcodedIconFixed.

Naming  a  component  within  the  renderer  with  $number  will  automatically  set  it  as  a  counter

component for the offset of the component within the list.

Styling the GenericListCellRenderer is slightly different, the renderer uses the UIID of the Container
passed to the generic list cell renderer, and the background focus uses that same UIID with the word
"Focus" appended to it.

It is important to notice that the generic list cell renderer will grant focus to the child components

of the selected entry if they are focusable, thus changing the style of said entries. E.g. a Container
[https://www.codenameone.com/javadoc/com/codename1/ui/Container.html] might have a child Label that has
one style when the parent container is unselected and another when it’s selected (focused), this can

be easily achieved by defining the label as focusable. Notice that the component will never receive

direct focus, since it is still part of a renderer.

Last but not least, the generic list cell renderer accepts two or four instances of a Container, rather

than  the  obvious  choice  of  accepting  only  one  instance.  This  allows  the  renderer  to  treat  the

selected entry differently, which is especially important to tickering, although it’s also useful for the
fisheye effect [4]. Since it might not be practical to seamlessly clone the Container for the renderer’s
needs,  Codename  One  expects  the  developer  to  provide  two  separate  instances,  they  can  be

identical  in  all  respects,  but  they  must  be  separate  instances  for  tickering  to  work.  The  renderer

also  allows  for  a  fisheye  effect,  where  the  selected  entry  is  actually  different  from  the  unselected

entry in its structure, it also allows for a pinstripe effect, where odd/even rows have different styles

(this is accomplished by providing 4 instances of the containers selected/unselected for odd/even).

The best way to learn about the generic list cell renderer and the Map model is by playing with them
in the old GUI builder. Notice they can be used in code without any dependency on the GUI builder

and can be quite useful at that.

Here is a simple example of a list with checkboxes that gets updated automatically:

238

com.codename1.ui.List list = new com.codename1.ui.List(createGenericListCellRendererModelData());
list.setRenderer(new GenericListCellRenderer(createGenericRendererContainer(), createGenericRendererContainer()));

private Container createGenericRendererContainer() {
    Label name = new Label();
    name.setFocusable(true);
    name.setName("Name");
    Label surname = new Label();
    surname.setFocusable(true);
    surname.setName("Surname");
    CheckBox selected = new CheckBox();
    selected.setName("Selected");
    selected.setFocusable(true);
    Container c = BorderLayout.center(name).
            add(BorderLayout.SOUTH, surname).
            add(BorderLayout.WEST, selected);
    c.setUIID("ListRenderer");
    return c;
}

private Object[] createGenericListCellRendererModelData() {
    Map<String,Object>[] data = new HashMap[5];
    data[0] = new HashMap<>();
    data[0].put("Name", "Shai");
    data[0].put("Surname", "Almog");
    data[0].put("Selected", Boolean.TRUE);
    data[1] = new HashMap<>();
    data[1].put("Name", "Chen");
    data[1].put("Surname", "Fishbein");
    data[1].put("Selected", Boolean.TRUE);
    data[2] = new HashMap<>();
    data[2].put("Name", "Ofir");
    data[2].put("Surname", "Leitner");
    data[3] = new HashMap<>();
    data[3].put("Name", "Yaniv");
    data[3].put("Surname", "Vakarat");
    data[4] = new HashMap<>();
    data[4].put("Name", "Meirav");
    data[4].put("Surname", "Nachmanovitch");
    return data;
}

Figure 227. GenericListCellRenderer demo code

239

Custom UIID Of Entry in GenenricListCellRenderer/MultiList

MultiList 

With 
[https://www.codenameone.com/javadoc/com/codename1/ui/list/MultiList.html
]/GenenricListCellRenderer  one  of  the  common  issues  is  making  a  UI  where  a  specific  component
within the list renderer has a different UIID style based on data. E.g. this can be helpful to mark a

label within the list as red, for instance, in the case of a list of monetary transactions.

This can be achieved with a custom renderer, but that is a pretty difficult task.
GenericListCellRenderer (MultiList uses GenericListCellRenderer internally) has another option.

Normally, to build the model for a renderer of this type, we use something like:

map.put("componentName", "Component Value");

What if we want componentName to be red? Just use:

map.put("componentName_uiid", "red");

This will apply the UIID "red" to the component, which you can then style in the theme. Notice that

once you start doing this, you need to define this entry for all entries, e.g.:

map.put("componentName_uiid", "blue");

Otherwise  the  component  will  stay  red  for  the  next  entry  (since  the  renderer  acts  like  a  rubber

stamp).

Rendering Prototype

Because of the rendering architecture of a List its pretty hard to calculate the right preferred size
for such a component. The default behavior includes querying a few entries from the model then

constructing their renderers to get a "sample" of the preferred size value.

As you might guess this triggers a performance penalty that is paid with every reflow of the UI. The
solution is to use setRenderingPrototype.

setRenderingPrototype accepts a "fake" value that represents a reasonably large amount of data and
it will be used to calculate the preferred size. E.g. for a multiList that should render 2 lines of text

with 20 characters and a 5mm square icon I can do something like this:

Map<String, Object> proto = new HashMap<>();
map.put("Line1", "WWWWWWWWWWWWWWWWWWWW");
map.put("Line2", "WWWWWWWWWWWWWWWWWWWW");
int mm5 = Display.getInstance().convertToPixels(5, true);
map.put("icon", Image.create(mm5, mm5));
myMultiList.setRenderingPrototype(map);

240

6.17.9. ComboBox

ComboBox 

a
The 
specialization  of  List  that  displays  a  single  selected  entry.  When  clicking  that  entry  a  popup  is
presented allowing the user to pick an entry from the full list of entries.

[https://www.codenameone.com/javadoc/com/codename1/ui/ComboBox.html] 

is 



The ComboBox UI paradigm isn’t as common on OS’s such as iOS where there is no
the  Picker
native 

recommend  using 

equivalent 

it.  We 

either 

to 

[https://www.codenameone.com/javadoc/com/codename1/ui/spinner/Picker.html]  class  or  the

AutoCompleteTextField 

[https://www.codenameone.com/javadoc/com/codename1/ui/

AutoCompleteTextField.html].

ComboBox is notoriously hard to style properly as it relies on a complex dynamic of popup renderer
and  instantly  visible  renderer.  The  UIID  for  the  ComboBox  is  ComboBox  however  if  you  set  it  to
something  else  all  the  other  UIID’s  will  also  change  their  prefix.  E.g.  the  ComboBoxPopup  UIID  will
become MyNewUIIDPopup.

The combo box defines the following UIID’s by default:

• ComboBox

• ComboBoxItem

• ComboBoxFocus

• PopupContentPane

• PopupItem

• PopupFocus

The  ComboBox  also  defines  theme  constants  that  allow  some  native  themes  to  manipulate  its
behavior e.g.:

• popupTitleBool - shows the "label for" value as the title of the popup dialog

• popupCancelBodyBool - Adds a cancel button into the popup dialog

• centeredPopupBool  -  shows  the  popup  dialog  in  the  center  of  the  screen  instead  of  under  the

popup

• otherPopupRendererBool - Uses a different list cell render for the popup than the one used for the
ComboBox  itself.  When  this  is  false  PopupItem  &  PopupFocus  become  irrelevant.  Notice  that  the
Android native theme defines this to true.

Since a ComboBox is really a List you can use everything we learned about a List to build a ComboBox
including models, GenericListCellRenderer etc.

E.g. the demo below uses the GRRM demo data from above to build a ComboBox:

241

Form hi = new Form("ComboBox", new BoxLayout(BoxLayout.Y_AXIS));
ComboBox<Map<String, Object>> combo = new ComboBox<> (
        createListEntry("A Game of Thrones", "1996"),
        createListEntry("A Clash Of Kings", "1998"),
        createListEntry("A Storm Of Swords", "2000"),
        createListEntry("A Feast For Crows", "2005"),
        createListEntry("A Dance With Dragons", "2011"),
        createListEntry("The Winds of Winter", "2016 (please, please, please)"),
        createListEntry("A Dream of Spring", "Ugh"));

combo.setRenderer(new GenericListCellRenderer<>(new MultiButton(), new MultiButton()));

Figure 228. GRRM ComboBox

6.18. Slider

A Slider [https://www.codenameone.com/javadoc/com/codename1/ui/Slider.html] is an empty component that

can  be  filled  horizontally  or  vertically  to  allow  indicating  progress,  setting  volume  etc.  It  can  be

editable to allow the user to determine its value or none editable to just relay that information to

the user. It can have a thumb on top to show its current position.

Figure 229. Slider

The interesting part about the slider is that it has two separate style UIID’s, Slider & SliderFull. The
Slider  UIID  is  always  painted  and  SliderFull  is  rendered  on  top  based  on  the  amount  the  Slider
should be filled.

Slider  is  highly  customizable  e.g.  a  slider  can  be  used  to  replicate  a  5  star  rating  widget  as  such.
Notice  that  this  slider  will  only  work  when  its  given  its  preferred  size  otherwise  additional  stars
will appear. That’s why we place it within a FlowLayout:

Form hi = new Form("Star Slider", new BoxLayout(BoxLayout.Y_AXIS));
hi.add(FlowLayout.encloseCenter(createStarRankSlider()));
hi.show();

The slider itself is initialized in the code below. Notice that you can achieve almost the same result
using a theme by setting the Slider & SliderFull UIID’s (both in selected & unselected states).

In fact doing this in the theme might be superior as you could use one image that contains 5 stars

already and that way you won’t need the preferred size hack below:

242

private void initStarRankStyle(Style s, Image star) {
    s.setBackgroundType(Style.BACKGROUND_IMAGE_TILE_BOTH);
    s.setBorder(Border.createEmpty());
    s.setBgImage(star);
    s.setBgTransparency(0);
}

private Slider createStarRankSlider() {
    Slider starRank = new Slider();
    starRank.setEditable(true);
    starRank.setMinValue(0);
    starRank.setMaxValue(10);
    Font fnt = Font.createTrueTypeFont("native:MainLight", "native:MainLight").
            derive(Display.getInstance().convertToPixels(5, true), Font.STYLE_PLAIN);
    Style s = new Style(0xffff33, 0, fnt, (byte)0);
    Image fullStar = FontImage.createMaterial(FontImage.MATERIAL_STAR, s).toImage();
    s.setOpacity(100);
    s.setFgColor(0);
    Image emptyStar = FontImage.createMaterial(FontImage.MATERIAL_STAR, s).toImage();
    initStarRankStyle(starRank.getSliderEmptySelectedStyle(), emptyStar);
    initStarRankStyle(starRank.getSliderEmptyUnselectedStyle(), emptyStar);
    initStarRankStyle(starRank.getSliderFullSelectedStyle(), fullStar);
    initStarRankStyle(starRank.getSliderFullUnselectedStyle(), fullStar);
    starRank.setPreferredSize(new Dimension(fullStar.getWidth() * 5, fullStar.getHeight()));
    return starRank;
}
private void showStarPickingForm() {
  Form hi = new Form("Star Slider", new BoxLayout(BoxLayout.Y_AXIS));
  hi.add(FlowLayout.encloseCenter(createStarRankSlider()));
  hi.show();
}

Figure 230. Star Slider set to 5 (its between 0 - 10)



This slider goes all the way to 0 stars which is less common. You can use a Label to
represent the first star and have the slider work between 0 - 8 values to provide 4

additional stars.

6.19. Table

Table  [https://www.codenameone.com/javadoc/com/codename1/ui/table/Table.html]  is  a  composite  component

(but it isn’t a lead component), this means it is a subclass of Container [https://www.codenameone.com/

javadoc/com/codename1/ui/Container.html]. It’s effectively built from multiple components.

243



Table  is  heavily  based  on  the  TableLayout  [https://www.codenameone.com/javadoc/com/
codename1/ui/table/TableLayout.html]  class.  It’s  important  to  be  familiar  with  that
layout manager when working with Table.

Here is a trivial sample of using the standard table component:

Form hi = new Form("Table", new BorderLayout());
TableModel model = new DefaultTableModel(new String[] {"Col 1", "Col 2", "Col 3"}, new Object[][] {
    {"Row 1", "Row A", "Row X"},
    {"Row 2", "Row B", "Row Y"},
    {"Row 3", "Row C", "Row Z"},
    {"Row 4", "Row D", "Row K"},
    }) {
        public boolean isCellEditable(int row, int col) {
            return col != 0;
        }
    };
Table table = new Table(model);
hi.add(BorderLayout.CENTER, table);
hi.show();

Figure 231. Simple Table usage

 In the sample above the title area and first column aren’t editable. The other two

columns are editable.

The more "interesting" capabilities of the Table class can be utilized via the TableLayout. You can use
the layout constraints (also exposed in the table class) to create spanning and elaborate UI’s.

E.g.:

244

Form hi = new Form("Table", new BorderLayout());
TableModel model = new DefaultTableModel(new String[] {"Col 1", "Col 2", "Col 3"}, new Object[][] {
    {"Row 1", "Row A", "Row X"},
    {"Row 2", "Row B can now stretch", null},
    {"Row 3", "Row C", "Row Z"},
    {"Row 4", "Row D", "Row K"},
    }) {
        public boolean isCellEditable(int row, int col) {
            return col != 0;
        }
    };
Table table = new Table(model) {
    @Override
    protected TableLayout.Constraint createCellConstraint(Object value, int row, int column) {
        TableLayout.Constraint con =  super.createCellConstraint(value, row, column);
        if(row == 1 && column == 1) {
            con.setHorizontalSpan(2);
        }
        con.setWidthPercentage(33);
        return con;
    }
};
hi.add(BorderLayout.CENTER, table);

Figure 232. Table with spanning & fixed widths to 33%

In  order  to  customize  the  table  cell  behavior  you  can  derive  the  Table  to  create  a  "renderer  like"
widget,  however  unlike  the  list  this  component  is  "kept"  and  used  as  is.  This  means  you  can  bind

listeners to this component and work with it as you would with any other component in Codename

One.

So lets fix the example above to include far more capabilities:

245

Table table = new Table(model) {
    @Override
    protected Component createCell(Object value, int row, int column, boolean editable) { ①
        Component cell;
        if(row == 1 && column == 1) {  ②
            Picker p = new Picker();
            p.setType(Display.PICKER_TYPE_STRINGS);
            p.setStrings("Row B can now stretch", "This is a good value", "So Is This", "Better than text field");
            p.setSelectedString((String)value);  ③
            p.setUIID("TableCell");
            p.addActionListener((e) -> getModel().setValueAt(row, column, p.getSelectedString()));  ④
            cell = p;
        } else {
            cell = super.createCell(value, row, column, editable);
        }
        if(row > -1 && row % 2 == 0) {  ⑤
            // pinstripe effect
            cell.getAllStyles().setBgColor(0xeeeeee);
            cell.getAllStyles().setBgTransparency(255);
        }
        return cell;
    }

    @Override
    protected TableLayout.Constraint createCellConstraint(Object value, int row, int column) {
        TableLayout.Constraint con =  super.createCellConstraint(value, row, column);
        if(row == 1 && column == 1) {
            con.setHorizontalSpan(2);
        }
        con.setWidthPercentage(33);
        return con;
    }
};

① The  createCell  method  is  invoked  once  per  component  but  is  similar  conceptually  to  the  List
renderer. Notice that it doesn’t return a "rubber stamp" though, it returns a full component.

② We only apply the picker to one cell for simplicities sake.

③ We need to set the value of the component manually, this is crucial since the Table doesn’t "see"

this.

④ We need to track the event and update the model in this case as the Table isn’t aware of the data

change.

⑤ We set the "pinstripe" effect by coloring even rows. Notice that unlike renderers we only need to

apply the coloring once as the Components are stateful.

246

Figure 233. Table with customize cells using the pinstripe effect

Figure 234. Picker table cell during edit

To  line  wrap  table  cells  we  can  just  override  the  createCell  method  and  return  a  TextArea
TextField
[https://www.codenameone.com/javadoc/com/codename1/ui/TextArea.html] 
[https://www.codenameone.com/javadoc/com/codename1/ui/TextField.html]  since  the  TextArea  defaults  to  the
multi-line behavior this should work seamlessly. E.g.:

instead 

of 

a 

247

Form hi = new Form("Table", new BorderLayout());
TableModel model = new DefaultTableModel(new String[] {"Col 1", "Col 2", "Col 3"}, new Object[][] {
    {"Row 1", "Row A", "Row X"},
    {"Row 2", "Row B can now stretch very long line that should span multiple rows as much as possible", "Row Y"},
    {"Row 3", "Row C", "Row Z"},
    {"Row 4", "Row D", "Row K"},
    }) {
        public boolean isCellEditable(int row, int col) {
            return col != 0;
        }
    };
Table table = new Table(model) {
    @Override
    protected Component createCell(Object value, int row, int column, boolean editable) {
        TextArea ta = new TextArea((String)value);
        ta.setUIID("TableCell");
        return ta;
    }

    @Override
    protected TableLayout.Constraint createCellConstraint(Object value, int row, int column) {
        TableLayout.Constraint con =  super.createCellConstraint(value, row, column);
        con.setWidthPercentage(33);
        return con;
    }
};
hi.add(BorderLayout.CENTER, table);
hi.show();



Notice  that  we  don’t  really  need  to  do  anything  else  as  binding  to  the  TextArea  is
builtin to the Table.



We  must  set  the  column  width  constraint  when  we  want  multi-line  to  work.

Otherwise the preferred size of the column might be too wide and the remaining

columns might not have space left.

Figure 235. Multiline table cell in portrait mode

Figure 236. Multiline table cell in landscape mode. Notice the cell row count adapts seamlessly

248

6.19.1. Sorting Tables

Sorting tables by clicking the titles is something that should generally work out of the box by using
an API like setSortSupported(true).

Form hi = new Form("Table", new BorderLayout());
TableModel model = new DefaultTableModel(new String[] {"Col 1", "Col 2", "Col 3"}, new Object[][] {
    {"Row 1", "Row A", 1},
    {"Row 2", "Row B", 4},
    {"Row 3", "Row C", 7.5},
    {"Row 4", "Row D", 2.24},
    });
Table table = new Table(model);
table.setSortSupported(true);
hi.add(BorderLayout.CENTER, table);
hi.add(NORTH, new Button("Button"));
hi.show();

Notice this works with numbers, Strings and might work with dates but you can generally support
any  object  type  by  overriding  the  method  protected  Comparator  createColumnSortComparator(int
column) which should return a comparator for your custom object type in the column.

6.20. Tree

Tree 

[https://www.codenameone.com/javadoc/com/codename1/ui/tree/Tree.html] 

allows 

displaying

hierarchical  data  such  as  folders  and  files  in  a  collapsible/expandable  UI.  Like  the  Table  it  is  a
composite  component  (but  it  isn’t  a  lead  component).  Like  the  Table  it  works  in  consort  with  a
model to construct its user interface on the fly but doesn’t use a stateless renderer (as List does).

The data of the Tree arrives from a model model e.g. this:

249

class StringArrayTreeModel implements TreeModel {
    String[][] arr = new String[][] {
            {"Colors", "Letters", "Numbers"},
            {"Red", "Green", "Blue"},
            {"A", "B", "C"},
            {"1", "2", "3"}
        };

    public Vector getChildren(Object parent) {
        if(parent == null) {
            Vector v = new Vector();
            for(int iter = 0 ; iter < arr[0].length ; iter++) {
                v.addElement(arr[0][iter]);
            }
            return v;
        }
        Vector v = new Vector();
        for(int iter = 0 ; iter < arr[0].length ; iter++) {
            if(parent == arr[0][iter]) {
                if(arr.length > iter + 1 && arr[iter + 1] != null) {
                    for(int i = 0 ; i < arr[iter + 1].length ; i++) {
                        v.addElement(arr[iter + 1][i]);
                    }
                }
            }
        }
        return v;
    }

    public boolean isLeaf(Object node) {
        Vector v = getChildren(node);
        return v == null || v.size() == 0;
    }
}

Tree dt = new Tree(new StringArrayTreeModel());

Will result in this:

Figure 237. Tree

250

 Since  Tree  is  hierarchy  based  we  can’t  have  a  simple  model  like  we  have  for  the

Table as deep hierarchy is harder to represent with arrays.

A  more  practical  "real  world"  example  would  be  working  with  XML  data.  We  can  use  something
like this to show an XML Tree:

Form hi = new Form("XML Tree", new BorderLayout());
InputStream is = Display.getInstance().getResourceAsStream(getClass(), "/build.xml");
try(Reader r = new InputStreamReader(is, "UTF-8");) {
    Element e = new XMLParser().parse(r);
    Tree xmlTree = new Tree(new XMLTreeModel(e)) {
        @Override
        protected String childToDisplayLabel(Object child) {
            if(child instanceof Element) {
                return ((Element)child).getTagName();
            }
            return child.toString();
        }
    };
    hi.add(BorderLayout.CENTER, xmlTree);
} catch(IOException err) {
    Log.e(err);
}

 The  try(Stream)  syntax  is  a  try  with  resources  clogic  that  implicitly  closes  the

stream.

Figure 238. XML Tree

The model for the XML hierarchy is implemented as such:

251

class XMLTreeModel implements TreeModel {
    private Element root;
    public XMLTreeModel(Element e) {
        root = e;
    }

    public Vector getChildren(Object parent) {
        if(parent == null) {
            Vector c = new Vector();
            c.addElement(root);
            return c;
        }
        Vector result = new Vector();
        Element e = (Element)parent;
        for(int iter = 0 ; iter < e.getNumChildren() ; iter++) {
            result.addElement(e.getChildAt(iter));
        }
        return result;
    }

    public boolean isLeaf(Object node) {
        Element e = (Element)node;
        return e.getNumChildren() == 0;
    }
}

6.21. ShareButton

ShareButton 

[https://www.codenameone.com/javadoc/com/codename1/components/ShareButton.html] 

is  a

button you can add into the UI to let a user share an image or block of text.

The  ShareButton  uses  a  set  of  predefined  share  options  on  the  simulator.  On  Android  &  iOS  the
ShareButton is mapped to the OS native sharing functionality and can share the image/text with the
services configured on the device (e.g. Twitter, Facebook etc.).



Sharing  text  is  trivial  but  to  share  an  image  we  need  to  save  it  to  the

FileSystemStorage 

[https://www.codenameone.com/javadoc/com/codename1/io/

FileSystemStorage.html]. Notice that saving to Storage won’t work!

In  the  sample  code  below  we  take  a  screenshot  which  is  saved  to  FileSystemStorage

[https://www.codenameone.com/javadoc/com/codename1/io/FileSystemStorage.html] for sharing:

252

Form hi = new Form("ShareButton");
ShareButton sb = new ShareButton();
sb.setText("Share Screenshot");
hi.add(sb);

Image screenshot = Image.createImage(hi.getWidth(), hi.getHeight());
hi.revalidate();
hi.setVisible(true);
hi.paintComponent(screenshot.getGraphics(), true);

String imageFile = FileSystemStorage.getInstance().getAppHomePath() + "screenshot.png";
try(OutputStream os = FileSystemStorage.getInstance().openOutputStream(imageFile);) {
    ImageIO.getImageIO().save(screenshot, os, ImageIO.FORMAT_PNG, 1);
} catch(IOException err) {
    Log.e(err);
}
sb.setImageToShare(imageFile, "image/png");

Figure 239. The share button running on the simulator

 ShareButton behaves very differently on the device…

Figure 240. The share button running on the Android device and screenshot sent into twitter

253



The ShareButton features some share service classes to allow plugging in additional
share services. However, this functionality is only relevant to devices where native

sharing isn’t supported. So this code isn’t used on iOS/Android…

6.22. Tabs

[https://www.codenameone.com/javadoc/com/codename1/ui/Tabs.html] 

The  Tabs 
arranges
components  into  groups  within  "tabbed"  containers.  Tabs  is  a  container  type  that  allows  leafing
through its children using labeled toggle buttons. The tabs can be placed in multiple different ways

Container 

(top, bottom, left or right) with the default being determined by the platform. This class also allows

swiping  between  components  to  leaf  between  said  tabs  (for  this  purpose  the  tabs  themselves  can

also be hidden).

Since  Tabs  are  a  Container  its  a  common  mistake  to  try  and  add  a  Tab  using  the  add  method.  That
method won’t work since a Tab can have both an Image and text String associated with it.

Form hi = new Form("Tabs", new BorderLayout());

Tabs t = new Tabs();
Style s = UIManager.getInstance().getComponentStyle("Tab");
FontImage icon1 = FontImage.createMaterial(FontImage.MATERIAL_QUESTION_ANSWER, s);

Container container1 = BoxLayout.encloseY(new Label("Label1"), new Label("Label2"));
t.addTab("Tab1", icon1, container1);
t.addTab("Tab2", new SpanLabel("Some text directly in the tab"));

hi.add(BorderLayout.CENTER, t);

Figure 241. Simple usage of Tabs

A  common  usage  for  Tabs  is  the  the  swipe  to  proceed  effect  which  is  very  common  in  iOS
applications.  In  the  code  below  we  use  RadioButton  [https://www.codenameone.com/javadoc/com/

codename1/ui/RadioButton.html]  and  LayeredLayout  [https://www.codenameone.com/javadoc/com/codename1/

ui/layouts/LayeredLayout.html] with hidden tabs to produce that effect:

254

Form hi = new Form("Swipe Tabs", new LayeredLayout());
Tabs t = new Tabs();
t.hideTabs();

Style s = UIManager.getInstance().getComponentStyle("Button");
FontImage radioEmptyImage = FontImage.createMaterial(FontImage.MATERIAL_RADIO_BUTTON_UNCHECKED, s);
FontImage radioFullImage = FontImage.createMaterial(FontImage.MATERIAL_RADIO_BUTTON_CHECKED, s);
((DefaultLookAndFeel)UIManager.getInstance().getLookAndFeel()).setRadioButtonImages(radioFullImage, radioEmptyImage,
radioFullImage, radioEmptyImage);

Container container1 = BoxLayout.encloseY(new Label("Swipe the tab to see more"),
        new Label("You can put anything here"));
t.addTab("Tab1", container1);
t.addTab("Tab2", new SpanLabel("Some text directly in the tab"));

RadioButton firstTab = new RadioButton("");
RadioButton secondTab = new RadioButton("");
firstTab.setUIID("Container");
secondTab.setUIID("Container");
new ButtonGroup(firstTab, secondTab);
firstTab.setSelected(true);
Container tabsFlow = FlowLayout.encloseCenter(firstTab, secondTab);

hi.add(t);
hi.add(BorderLayout.south(tabsFlow));

t.addSelectionListener((i1, i2) -> {
    switch(i2) {
        case 0:
            if(!firstTab.isSelected()) {
                firstTab.setSelected(true);
            }
            break;
        case 1:
            if(!secondTab.isSelected()) {
                secondTab.setSelected(true);
            }
            break;
     }
});

Figure 242. Swipeable Tabs with an iOS carousel effect page 1

255

Figure 243. Swipeable Tabs with an iOS carousel effect page 2

 Notice that we used setRadioButtonImages to explicitly set the radio button images

to the look we want for the carousel.

6.23. MediaManager & MediaPlayer



MediaPlayer is a peer component, understanding this is crucial if your application
depends  on  such  a  component.  You  can  learn  about  peer  components  and  their

issues 

here 

[https://www.codenameone.com/manual/advanced-topics.html#native-peer-

components].

The  MediaPlayer 
[https://www.codenameone.com/javadoc/com/codename1/components/MediaPlayer.html]
allows you to control video playback. To use the MediaPlayer we need to first load the Media object
from the MediaManager [https://www.codenameone.com/javadoc/com/codename1/media/MediaManager.html].

The MediaManager is the core class responsible for media interaction in Codename One.



You  should  also  check  out  the  Capture  [https://www.codenameone.com/javadoc/com/

codename1/capture/Capture.html]  class  for 
MediaManager.

things 

that  aren’t  covered  by 

the

In  the  demo  code  below  we  use  the  gallery  functionality  to  pick  a  video  from  the  device’s  video

gallery.

256

final Form hi = new Form("MediaPlayer", new BorderLayout());
hi.setToolbar(new Toolbar());
Style s = UIManager.getInstance().getComponentStyle("Title");
FontImage icon = FontImage.createMaterial(FontImage.MATERIAL_VIDEO_LIBRARY, s);
hi.getToolbar().addCommandToRightBar("", icon, (evt) -> {
    Display.getInstance().openGallery((e) -> {
        if(e != null && e.getSource() != null) {
            String file = (String)e.getSource();
            try {
                Media video = MediaManager.createMedia(file, true);
                hi.removeAll();
                hi.add(BorderLayout.CENTER, new MediaPlayer(video));
                hi.revalidate();
            } catch(IOException err) {
                Log.e(err);
            }
        }
    }, Display.GALLERY_VIDEO);
});
hi.show();

Figure 244. Video playback running on the simulator

Figure 245. Video playback running on an Android device. Notice the native playback controls that appear

when the video is tapped

257

 Video  playback  in  the  simulator  will  only  work  with  JavaFX  enabled.  This  is  the

default for Java 8 or newer so we recommend using that.

6.24. ImageViewer

The 

ImageViewer 

[https://www.codenameone.com/javadoc/com/codename1/components/ImageViewer.html]

allows  us  to  inspect,  zoom  and  pan  into  an  image.  It  also  allows  swiping  between  images  if  you

have a set of images (using an image list model).



The ImageViewer is a complex rich component designed for user interaction. If you
just  want  to  display  an  image  use  Label  [https://www.codenameone.com/javadoc/com/

codename1/ui/Label.html] 

if  you  want 

the 

image 

to  scale  seamlessly  use

ScaleImageLabel 

[https://www.codenameone.com/javadoc/com/codename1/components/

ScaleImageLabel.html].

You can use the ImageViewer as a tool to view a single image which allows you to zoom in/out to that
image as such:

Form hi = new Form("ImageViewer", new BorderLayout());
ImageViewer iv = new ImageViewer(duke);
hi.add(BorderLayout.CENTER, iv);



You  can  simulate  pinch  to  zoom  on  the  simulator  by  dragging  the  right  button

away from the top left corner to zoom in and towards the top left corner to zoom

out. On Mac touchpads you can drag two fingers to achieve that.

Figure 246. ImageViewer as the demo loads with the image from the default icon

258

Figure 247. ImageViewer zoomed in

We can work with a list of images to produce a swiping effect for the image viewer where you can

swipe from one image to the next and also zoom in/out on a specific image:

Form hi = new Form("ImageViewer", new BorderLayout());

Image red = Image.createImage(100, 100, 0xffff0000);
Image green = Image.createImage(100, 100, 0xff00ff00);
Image blue = Image.createImage(100, 100, 0xff0000ff);
Image gray = Image.createImage(100, 100, 0xffcccccc);

ImageViewer iv = new ImageViewer(red);
iv.setImageList(new DefaultListModel<>(red, green, blue, gray));
hi.add(BorderLayout.CENTER, iv);

Figure 248. An ImageViewer with multiple elements is indistinguishable from a single ImageViewer with

the exception of swipe

Notice that we use a ListModel [https://www.codenameone.com/javadoc/com/codename1/ui/list/ListModel.html]

to allow swiping between images.



EncodedImage’s aren’t always fully loaded and so when you swipe if the images are
really large you might see delays!

You  can  dynamically  download  images  directly  into  the  ImageViewer  with  a  custom  list  model  like
this:

259

Form hi = new Form("ImageViewer", new BorderLayout());
final EncodedImage placeholder = EncodedImage.createFromImage(
        FontImage.createMaterial(FontImage.MATERIAL_SYNC, s).
                scaled(300, 300), false);

class ImageList implements ListModel<Image> {
    private int selection;
    private String[] imageURLs = {
        "http://awoiaf.westeros.org/images/thumb/9/93/AGameOfThrones.jpg/300px-AGameOfThrones.jpg",
        "http://awoiaf.westeros.org/images/thumb/3/39/AClashOfKings.jpg/300px-AClashOfKings.jpg",
        "http://awoiaf.westeros.org/images/thumb/2/24/AStormOfSwords.jpg/300px-AStormOfSwords.jpg",
        "http://awoiaf.westeros.org/images/thumb/a/a3/AFeastForCrows.jpg/300px-AFeastForCrows.jpg",
        "http://awoiaf.westeros.org/images/7/79/ADanceWithDragons.jpg"
    };
    private Image[] images;
    private EventDispatcher listeners = new EventDispatcher();

    public ImageList() {
        this.images = new EncodedImage[imageURLs.length];
    }

    public Image getItemAt(final int index) {
        if(images[index] == null) {
            images[index] = placeholder;
            Util.downloadUrlToStorageInBackground(imageURLs[index], "list" + index, (e) -> {
                    try {
                        images[index] = EncodedImage.create(Storage.getInstance().createInputStream("list" + index));
                        listeners.fireDataChangeEvent(index, DataChangedListener.CHANGED);
                    } catch(IOException err) {
                        err.printStackTrace();
                    }
            });
        }
        return images[index];
    }

    public int getSize() {
        return imageURLs.length;
    }

    public int getSelectedIndex() {
        return selection;
    }

    public void setSelectedIndex(int index) {
        selection = index;
    }

    public void addDataChangedListener(DataChangedListener l) {
        listeners.addListener(l);
    }

    public void removeDataChangedListener(DataChangedListener l) {
        listeners.removeListener(l);
    }

    public void addSelectionListener(SelectionListener l) {
    }

    public void removeSelectionListener(SelectionListener l) {
    }

    public void addItem(Image item) {
    }

260

    public void removeItem(int index) {
    }
};

ImageList imodel = new ImageList();

ImageViewer iv = new ImageViewer(imodel.getItemAt(0));
iv.setImageList(imodel);
hi.add(BorderLayout.CENTER, iv);

Figure 249. Dynamically fetching an image URL from the internet [5]

This  fetches  the  images  in  the  URL  asynchronously  and  fires  a  data  change  event  when  the  data
arrives to automatically refresh the ImageViewer when that happens.

6.25. ScaleImageLabel & ScaleImageButton

ScaleImageLabel [https://www.codenameone.com/javadoc/com/codename1/components/ScaleImageLabel.html] &

ScaleImageButton  [https://www.codenameone.com/javadoc/com/codename1/components/ScaleImageButton.html]

allow us to position an image that will grow/shrink to fit available space. In that sense they differ

from Label & Button which keeps the image at the same size.



The  default  UIID  of  ScaleImageLabel  is  “Label”,  however  the  default  UIID  of
ScaleImageButton  is  “ScaleImageButton”.  The  reasoning  for  the  difference  is  that
the “Button” UIID includes a border and a lot of legacy.

You can use ScaleImageLabel/ScaleImageButton interchangeably. The only major difference between
these components is the buttons ability to handle click events/focus.

Here  is  a  simple  example  that  also  shows  the  difference  between  the  scale  to  fill  and  scale  to
fit modes:

261

TableLayout tl = new TableLayout(2, 2);
Form hi = new Form("ScaleImageButton/Label", tl);
Style s = UIManager.getInstance().getComponentStyle("Button");
Image icon = FontImage.createMaterial(FontImage.MATERIAL_WARNING, s);
ScaleImageLabel fillLabel = new ScaleImageLabel(icon);
fillLabel.setBackgroundType(Style.BACKGROUND_IMAGE_SCALED_FILL);
ScaleImageButton fillButton = new ScaleImageButton(icon);
fillButton.setBackgroundType(Style.BACKGROUND_IMAGE_SCALED_FILL);
hi.add(tl.createConstraint().widthPercentage(20), new ScaleImageButton(icon)).
        add(tl.createConstraint().widthPercentage(80), new ScaleImageLabel(icon)).
        add(fillLabel).
        add(fillButton);
hi.show();

Figure 250. ScaleImageLabel/Button, the top row includes scale to fit versions (the default) whereas the

bottom row includes the scale to fill versions



When  styling  these  components  keep  in  mind  that  changing  attributes  such  as

background  behavior  might  cause  an  issue  with  their  functionality  or  might  not

work.

6.26. Toolbar

The  Toolbar  [https://www.codenameone.com/javadoc/com/codename1/ui/Toolbar.html]  API  provides  deep

customization  of 

the 

title  bar  area  with  more 

flexibility  e.g.  placing  a  TextField

[https://www.codenameone.com/javadoc/com/codename1/ui/TextField.html] for search or buttons in arbitrary
title  area  positions.  The  Toolbar  API  replicates  some  of  the  native  functionality  available  on
Android/iOS  and  integrates  with  features  such  as  the  side  menu  to  provide  very  fine  grained

control over the title area behavior.

The Toolbar needs to be installed into the Form in order for it to work. You can setup the Toolbar in
one of these three ways:

1. form.setToolbar(new  Toolbar());  -  allows  you  to  activate  the  Toolbar  to  a  specific  Form  and  not

for the entire application

2. Toolbar.setGlobalToolbar(true); - enables the Toolbar for all the forms in the app

3. Theme constant globalToobarBool - this is equivalent to Toolbar.setGlobalToolbar(true);

The  basic  functionality  of  the  Toolbar  includes  the  ability  to  add  a  command  to  the  following  4
places:

• Left side of the title - addCommandToLeftBar

• Right side of the title - addCommandToRightBar

262

• Side  menu  bar  (the  drawer  that  opens  when  you  click  the  icon  on  the  top  left  or  swipe  the

screen from left to right) - addCommandToSideMenu

• Overflow menu (the menu that opens when you tap the 3 vertical dots in the top right corner) -

addCommandToOverflowMenu

The code below provides a brief overview of these options:

Toolbar.setGlobalToolbar(true);

Form hi = new Form("Toolbar", new BoxLayout(BoxLayout.Y_AXIS));
hi.getToolbar().addCommandToLeftBar("Left", icon, (e) -> Log.p("Clicked"));
hi.getToolbar().addCommandToRightBar("Right", icon, (e) -> Log.p("Clicked"));
hi.getToolbar().addCommandToOverflowMenu("Overflow", icon, (e) -> Log.p("Clicked"));
hi.getToolbar().addCommandToSideMenu("Sidemenu", icon, (e) -> Log.p("Clicked"));
hi.show();

Figure 251. The Toolbar

Figure 252. The default sidemenu of the Toolbar

Figure 253. The overflow menu of the Toolbar

Normally  you  can  just  set  a  title  with  a  String  but  if  you  would  want  the  component  to  be  a  text
field or a multi line label you can use setTitleComponent(Component) which allows you to install any
component into the title area.



The  code  below  demonstrates  searching  using  custom  code  however  the  Toolbar

also has builtin support for search covered in the next section

The  customization  of  the  title  area  allows  for  some  pretty  powerful  UI  effects  e.g.  the  code  below

allows searching dynamically within a set of entries and uses some very neat tricks:

263

Toolbar.setGlobalToolbar(true);
Style s = UIManager.getInstance().getComponentStyle("Title");

Form hi = new Form("Toolbar", new BoxLayout(BoxLayout.Y_AXIS));
TextField searchField = new TextField("", "Toolbar Search"); ①
searchField.getHintLabel().setUIID("Title");
searchField.setUIID("Title");
searchField.getAllStyles().setAlignment(Component.LEFT);
hi.getToolbar().setTitleComponent(searchField);
FontImage searchIcon = FontImage.createMaterial(FontImage.MATERIAL_SEARCH, s);
searchField.addDataChangeListener((i1, i2) -> { ②
    String t = searchField.getText();
    if(t.length() < 1) {
        for(Component cmp : hi.getContentPane()) {
            cmp.setHidden(false);
            cmp.setVisible(true);
        }
    } else {
        t = t.toLowerCase();
        for(Component cmp : hi.getContentPane()) {
            String val = null;
            if(cmp instanceof Label) {
                val = ((Label)cmp).getText();
            } else {
                if(cmp instanceof TextArea) {
                    val = ((TextArea)cmp).getText();
                } else {
                    val = (String)cmp.getPropertyValue("text");
                }
            }
            boolean show = val != null && val.toLowerCase().indexOf(t) > -1;
            cmp.setHidden(!show); ③
            cmp.setVisible(show);
        }
    }
    hi.getContentPane().animateLayout(250);
});
hi.getToolbar().addCommandToRightBar("", searchIcon, (e) -> {
    searchField.startEditingAsync(); ④
});

hi.add("A Game of Thrones").
        add("A Clash Of Kings").
        add("A Storm Of Swords").
        add("A Feast For Crows").
        add("A Dance With Dragons").
        add("The Winds of Winter").
        add("A Dream of Spring");
hi.show();

264

① We use a TextField the whole time and just style it to make it (and its hint) look like a regular

title. An alternative way is to replace the title component dynamically.

② We use the DataChangeListener to update the search results as we type them.

③ Hidden  &  Visible  use  the  opposite  flag  values  to  say  similar  things  (e.g.  when  hidden  is  set  to

false you would want to set visible to true).

Visible indicates whether a component can be seen. It will still occupy the physical space on the

screen even when it isn’t visible. Hidden will remove the space occupied by the component from

the screen, but some code might still try to paint it. Normally, visible is redundant but we use it

with hidden for good measure.

④ The search button is totally unnecessary here. We can just click the TextField!

However, that isn’t intuitive to most users so we added the button to start editing.

Figure 254. Search field within the toolbar

Figure 255. Search field after typing a couple of letters

6.26.1. Search Mode

While  you  can  implement  search  manually  using  the  builtin  search  offers  a  simpler  and  more

uniform UI.

Figure 256. Builtin toolbar search functionality

265

You  can  customize  the  appearance  of  the  search  bar  by  using  the  UIID’s:  ToolbarSearch,
TextFieldSearch & TextHintSearch.

In the sample below we fetch all the contacts from the device and enable search thru them, notice it
expects and image called duke.png which is really just the default Codename One icon renamed and
placed in the src folder:

Image duke = null;
try {
    duke = Image.createImage("/duke.png");
} catch(IOException err) {
    Log.e(err);
}
int fiveMM = Display.getInstance().convertToPixels(5);
final Image finalDuke = duke.scaledWidth(fiveMM);
Toolbar.setGlobalToolbar(true);
Form hi = new Form("Search", BoxLayout.y());
hi.add(new InfiniteProgress());
Display.getInstance().scheduleBackgroundTask(()-> {
    // this will take a while...
    Contact[] cnts = Display.getInstance().getAllContacts(true, true, true, true, false, false);
    Display.getInstance().callSerially(() -> {
        hi.removeAll();
        for(Contact c : cnts) {
            MultiButton m = new MultiButton();
            m.setTextLine1(c.getDisplayName());
            m.setTextLine2(c.getPrimaryPhoneNumber());
            Image pic = c.getPhoto();
            if(pic != null) {
                m.setIcon(fill(pic, finalDuke.getWidth(), finalDuke.getHeight()));
            } else {
                m.setIcon(finalDuke);
            }
            hi.add(m);
        }
        hi.revalidate();
    });
});

hi.getToolbar().addSearchCommand(e -> {
    String text = (String)e.getSource();
    if(text == null || text.length() == 0) {
        // clear search
        for(Component cmp : hi.getContentPane()) {
            cmp.setHidden(false);
            cmp.setVisible(true);
        }
        hi.getContentPane().animateLayout(150);
    } else {
        text = text.toLowerCase();
        for(Component cmp : hi.getContentPane()) {
            MultiButton mb = (MultiButton)cmp;
            String line1 = mb.getTextLine1();
            String line2 = mb.getTextLine2();

266

            boolean show = line1 != null && line1.toLowerCase().indexOf(text) > -1 ||
                    line2 != null && line2.toLowerCase().indexOf(text) > -1;
            mb.setHidden(!show);
            mb.setVisible(show);
        }
        hi.getContentPane().animateLayout(150);
    }
}, 4);

hi.show();

6.26.2. South Component

A common feature in side menu bar is the ability to add a component to the "south" part of the side

menu.

Notice that this feature only works with the on-top and permanent versions of the side menu and

not with the legacy versions:

toolbar.setComponentToSideMenuSouth(myComponent);

This places the component below the side menu bar. Notice that this component controls its entire
UIID & is separate from the SideNavigationPanel UIID so if you set that component you might want
to place it within a container that has the SideNavigationPanel UIID so it will blend with the rest of
the UI.

6.26.3. Title Animations

Modern  UI’s  often  animate  the  title  upon  scrolling  to  balance  the  highly  functional  smaller  title

advantage with the gorgeous large image based title. This is pretty easy to do with the Toolbar API

thru the Title animation API.

The  code  below  shows  off  an  attractive  title  based  on  a  book  by  GRRM  on  top  of  text  [6]  that  is
scrollable. As the text is scrolled the title fades out.

267

Toolbar.setGlobalToolbar(true);

Form hi = new Form("Toolbar", new BoxLayout(BoxLayout.Y_AXIS));
EncodedImage placeholder = EncodedImage.createFromImage(Image.createImage(hi.getWidth(), hi.getWidth() / 5, 0xffff0000),
true);
URLImage background = URLImage.createToStorage(placeholder, "400px-AGameOfThrones.jpg",
        "http://awoiaf.westeros.org/images/thumb/9/93/AGameOfThrones.jpg/400px-AGameOfThrones.jpg");
background.fetch();
Style stitle = hi.getToolbar().getTitleComponent().getUnselectedStyle();
stitle.setBgImage(background);
stitle.setBackgroundType(Style.BACKGROUND_IMAGE_SCALED_FILL);
stitle.setPaddingUnit(Style.UNIT_TYPE_DIPS, Style.UNIT_TYPE_DIPS, Style.UNIT_TYPE_DIPS, Style.UNIT_TYPE_DIPS);
stitle.setPaddingTop(15);
SpanButton credit = new SpanButton("This excerpt is from A Wiki Of Ice And Fire. Please check it out by clicking here!");
credit.addActionListener((e) -> Display.getInstance().execute("http://awoiaf.westeros.org/index.php/A_Game_of_Thrones"));
hi.add(new SpanLabel("A Game of Thrones is the first of seven planned novels in A Song of Ice and Fire, an epic fantasy
series by American author George R. R. Martin. It was first published on 6 August 1996. The novel was nominated for the
1998 Nebula Award and the 1997 World Fantasy Award,[1] and won the 1997 Locus Award.[2] The novella Blood of the Dragon,
comprising the Daenerys Targaryen chapters from the novel, won the 1997 Hugo Award for Best Novella. ")).
        add(new Label("Plot introduction", "Heading")).
        add(new SpanLabel("A Game of Thrones is set in the Seven Kingdoms of Westeros, a land reminiscent of Medieval
Europe. In Westeros the seasons last for years, sometimes decades, at a time.\n\n" +
            "Fifteen years prior to the novel, the Seven Kingdoms were torn apart by a civil war, known alternately as
\"Robert's Rebellion\" and the \"War of the Usurper.\" Prince Rhaegar Targaryen kidnapped Lyanna Stark, arousing the ire
of her family and of her betrothed, Lord Robert Baratheon (the war's titular rebel). The Mad King, Aerys II Targaryen,
had Lyanna's father and eldest brother executed when they demanded her safe return. Her second brother, Eddard, joined
his boyhood friend Robert Baratheon and Jon Arryn, with whom they had been fostered as children, in declaring war against
the ruling Targaryen dynasty, securing the allegiances of House Tully and House Arryn through a network of dynastic
marriages (Lord Eddard to Catelyn Tully and Lord Arryn to Lysa Tully). The powerful House Tyrell continued to support the
King, but House Lannister and House Martell both stalled due to insults against their houses by the Targaryens. The civil
war climaxed with the Battle of the Trident, when Prince Rhaegar was killed in battle by Robert Baratheon. The Lannisters
finally agreed to support King Aerys, but then brutally... ")).
        add(credit);

ComponentAnimation title = hi.getToolbar().getTitleComponent().createStyleAnimation("Title", 200);
hi.getAnimationManager().onTitleScrollAnimation(title);
hi.show();

Figure 257. The Toolbar starts with the large URLImage fetched from the web

268

Figure 258. As we scroll down the image fades and the title shrinks in size returning to the default UIID look

Figure 259. As scrolling continues the title reaches standard size

Almost all of the code above just creates the "look" of the application. The key piece of code above is

this:

ComponentAnimation title = hi.getToolbar().getTitleComponent().createStyleAnimation("Title", 200);
hi.getAnimationManager().onTitleScrollAnimation(title);

In the first line we create a style animation that will translate the style from the current settings to

the destination UIID (the first argument) within 200 pixels of scrolling. We then bind this animation

to the title scrolling animation event.

6.27. BrowserComponent & WebBrowser



BrowserComponent  is  a  peer  component,  understanding  this  is  crucial  if  your
application depends on such a component. You can learn about peer components

and  their  issues  here  [https://www.codenameone.com/manual/advanced-topics.html#native-

peer-components].

The  WebBrowser 

[https://www.codenameone.com/javadoc/com/codename1/components/WebBrowser.html]

component  shows  the  native  device  web  browser  when  supported  by  the  device  and  the

HTMLComponent 

[https://www.codenameone.com/javadoc/com/codename1/ui/html/HTMLComponent.html]

when  the  web  browser  isn’t  supported  on  the  given  device.  If  you  only  intend  to  target

smartphones  you  should  use  the  BrowserComponent  [https://www.codenameone.com/javadoc/com/
codename1/ui/BrowserComponent.html] directly instead of the WebBrowser.

269

The BrowserComponent can point at an arbitrary URL to load it:

Form hi = new Form("Browser", new BorderLayout());
BrowserComponent browser = new BrowserComponent();
browser.setURL("https://www.codenameone.com/");
hi.add(BorderLayout.CENTER, browser);

Figure 260. Browser Component showing the Codename One website on the simulator

 The  scrollbars  only  appear  in  the  simulator,  device  versions  of  the  browser

component act differently and support touch scrolling.



A  BrowserComponent  should  be  in  the  center  of  a  BorderLayout.  Otherwise  its
preferred size might be zero before the HTML finishes loading/layout in the native

layer and layout might be incorrect as a result.

You can use WebBrowser and BrowserComponent interchangeably for most basic usage. However, if you
need access to JavaScript or native browser functionality then there is really no use in going thru
the WebBrowser abstraction.

The BrowserComponent has full support for executing local web pages from within the jar. The basic
support uses the jar:/// URL as such:

BrowserComponent wb = new BrowserComponent();
wb.setURL("jar:///Page.html");



On Android a native indicator might show up when the web page is loading. This
can  be  disabled  using  the  Display.getInstance().setProperty("WebLoadingHidden",
"true"); call. You only need to invoke this once.

270

6.27.1. BrowserComponent Hierarchy

When  Codename  One  packages  applications  into  native  apps  it  hides  a  lot  of  details  to  make  the

process simpler. One of the things hidden is the fact that we aren’t dealing with a JAR anymore, so
getResource/getResourceAsStream  are  problematic…  Both  of  these  API’s  support  hierarchies  and  a
concept of package relativity both of which might not be supported on all OS’s.

Codename One has its own getResourceAsSteam in the Display [https://www.codenameone.com/javadoc/

com/codename1/ui/Display.html] class and that works just fine, but it requires that all files be in the src

root directory.



That’s  why  we  recommend  that  you  place  files  inside  res  files.  A  resource  file

allows you to add arbitrary data files and you can have as many resource files as

you need.

For  web  developers  this  isn’t  enough  since  hierarchies  are  used  often  to  represent  the  various

dependencies, this means that many links & references are relative. To work with such hierarchies

just  place  all  of  your  resources  in  a  hierarchy  under  the  html  package  in  the  project  source
directory  (src/html).  The  build  server  will  tar  the  entire  content  of  that  package  and  add  an
html.tar  file  into  the  native  package.  This  tar  is  seamlessly  extracted  on  the  device  when  you
actually  need  the  resources  and  only  with  new  application  versions  (not  on  every  launch).  So

assuming the resources are under the html root package they can be displayed with code like this:

try {
    browserComponent.setURLHierarchy("/htmlFile.html");
} catch(IOException err) {
    ...
}

Notice that the path is relative to the html directory and starts with / but inside the HTML files you
should use relative (not absolute) paths.

Also  notice  that  an  IOException  can  be  thrown  due  to  the  process  of  untarring.  Its  unlikely  to
happen but is entirely possible.

6.27.2. NavigationCallback

At 

the 

core 

of 

the 

BrowserComponent  we 

have 

the  BrowserNavigationCallback

[https://www.codenameone.com/javadoc/com/codename1/ui/events/BrowserNavigationCallback.html]. It might not

seem  like  the  most  important  interface  within  the  browser  but  it  is  the  "glue"  that  allows  the

JavaScript code to communicate back into the Java layer.

You  can  bind  a  BrowserNavigationCallback  by  invoking  setBrowserNavigationCallback  on  the
BrowserComponent.  At  that  point  with  every  navigation  within  the  browser  the  callback  will  get
invoked.

271



The  shouldNavigate  method  from  the  BrowserNavigationCallback  is  invoked  in  a
native thread and NOT ON THE EDT!

It is crucial that this method returns immediately and that it won’t do any changes

on the UI.

The shouldNavigate indicates to the native code whether navigation should proceed or not. E.g. if a
user clicks a specific link we might choose to do something in the Java code so we can just return

false  and  block  the  navigation.  We  can  invoke  callSerially  [https://www.codenameone.com/javadoc/com/

codename1/ui/Display.html#callSerially-java.lang.Runnable-] to do the actual task in the Java side.

Form hi = new Form("BrowserComponent", new BorderLayout());
BrowserComponent bc = new BrowserComponent();
bc.setPage( "<html lang=\"en\">\n" +
            "    <head>\n" +
            "        <meta charset=\"utf-8\">\n" +
            "        <script>\n" +
            "          function  fnc(message) {\n" +
            "         document.write(message);\n" +
            "            };\n" +
            "        </script>\n" +
            "    </head>\n" +
            "    <body >\n" +
            "        <p><a href=\"http://click\">Demo</a></p>\n" +
            "    </body>\n" +
            "</html>", null);
hi.add(BorderLayout.CENTER, bc);
bc.setBrowserNavigationCallback((url) -> {
    if(url.startsWith("http://click")) {
        Display.getInstance().callSerially(() -> bc.execute("fnc('<p>You clicked!</p>')"));
        return false;
    }
    return true;
});

Figure 261. Before the link is clicked for the "shouldNavigate" call

Figure 262. After the link is clicked for the "shouldNavigate" call

 The JavaScript Bridge is implemented on top of the BrowserNavigationCallback.

6.27.3. JavaScript

272



The  JavaScript  bridge  is  sometimes  confused  with  the  JavaScript  Port.  The

JavaScript  bridge  allows  us  to  communicate  with  JavaScript  from  Java  (and  visa

versa).  The  JavaScript  port  allows  you  to  compile  the  Codename  One  application

into  a  JavaScript  application  that  runs  in  a  standard  web  browser  without  code

changes  (think  GWT  without  source  changes  and  with  thread  support).+  We

discuss the JavaScript port further later in the guide.

Codename One 4.0 introduced a new API for interacting with Javascript in Codename One. This API
is part of the BrowserComponent class, and effectively replaces the com.codename1.javascript package
is  now
[https://www.codenameone.com/javadoc/com/codename1/javascript/package-summary.html],  which 

deprecated.

So what was wrong with the old API?

The  old  API  provided  a  synchronous  wrapper  around  an  inherently  asynchronous  process,  and
made  extensive  use  of  invokeAndBlock()  underneath  the  covers.  This  resulted  in  a  very  nice  API
with  high-level  abstractions  that  played  nicely  with  a  synchronous  programming  model,  but  it

came  with  a  price-tag  in  terms  of  performance,  complexity,  and  predictability.  Let’s  take  a  simple

example, getting a reference to the “window” object:

JSObject window = ctx.get("window");

This  code  looks  harmless  enough,  but  this  is  actually  quite  expensive.  It  issues  a  command  to  the
BrowserComponent, and uses invokeAndBlock() to wait for the command to go through and send back
a response. invokeAndBlock() is a magical tool that allows you to “block” without blocking the EDT,
but  it  has  its  costs,  and  shouldn’t  be  overused.  Most  of  the  Codename  One  APIs  that  use
invokeAndBlock() indicate this in their name. E.g. Component.animateLayoutAndWait(). This gives you
the expectation that this call could take some time, and helps to alert you to the underlying cost.

The  problem  with  the  ctx.get("window")  call  is  that  it  looks  the  same  as  a  call  to  Map.get(key).
There’s no indication that this call is expensive and could take time. One call like this probably isn’t

a big deal, but it doesn’t take long before you have dozens or even hundreds of calls like this littered

throughout your codebase, and they can be hard to pick out.

The New API

The  new  API  fully  embraces  the  asynchronous  nature  of  Javascript.  It  uses  callbacks  instead  of

return  values,  and  provides  convenience  wrappers  with  the  appropriate  “AndWait()”  naming

convention to allow for synchronous usage. Let’s look at a simple example:



In all of the sample code below, you can assume that variables named bc represent
[https://www.codenameone.com/javadoc/com/
an 

instance  of  BrowserComponent 

codename1/ui/BrowserComponent.html].

273

bc.execute(
    "callback.onSuccess(3+4)",
    res -> Log.p("The result was "+res.getInt())
);

This  code  should  output  “The  result  was  7”  to  the  console.  It  is  fully  asynchronous,  so  you  can

include  this  code  anywhere  without  worrying  about  it  “bogging  down”  your  code.  The  full

signature  of  this  form  of  the  execute()  [https://www.codenameone.com/javadoc/com/codename1/ui/

BrowserComponent.html#execute-java.lang.String-com.codename1.util.SuccessCallback-] method is:

public void execute(String js, SuccessCallback<JSRef> callback)

The  first  parameter 
javascript  MUST  call  either
callback.onSuccess(result) or callback.onError(message, errCode) at some point in order for your
callback to be called.

javascript  expression.  This 

just  a 

is 

The  second  parameter  is  your  callback  that  is  executed  from  the  javascript  side,  when
callback.onSuccess(res) 
[https://www.codenameone.com/javadoc/com/codename1/ui/BrowserComponent.JSRef.html]  which  is  a  generic

is  called.  The  callback  takes  a  single  parameter  of  type  JSRef

wrapper  around  a  javascript  variable.  JSRef  has  accessors  to  retrieve  the  value  as  some  of  the
primitive  types.  E.g.  getBoolean(),  getDouble(),  getInt(),  toString(),  and  it  provides  some
introspection via the getType() method.



It is worth noting that the callback method can only take a single parameter. If you

need  to  pass  multiple  parameters,  you  may  consider  including  them  in  a  single

string which you parse in your callback.

Synchronous Wrappers

As  mentioned  before,  the  new  API  also  provides  an  executeAndWait()  wrapper  for  execute()  that
will work synchronously. It, as its name suggests, uses invokeAndBlock under the hood so as not to
block the EDT while it is waiting.

E.g.

JSRef res = bc.executeAndWait("callback.onSuccess(3+4)");
Log.p("The result was "+res.Int());

Prints “The result was 7”.



When using the andWait() variant, it is extremely important that your Javascript
calls your callback method at some point - otherwise it will block indefinitely. We

provide  variants  of  executeAndWait()  that  include  a  timeout  in  case  you  want  to

hedge against this possibility.

274

Multi-use Callbacks

The  callbacks  you  pass  to  execute()  and  executeAndWait()  are  single-use  callbacks.  You  can’t,  for
example, store the callback variable on the javascript side for later use (e.g. to respond to a button
click event). If you need a “multi-use” callback, you should use the addJSCallback() method instead.
Its usage looks identical to execute(), the only difference is that the callback will life on after its first
use. E.g. Consider the following code:

bc.execute(
    "$('#somebutton').click(function(){callback.onSuccess('Button was clicked')})",
    res -> Log.p(res.toString())
);

The above example, assumes that jQuery is loaded in the webpage that we are interacting with, and

we  are  adding  a  click  handler  to  a  button  with  ID  “somebutton”.  The  click  handler  calls  our

callback.

If you run this example, the first time the button is clicked, you’ll see “Button was clicked” printed

to the console as expected. However, the 2nd time, you’ll just get an exception. This is because the
callback passed to execute() is only single-use.

We need to modify this code to use the addJSCallback() method as follows:

bc.addJSCallback(
    "$('#somebutton').click(function(){callback.onSuccess('Button was clicked')})",
    res -> Log.p(res.toString())
);

Now it will work no matter how many times the button is clicked.

Passing Parameters to Javascript

In many cases, the javascript expressions that you execute will include parameters from your java

code.  Properly  escaping  these  parameters  is  tricky  at  worst,  and  annoying  at  best.  E.g.  If  you’re

passing  a  string,  you  need  to  make  sure  that  it  escapes  quotes  and  new  lines  properly  or  it  will
cause  the  javascript  to  have  a  syntax  error.  Luckily  we  provide  variants  of  execute()  and
[https://www.codenameone.com/javadoc/com/codename1/ui/BrowserComponent.html#
addJSCallback() 

addJSCallback-java.lang.String-com.codename1.util.SuccessCallback-] that allow you to pass your parameters

and have them automatically escaped.

For example, suppose we want to pass a string with text to set in a textarea within the webpage. We

can do something like:

275

bc.execute(
    "jQuery('#bio').text(${0}); jQuery('#age').text(${1})",
    new Object[]{
       "A multi-line\n string with \"quotes\"",
       27
    }
);

The  gist  is  that  you  embed  placeholders  in  the  javascript  expression  that  are  replaced  by  the
corresponding entry in an array of parameters. The ${0} placeholder is replaced by the first item in
the parameters array, the ${1} placeholder is replaced by the 2nd, and so on.

Proxy Objects

The  new  API  also 

includes  a 

JSProxy 

[https://www.codenameone.com/javadoc/com/codename1/ui/

BrowserComponent.JSProxy.html]  class  that  encapsulates  a  Javascript  object  simplify  the  getting  and

setting of properties on Javascript objects - and the calling of their methods. It provides essentially

three core methods, along with several variants of each to allow for async or synchronous usages,

parameters, and timeouts.

E.g.  We  might  want  to  create  a  proxy  for  the  window.location  [https://developer.mozilla.org/en-US/docs/

Web/API/Window/location] object so that we can access its properties more easily from Java.

JSProxy location = bc.createJSProxy("window.location");

Then we can retrieve its properties using the get() method:

location.get("href", res -> Log.p("location.href="+res));

Or synchronously:

JSRef href = location.getAndWait("href");
Log.p("location.href="+href);

We can also set its properties:

location.set("href", "http://www.google.com");

And call its methods:

location.call("replace", new Object[]{"http://www.google.com"},
    res -> Log.p("Return value was "+res)
);

276

Legacy JSObject Support

This section describes the now deprecated JSObject approach. It’s here for reference by developers
working with older code. We suggest using the new API when starting a new project.

BrowserComponent  can  communicate  with  the  HTML  code  using  JavaScript  calls.  E.g.  we  can  create
HTML like this:

Form hi = new Form("BrowserComponent", new BorderLayout());
BrowserComponent bc = new BrowserComponent();
bc.setPage( "<html lang=\"en\">\n" +
            "    <head>\n" +
            "        <meta charset=\"utf-8\">\n" +
            "        <script>\n" +
            "          function  fnc(message) {\n" +
            "         document.write(message);\n" +
            "            };\n" +
            "        </script>\n" +
            "    </head>\n" +
            "    <body >\n" +
            "        <p>Demo</p>\n" +
            "    </body>\n" +
            "</html>", null);
TextField tf = new TextField();
hi.add(BorderLayout.CENTER, bc).
        add(BorderLayout.SOUTH, tf);
bc.addWebEventListener("onLoad", (e) ->  bc.execute("fnc('<p>Hello World</p>')"));
tf.addActionListener((e) -> bc.execute("fnc('<p>" + tf.getText() +"</p>')"));
hi.show();

Figure 263. JavaScript code was invoked to append text into the browser image above

 Notice that opening an alert in an embedded native browser might not work

We  use  the  execute  method  above  to  execute  custom  JavaScript  code.  We  also  have  an
executeAndReturnString method that allows us to receive a response value from the JavaScript side.

Coupled with shouldNavigate we can effectively do everything which is exactly what the JavaScript
Bridge tries to do.

277

The JavaScript Bridge

While  it’s  possible  to  just  build  everything  on  top  of  execute  and  shouldNavigate,  both  of  these
methods  have  their  limits.  That  is  why  we  introduced  the  javascript  package,  it  allows  you  to

communicate with JavaScript using intuitive code/syntax.

The 

JavascriptContext 

[https://www.codenameone.com/javadoc/com/codename1/javascript/

JavascriptContext.html] class lays the foundation by enabling you to call JavaScript code directly from

Java. It provides automatic type conversion between Java and JavaScript types as follows:

Table 5. Java to JavaScript

Java Type

String

Double/Integer/Float/Long

Boolean

JSObject

null

Other

Table 6. JavaScript to Java

Javascript Type

String

Number

Boolean

Object

Function

Array

null

undefined

Javascript Type

String

Number

Boolean

Object

null

Not Allowed

Java Type

String

Double

Boolean

JSObject

JSObject

JSObject

null

null

This  conversion  table  is  more  verbose  than  necessary,  since  JavaScript  functions



and  arrays  are,  in  fact  Objects  themselves,  so  those  rows  are  redundant.  All

JavaScript  objects  are  converted  to  JSObject  [https://www.codenameone.com/javadoc/

com/codename1/javascript/JSObject.html].

We can access JavaScript variables easily from the context by using code like this:

278

Form hi = new Form("BrowserComponent", new BorderLayout());
BrowserComponent bc = new BrowserComponent();
bc.setPage( "<html lang=\"en\">\n" +
            "    <head>\n" +
            "        <meta charset=\"utf-8\">\n" +
            "    </head>\n" +
            "    <body >\n" +
            "        <p>This will appear twice...</p>\n" +
            "    </body>\n" +
            "</html>", null);
hi.add(BorderLayout.CENTER, bc);
bc.addWebEventListener("onLoad", (e) -> {
    // Create a Javascript context for this BrowserComponent
    JavascriptContext ctx = new JavascriptContext(bc);

    String pageContent = (String)ctx.get("document.body.innerHTML");
    hi.add(BorderLayout.SOUTH, pageContent);
    hi.revalidate();
});
hi.show();

Figure 264. The contents was copied from the DOM and placed in the south position of the form

Notice that when you work with numeric values or anything related to the types mentioned above
your code must be aware of the typing. E.g. in this case the type is Double and not String:

Double outerWidth = (Double)ctx.get("window.outerWidth");

You can also query the context for objects and modify their value e.g.

279

Form hi = new Form("BrowserComponent", new BorderLayout());
BrowserComponent bc = new BrowserComponent();
bc.setPage( "<html lang=\"en\">\n" +
            "    <head>\n" +
            "        <meta charset=\"utf-8\">\n" +
            "    </head>\n" +
            "    <body >\n" +
            "        <p>Please Wait...</p>\n" +
            "    </body>\n" +
            "</html>", null);
hi.add(BorderLayout.CENTER, bc);
bc.addWebEventListener("onLoad", (e) -> {
    // Create a Javascript context for this BrowserComponent
    JavascriptContext ctx = new JavascriptContext(bc);

    JSObject jo = (JSObject)ctx.get("window");
    jo.set("location", "https://www.codenameone.com/");
});

This  code  effectively  navigates  to  the  Codename  One  home  page  by  fetching  the  DOM’s  window

object 

and 

setting 

its 

location 

property 

to 

https://www.codenameone.com/

[https://www.codenameone.com/].

6.27.4. Cordova/PhoneGap Integration

PhoneGap was one of the first web app packager tools in the market. It’s a tool that is effectively a

browser component within a native wrapper coupled with native access API’s. Cordova is the open

source extension of this popular project.

Codename  One  supports  embedding  PhoneGap/Cordova  applications  directly  into  Codename  One
applications. This is relatively easy to do with the BrowserComponent and JavaScript integration. The
main aspect that this integration requires is support for Cordova plugins & its JavaScript API’s.

The  effort  to  integrate  Cordova/PhoneGap  support  into  Codename  One  is  handled  within  an  open

source  github  project  here  [https://github.com/codenameone/CN1Cordova].  The  chief  benefits  of  picking

Codename One rather than using Cordova directly are:

• Build Cloud

• Better Native Code Support

• Better Protection Of IP

• IDE Integration Java - JavaScript - HTML

• Easy, Doesn’t Require A Mac, Automates Certificates/Signing

• Migration To Java

This  is  discussed  further  in  the  original  announcement  [https://www.codenameone.com/blog/phonegap-

cordova-compatibility-for-codename-one.html].

280

6.28. AutoCompleteTextField

The 

AutoCompleteTextField 

[https://www.codenameone.com/javadoc/com/codename1/ui/

AutoCompleteTextField.html] allows us to write text into a text field and select a completion entry from

the list in a similar way to a search engine.

This  is  really  easy  to  incorporate  into  your  code,  just  replace  your  usage  of  TextField
[https://www.codenameone.com/javadoc/com/codename1/ui/TextField.html]  with  AutoCompleteTextField  and
define  the  data  that  the  autocomplete  should  work  from.  There  is  a  default  implementation  that
accepts  a  String  array  or  a  ListModel  [https://www.codenameone.com/javadoc/com/codename1/ui/list/
ListModel.html]  for  completion  strings,  this  can  work  well  for  a  "small"  set  of  thousands  (or  tens  of

thousands) of entries.

E.g. This is a trivial use case that can work well for smaller sample sizes:

Form hi = new Form("Auto Complete", new BoxLayout(BoxLayout.Y_AXIS));
AutoCompleteTextField ac = new AutoCompleteTextField("Short", "Shock", "Sholder", "Shrek");
ac.setMinimumElementsShownInPopup(5);
hi.add(ac);

Figure 265. Autocomplete Text Field

However,  if  you  wish  to  query  a  database  or  a  web  service  you  will  need  to  derive  the  class  and
perform more advanced filtering by overriding the filter method:

281

public void showForm() {
  final DefaultListModel<String> options = new DefaultListModel<>();
  AutoCompleteTextField ac = new AutoCompleteTextField(options) {
      @Override
      protected boolean filter(String text) {
          if(text.length() == 0) {
              return false;
          }
          String[] l = searchLocations(text);
          if(l == null || l.length == 0) {
              return false;
          }

          options.removeAll();
          for(String s : l) {
              options.addItem(s);
          }
          return true;
      }

  };
  ac.setMinimumElementsShownInPopup(5);
  hi.add(ac);
  hi.add(new SpanLabel("This demo requires a valid google API key to be set below "
           + "you can get this key for the webservice (not the native key) by following the instructions here: "
           + "https://developers.google.com/places/web-service/get-api-key"));
  hi.add(apiKey);
  hi.getToolbar().addCommandToRightBar("Get Key", null, e ->
Display.getInstance().execute("https://developers.google.com/places/web-service/get-api-key"));
  hi.show();
}

TextField apiKey = new TextField();

String[] searchLocations(String text) {
    try {
        if(text.length() > 0) {
            ConnectionRequest r = new ConnectionRequest();
            r.setPost(false);
            r.setUrl("https://maps.googleapis.com/maps/api/place/autocomplete/json");
            r.addArgument("key", apiKey.getText());
            r.addArgument("input", text);
            NetworkManager.getInstance().addToQueueAndWait(r);
            Map<String,Object> result = new JSONParser().parseJSON(new InputStreamReader(new
ByteArrayInputStream(r.getResponseData()), "UTF-8"));
            String[] res = Result.fromContent(result).getAsStringArray("//description");
            return res;
        }
    } catch(Exception err) {
        Log.e(err);
    }
    return null;
}

Figure 266. Autocomplete Text Field with a webservice

282

6.28.1. Using Images In AutoCompleteTextField

One question I got a few times is "How do you customize the results of the auto complete field"?

This  sounds  difficult  to  most  people  as  we  can  only  work  with  Strings  so  how  do  we  represent

additional data or format the date correctly?

The  answer  is  actually  pretty  simple,  we  still  need  to  work  with  Strings  because  auto-complete  is

first and foremost a text field. However, that doesn’t preclude our custom renderer from fetching

data that might be placed in a different location and associated with the result.

The  following  source  code  presents  an  auto-complete  text  field  with  images  in  the  completion

popup and two lines for every entry:

283

final String[] characters = { "Tyrion Lannister", "Jaime Lannister", "Cersei Lannister", "Daenerys Targaryen",
    "Jon Snow", "Petyr Baelish", "Jorah Mormont", "Sansa Stark", "Arya Stark", "Theon Greyjoy"
    // snipped the rest for clarity
};

Form current = new Form("AutoComplete", BoxLayout.y());

AutoCompleteTextField ac = new AutoCompleteTextField(characters);

final int size = Display.getInstance().convertToPixels(7);
final EncodedImage placeholder = EncodedImage.createFromImage(Image.createImage(size, size, 0xffcccccc), true);

final String[] actors = { "Peter Dinklage", "Nikolaj Coster-Waldau", "Lena Headey"}; ①
final Image[] pictures = {
    URLImage.createToStorage(placeholder, "tyrion","http://i.lv3.hbo.com/assets/images/series/game-of-
thrones/character/s5/tyrion-lannister-512x512.jpg"),
    URLImage.createToStorage(placeholder, "jaime","http://i.lv3.hbo.com/assets/images/series/game-of-
thrones/character/s5/jamie-lannister-512x512.jpg"),
    URLImage.createToStorage(placeholder, "cersei","http://i.lv3.hbo.com/assets/images/series/game-of-
thrones/character/s5/cersei-lannister-512x512.jpg")
};

ac.setCompletionRenderer(new ListCellRenderer() {
    private final Label focus = new Label(); ②
    private final Label line1 = new Label(characters[0]);
    private final Label line2 = new Label(actors[0]);
    private final Label icon = new Label(pictures[0]);
    private final Container selection = BorderLayout.center(
            BoxLayout.encloseY(line1, line2)).add(BorderLayout.EAST, icon);

    @Override
    public Component getListCellRendererComponent(com.codename1.ui.List list, Object value, int index, boolean
isSelected) {
        for(int iter = 0 ; iter < characters.length ; iter++) {
            if(characters[iter].equals(value)) {
                line1.setText(characters[iter]);
                if(actors.length > iter) {
                    line2.setText(actors[iter]);
                    icon.setIcon(pictures[iter]);
                } else {
                    line2.setText(""); ③
                    icon.setIcon(placeholder);
                }
                break;
            }
        }
        return selection;
    }

    @Override
    public Component getListFocusComponent(com.codename1.ui.List list) {
        return focus;
    }
});
current.add(ac);

current.show();

① We have duplicate arrays that are only partial for clarity. This is a separate list of data element

but you can fetch the additional data from anywhere

② We create the renderer UI instantly in the fields with the helper methods for wrapping elements

which is pretty cool & terse

284

③ In a renderer it’s important to always set the value especially if you don’t have a value in place

Figure 267. Auto complete with images

6.29. Picker

Picker  [https://www.codenameone.com/javadoc/com/codename1/ui/spinner/Picker.html]  occupies  the  limbo
between native widget and lightweight widget. Picker is more like TextField/TextArea in the sense
that it’s a Codename One widget that calls the native code only during editing.

The  reasoning  for  this  is  the  highly  native  UX  and  functionality  related  to  this  widget  type  which

should be quite obvious from the screenshots below.

At this time there are 4 types of pickers:

• Time

• Date & Time

• Date

• Strings

If a platform doesn’t support native pickers an internal fallback implementation is used. This is the

implementation we always use in the simulator so assume different behavior when building for the

device.



While  Android  supports  Date,  Time  native  pickers  it  doesn’t  support  the  Date  &

Time native picker UX and will fallback in that case.

The sample below includes al picker types:

285

Form hi = new Form("Picker", new BoxLayout(BoxLayout.Y_AXIS));
Picker datePicker = new Picker();
datePicker.setType(Display.PICKER_TYPE_DATE);
Picker dateTimePicker = new Picker();
dateTimePicker.setType(Display.PICKER_TYPE_DATE_AND_TIME);
Picker timePicker = new Picker();
timePicker.setType(Display.PICKER_TYPE_TIME);
Picker stringPicker = new Picker();
stringPicker.setType(Display.PICKER_TYPE_STRINGS);
Picker durationPicker = new Picker();
durationPicker.setType(Display.PICKER_TYPE_DURATION);
Picker minuteDurationPicker = new Picker();
minuteDurationPicker.setType(Display.PICKER_TYPE_DURATION_MINUTES);
Picker hourDurationPicker = new Picker();
hourDurationPicker.setType(Display.PICKER_TYPE_DURATION_HOURS);

datePicker.setDate(new Date());
dateTimePicker.setDate(new Date());
timePicker.setTime(10 * 60); // 10:00AM = Minutes since midnight
stringPicker.setStrings("A Game of Thrones", "A Clash Of Kings", "A Storm Of Swords", "A Feast For Crows",
        "A Dance With Dragons", "The Winds of Winter", "A Dream of Spring");
stringPicker.setSelectedString("A Game of Thrones");

hi.add(datePicker).add(dateTimePicker).add(timePicker)
  .add(stringPicker).add(durationPicker)
  .add(minuteDurationPicker).add(hourDurationPicker);
hi.show();

Figure 268. The various picker components

Figure 269. The date & time picker on the simulator

286

Figure 270. The date picker component on the Android device

Figure 271. Date & time picker on Android. Notice it didn’t use a builtin widget since there is none

Figure 272. String picker on the native Android device

287

Figure 273. Time picker on the Android device

Figure 274. Duration picker on Android device

Figure 275. Hours Duration picker on Android device

Figure 276. Minutes Duration picker on Android device

The  text  displayed  by  the  picker  on  selection  is  generated  automatically  by  the  updateValue()
method. You can override it to display a custom formatted value and call setText(String) with the
correct display string.

A common use case is to format date values based on a specific appearance and Picker has builtin
support for a custom display formatter. Just use the setFormatter(SimpleDateFormat) method and set
the appearance for the field.

288

6.30. SwipeableContainer

The  SwipeableContainer  [https://www.codenameone.com/javadoc/com/codename1/ui/SwipeableContainer.html]

allows  us  to  place  a  component  such  as  a  MultiButton  [https://www.codenameone.com/javadoc/com/

codename1/components/MultiButton.html] on top of additional "options" that can be exposed by swiping

the component to the side.

This swipe gesture is commonly used in touch interfaces to expose features such as delete, edit etc.

It’s trivial to use this component by just determining the components placed on top and bottom (the

revealed component).

SwipeableContainer swip = new SwipeableContainer(bottom, top);

We can combine some of the demos above including the Slider stars demo to rank GRRM’s books in

an interactive way:

Form hi = new Form("Swipe", new BoxLayout(BoxLayout.Y_AXIS));
hi.add(createRankWidget("A Game of Thrones", "1996")).
    add(createRankWidget("A Clash Of Kings", "1998")).
    add(createRankWidget("A Storm Of Swords", "2000")).
    add(createRankWidget("A Feast For Crows", "2005")).
    add(createRankWidget("A Dance With Dragons", "2011")).
    add(createRankWidget("The Winds of Winter", "TBD")).
    add(createRankWidget("A Dream of Spring", "TBD"));
hi.show();

public SwipeableContainer createRankWidget(String title, String year) {
    MultiButton button = new MultiButton(title);
    button.setTextLine2(year);
    return new SwipeableContainer(FlowLayout.encloseCenterMiddle(createStarRankSlider()),
            button);
}

Figure 277. SwipableContainer showing a common use case of ranking on swipe

289

6.31. EmbeddedContainer

EmbeddedContainer  [https://www.codenameone.com/javadoc/com/codename1/ui/util/EmbeddedContainer.html]

solves a problem that exists only within the GUI builder and the class makes no sense outside of the
context of the GUI builder. The necessity for EmbeddedContainer came about due to iPhone inspired
designs that relied on tabs (iPhone style tabs at the bottom of the screen) where different features

of the application are within a different tab.

This didn’t mesh well with the GUI builder navigation logic and so we needed to rethink some of it.

We wanted to reuse GUI as much as possible while still enjoying the advantage of navigation being

completely managed for me.

Android does this with Activities and the iPhone itself has a view controller, both approaches are

problematic for Codename One. The problem is that you have what is effectively two incompatible

hierarchies to mix and match.

The  Component/Container  hierarchy  is  powerful  enough  to  represent  such  a  UI  but  we  needed  a

"marker"  to  indicate  to  the  UIBuilder  [https://www.codenameone.com/javadoc/com/codename1/ui/util/

UIBuilder.html]  where  a  "root"  component  exists  so  navigation  occurs  only  within  the  given  "root".
Here  EmbeddedContainer  comes  into  play,  its  a  simple  container  that  can  only  contain  another  GUI
from the GUI builder. Nothing else. So we can place it in any form of UI and effectively have the UI

change appropriately and navigation would default to "sensible values".

Navigation replaces the content of the embedded container; it finds the embedded container based

on  the  component  that  broadcast  the  event.  If  you  want  to  navigate  manually  just  use  the

showContainer()  method  which  accepts  a  component,  you  can  give  any  component  that  is  under
the EmbeddedContainer you want to replace and Codename One will be smart enough to replace only
that component.

The nice part about using the EmbeddedContainer is that the resulting UI can be very easily refactored
to provide a more traditional form based UI without duplicating effort and can be easily adapted to

a more tablet oriented UI (with a side bar) again without much effort.

6.32. MapComponent

The  MapComponent  uses  a  somewhat  outdated  tiling  API  which  is  not  as  rich  as



modern  native  maps.  We  recommend  using  the  GoogleMap’s  Native  cn1lib

[https://github.com/codenameone/codenameone-google-maps/]  to  integrate  native  mapping

functionality into the Codename One app.

The  MapComponent  [https://www.codenameone.com/javadoc/com/codename1/maps/MapComponent.html]  uses

the OpenStreetMap webservice by default to display a navigatable map.

The code was contributed by Roman Kamyk and was originally used for a LWUIT application.

290

Figure 278. Map Component

The screenshot above was produced using the following code:

Form map = new Form("Map");
map.setLayout(new BorderLayout());
map.setScrollable(false);
final MapComponent mc = new MapComponent();

try {
   //get the current location from the Location API
   Location loc = LocationManager.getLocationManager().getCurrentLocation();

  Coord lastLocation = new Coord(loc.getLatitude(), loc.getLongtitude());
   Image i = Image.createImage("/blue_pin.png");
   PointsLayer pl = new PointsLayer();
   pl.setPointIcon(i);
   PointLayer p = new PointLayer(lastLocation, "You Are Here", i);
   p.setDisplayName(true);
   pl.addPoint(p);
   mc.addLayer(pl);
} catch (IOException ex) {
   ex.printStackTrace();
}
mc.zoomToLayers();

map.addComponent(BorderLayout.CENTER, mc);
map.addCommand(new BackCommand());
map.setBackCommand(new BackCommand());
map.show();

The example below shows how to integrate the MapComponent [https://www.codenameone.com/javadoc/

com/codename1/maps/MapComponent.html] with the Google Location [https://www.codenameone.com/javadoc/

com/codename1/location/Location.html]  API.  make  sure  to  obtain  your  secret  api  key  from  the  Google

291

Location 

[https://www.codenameone.com/javadoc/com/codename1/location/Location.html]  data  API  at:

https://developers.google.com/maps/documentation/places/

Figure 279. MapComponent with Google Location API

          final Form map = new Form("Map");
           map.setLayout(new BorderLayout());
           map.setScrollable(false);
           final MapComponent mc = new MapComponent();
           Location loc = LocationManager.getLocationManager().getCurrentLocation();
           //use the code from above to show you on the map
           putMeOnMap(mc);
           map.addComponent(BorderLayout.CENTER, mc);
           map.addCommand(new BackCommand());
           map.setBackCommand(new BackCommand());

           ConnectionRequest req = new ConnectionRequest() {

               protected void readResponse(InputStream input) throws IOException {
                   JSONParser p = new JSONParser();
                   Hashtable h = p.parse(new InputStreamReader(input));
                   // "status" : "REQUEST_DENIED"
                   String response = (String)h.get("status");
                   if(response.equals("REQUEST_DENIED")){
                       System.out.println("make sure to obtain a key from "
                               + "https://developers.google.com/maps/documentation/places/");
                       progress.dispose();
                       Dialog.show("Info", "make sure to obtain an application key from "
                               + "google places api's"
                               , "Ok", null);
                       return;
                   }

                   final Vector v = (Vector) h.get("results");

                   Image im = Image.createImage("/red_pin.png");
                   PointsLayer pl = new PointsLayer();
                   pl.setPointIcon(im);
                   pl.addActionListener(new ActionListener() {

                       public void actionPerformed(ActionEvent evt) {
                           PointLayer p = (PointLayer) evt.getSource();
                           System.out.println("pressed " + p);

292

                           Dialog.show("Details", "" + p.getName(), "Ok", null);
                       }
                   });

                   for (int i = 0; i < v.size(); i++) {
                       Hashtable entry = (Hashtable) v.elementAt(i);
                       Hashtable geo = (Hashtable) entry.get("geometry");
                       Hashtable loc = (Hashtable) geo.get("location");
                       Double lat = (Double) loc.get("lat");
                       Double lng = (Double) loc.get("lng");
                       PointLayer point = new PointLayer(new Coord(lat.doubleValue(), lng.doubleValue()),
                               (String) entry.get("name"), null);
                       pl.addPoint(point);
                   }
                   progress.dispose();

                   mc.addLayer(pl);
                   map.show();
                   mc.zoomToLayers();

               }
           };
           req.setUrl("https://maps.googleapis.com/maps/api/place/search/json");
           req.setPost(false);
           req.addArgument("location", "" + loc.getLatitude() + "," + loc.getLongtitude());
           req.addArgument("radius", "500");
           req.addArgument("types", "food");
           req.addArgument("sensor", "false");

           //get your own key from https://developers.google.com/maps/documentation/places/
           //and replace it here.
           String key = "yourAPIKey";

           req.addArgument("key", key);

           NetworkManager.getInstance().addToQueue(req);
       }
       catch (IOException ex) {
           ex.printStackTrace();
       }
   }

6.33. Chart Component

The  charts  package  enables  Codename  One  developers  to  add  charts  and  visualizations  to  their
apps  without  having  to  include  external  libraries  or  embedding  web  views.  We  also  wanted  to

harness the new features in the graphics pipeline to maximize performance.

6.33.1. Device Support

Since  the  charts  package  makes  use  of  2D  transformations  and  shapes,  it  requires  some  of  the

graphics features that are not yet available on all platforms. Currently the following platforms are

supported:

293

1. Simulator

2. Android

3. iOS

6.33.2. Features

1. Built-in support for many common types of charts including bar charts, line charts, stacked

charts, scatter charts, pie charts and more.

2. Pinch  Zoom  -  The  ChartComponent  [https://www.codenameone.com/javadoc/com/codename1/charts/

ChartComponent.html] class includes optional pinch zoom support.

3. Panning  Support  -  The  ChartComponent  [https://www.codenameone.com/javadoc/com/codename1/

charts/ChartComponent.html] class includes optional support for panning.

6.33.3. Chart Types

The  com.codename1.charts  package  includes  models  and  renderers  for  many  different  types  of
charts.  It  is  also  extensible  so  that  you  can  add  your  own  chart  types  if  required.  The  following

screen shots demonstrate a small sampling of the types of charts that can be created.

Figure 280. Line Charts

Figure 281. Cubic Line Charts

Figure 282. Bar Charts

294

Figure 283. Stacked Bar Charts

Figure 284. Range Bar Charts

Figure 285. Pie Charts

Figure 286. Doughnut Charts

Figure 287. Scatter Charts

Figure 288. Dial Charts

Figure 289. Combined Charts

295

Figure 290. Bubble Charts

Figure 291. Time Charts



The  above  screenshots  were  taken  from  the  ChartsDemo  app  [https://github.com/

codenameone/codenameone-demos/tree/master/ChartsDemo].  You  can  start  playing  with

this app by checking it out from our git repository.

6.33.4. How to Create A Chart

Adding a chart to your app involves four steps:

1. Build the model. You can construct a model (aka data set) for the chart using one of the existing
model classes in the com.codename1.charts.models package. Essentially, this is just where you add
the data that you want to display.

2. Set up a renderer. You can create a renderer for your chart using one of the existing renderer
classes in the com.codename1.charts.renderers package. The renderer allows you to specify how
the chart should look. E.g. the colors, fonts, styles, to use.

3. Create  the  Chart  View.  Use  one  of  the  existing  view  classes  in  the  com.codename1.charts.views

package.

4. Create 

a 

ChartComponent 

[https://www.codenameone.com/javadoc/com/codename1/charts/

ChartComponent.html].  In  order  to  add  your  chart  to  the  UI,  you  need  to  wrap  it  in  a

ChartComponent 

[https://www.codenameone.com/javadoc/com/codename1/charts/ChartComponent.html]

object.

You  can  check  out  the  ChartsDemo  [https://github.com/codenameone/codenameone-demos/tree/master/

ChartsDemo] app for specific examples, but here is a high level view of some code that creates a Pie

Chart.

/**
 * Creates a renderer for the specified colors.
 */
private DefaultRenderer buildCategoryRenderer(int[] colors) {
    DefaultRenderer renderer = new DefaultRenderer();
    renderer.setLabelsTextSize(15);
    renderer.setLegendTextSize(15);
    renderer.setMargins(new int[]{20, 30, 15, 0});
    for (int color : colors) {

296

        SimpleSeriesRenderer r = new SimpleSeriesRenderer();
        r.setColor(color);
        renderer.addSeriesRenderer(r);
    }
    return renderer;
}

/**
 * Builds a category series using the provided values.
 *
 * @param titles the series titles
 * @param values the values
 * @return the category series
 */
protected CategorySeries buildCategoryDataset(String title, double[] values) {
    CategorySeries series = new CategorySeries(title);
    int k = 0;
    for (double value : values) {
        series.add("Project " + ++k, value);
    }

    return series;
}

public Form createPieChartForm() {

    // Generate the values
    double[] values = new double[]{12, 14, 11, 10, 19};

    // Set up the renderer
    int[] colors = new int[]{ColorUtil.BLUE, ColorUtil.GREEN, ColorUtil.MAGENTA, ColorUtil.YELLOW, ColorUtil.CYAN};
    DefaultRenderer renderer = buildCategoryRenderer(colors);
    renderer.setZoomButtonsVisible(true);
    renderer.setZoomEnabled(true);
    renderer.setChartTitleTextSize(20);
    renderer.setDisplayValues(true);
    renderer.setShowLabels(true);
    SimpleSeriesRenderer r = renderer.getSeriesRendererAt(0);
    r.setGradientEnabled(true);
    r.setGradientStart(0, ColorUtil.BLUE);
    r.setGradientStop(0, ColorUtil.GREEN);
    r.setHighlighted(true);

    // Create the chart ... pass the values and renderer to the chart object.
    PieChart chart = new PieChart(buildCategoryDataset("Project budget", values), renderer);

    // Wrap the chart in a Component so we can add it to a form
    ChartComponent c = new ChartComponent(chart);

    // Create a form and show it.
    Form f = new Form("Budget");
    f.setLayout(new BorderLayout());
    f.addComponent(BorderLayout.CENTER, c);
    return f;

}

6.34. Calendar

The  Calendar  [https://www.codenameone.com/javadoc/com/codename1/ui/Calendar.html]  class  allows  us  to

display a traditional calendar picker and optionally highlight days in various ways.

297

 We  normally  recommend  developers  use  the  Picker  UI  rather  than  use  the

calendar to pick a date. It looks better on the devices.

Simple usage of the Calendar class looks something like this:

Form hi = new Form("Calendar", new BorderLayout());
Calendar cld = new Calendar();
cld.addActionListener((e) -> Log.p("You picked: " + new Date(cld.getSelectedDay())));
hi.add(BorderLayout.CENTER, cld);

Figure 292. The Calendar component

6.35. ToastBar

The ToastBar [https://www.codenameone.com/javadoc/com/codename1/components/ToastBar.html] class allows

us to display none-obtrusive status messages to the user at the bottom of the screen. This is useful

for  such  things  as  informing  the  user  of  a  long-running  task  (like  downloading  a  file  in  the

background), or popping up an error message that doesn’t require a response from the user.

Simple usage of the ToastBar class looks something like this:

Status status = ToastBar.getInstance().createStatus();
status.setMessage("Downloading your file...");
status.show();

//  ... Later on when download completes
status.clear();

298

Figure 293. ToastBar with message

We can show a progress indicator in the ToastBar like this:

Status status = ToastBar.getInstance().createStatus();
status.setMessage("Hello world");
status.setShowProgressIndicator(true);
status.show();

Figure 294. Status Message with Progress Bar

We can automatically clear a status message/progress after a timeout using the setExpires method
as such:

Status status = ToastBar.getInstance().createStatus();
status.setMessage("Hello world");
status.setExpires(3000);  // only show the status for 3 seconds, then have it automatically clear
status.show();

We can also delay the showing of the status message using showDelayed as such:

299

Status status = ToastBar.getInstance().createStatus();
status.setMessage("Hello world");
status.showDelayed(300); // Wait 300 ms to show the status

// ... Some time later, clear the status... this may be before it shows at all
status.clear();

Figure 295. ToastBar with a multiline message

6.35.1. Actions In ToastBar

Probably  the  best  usage  example  for  actions  in  toast  is  in  the  gmail  style  undo.  If  you  are  not  a

gmail user then the gmail app essentially never prompts for confirmation!

It just does whatever you ask and pops a "toast message" with an option to undo. So if you clicked

by mistake you have 3-4 seconds to take that back.

This simple example shows you how you can undo any addition to the UI in a similar way to gmail:

Form hi = new Form("Undo", BoxLayout.y());
Button add = new Button("Add");

add.addActionListener(e -> {
    Label l = new Label("Added this");
    hi.add(l);
    hi.revalidate();
    ToastBar.showMessage("Added, click here to undo...", FontImage.MATERIAL_UNDO,
            ee -> {
                l.remove();
                hi.revalidate();
            });
});
hi.add(add);
hi.show();

300

6.36. SignatureComponent

The 

SignatureComponent 

[https://www.codenameone.com/javadoc/com/codename1/components/

SignatureComponent.html] provides a widget that allows users to draw their signature in the app.

Simple usage of the SignatureComponent class looks like:

Form hi = new Form("Signature Component");
hi.setLayout(new BoxLayout(BoxLayout.Y_AXIS));
hi.add("Enter Your Name:");
hi.add(new TextField());
hi.add("Signature:");
SignatureComponent sig = new SignatureComponent();
sig.addActionListener((evt)-> {
    System.out.println("The signature was changed");
    Image img = sig.getSignatureImage();
    // Now we can do whatever we want with the image of this signature.
});
hi.addComponent(sig);
hi.show();

Figure 296. The signature Component

6.37. Accordion

The  Accordion  [https://www.codenameone.com/javadoc/com/codename1/components/Accordion.html]  displays

collapsible content panels.

Simple usage of the Accordion class looks like:

301

Form f = new Form("Accordion", new BoxLayout(BoxLayout.Y_AXIS));
f.setScrollableY(true);
Accordion accr = new Accordion();
accr.addContent("Item1", new SpanLabel("The quick brown fox jumps over the lazy dog\n"
        + "The quick brown fox jumps over the lazy dog"));
accr.addContent("Item2", new SpanLabel("The quick brown fox jumps over the lazy dog\n"
        + "The quick brown fox jumps over the lazy dog\n "
        + "The quick brown fox jumps over the lazy dog\n "
        + "The quick brown fox jumps over the lazy dog\n "
        + ""));

accr.addContent("Item3", BoxLayout.encloseY(new Label("Label"), new TextField(), new Button("Button"), new
CheckBox("CheckBox")));

f.add(accr);
f.show();

Figure 297. The Accordion Component

6.38. Floating Hint

FloatingHint  [https://www.codenameone.com/javadoc/com/codename1/components/FloatingHint.html]  wraps  a

text component with a special container that can animate the hint label into a title label when the

text component is edited or has content within it.

302

Form hi = new Form("Floating Hint", BoxLayout.y());
TextField first = new TextField("", "First Field");
TextField second = new TextField("", "Second Field");
hi.add(new FloatingHint(first)).
        add(new FloatingHint(second)).
        add(new Button("Go"));
hi.show();

Figure 298. The FloatingHint component with one component that contains text and another that doesn’t

6.39. Floating Button

The material design floating action button is a powerful tool for promoting an action within your

application.

FloatingActionButton 

[https://www.codenameone.com/javadoc/com/codename1/components/

FloatingActionButton.html] is a round button that resides on top of the UI typically in the bottom right

hand side.

It  has  a  drop  shadow  to  distinguish  it  from  the  UI  underneath  and  it  can  hide  two  or  more

additional actions under the surface. E.g. we can create a simple single click button such as this:

FloatingActionButton fab = FloatingActionButton.createFAB(FontImage.MATERIAL_ADD);
fab.addActionListener(e -> ToastBar.showErrorMessage("Not implemented yet..."));
fab.bindFabToContainer(form.getContentPane());

Which will place a + sign button that will perform the action. Alternatively we can create a nested
action where a click on the button will produce a submenu for users to pick from e.g.:

FloatingActionButton fab = FloatingActionButton.createFAB(FontImage.MATERIAL_ADD);
fab.createSubFAB(FontImage.MATERIAL_PEOPLE, "");
fab.createSubFAB(FontImage.MATERIAL_IMPORT_CONTACTS, "");
fab.bindFabToContainer(form.getContentPane());

Figure 299. FloatingActionButton with submenu expanded

Those  familiar  with  this  widget  know  that  there  are  many  nuances  to  this  UI  that  we  might

303

implement/expose in the future. At the moment we chose to keep the API simple and minimal for

the common use cases and refine it based on feedback.

6.39.1. Using Floating Button as a Badge

Floating  buttons  can  also  be  used  to  badge  an  arbitrary  component  in  the  style  popularized  by

iOS/Mac OS. A badge appears at the top right corner and includes special numeric details such as

"unread count"..

The code below adds a simple badge to an icon button:

Form hi = new Form("Badge");

Button chat = new Button("");
FontImage.setMaterialIcon(chat, FontImage.MATERIAL_CHAT, 7);

FloatingActionButton badge = FloatingActionButton.createBadge("33");
hi.add(badge.bindFabToContainer(chat, Component.RIGHT, Component.TOP));

TextField changeBadgeValue = new TextField("33");
changeBadgeValue.addDataChangedListener((i, ii) -> {
    badge.setText(changeBadgeValue.getText());
    badge.getParent().revalidate();
});
hi.add(changeBadgeValue);

hi.show();

The code above results in this, notice you can type into the text field to change the badge value:

Figure 300. Badge floating button in action

6.40. SplitPane

The split pane component is a bit desktop specific but works reasonably well on devices. To get the
image below we changed SalesDemo.java in the kitchen sink by changing this:

304

private Container encloseInMaximizableGrid(Component cmp1, Component cmp2) {
    GridLayout gl = new GridLayout(2, 1);
    Container grid = new Container(gl);
    gl.setHideZeroSized(true);

    grid.add(encloseInMaximize(grid, cmp1)).
            add(encloseInMaximize(grid, cmp2));
    return grid;
}

To:

private Container encloseInMaximizableGrid(Component cmp1, Component cmp2) {
    return new SplitPane(SplitPane.VERTICAL_SPLIT, cmp1, cmp2, "25%", "50%", "75%");
}

Figure 301. Split Pane in the Kitchen Sink Demo

This is mostly self explanatory but only "mostly". We have 5 arguments the first 3 make sense:

• Split orientation

• Components to split

The last 3 arguments seem weird but they also make sense once you understand them, they are:

• The minimum position of the split - 1/4 of available space

• The default position of the split - middle of the screen

• The maximum position of the split - 3/4 of available space

The units don’t have to be percentages they can be mm (millimeters) or px (pixels).

[2] String width is the real expensive part here, the complexity of font kerning and the recursion required to reflow text is a big

305

performance hurdle

[3] Image by RegisFrey - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=10298177

[4] Fisheye is an effect where the selection stays in place as the list moves around it

[5] Image was fetched from http://awoiaf.westeros.org/index.php/Portal:Books

[6] The text below is from A Wiki of Ice & Fire: http://awoiaf.westeros.org/index.php/A_Game_of_Thrones

306

7. Animations

There  are  many  ways  to  animate  and  liven  the  data  within  a  Codename  One  application,  layout

animations  are  probably  chief  among  them.  But  first  we  need  to  understand  some  basics  such  as

layout reflows.

7.1. Layout Reflow

Layout  in  tools  such  as  HTML  is  implicit,  when  you  add  something  into  the  UI  it  is  automatically

placed  correctly.  Other  tools  such  as  Codename  One  use  explicit  layout,  that  means  you  have  to

explicitly request the UI to layout itself after making changes!

 Like many such rules exceptions occur. E.g. if the device is rotated or window size

changes a layout will occur automatically.

When adding a component to a UI that is already visible, the component will not show by default.



When adding a component to a form which isn’t shown on the screen, there is no

need to tell the UI to repaint or reflow. This happens implicitly.

The chief advantage of explicit layout is performance.

E.g. imagine adding 100 components to a form. If the form was laid out automatically, layout would

have  happened  100  times  instead  of  once  when  adding  was  finished.  In  fact  layout  reflows  are

often considered the #1 performance issue for HTML/JavaScript applications.



Smart  layout  reflow  logic  can  alleviate  some  of  the  pains  of  the  automatic  layout

reflows  however  since  the  process  is  implicit  it’s  almost  impossible  to  optimize

complex usages across browsers/devices. A major JavaScript performance tip is to

use absolute positioning which is akin to not using layouts at all!

That  is  why,  when  you  add  components  to  a  form  that  is  already  showing,  you  should  invoke
revalidate() or animate the layout appropriately. This also enables the layout animation behavior
explained below.

7.2. Layout Animations

To  understand  animations  you  need  to  understand  a  couple  of  things  about  Codename  One

components. When we add a component to a container, it’s generally just added but not positioned
anywhere. A novice might notice the setX/setY/setWidth/setHeight methods on a component and just
try to position it absolutely.

This won’t work since these methods are meant for the layout manager, which is implicitly invoked

when  a  form  is  shown  (internally  in  Codename  One).  The  layout  manager  uses  these  methods  to

position/size the components based on the hints given to it.

If  you  add  components  to  a  form  that  is  currently  showing,  it  is  your  responsibility  to  invoke

307

revalidate/layoutContainer to arrange the newly added components (see Layout Reflows).

animateLayout() method is a fancy form of revalidate that animates the components into their laid
out position. After changing the layout & invoking this method the components move to their new

sizes/positions seamlessly.

This sort of behavior creates a special case where setting the size/position makes sense. When we

set  the  size/position  in  the  demo  code  here  we  are  positioning  the  components  at  the  animation

start position above the frame.

Form hi = new Form("Layout Animations", new BoxLayout(BoxLayout.Y_AXIS));
Button fall = new Button("Fall"); ①
fall.addActionListener((e) -> {
    for(int iter = 0 ; iter < 10 ; iter++) {
        Label b = new Label ("Label " + iter);
        b.setWidth(fall.getWidth());
        b.setHeight(fall.getHeight());
        b.setY(-fall.getHeight());
        hi.add(b);
    }
    hi.getContentPane().animateLayout(20000); ②
});
hi.add(fall);

There are a couple of things that you should notice about this example:

① We used a button to do the animation rather than doing it on show. Since show() implicitly lays

out the components it wouldn’t have worked correctly.

② We used hi.getContentPane().animateLayout(20000); & not hi.animateLayout(20000);. You need to

animate the "actual" container and Form is a special case.

This results in:

308

309

 
 
310

 
7.2.1. Unlayout Animations

While  layout  animations  are  really  powerful  effects  for  adding  elements  into  the  UI  and  drawing

attention  to  them.  The  inverse  of  removing  an  element  from  the  UI  is  often  more  important.  E.g.

when we delete or remove an element we want to animate it out.

Layout  animations  don’t  really  do  that  since  they  will  try  to  bring  the  animated  item  into  place.

What we want is the exact opposite of a layout animation and that is the "unlayout animation".

The "unlayout animation" takes a valid laid out state and shifts the components to an invalid state

that we defined in advance. E.g. we can fix the example above to flip the "fall" button into a "rise"

button when the buttons come into place and this will allow the buttons to float back up to where

they came from in the exact reverse order.

 An unlayout animation always leaves the container in an invalidated state.

Form hi = new Form("Layout Animations", new BoxLayout(BoxLayout.Y_AXIS));
Button fall = new Button("Fall");
fall.addActionListener((e) -> {
    if(hi.getContentPane().getComponentCount() == 1) {
        fall.setText("Rise");
        for(int iter = 0 ; iter < 10 ; iter++) {
            Label b = new Label ("Label " + iter);
            b.setWidth(fall.getWidth());
            b.setHeight(fall.getHeight());
            b.setY(-fall.getHeight());
            hi.add(b);
        }
        hi.getContentPane().animateLayout(20000);
    } else {
        fall.setText("Fall");
        for(int iter = 1 ; iter < hi.getContentPane().getComponentCount() ; iter++) { ①
            Component c = hi.getContentPane().getComponentAt(iter);
            c.setY(-fall.getHeight()); ②
        }
        hi.getContentPane().animateUnlayoutAndWait(20000, 255); ③
        hi.removeAll(); ④
        hi.add(fall);
        hi.revalidate();
    }
});
hi.add(fall);

You  will  notice  some  similarities  with  the  unlayout  animation  but  the  differences  represent  the

exact opposite of the layout animation:

① We loop over existing components (not newly created ones)

② We set the desired end position not the desired starting position

③ We used the AndWait variant of the animate unlayout call. We could have used the async call as

311

well.

④ After the animation completes we need to actually remove the elements since the UI is now in

an invalid position with elements outside of the screen but still physically there!

7.2.2. Hiding & Visibility

A common trick for animating Components in Codename One is to set their preferred size to 0 and
then invoke animateLayout() thus triggering an animation to hide said Component. There are several
issues  with  this  trick  but  one  of  the  biggest  ones  is  the  fact  that  setPreferredSize  has  been
deprecated for quite a while.

Instead  of  using  that  trick  you  can  use  setHidden/isHidden  who  effectively  encapsulate  this
functionality and a bit more.

One of the issues setHidden tries to solve is the fact that preferred size doesn’t include the margin in
the  total  and  thus  a  component  might  still  occupy  space  despite  being  hidden.  To  solve  this  the
margin  is  set  to  0  when  hiding  and  restored  to  its  original  value  when  showing  the  component
again by resetting the UIID (which resets all style modifications).

This  functionality  might  be  undesirable  which  is  why  there  is  a  version  of  the  setHidden  method
that  accepts  a  boolean  flag  indicating  whether  the  margin/UIID  should  be  manipulated.  You  can
effectively hide/show a component without deprecated code using something like this:

Button toHide = new Button("Will Be Hidden");
Button hide = new Button("Hide It");
hide.addActionListener((e) -> {
    hide.setEnabled(false);
    boolean t = !toHide.isHidden();
    toHide.setHidden(t);
    toHide.getParent().animateLayoutAndWait(200);
    toHide.setVisible(!t);
    hide.setEnabled(true);
});



Notice  that  the  code  above  uses  setVisible(),  which  shouldn’t  be  confused  with
setHidden.  setVisible()  just  toggles  the  visibility  of  the  component  it  would  still
occupy the same amount of space

7.2.3. Synchronicity In Animations

Most animations have two or three variants:

• Standard animation e.g. animateLayout(int)

• And wait variant e.g. animateLayoutAndWait(int)

• Callback variant e.g. animateUnlayout(int, int, Runnable)

The standard animation is invoked when we don’t care about the completion of the animation. We

312

can do this for a standard animation.



The unlayout animations don’t have a standard variant. Since they leave the UI in

an invalid state we must always do something once the animation completes so a

standard variant makes no sense

The AndWait variant blocks the calling thread until the animation completes. This is really useful for
sequencing animations one after the other e.g this code from the kitchen sink demo:

arrangeForInterlace(effects);
effects.animateUnlayoutAndWait(800, 20);
effects.animateLayoutFade(800, 20);

First the UI goes thru an "unlayout" animation, once that completes the layout itself is performed.



The AndWait calls needs to be invoked on the Event Dispatch Thread despite being
"blocking". This is a common convention in Codename One powered by a unique
capability of Codename One: invokeAndBlock.
You 

invokeAndBlock 

learn  more 

the  EDT 

section

about 

can 

in 

[https://www.codenameone.com/manual/edt.html].

The callback variant is similar to the invokeAndBlock variant but uses a more conventional callback
semantic  which  is  more  familiar  to  some  developers.  It  accepts  a  Runnable  callback  that  will  be
invoked  after  the  fact.  E.g.  we  can  change  the  unlayout  call  from  before  to  use  the  callback

semantics as such:

hi.getContentPane().animateUnlayout(20000, 255, () -> {
    hi.removeAll();
    hi.add(fall);
    hi.revalidate();
});

Animation Fade and Hierarchy

There are several additional variations on the standard animate methods. Several methods accept a
numeric fade argument. This is useful to fade out an element in an "unlayout" operation or fade in
a regular animation.

The  value  for  the  fade  argument  is  a  number  between  0  and  255  where  0  represents  full

transparency and 255 represents full opacity.

Some  animate  layout  methods  are  hierarchy  based.  They  work  just  like  the  regular  animateLayout
methods  but  recurse  into  the  entire  Container  [https://www.codenameone.com/javadoc/com/codename1/ui/

Container.html]  hierarchy.  These  methods  work  well  when  you  have  components  in  a  nested

hierarchy  that  need  to  animate  into  place.  This  is  demonstrated  in  the  opening  sequence  of  the

kitchen sink demo:

313

for(int iter = 0 ; iter < demoComponents.size() ; iter++) {
    Component cmp = (Component)demoComponents.elementAt(iter);
    if(iter < componentsPerRow) {
        cmp.setX(-cmp.getWidth());
    } else {
        if(iter < componentsPerRow * 2) {
            cmp.setX(dw);
        } else {
            cmp.setX(-cmp.getWidth());
        }
    }
}
boxContainer.setShouldCalcPreferredSize(true);
boxContainer.animateHierarchyFade(3000, 30);

The demoComponents Vector contains components from separate containers and this code would not
work with a simple animate layout.



We  normally  recommend  avoiding  the  hierarchy  version.  Its  slower  but  more
importantly, it’s flaky. Since the size/position of the Container might be affected by
the layout the animation could get clipped and skip. These are very hard issues to

debug.

7.2.4. Sequencing Animations Via AnimationManager

All  the  animations  go  thru  a  per-form  queue:  the  AnimationManager  [https://www.codenameone.com/

javadoc/com/codename1/ui/AnimationManager.html].  This  effectively  prevents  two  animations  from

mutating  the  UI  in  parallel  so  we  won’t  have  collisions  between  two  conflicting  sides.  Things  get

more interesting when we try to do something like this:

cnt.add(myButton);
int componentCount = cnt.getComponentCount();
cnt.animateLayout(300);
cnt.removeComponent(myButton);
if(componentCount == cnt.getComponentCount()) {
    // this will happen...
}

The reason this happens is that the second remove gets postponed to the end of the animation so it

won’t  break  the  animation.  This  works  for  remove  and  add  operations  on  a  Container

[https://www.codenameone.com/javadoc/com/codename1/ui/Container.html] as well as other animations.

The simple yet problematic fix would be:

314

cnt.add(myButton);
int componentCount = cnt.getComponentCount();
cnt.animateLayoutAndWait(300);
cnt.removeComponent(myButton);
if(componentCount == cnt.getComponentCount()) {
    // this probably won't happen...
}

So why that might still fail?

Events  come  in  constantly  during  the  run  of  the  EDT  [7],  so  an  event  might  come  in  that  might
trigger an animation in your code. Even if you are on the EDT keep in mind that you don’t actually

block it and an event might come in.

In those cases an animation might start and you might be unaware of that animation and it might

still be in action when you expect remove to work.

Animation Manager to the Rescue

AnimationManager  [https://www.codenameone.com/javadoc/com/codename1/ui/AnimationManager.html]  has

builtin support to fix this exact issue.

We  can  flush  the  animation  queue  and  run  synchronously  after  all  the  animations  finished  and

before new ones come in by using something like this:

cnt.add(myButton);
int componentCount = cnt.getComponentCount();
cnt.animateLayout(300);
cnt.getAnimationManager().flushAnimation(() -> {
    cnt.removeComponent(myButton);
    if(componentCount == cnt.getComponentCount()) {
        // this shouldn't happen...
    }
});

7.3. Low Level Animations

The Codename One event dispatch thread has a special animation “pulse” allowing an animation to

update  its  state  and  draw  itself.  Code  can  make  use  of  this  pulse  to  implement  repetitive  polling

tasks that have very little to do with drawing.

This is helpful since the callback will always occur on the event dispatch thread.

Every  component  in  Codename  One  contains  an  animate()  method  that  returns  a  boolean  value,
implement  the  Animation  [https://www.codenameone.com/javadoc/com/codename1/ui/
you  can  also 

animations/Animation.html] interface in an arbitrary component to implement your own animation. In

order  to  receive  animation  events  you  need  to  register  yourself  within  the  parent  form,  it  is  the
responsibility of the parent for to call animate().

315

If  the  animate  method  returns  true  then  the  animation  will  be  painted  (the  paint  method  of  the
Animation interface would be invoked).



It  is  important  to  deregister  animations  when  they  aren’t  needed  to  conserve

battery life.

If  you  derive  from  a  component,  which  has  its  own  animation  logic  you  might  damage  its

animation behavior by deregistering it, so tread gently with the low level API’s.

E.g. you can add additional animation logic using code like this:

myForm.registerAnimated(this);

private int spinValue;
public boolean animate() {
   if(userStatusPending) {
       spinValue++;
       super.animate();
       return true;
   }
   return super.animate();
}

7.3.1. Why Not Just Write Code In Paint?

Animations are comprised of two parts, the logic (deciding the position etc) and the painting. The

paint method should be dedicated to painting only, not to the actual moving of the components.

The  separation  of  concerns  allows  us  to  avoid  redundant  painting  e.g.  if  animate  didn’t  trigger  a
change just return false to avoid the overhead related to animations.

We  discuss  low  level  animations  in  more  details  within  the  animation  section  of  the  clock  demo

[https://www.codenameone.com/manual/graphics.html#clock-animation-section].

7.4. Transitions

Transitions  allow  us  to  replace  one  component  with  another,  most  typically  forms  or  dialogs  are

replaced with a transition however a transition can be applied to replace any arbitrary component.

Developers can implement their own custom transition and install it to components by deriving the

Transition 

[https://www.codenameone.com/javadoc/com/codename1/ui/animations/Transition.html] 

class,

although  most  commonly  the  built  in  CommonTransitions  [https://www.codenameone.com/javadoc/com/

codename1/ui/animations/CommonTransitions.html] class is used for almost everything.

You  can  define  transitions  for  forms/dialogs/menus  globally  either  via  the  theme  constants  or  via

the  LookAndFeel 

[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/LookAndFeel.html]  class.

Alternatively you can install a transition on top-level components via setter methods.

316

In/Out Transitions

When  defining  a  transition  we  define  the  entering  transition  and  the  exiting  transition.  For

most  cases  only  one  of  those  is  necessary  and  we  default  to  the  exiting  (out  transition)  as  a

convention.

So  for  almost  all  cases  the  method  setFormTransitonIn  should  go  unused.  That  API  exists  for
some  elaborate  custom  transitions  that  might  need  to  have  a  special  effect  both  when

transitioning  in  and  out  of  a  specific  form.  However,  most  of  these  effects  are  easier  to

achieve with layout animations (e.g. components dropping into place etc.).

In the case of Dialog the transition in shows its appearance and the transition out shows its
disposal. So in that case both transitions make a lot of sense.

Back/Forward Transitions

Transitions have a direction and can all be played either in incoming or outgoing direction. A
transition  can  be  flipped  (played  in  reverse)  when  we  use  an  RTL  language  [8]  or  when  we
simply traverse backwards in the form navigation hierarchy.

Normally Form.show() displays the next Form with an incoming transition based on the current
RTL mode. If we use Form.showBack() it will play the transition in reverse.



When  working  with  high  level  animations  you  can  select  Slow Motion  option  in

the simulator to slow down animations and inspect their details

Themes define the default transitions used when showing a form, these differ based on the OS. In
most platforms the default is Slide whereas in iOS the default is SlideFade which slides the content
pane and title while fading in/out the content of the title area.



SlideFade  is  problematic  without  a  title  area.  If  you  have  a  Form  that  lacks  a  title
area we would recommend to disable SlideFade at least for that Form.

Check  out 

the 

full 

set  of 

theme 

constants 

in 

the  Theme  Constants 

Section

[https://www.codenameone.com/manual/advanced-theming.html#theme-constants-section].

7.4.1. Replace

To apply a transition to a component we can just use the Container.replace() method as such:

317

Form hi = new Form("Replace", new BoxLayout(BoxLayout.Y_AXIS));
Button replace = new Button("Replace Pending");
Label replaceDestiny = new Label("Destination Replace");
hi.add(replace);
replace.addActionListener((e) -> {
    replace.getParent().replaceAndWait(replace, replaceDestiny,
CommonTransitions.createCover(CommonTransitions.SLIDE_VERTICAL, true, 800));
    replaceDestiny.getParent().replaceAndWait(replaceDestiny, replace,
CommonTransitions.createUncover(CommonTransitions.SLIDE_VERTICAL, true, 800));
});

Replace  even  works  when  you  have  a  layout  constraint  in  place  e.g.  replacing  a



component  in  a  border  layout  will  do  the  "right  thing".  However,  some  layouts
such  as  TableLayout  might  be  tricky  in  such  cases  so  we  recommend  wrapping  a
potentially replaceable Component in a border layout and replacing the content.

Container.replace() can also be used with a null transition at which point it replaces instantly with
no transition.

7.4.2. Slide Transitions

The slide transitions are used to move the Form/Component in a sliding motion to the side or up/down.
There are 4 basic types of slide transitions:

1. Slide - the most commonly used transition

2. Fast  Slide  -  historically  this  provided  better  performance  for  old  device  types.  It  is  no  longer

recommended for newer devices

3. Slide Fade - the iOS default where the title area features a fade transition

4. Cover/Uncover - a type of slide transition where only the source or destination form slides while

the other remains static in place

The code below demonstrates the usage of all the main transitions:

318

Toolbar.setGlobalToolbar(true);
Form hi = new Form("Transitions", new BoxLayout(BoxLayout.Y_AXIS));
Style bg = hi.getContentPane().getUnselectedStyle();
bg.setBgTransparency(255);
bg.setBgColor(0xff0000);
Button showTransition = new Button("Show");
Picker pick = new Picker();
pick.setStrings("Slide", "SlideFade", "Cover", "Uncover", "Fade", "Flip");
pick.setSelectedString("Slide");
TextField duration = new TextField("10000", "Duration", 6, TextArea.NUMERIC);
CheckBox horizontal = CheckBox.createToggle("Horizontal");
pick.addActionListener((e) -> {
    String s = pick.getSelectedString().toLowerCase();
    horizontal.setEnabled(s.equals("slide") || s.indexOf("cover") > -1);
});
horizontal.setSelected(true);
hi.add(showTransition).
    add(pick).
    add(duration).
    add(horizontal);

Form dest = new Form("Destination");
bg = dest.getContentPane().getUnselectedStyle();
bg.setBgTransparency(255);
bg.setBgColor(0xff);
dest.setBackCommand(
        dest.getToolbar().addCommandToLeftBar("Back", null, (e) -> hi.showBack()));

showTransition.addActionListener((e) -> {
    int h = CommonTransitions.SLIDE_HORIZONTAL;
    if(!horizontal.isSelected()) {
        h = CommonTransitions.SLIDE_VERTICAL;
    }
    switch(pick.getSelectedString()) {
        case "Slide":
            hi.setTransitionOutAnimator(CommonTransitions.createSlide(h, true, duration.getAsInt(3000)));
            dest.setTransitionOutAnimator(CommonTransitions.createSlide(h, true, duration.getAsInt(3000)));
            break;
        case "SlideFade":
            hi.setTransitionOutAnimator(CommonTransitions.createSlideFadeTitle(true, duration.getAsInt(3000)));
            dest.setTransitionOutAnimator(CommonTransitions.createSlideFadeTitle(true, duration.getAsInt(3000)));
            break;
        case "Cover":
            hi.setTransitionOutAnimator(CommonTransitions.createCover(h, true, duration.getAsInt(3000)));
            dest.setTransitionOutAnimator(CommonTransitions.createCover(h, true, duration.getAsInt(3000)));
            break;
        case "Uncover":
            hi.setTransitionOutAnimator(CommonTransitions.createUncover(h, true, duration.getAsInt(3000)));
            dest.setTransitionOutAnimator(CommonTransitions.createUncover(h, true, duration.getAsInt(3000)));
            break;
        case "Fade":
            hi.setTransitionOutAnimator(CommonTransitions.createFade(duration.getAsInt(3000)));
            dest.setTransitionOutAnimator(CommonTransitions.createFade(duration.getAsInt(3000)));
            break;
        case "Flip":
            hi.setTransitionOutAnimator(new FlipTransition(-1, duration.getAsInt(3000)));
            dest.setTransitionOutAnimator(new FlipTransition(-1, duration.getAsInt(3000)));
            break;
    }
    dest.show();
});
hi.show();

319

Figure 302. The slide transition moves both incoming and outgoing forms together

Figure 303. The slide transition can be applied vertically as well

Figure 304. Slide fade fades in the destination title while sliding the content pane it is the default on iOS



SlideFade  is  problematic  without  a  title  area.  If  you  have  a  Form  that  lacks  a  title
area we would recommend to disable SlideFade at least for that Form.

Figure 305. With cover transitions the source form stays in place as it is covered by the destination. This

transition can be played both horizontally and vertically

Figure 306. Uncover is the inverse of cover. The destination form stays in place while the departing form

moves away

7.4.3. Fade and Flip Transitions

The fade transition is pretty trivial and only accepts a time value since it has no directional context.

320

Figure 307. Fade transition is probably the simplest one around

The  FlipTransition  [https://www.codenameone.com/javadoc/com/codename1/ui/animations/FlipTransition.html]
is  also  pretty  simple  but  unlike  the  others  it  isn’t  a  part  of  the  CommonTransitions.  It  has  its  own
FlipTransition class.

 This  transition  looks  very  different  on  devices  as  it  uses  native  perspective

transforms available only there

Figure 308. Fade transition is probably the simplest one around

7.4.4. Bubble Transition

BubbleTransiton  [https://www.codenameone.com/javadoc/com/codename1/ui/animations/BubbleTransition.html]

morphs a component into another component using a circular growth motion.

The  BubbleTransition  accepts  the  component  that  will  grow  into  the  bubble  effect  as  one  of  its
arguments. It’s generally designed for Dialog transitions although it could work for more creative
use cases:

 The code below manipulates styles and look. This is done to make the code more

"self contained". Real world code should probably use the theme

321

Form hi = new Form("Bubble");
Button showBubble = new Button("+");
showBubble.setName("BubbleButton");
Style buttonStyle = showBubble.getAllStyles();
buttonStyle.setBorder(Border.createEmpty());
buttonStyle.setFgColor(0xffffff);
buttonStyle.setBgPainter((g, rect) -> {
    g.setColor(0xff);
    int actualWidth = rect.getWidth();
    int actualHeight = rect.getHeight();
    int xPos, yPos;
    int size;
    if(actualWidth > actualHeight) {
        yPos = rect.getY();
        xPos = rect.getX() + (actualWidth - actualHeight) / 2;
        size = actualHeight;
    } else {
        yPos = rect.getY() + (actualHeight - actualWidth) / 2;
        xPos = rect.getX();
        size = actualWidth;
    }
    g.setAntiAliased(true);
    g.fillArc(xPos, yPos, size, size, 0, 360);
});
hi.add(showBubble);
hi.setTintColor(0);
showBubble.addActionListener((e) -> {
    Dialog dlg = new Dialog("Bubbled");
    dlg.setLayout(new BorderLayout());
    SpanLabel sl = new SpanLabel("This dialog should appear with a bubble transition from the button", "DialogBody");
    sl.getTextUnselectedStyle().setFgColor(0xffffff);
    dlg.add(BorderLayout.CENTER, sl);
    dlg.setTransitionInAnimator(new BubbleTransition(500, "BubbleButton"));
    dlg.setTransitionOutAnimator(new BubbleTransition(500, "BubbleButton"));
    dlg.setDisposeWhenPointerOutOfBounds(true);
    dlg.getTitleStyle().setFgColor(0xffffff);

    Style dlgStyle = dlg.getDialogStyle();
    dlgStyle.setBorder(Border.createEmpty());
    dlgStyle.setBgColor(0xff);
    dlgStyle.setBgTransparency(0xff);
    dlg.showPacked(BorderLayout.NORTH, true);
});

hi.show();

Figure 309. Bubble transition converting a circular button to a Dialog

322

7.4.5. Morph Transitions

Android’s  material  design  has  a  morphing  effect  where  an  element  from  the  previous  form

(activity) animates into a different component on a new activity. Codename One has a morph effect

in  the  Container  [https://www.codenameone.com/javadoc/com/codename1/ui/Container.html]  class  but  it

doesn’t work as a transition between forms and doesn’t allow for multiple separate components to

transition at once.

Figure 310. Morph Transition

To  support  this  behavior  we  have  the  MorphTransition  [https://www.codenameone.com/javadoc/com/

codename1/ui/animations/MorphTransition.html] class that provides this same effect coupled with a fade

to the rest of the UI (see Figure 310, “Morph Transition”).

Since the transition is created before the form exists we can’t reference explicit components within

the  form  when  creating  the  morph  transition  (in  order  to  indicate  which  component  becomes
which)  so  we  need  to  refer  to  them  by  name.  This  means  we  need  to  use  setName(String)  on  the
components in the source/destination forms so the transition will be able to find them.

Form demoForm = new Form(currentDemo.getDisplayName());
demoForm.setScrollable(false);
demoForm.setLayout(new BorderLayout());
Label demoLabel = new Label(currentDemo.getDisplayName());
demoLabel.setIcon(currentDemo.getDemoIcon());
demoLabel.setName("DemoLabel");
demoForm.addComponent(BorderLayout.NORTH, demoLabel);
demoForm.addComponent(BorderLayout.CENTER, wrapInShelves(n));
....
demoForm.setBackCommand(backCommand);
demoForm.setTransitionOutAnimator(
    MorphTransition.create(3000).morph(
        currentDemo.getDisplayName(),
        "DemoLabel"));
f.setTransitionOutAnimator(
    MorphTransition.create(3000).
        morph(currentDemo.getDisplayName(),
        "DemoLabel"));
demoForm.show();

7.4.6. SwipeBackSupport

iOS7+ allows swiping back one form to the previous form, Codenmae One has an API to enable back

swipe transition:

323

SwipeBackSupport.bindBack(Form currentForm, LazyValue<Form> destination);

That 

one 

command  will 

enable 

swiping 

back 

from 

currentForm. 

LazyValue

[https://www.codenameone.com/javadoc/com/codename1/util/LazyValue.html] allows us to pass a value lazily:

public interface LazyValue<T> {
    public T get(Object... args);
}

This effectively allows us to pass a form and only create it as necessary (e.g. for a GUI builder app

we  don’t  have  the  actual  previous  form  instance),  notice  that  the  arguments  aren’t  used  for  this

case but will be used in other cases.

The code below should work for the transition sample above. Notice that this API was designed to

work with "Slide Fade" transition and might have issues with other transition types:

SwipeBackSupport.bindBack(dest, (args) -> hi);

[7] Event Dispatch Thread

[8] Right to left/bidi language such as Hebrew or Arabic

324

8. The EDT - Event Dispatch Thread

8.1. What Is The EDT

Codename  One  allows  developers  to  create  as  many  threads  as  they  want;  however  in  order  to

interact with the Codename One user interface components a developer must use the EDT. The EDT

stands for "Event Dispatch Thread" but it handles a lot more than just "events".

The EDT is the main thread of Codename One, by using just one thread Codename One can avoid

complex synchronization code and focus on simple functionality that assumes only one thread.



This  has  huge  advantages  for  your  code.  You  can  normally  assume  that  all  code

will occur on a single thread and avoid complex synchronization logic.

You can visualize the EDT as a loop such as this:

while(codenameOneRunning) {
     performEventCallbacks();
     performCallSeriallyCalls();
     drawGraphicsAndAnimations();
     sleepUntilNextEDTCycle();
}

Normally, every call you receive from Codename One will occur on the EDT. E.g. every event, calls

to paint(), lifecycle calls (start etc.) should all occur on the EDT.

This is pretty powerful, however it means that as long as your code is processing nothing else can

happen in Codename One!



If  your  code  takes  too  long  to  execute  then  no  painting  or  event  processing
will  occur  during  that  time,  so  a  call  to  Thread.sleep()  will  actually  stop
everything!

The solution is pretty simple, if you need to perform something that requires intensive CPU you can

spawn a thread.

Codename  One’s  networking  code  automatically  spawns  its  own  network  thread  (see  the

NetworkManager 

[https://www.codenameone.com/javadoc/com/codename1/io/NetworkManager.html]).

However, this also poses a problem…

Codename One assumes all modifications to the UI are performed on the EDT but if we spawned a

separate thread. How do we force our modifications back into the EDT?

Codename One includes 3 methods in the Display [https://www.codenameone.com/javadoc/com/codename1/
callSerially(Runnable)  &

situations: 

isEDT(), 

to  help 

these 

class 

in 

ui/Display.html] 
callSeriallyAndWait(Runnable).

325

isEDT()  is  useful  for  generic  code  that  needs  to  test  whether  the  current  code  is  executing  on  the
EDT.

8.2. Call Serially (And Wait)

callSerially(Runnable)  should  normally  be  called  off  the  EDT  (in  a  separate  thread),  the  run
method within the submitted runnable will be invoked on the EDT.

 The Runnable passed to the callSerially and callSeriallyAndWait methods is not a

Thread. We just use the Runnable interface as a convenient callback interface.

// this code is executing in a separate thread
final String res = methodThatTakesALongTime();
Display.getInstance().callSerially(new Runnable() {
     public void run() {
          // this occurs on the EDT so I can make changes to UI components
          resultLabel.setText(res);
     }
});



You can write this code more concisely using Java 8 lambda code as such:

// this code is executing in a separate thread
String res = methodThatTakesALongTime();
Display.getInstance().callSerially(() -> resultLabel.setText(res));

This allows code to leave the EDT and then later on return to it to perform things within the EDT.

The  callSeriallyAndWait(Runnable)  method  blocks  the  current  thread  until  the  method  completes,
this is useful for cases such as user notification e.g.:

// this code is executing in a separate thread
methodThatTakesALongTime();
Display.getInstance().callSeriallyAndWait(() -> {
  // this occurs on the EDT so I can make changes to UI components
  globalFlag = Dialog.show("Are You Sure?", "Do you want to continue?", "Continue", "Stop");
});
// this code is executing the separate thread
// global flag was already set by the call above
if(!globalFlag) {
   return;
}
otherMethod();



If you are unsure use callSerially. The use cases for callSeriallyAndWait are very
rare.

326

8.2.1. callSerially On The EDT

One of the misunderstood topics is why would we ever want to invoke callSerially when we are
still  on  the  EDT.  This  is  best  explained  by  example.  Say  we  have  a  button  that  has  quite  a  bit  of

functionality tied to its events e.g.:

1. A user added an action listener to show a Dialog.

2. A framework the user installed added some logging to the button.

3. The button repaints a release animation as its being released.

However, this might cause a problem if the first event that we handle (the dialog) might cause an
issue to the following events. E.g. a dialog will block the EDT (using invokeAndBlock), events will keep
happening but since the event we are in "already happened" the button repaint and the framework

logging won’t occur. This might also happen if we show a form which might trigger logic that relies

on the current form still being present.

One of the solutions to this problem is to just wrap the action listeners body with a callSerially. In
this  case  the  callSerially  will  postpone  the  event  to  the  next  cycle  (loop)  of  the  EDT  and  let  the
other events in the chain complete. Notice that you shouldn’t use this normally since it includes an

overhead and complicates application flow, however when you run into issues in event processing

we suggest trying this to see if its the cause.



You  should  never  invoke  callSeriallyAndWait  on  the  EDT  since  this  would

effectively mean sleeping on the EDT. We made that method throw an exception if

its invoked from the EDT.

8.3. Debugging EDT Violations

There are two types of EDT violations:

1. Blocking the EDT thread so the UI performance is considerably slower.

2. Invoking UI code on a separate thread

Codename One provides a tool to help you detect some of these violations some caveats may apply

though…

It’s an imperfect tool. It might fire “false positives” meaning it might detect a violation for perfectly

legal  code  and  it  might  miss  some  illegal  calls.  However,  it  is  a  valuable  tool  in  the  process  of

detecting  hard  to  track  bugs  that  are  sometimes  only  reproducible  on  the  devices  (due  to  race

condition behavior).

To  activate  this  tool  just  select  the  Debug  EDT  menu  option  in  the  simulator  and  pick  the  level  of

output you wish to receive:

327

Figure 311. Debug EDT

Full output will include stack traces to the area in the code that is suspected in the violation.

8.4. Invoke And Block

Invoke  and  block  is  the  exact  opposite  of  callSeriallyAndWait(),  it  blocks  the  EDT  and  opens  a
the  Foxtrot
separate 

the  runnable  call.  This 

functionality 

inspired  by 

thread 

for 

is 

[http://foxtrot.sourceforge.net/]  API,  which  is  a  remarkably  powerful  tool  most  Swing  developers  don’t

know about.

This  is  best  explained  by  an  example.  When  we  write  typical  code  in  Java  we  like  that  code  is  in

sequence as such:

doOperationA();
doOperationB();
doOperationC();

This works well normally but on the EDT it might be a problem, if one of the operations is slow it

might slow the whole EDT (painting, event processing etc.). Normally we can just move operations

into a separate thread e.g.:

doOperationA();
new Thread() {
    public void run() {
         doOperationB();
    }
}).start();
doOperationC();

Unfortunately, this means that operation C will happen in parallel to operation B which might be a

problem…

E.g. instead of using operation names lets use a more "real world" example:

328

updateUIToLoadingStatus();
readAndParseFile();
updateUIWithContentOfFile();

Notice  that  the  first  and  last  operations  must  be  conducted  on  the  EDT  but  the  middle  operation
might  be  really  slow!  Since  updateUIWithContentOfFile  needs  readAndParseFile  to  occur  before  it
starts doing the new thread won’t be enough.

A simplistic approach is to do something like this:

updateUIToLoadingStatus();
new Thread() {
    public void run() {
          readAndParseFile();
          updateUIWithContentOfFile();
    }
}).start();

But updateUIWithContentOfFile should be executed on the EDT and not on a random thread. So the
right way to do this would be something like this:

updateUIToLoadingStatus();
new Thread() {
    public void run() {
          readAndParseFile();
          Display.getInstance().callSerially(new Runnable() {
               public void run() {
                     updateUIWithContentOfFile();
               }
          });
    }
}).start();

This  is  perfectly  legal  and  would  work  reasonably  well,  however  it  gets  complicated  as  we  add

more and more features that need to be chained serially after all these are just 3 methods!

Invoke and block solves this in a unique way you can get almost the exact same behavior by using

this:

updateUIToLoadingStatus();
Display.getInstance().invokeAndBlock(new Runnable() {
    public void run() {
          readAndParseFile();
    }
});
updateUIWithContentOfFile();

329

Or this with Java 8 syntax:

updateUIToLoadingStatus();
Display.getInstance().invokeAndBlock(() -> readAndParseFile());
updateUIWithContentOfFile();

Invoke and block effectively blocks the current EDT in a legal way. It spawns a separate thread that
runs the run() method and when that run method completes it goes back to the EDT.

All  events  and  EDT  behavior  still  work  while  invokeAndBlock  is  running,  this  is  because
invokeAndBlock() keeps calling the main thread loop internally.



Notice that invokeAndBlock comes at a slight performance penalty. Also notice that
nesting invokeAndBlock calls (or over using them) isn’t recommended.
However, they are very convenient when working with multiple threads/UI.

Even if you never call invokeAndBlock directly you are probably using it indirectly in API’s such as
Dialog  [https://www.codenameone.com/javadoc/com/codename1/ui/Dialog.html]  that  show  a  dialog  while

blocking the current thread e.g.:

public void actionPerformed(ActionEvent ev) {
  // will return true if the user clicks "OK"
  if(!Dialog.show("Question", "How Are You", "OK", "Not OK")) {
  // ask what went wrong...
  }
}

Notice that the dialog show method will block the calling thread until the user clicks OK or Not OK…



Other  API’s  such  as  NetworkManager.addToQueueAndWait()  also  make  use  of  this
feature.  Pretty  much  every  "AndWait"  method  or  blocking  method  uses  this  API

internally!

To explain how invokeAndBlock works we can return to the sample above of how the EDT works:

while(codenameOneRunning) {
     performEventCallbacks();
     performCallSeriallyCalls();
     drawGraphicsAndAnimations();
     sleepUntilNextEDTCycle();
}

invokeAndBlock() works in a similar way to this pseudo code:

330

void invokeAndBlock(Runnable r) {
    openThreadForR(r);
    while(r is still running) {
         performEventCallbacks();
         performCallSeriallyCalls();
         drawGraphicsAndAnimations();
         sleepUntilNextEDTCycle();
    }
}

So the EDT is effectively "blocked" but we "redo it" within the invokeAndBlock method…

As  you  can  see  this  is  a  very  simple  approach  for  thread  programming  in  UI,  you  don’t  need  to

block your flow and track the UI thread. You can just program in a way that seems sequential (top

to bottom) but really uses multi-threading correctly without blocking the EDT.

331

332

9. Monetization

Codename One tries to make the lives of software developers easier by integrating several forms of

built-in monetization solutions such as ad network support, in-app-purchase etc.

A  lot  of  the  monetization  options  are  available  as  3rd  party  cn1lib’s  [https://www.codenameone.com/

cn1libs.html] that you can install thru the Codename One website.

9.1. Google Play Ads

The most effective network is the simplest banner ad support. To enable mobile ads just create an

ad  unit  [https://apps.admob.com/?pli=1#monetize/adunit:create]  in  Admob’s  website,  you  should  end  up

with the key similar to this:

ca-app-pub-8610616152754010/3413603324

this 

enable 

for  Android 

To 
8610616152754010/3413603324 
in
in  the  build  arguments  and  for 
ios.googleAdUnitId.  The  rest  is  seamless,  the  right  ad  will  be  created  for  you  at  the  bottom  of  the
screen  and  the  form  should  automatically  shrink  to  fit  the  ad.  This  shrinking  is  implemented

iOS  use  the  same  as 

android.googleAdUnitId=ca-app-pub-

define 

just 

the 

differently between iOS and Android due to some constraints but the result should be similar and

this should work reasonably well with device rotation as well.

Figure 312. Google play ads

special  ad  unit 

specify  ca-app-pub-
There’s  a 
3940256099942544/6300978111,  you’ll  get  test  ads  for  your  development  phase.  This  is  important
because you’re not allowed to click on your own ads. When it’s time to create a production release,

test  ads. 

to  use 

If  you 

for 

id 

you should replace this with the real value you generated in adMob.

9.2. In App Purchase

In-app purchase is a helpful tool for making app development profitable. Codename One supports

in-app  purchases  of  consumable/non-consumable  products  on  Android  &  iOS.  It  also  features

support  for  subscriptions.  For  such  a  seemingly  simple  task,  in-app  purchase  involves  a  lot  of

moving parts - especially when it comes to subscriptions.

9.2.1. The SKU

In-app purchase support centers around your set of SKUs that you want to sell. Each product that

you sell, whether it be a 1-month subscription, an upgrade to the "Pro" version, "10 disco credits",

will  have  a  SKU  (stock-keeping-unit).  Ideally  you  will  be  able  to  use  the  same  SKU  across  all  the

stores that you sell your app in.

333

9.2.2. Types of Products

There are generally 4 classifications for products:

1. Non-consumable  Product  -  This  is  a  product  that  the  user  purchases  once  to  "own".  They

cannot re-purchase it. One example is a product that upgrades your app to a "Pro" version.

2. Consumable Product - This is a product that the user can buy more than once. E.g. You might

have a product for "10 Credits" that allows the user to buy items in a game.

3. Non-Renewable  Subscription  -  A  subscription  that  you  buy  once,  and  will  not  be  "auto-

renewed"  by  the  app  store.  These  are  almost  identical  to  consumable  products,  except  that

subscriptions  need  to  be  transferable  across  all  the  user’s  devices.  This  means  that  non-

renewable subscriptions require that you have a server that keeps track of the subscriptions.

4. Renewable  Subscriptions  -  A  subscription  that  the  app  store  manages.  The  user  will  be

automatically billed when the subscription period ends, and the subscription will renew.



These subscription categories may not be explicitly supported by a given store, or

they  may  carry  a  different  name.  You  can  integrate  each  product  type  in  a  cross

platform  way  using  Codename  One.  E.g.  In  Google  Play  there  is  no  distinction

between  consumable  products  and  non-renewable  subscriptions,  but  in  iTunes

there is a distinction.

9.2.3. The "Hello World" of In-App Purchase

Let’s start with a simple example of an app that sells "Worlds". The first thing we do is pick the SKU

for our product. I’ll choose "com.codename1.world" for the SKU.

public static final String SKU_WORLD = "com.codename1.world";



While we chose to use the package name convention for an SKU you can use any
name you want e.g UA8879

Next, our app’s main class needs to implement the PurchaseCallback interface

334

public class HelloWorldIAP implements PurchaseCallback {
    ....

    @Override
    public void itemPurchased(String sku) {
        ...
    }

    @Override
    public void itemPurchaseError(String sku, String errorMessage) {
        ...
    }

    @Override
    public void itemRefunded(String sku) {
        ...
    }

    @Override
    public void subscriptionStarted(String sku) {
        ...
    }

    @Override
    public void subscriptionCanceled(String sku) {
        ...
    }

    @Override
    public void paymentFailed(String paymentCode, String failureReason) {
       ...
    }

    @Override
    public void paymentSucceeded(String paymentCode, double amount, String currency) {
        ...
    }

}

Using  these  callbacks,  we’ll  be  notified  whenever  something  changes  in  our  purchases.  For  our
simple app we’re only interested in itemPurchased() and itemPurchaseError().

Now in the start method, we’ll add a button that allows the user to buy the world:

335

    public void start() {
        if(current != null){
            current.show();
            return;
        }
        Form hi = new Form("Hi World");
        Button buyWorld = new Button("Buy World");
        buyWorld.addActionListener(e->{
            if (Purchase.getInAppPurchase().wasPurchased(SKU_WORLD)) {
                Dialog.show("Can't Buy It", "You already Own It", "OK", null);
            } else {
                Purchase.getInAppPurchase().purchase(SKU_WORLD);
            }
        });

        hi.addComponent(buyWorld);
        hi.show();
    }

At this point, we already have a functional app that will track the sale of the world. To make it more
interesting, let’s add some feedback with the ToastBar to show when the purchase completes.

    @Override
    public void itemPurchased(String sku) {
        ToastBar.showMessage("Thanks.  You now own the world", FontImage.MATERIAL_THUMB_UP);
    }

    @Override
    public void itemPurchaseError(String sku, String errorMessage) {
        ToastBar.showErrorMessage("Failure occurred: "+errorMessage);
    }



You can test out this code in the simulator without doing any additional setup and

it will work. If you want the code to work properly on Android and iOS, you’ll need

to set up the app and in-app purchase settings in the Google Play and iTunes stores

respectively as explained below

When the app first opens we see our button:

336

Figure 313. In-app purchase demo app

In the simulator, clicking on the "Buy World" button will bring up a prompt to ask you if you want

to approve the purchase.

Figure 314. Approving the purchase in the simulator

Now if I try to buy the product again, it pops up the dialog to let me know that I already own it.

337

Figure 315. In App purchase already owned

9.2.4. Making it Consumable

In the "Buy World" example above, the "world" product was non-consumable, since we could only

buy  the  world  once. We  could  change  it  to  a  consumable  product  by  disregarding  whether  it  was

purchased before & keeping track of how many times it had been purchased.

We’ll  use  storage  to  keep  track  of  the  number  of  worlds  that  the  user  purchased.  We  need  two

methods to manage this count. One method gets the number of worlds that we own, and another

adds a world to this count.

private static final String NUM_WORLDS_KEY = "NUM_WORLDS.dat";
public int getNumWorlds() {
    synchronized (NUM_WORLDS_KEY) {
        Storage s = Storage.getInstance();
        if (s.exists(NUM_WORLDS_KEY)) {
            return (Integer)s.readObject(NUM_WORLDS_KEY);
        } else {
            return 0;
        }
    }
}

public void addWorld() {
    synchronized (NUM_WORLDS_KEY) {
        Storage s = Storage.getInstance();
        int count = 0;
        if (s.exists(NUM_WORLDS_KEY)) {
            count = (Integer)s.readObject(NUM_WORLDS_KEY);
        }
        count++;
        s.writeObject(NUM_WORLDS_KEY, new Integer(count));
    }
}

338

Now we’ll change our purchase code as follows:

buyWorld.addActionListener(e->{
    if (Dialog.show("Confirm", "You own "+getNumWorlds()+
           " worlds.  Do you want to buy another one?", "Yes", "No")) {
        Purchase.getInAppPurchase().purchase(SKU_WORLD);
    }
});

And our itemPurchased() callback will need to add a world:

@Override
public void itemPurchased(String sku) {
    addWorld();
    ToastBar.showMessage("Thanks.  You now own "+getNumWorlds()+" worlds", FontImage.MATERIAL_THUMB_UP);
}



When we set up the products in the iTunes store we will need to mark the product

as a consumable product or iTunes will prevent us from purchasing it more than

once

9.2.5. Non-Renewable Subscriptions

As we discussed before, there are two types of subscriptions:

1. Non-renewable

2. Auto-renewable

Non-renewable subscriptions are the same as consumable products, except that they are shareable

across  devices.  Auto-renewable  subscriptions  will  continue  as  long  as  the  user  doesn’t  cancel  the

subscription.  They  will  be  re-billed  automatically  by  the  appropriate  app-store  when  the  chosen

period expires, and the app-store handles the management details itself.





The  concept  of  an  "Non-renewable"  subscription  is  unique  to  iTunes.  Google  Play

has no formal similar option. In order to create a non-renewable subscription SKU

that  behaves  the  same  in  your  iOS  and  Android  apps  you  would  create  it  as  a

regular product in Google play, and a Non-renewable subscription in the iTunes

store. We’ll learn more about that in a later post when we go into the specifics of

app store setup.

The  Purchase  class  includes  both  a  purchase()  method  and  a  subscribe()  method.
On  some  platforms  it  makes  no  difference  which  one  you  use,  but  on  Android  it

matters. If the product is set up as a subscription in Google Play, then you must use
subscribe() to purchase the product. If it is set up as a regular product, then you
must  use  purchase().  Since  we  enter  "Non-renewable"  subscriptions  as  regular
products in the play store, we would use the purchase() method.

339

9.2.6. The Server-Side

Since a subscription purchased on one user device needs to be available across the user’s devices

(Apple’s rules for non-renewable subscriptions), our app will need to have a server-component. In

this  section,  we’ll  gloss  over  that  &  "mock"  the  server  interface.  We’ll  go  into  the  specifics  of  the

server-side below.

The Receipts API

Subscriptions, in Codename One use the "Receipts" API. It’s up to you to register a receipt store with

the In-App purchase instance, which allows Codename one to load receipts (from your server), and
submit new receipts to your server. A Receipt includes information such as:

1. Store code (since you may be dealing with receipts from itunes, google play & Microsoft)

2. SKU

3. Transaction ID (store specific)

4. Expiry Date

5. Cancellation date

6. Purchase date

7. Order  Data  (that  you  can  use  on  the  server-side  to  verify  the  receipt  and  load  receipt  details

directly from the store it originated from).

The Purchase provides a set of methods for interacting with the receipt store, such as:

1. isSubscribed([skus])  -  Checks  to  see  if  the  user  is  currently  subscribed  to  any  of  the  provided

skus.

2. getExpiryDate([skus]) - Checks the expiry date for a set of skus.

3. synchronizeReceipts()  -  Synchronizes  the  receipts  with  the  receipt  store.  This  will  attempt  to
submit  any  pending  purchase  receipts  to  the  receipt  store,  and  the  reload  receipts  from  the

receipt store.

In order for any of this to work, you must implement the ReceiptStore interface, and register it with
the Purchase instance. Your receipt store must implement two methods:

1. fetchReceipts(SuccessCallback<Receipt[]>  callback)  -  Loads  all  of  the  receipts  from  your

receipt store for the current user.

2. submitReceipt(Receipt receipt, SuccessCallback<Boolean> callback) - Submits a receipt to your
receipt store. This gives you an opportunity to add details to the receipt such as an expiry date.

9.2.7. The "Hello World" of Non-Renewable Subscriptions

We’ll expand on the theme of "Buying" the world for this app, except, this time we will "Rent" the

world for a period of time. We’ll have two products:

1. A 1 month subscription

2. A 1 year subscription

340

public static final String SKU_WORLD_1_MONTH = "com.codename1.world.subscribe.1month";
public static final String SKU_WORLD_1_YEAR = "com.codename1.world.subscribe.1year";

public static final String[] PRODUCTS = {
    SKU_WORLD_1_MONTH,
    SKU_WORLD_1_YEAR
};

Notice  that  we  create  two  separate  SKUs  for  the  1  month  and  1  year  subscription.  Each
subscription period must have its own SKU. I have created an array (PRODUCTS) that contains both
of the SKUs. This is handy, as you’ll see in the examples ahead, because the APIs for checking status

and expiry date of a subscription take the SKUs in a "subscription group" as input.



Different SKUs that sell the same service/product but for different periods form a

"subscription  group".  Conceptually,  customers  are  not  subscribing  to  a  particular

SKU,  they  are  subscribing  to  the  subscription  group  of  which  that  SKU  is  a

member. As an example, if a user purchases a 1 month subscription to "the world",

they are actually subscribing to "the world" subscription group.

It’s  up  to  you  to  know  the  grouping  of  your  SKUs.  Any  methods  in  the  Purchase  class  that  check
subscription  status  or  expiry  date  of  a  SKU  should  be  passed  all  SKUs  of  that  subscription  group.
E.g. If you want to know if the user is subscribed to the SKU_WORLD_1_MONTH subscription, it would not
be sufficient to call iap.isSubscribed(SKU_WORLD_1_MONTH), because that wouldn’t take into account if
the  user  had  purchased  a  1  year  subscription.  The  correct  way 
to  always  call
iap.isSubscribed(SKU_WORLD_1_MONTH, SKU_WORLD_1_YEAR), or simply iap.isSubscribed(PRODUCTS) since
we have placed both SKUs into our PRODUCTS array.

is 

Implementing the Receipt Store

The  receipt  store  is  intended  to  interface  with  a  server  so  that  the  subscriptions



can  be  synced  with  multiple  devices,  as  required  by  Apple’s  guidelines.  For  this

post we’ll just store our receipts on device using internal storage. Moving the logic

to a server is a simple matter that we will cover in a future post when we cover the

server-side.

341

Figure 316. The Receipt store is a layer between your server and Codename One

A basic receipt store needs to implement just two methods:

1. fetchReceipts

2. submitReceipt

Generally we’ll register it in our app’s init() method so that it’s always available.

342

public void init(Object context) {
    ...

    Purchase.getInAppPurchase().setReceiptStore(new ReceiptStore() {

        @Override
        public void fetchReceipts(SuccessCallback<Receipt[]> callback) {
            // Fetch receipts from storage and pass them to the callback
        }

        @Override
        public void submitReceipt(Receipt receipt, SuccessCallback<Boolean> callback) {
            // Save a receipt to storage.  Make sure to call callback when done.
        }
    });
}

These methods are designed to be asynchronous since real-world apps will always be connecting to

some  sort  of  network  service.  Therefore,  instead  of  returning  a  value,  both  of  these  methods  are

instances  of 

passed 
to  call
callback.onSuccess() ALWAYS when the methods have completed, even if there is an error, or the
Purchase  class  will  just  assume  that  you’re  taking  a  long  time  to  complete  the  task,  and  will

the  SuccessCallback  class. 

to  make  sure 

important 

It’s 

continue to wait for you to finish.

Once implemented, our fetchReceipts() method will look like:

// static declarations used by receipt store

// Storage key where list of receipts are stored
private static final String RECEIPTS_KEY = "RECEIPTS.dat";

@Override
public void fetchReceipts(SuccessCallback<Receipt[]> callback) {
    Storage s = Storage.getInstance();
    Receipt[] found;
    synchronized(RECEIPTS_KEY) {
        if (s.exists(RECEIPTS_KEY)) {
            List<Receipt> receipts = (List<Receipt>)s.readObject(RECEIPTS_KEY);
            found = receipts.toArray(new Receipt[receipts.size()]);
        } else {
            found = new Receipt[0];
        }
    }
    // Make sure this is outside the synchronized block
    callback.onSucess(found);
}

This is fairly straight forward. We’re checking to see if we already have a list of receipts stored. If so

343

we return that list to the callback. If not we return an empty array of receipts.

 Receipt  implements  Externalizable  so  you  are  able  to  write  instances  directly  to

Storage.

The submitReceipt() method is a little more complex, as it needs to calculate the new expiry date for
our subscription.

@Override
public void submitReceipt(Receipt receipt, SuccessCallback<Boolean> callback) {
    Storage s = Storage.getInstance();
    synchronized(RECEIPTS_KEY) {
        List<Receipt> receipts;
        if (s.exists(RECEIPTS_KEY)) {
            receipts = (List<Receipt>)s.readObject(RECEIPTS_KEY);
        } else {
            receipts = new ArrayList<Receipt>();
        }
        // Check to see if this receipt already exists
        // This probably won't ever happen (that we'll be asked to submit an
        // existing receipt, but better safe than sorry
        for (Receipt r : receipts) {
            if (r.getStoreCode().equals(receipt.getStoreCode()) &&
                    r.getTransactionId().equals(receipt.getTransactionId())) {
                // If we've already got this receipt, we'll just this submission.
                return;
            }
        }

        // Now try to find the current expiry date
        Date currExpiry = new Date();
        List<String> lProducts = Arrays.asList(PRODUCTS);
        for (Receipt r : receipts) {
            if (!lProducts.contains(receipt.getSku())) {
                continue;
            }
            if (r.getCancellationDate() != null) {
                continue;
            }
            if (r.getExpiryDate() == null) {
                continue;
            }
            if (r.getExpiryDate().getTime() > currExpiry.getTime()) {
                currExpiry = r.getExpiryDate();
            }
        }

        // Now set the appropriate expiry date by adding time onto
        // the end of the current expiry date
        Calendar cal = Calendar.getInstance();

344

        cal.setTime(currExpiry);
        switch (receipt.getSku()) {
            case SKU_WORLD_1_MONTH:
                cal.add(Calendar.MONTH, 1);
                break;
            case SKU_WORLD_1_YEAR:
                cal.add(Calendar.YEAR, 1);
        }
        Date newExpiry = cal.getTime();

        receipt.setExpiryDate(newExpiry);
        receipts.add(receipt);
        s.writeObject(RECEIPTS_KEY, receipts);

    }
    // Make sure this is outside the synchronized block
    callback.onSucess(Boolean.TRUE);
}

The  main  logic  of  this  method  involves  iterating  through  all  of  the  existing  receipts  to  find  the

latest current expiry date, so that when the user purchases a subscription, it’s added onto the end

of the current subscription (if one exists) rather than going from today’s date. This enables users to

safely renew their subscription before the subscription has expired.

In the real-world, we would implement this logic on the server-side.



The iTunes store and Play store have no knowledge of your subscription durations.
This is why it’s up to you to set the expiry date in the submitReceipt method. Non-
renewable  subscriptions  are  essentially  no  different  than  regular  consumable

products. It’s up to you to manage the subscription logic - and Apple, in particular,

requires you to do so using a server.

Synchronizing Receipts

In order for your app to provide you with current data about the user’s subscriptions and expiry
dates,  you  need  to  synchronize  the  receipts  with  your  receipt  store.  Purchase  provides  a  set  of
methods  for  doing  this.  Generally  I’ll  call  one  of  them  inside  the  start()  method,  and  I  may
resynchronize at other strategic times if I suspect that the information may have changed.

The following methods can be used for synchronization:

1. synchronizeReceipts() - Asynchronously synchronizes receipts in the background. You won’t be

notified when it’s complete.

2. synchronizeReceiptsSync() - Synchronously synchronizes receipts, and blocks until it’s complete.

This is safe to use on the EDT as it employs invokeAndBlock under the covers.

3. synchronizeReceipts(final  long  ifOlderThanMs,  final  SuccessCallback<Boolean>  callback)  -
Asynchronously  synchronizes  receipts,  but  only  if  they  haven’t  been  synchronized  in  the

specified  time  period.  E.g.  In  your  start()  method  you  might  decide  that  you  only  want  to

345

synchronize  receipts  once  per  day.  This  also  includes  a  callback  that  will  be  called  when

synchronization is complete.

4. synchronizeReceiptsSync(long  ifOlderThanMs)  -  A  synchronous  version  that  will  only  refetch  if

data is older than given time.

In our hello world app we synchronize the subscriptions in a few places.

At the end of the start() method:

public void start() {

   ...

    // Now synchronize the receipts
    iap.synchronizeReceipts(0, res->{
        // Update the UI as necessary to reflect

    });
}

And we also provide a button to allow the user to manually synchronize the receipts.

Button syncReceipts = new Button("Synchronize Receipts");

syncReceipts.addActionListener(e->{

    iap.synchronizeReceipts(0, res->{
        // Update the UI
    });
});

Expiry Dates and Subscription Status

Now that we have a receipt store registered, and we have synchronized our receipts, we can query
the Purchase instance to see if a SKU or set of SKUs is currently subscribed. There are three useful
methods in this realm:

1. boolean isSubscribed(String… skus) - Checks to see if the user is currently subscribed to any of

the provided SKUs.

2. Date getExpiryDate(String… skus) - Gets the latest expiry date of a set of SKUs.

3. Receipt  getFirstReceiptExpiringAfter(Date  dt,  String…  skus)  -  This  method  will  return  the
earliest receipt with an expiry date after the given date. This is needed in cases where you need

to decide if the user should have access to some content based on its publication date. E.g. If you

published an issue of your e-zine on March 1, and the user purchased a subscription on March

15th, then they should get access to the March 1st issue even though it doesn’t necessarily fall in

the  subscription  period.  Being  able  to  easily  fetch  the  first  receipt  after  a  given  date  makes  it

easier to determine if a particular issue should be covered by a subscription.

346

If you need to know more information about subscriptions, you can always just call getReceipts()
to obtain a list of all of the current receipts and determine for yourself what the user should have

access to.

In the hello world app we’ll use this information in a few different places. On our main form we’ll

include  a  label  to  show  the  current  expiry  date,  and  we  allow  the  user  to  press  a  button  to

synchronize receipts manually if they think the value is out of date.

// ...

SpanLabel rentalStatus = new SpanLabel("Loading rental details...");
Button syncReceipts = new Button("Synchronize Receipts");

syncReceipts.addActionListener(e->{

    iap.synchronizeReceipts(0, res->{
        if (iap.isSubscribed(PRODUCTS)) {
            rentalStatus.setText("World rental expires "+iap.getExpiryDate(PRODUCTS));
        } else {
            rentalStatus.setText("You don't currently have a subscription to the world");
        }
        hi.revalidate();
    });
});

Allowing the User to Purchase the Subscription

You  should  now  have  all  of  the  background  required  to  implement  the  Hello  World  Subscription

app. So we’ll return to the code and see how the user purchases a subscription.

In  the  main  form,  we  want  two  buttons  to  subscribe  to  the  "World",  for  one  month  and  one  year

respectively. They look like:

347

Purchase iap = Purchase.getInAppPurchase();
// ...
Button rentWorld1M = new Button("Rent World 1 Month");
rentWorld1M.addActionListener(e->{
    String msg = null;
    if (iap.isSubscribed(PRODUCTS)) {  ①
        msg = "You are already renting the world until "
             +iap.getExpiryDate(PRODUCTS)  ②
             +".  Extend it for one more month?";
    } else {
        msg = "Rent the world for 1 month?";
    }
    if (Dialog.show("Confirm", msg, "Yes", "No")) {
        Purchase.getInAppPurchase().purchase(SKU_WORLD_1_MONTH); ③
        // Note: since this is a non-renewable subscription it is just a regular
        // product in the play store - therefore we use the purchase() method.
        // If it were a "subscription" product in the play store, then we
        // would use subscribe() instead.
    }
});

Button rentWorld1Y = new Button("Rent World 1 Year");
rentWorld1Y.addActionListener(e->{
    String msg = null;
    if (iap.isSubscribed(PRODUCTS)) {
        msg = "You are already renting the world until "+
               iap.getExpiryDate(PRODUCTS)+
              ".  Extend it for one more year?";
    } else {
        msg = "Rent the world for 1 year?";
    }
    if (Dialog.show("Confirm", msg, "Yes", "No")) {
        Purchase.getInAppPurchase().purchase(SKU_WORLD_1_YEAR);
        // Note: since this is a non-renewable subscription it is just a regular
        // product in the play store - therefore we use the purchase() method.
        // If it were a "subscription" product in the play store, then we
        // would use subscribe() instead.
    }
});

① In the event handler we check if the user is subscribed by calling isSubscribed(PRODUCTS). Notice

that we check it against the array of both the one month and one year subscription SKUs.

② We are able to tell the user when the current expiry date is so that they can gauge whether to

proceed.

③ Since  this  is  a  non-renewable  subscription,  we  use  the  Purchase.purchase()  method.  See

following note about subscribe() vs purchase()

348

9.2.8. subscribe() vs purchase()

The Purchase class includes two methods for initiating a purchase:

1. purchase(sku)

2. subscribe(sku)

Which one you use depends on the type of product that is being purchased. If your product is set up
as  a  subscription  in  the  Google  Play  store,  then  you  should  use  subscribe(sku).  Otherwise,  you
should use purchase(sku).

Handling Purchase Callbacks

The  purchase  callbacks  are  very  similar  to  the  ones  that  we  implemented  in  the  regular  in-app

purchase examples:

@Override
public void itemPurchased(String sku) {
    Purchase iap = Purchase.getInAppPurchase();

    // Force us to reload the receipts from the store.
    iap.synchronizeReceiptsSync(0);
    ToastBar.showMessage("Your subscription has been extended to "+iap.getExpiryDate(PRODUCTS),
FontImage.MATERIAL_THUMB_UP);
}

@Override
public void itemPurchaseError(String sku, String errorMessage) {
    ToastBar.showErrorMessage("Failure occurred: "+errorMessage);
}

Notice that, in itemPurchased() we don’t need to explicitly create any receipts or submit anything to
the  receipt  store.  This 
to
synchronizeReceiptsSync() but this is just to ensure that our toast message has the new expiry date
loaded already.

for  you  automatically.  We  do  make  a  call 

is  handled 

9.2.9. Screenshots

349

Figure 317. Main form

Figure 318. Dialog shown when subscribing to a product

350

Figure 319. Simulator confirm dialog when purchasing a subscription

Figure 320. Upon successful purchase, the toastbar message is shown

9.2.10. Summary

This  section  demonstrated  how  to  set  up  an  app  to  use  non-renewable  subscriptions  using  in-app

purchase.  Non-renewable  subscriptions  are  the  same  as  regular  consumable  products  except  for

the fact that they are shared by all of the user’s devices, and thus, require a server component. The

app store has no knowledge of the duration of your non-renewable subscriptions. It’s up to you to

specify  the  expiry  date  of  purchased  subscriptions  on  their  receipts  when  they  are  submitted.

Google  play  doesn’t  formally  have  a  "non-renewable"  subscription  product  type.  To  implement

them in Google play, you would just set up a regular product. It’s how you handle it internally that

makes it a subscription, and not just a regular product.

Codename One uses the Receipt class as the foundation for its subscriptions infrastructure. You, as
the developer, are responsible for implementing the ReceiptStore interface to provide the receipts.
The  Purchase  instance  will  load  receipts  from  your  ReceiptStore,  and  use  them  to  determine
whether the user is currently subscribed to a subscription, and when the subscription expires.

9.2.11. Auto-Renewable Subscriptions

Auto-renewable  subscriptions  provide,  arguably,  an  easier  path  to  recurring  revenue  than  non-

renewable subscriptions because all of the subscription stuff is handled by the app store. You defer

almost entirely to the app store (iTunes for iOS, and Play for Android) for billing and management.

If there is a down-side, it would be that you are also subject to the rules of each app store - and they

351

take their cut of the revenue.

1. For  more  information  about  Apple’s  auto-renewable  subscription  features  and  rules  see  this

document [https://developer.apple.com/app-store/subscriptions/].

2. For  more 

information  about 

subscriptions 

in  Google  play, 

see 

this  document

[https://developer.android.com/google/play/billing/billing_subscriptions.html].

9.2.12. Auto-Renewable vs Non-Renewable.  Best Choice?

When  deciding  between  auto-renewable  and  non-renewable  subscriptions,  as  always,  the  answer

will depend on your needs and preferences. Auto-renewables are nice because it takes the process

completely out of your hands. You just get paid. On the other hand, there are valid reasons to want

to use non-renewables. E.g. You can’t cancel an auto-renewable subscription for a user. They have

to do that themselves. You may also want more control over the subscription and renewal process,

in which case a non-renewable might make more sense.



There  are  some  developers  that  are  opposed  to  auto-renewable  subscriptions

[https://marco.org/2013/12/02/auto-renewable-subscriptions],  we  don’t  have  enough

information to make a solid recommendation on this matter

On  a  practical  level,  if  you  are  using  auto-renewable  subscriptions  (and  therefore  subscription
products in the Google play store) you must use the Purchase.subscribe(sku) method for initiating
the  purchase  workflow.  For  non-renewable  subscriptions  (and  therefore  regular  products  in  the
Google play store), you must use the Purchase.purchase(sku) method.

9.2.13. Learning By Example

In this section we’ll describe the general workflow of subscription management on the server. We

also demonstrate how use Apple’s and Google’s web services to validate receipts and stay informed

of important events (such as when users cancel or renew their subscriptions).

9.2.14. Building the IAP Demo Project

To aid in this process, we’ve created a fully-functional in-app purchase demo project that includes

both  a  client  app  [https://gist.github.com/shannah/b61b9b6b35ea0eac923a54163f5d4deb]  and  a  server  app

[https://github.com/shannah/cn1-iap-demo-server].

Setting up the Client Project

1. Create  a  new  Codename  One  project  in  Netbeans,  and  choose  the  "Bare-bones  Hello  World

Template".  You  should  make  your  package  name  something  unique  so  that  you  are  able  to

create real corresponding apps in both Google Play and iTunes connect.

2. Once 

the  project 

is 

created, 

copy 

this 

source 

file 

[https://gist.github.com/shannah/

b61b9b6b35ea0eac923a54163f5d4deb]  contents  into  your  main  class  file.  Then  change  the  package
name,  and  class  name  in  the  file  to  match  your  project  settings.  E.g.  change  package
ca.weblite.iapdemo;  to  package  <your.package.name.here>;  and  class  IAPDemo  implements
PurchaseCallback to class YourClassName implements PurchaseCallback.

352

3. Add  the  Generic  Web  Service  Client  [https://github.com/shannah/cn1-generic-webservice-client]  library

to  your  project  by  going  to  "Codename  Settings"  >  "Extensions",  finding  that  library,  and  click

"Download". Then "Refresh CN1 libs" as it suggests.

4. Change  the  localHost  property  to  point  to  your  local  machine’s  network  address.  Using
"http://localhost" is not going to cut it here because when the app is running on a phone, it needs

to  be  able  to  connect  to  your  web  server  over  the  network.  This  address  will  be  your  local

network address (e.g. 192.168.0.9, or something like that).

private static final String localHost = "http://10.0.1.32";

5. Add 

the 

ios.plistInject 

build 

hint 

to 

your 

project  with 

the 

value

"<key>NSAppTransportSecurity</key>  <dict>  <key>NSAllowsArbitraryLoads</key>  <true/>

</dict>".  This  is  so  that  we  can  use  http  urls  in  iOS.  Since  we  don’t  intend  to  fully  publish  this

app, we can cut corners like this. If you were creating a real app, you would use proper secure

URLs.

Setting up the Server Project

Download  the  CN1-IAP-Server  demo  project  from  Github,  and  run  its  "install-deps"  ANT  task  in

order to download and install its dependencies to your local Maven repo.

 For the following commands to work, make sure you have "ant", "mvn", and "git"

in your environment PATH.

$ git clone https://github.com/shannah/cn1-iap-demo-server
$ cd cn1-iap-demo-server
$ ant install-deps

Open the project in Netbeans

Setting up the Database

1. Create a new database in your preferred DBMS. Call it anything you like.

2. Create a new table named "RECEIPTS" in this database with the following structure:

353

create TABLE RECEIPTS
(
    TRANSACTION_ID VARCHAR(128) not null,
    USERNAME VARCHAR(64) not null,
    SKU VARCHAR(128) not null,
    ORDER_DATA VARCHAR(32000),
    PURCHASE_DATE BIGINT,
    EXPIRY_DATE BIGINT,
    CANCELLATION_DATE BIGINT,
    LAST_VALIDATED BIGINT,
    STORE_CODE VARCHAR(20) default '' not null,
    primary key (TRANSACTION_ID, STORE_CODE)
)

3. Open the "persistence.xml" file in the server netbeans project.

4. Change the data source to the database you just created.

If you’re not sure how to create a data source, see my previous tutorial on connecting to a MySQL

database [https://www.codenameone.com/blog/connecting-to-a-mysql-database-part-2.html].

Testing the Project

At this point we should be able to test out the project in the Codename One simulator to make sure

it’s working.

1. Build and Run the server project in Netbeans. You may need to tell it which application server

you wish to run it on. I am running it on the Glassfish 4.1 that comes bundled with Netbeans.

2. Build and run the client project in Netbeans. This should open the Codename One simulator.

When the app first opens you’ll see a screen as follows:

354

Figure 321. First screen of app

This screen is for testing consumable products, so we won’t be making use of this right now.

Open the hamburger menu and select "Subscriptions". You should see something like this:

Figure 322. Subscriptions form

Click on the "Subscribe 1 Month No Ads" button. You will be prompted to accept the purchase:

355

Figure 323. Approve purchase dialog

Upon  completion,  the  app  will  submit  the  purchase  to  your  server,  and  if  all  went  well,  it  will

retrieve the updated list of receipts from your server also, and update the label on this form to say

"No Ads. Expires <some date>":

Figure 324. After successful purchase



This project is set up to use an expedited expiry date schedule for purchases from

the simulator. 1 month = 5 minutes. 3 months = 15 minutes. This helps for testing.

That is why your expiry date may be different than expected.

Just  to  verify  that  the  receipt  was  inserted  correctly,  you  should  check  the  contents  of  your

"RECEIPTS"  table  in  your  database.  In  Netbeans,  I  can  do  this  easily  from  the  "Services"  pane.

Expand  the  database  connection  down  to  the  RECEIPTS  table,  right  click  "RECEIPTS"  and  select

"View Data". This will open a data table similar the the following:

356

Figure 325. Receipts table after insertion

Figure 326. Table view

A few things to mention here:

1. The "username" was provided by the client. It’s hard-coded to "admin", but the idea is that you

would have the user log in and you would have access to their real username.

2. All dates are stored as unix timestamps in milliseconds.

If you delete the receipt from your database, then press the "Synchronize Receipts" button in your

app, the app will again say "No subscriptions." Similarly if you wait 5 minutes and hit "Synchronize

receipts" the app will say no subscriptions found, and the "ads" will be back.

Troubleshooting

Let’s not pretend that everything worked for you on the first try. There’s a lot that could go wrong

here. If you make a purchase and nothing appears to happen, the first thing you should do is check

the  Network  Monitor  in  the  simulator  ("Simulate"  >  "Network"  >  "Network  Monitor").  You  should

see  a  list  of  network  requests.  Some  will  be  GET  requests  and  there  will  be  at  least  one  POST

request. Check the response of these requests to see if they succeeded.

Also check the Glassfish server log to see if there is an exception.

Common problems would be that the URL you have set in the client app for endpointURL is incorrect,
or that there is a database connection problem.

9.2.15. Looking at the Source of the App

Now that we’ve set up and built the app, let’s take a look at the source code so you can see how it all

works.

Client Side

I  use  the  Generic  Webservice  Client  Library  [https://github.com/shannah/cn1-generic-webservice-client]

357

from inside my ReceiptStore implementation to load receipts from the web service, and insert new
receipts to the database.

The source for my ReceiptStore is as follows:

private ReceiptStore createReceiptStore() {
    return new ReceiptStore() {

        RESTfulWebServiceClient client = createRESTClient(receiptsEndpoint);

        @Override
        public void fetchReceipts(SuccessCallback<Receipt[]> callback) {
            RESTfulWebServiceClient.Query query = new RESTfulWebServiceClient.Query() {

                @Override
                protected void setupConnectionRequest(RESTfulWebServiceClient client, ConnectionRequest req) {
                    super.setupConnectionRequest(client, req);
                    req.setUrl(receiptsEndpoint);
                }

            };
            client.find(query, rowset->{
                List<Receipt> out = new ArrayList<Receipt>();
                for (Map m : rowset) {
                    Result res = Result.fromContent(m);
                    Receipt r = new Receipt();
                    r.setTransactionId(res.getAsString("transactionId"));
                    r.setPurchaseDate(new Date(res.getAsLong("purchaseDate")));
                    r.setQuantity(1);
                    r.setStoreCode(m.getAsString("storeCode"));
                    r.setSku(res.getAsString("sku"));

                    if (m.containsKey("cancellationDate") && m.get("cancellationDate") != null) {
                        r.setCancellationDate(new Date(res.getAsLong("cancellationDate")));
                    }
                    if (m.containsKey("expiryDate") && m.get("expiryDate") != null) {
                        r.setExpiryDate(new Date(res.getAsLong("expiryDate")));
                    }
                    out.add(r);

                }
                callback.onSucess(out.toArray(new Receipt[out.size()]));
            });
        }

        @Override
        public void submitReceipt(Receipt r, SuccessCallback<Boolean> callback) {
            Map m = new HashMap();
            m.put("transactionId", r.getTransactionId());
            m.put("sku", r.getSku());
            m.put("purchaseDate", r.getPurchaseDate().getTime());
            m.put("orderData", r.getOrderData());
            m.put("storeCode", r.getStoreCode());
            client.create(m, callback);
        }

    };
}

358

Notice  that  we  are  not  doing  any  calculation  of  expiry  dates  in  our  client  app,  as  we  did  in  the

previous post (on non-renewable receipts). Since we are using a server now, it makes sense to move

all of that logic over to the server.

The  createRESTClient()  method  shown  there  simply  creates  a  RESTfulWebServiceClient  and
configuring it to use basic authentication with a username and password. The idea is that your user

would have logged into your app at some point, and you would have a username and password on

hand to pass back to the web service with the receipt data so that you can connect the subscription

to a user account. The source of that method is listed here:

/**
 * Creates a REST client to connect to a particular endpoint.  The REST client
 * generated here will automatically add the Authorization header
 * which tells the service what platform we are on.
 * @param url The url of the endpoint.
 * @return
 */
private RESTfulWebServiceClient createRESTClient(String url) {
    return new RESTfulWebServiceClient(url) {

        @Override
        protected void setupConnectionRequest(ConnectionRequest req) {
            try {
                req.addRequestHeader("Authorization", "Basic " +
Base64.encode((getUsername()+":"+getPassword()).getBytes("UTF-8")));
            } catch (Exception ex) {}
        }

    };
}

Server-Side

On  the  server-side,  our  REST  controller  is  a  standard  JAX-RS  REST  interface.  I  used  Netbeans  web

service  wizard  to  generate  it  and  then  modified  it  to  suit  my  purposes.  The  methods  of  the
ReceiptsFacadeREST class pertaining to the REST API are shown here:

359

@Stateless
@Path("com.codename1.demos.iapserver.receipts")
public class ReceiptsFacadeREST extends AbstractFacade<Receipts> {

    // ...

    @POST
    @Consumes({"application/xml", "application/json"})
    public void create(Receipts entity) {

        String username = credentialsWithBasicAuthentication(request).getName();
        entity.setUsername(username);

        // Save the receipt first in case something goes wrong in the validation stage
        super.create(entity);

        // Let's validate the receipt
        validateAndSaveReceipt(entity);
            // validates the receipt against appropriate web service
            // and updates database if expiry date has changed.
    }

    // ...
    @GET
    @Override
    @Produces({"application/xml", "application/json"})
    public List<Receipts> findAll() {
        String username = credentialsWithBasicAuthentication(request).getName();
        return getEntityManager()
                .createNamedQuery("Receipts.findByUsername")
                .setParameter("username", username)
                .getResultList();
    }
}

The magic happens inside that validateAndSaveReceipt() method, which I’ll cover in detail soon.

Notifications

It’s  important  to  note  that  you  will  not  be  notified  by  apple  or  google  when  changes  are  made  to

subscriptions. It’s up to you to periodically "poll" their web service to find if any changes have been

made.  Changes  we  would  be  interested  in  are  primarily  renewals  and  cancellations.  In  order  to

deal  with  this,  set  up  a  method  to  run  periodically  (once-per  day  might  be  enough).  For  testing,  I

actually set it up to run once per minute as shown below:

360

private static final long ONE_DAY = 24 * 60 * 60 * 1000;
private static final long ONE_DAY_SANDBOX = 10 * 1000;
@Schedule(hour="*", minute="*")
public void validateSubscriptionsCron() {
    System.out.println("----------- DOING TIMED TASK ---------");
    List<Receipts> res = null;
    final Set<String> completedTransactionIds = new HashSet<String>();
    for (String storeCode : new String[]{Receipt.STORE_CODE_ITUNES, Receipt.STORE_CODE_PLAY}) {
        while (!(res = getEntityManager().createNamedQuery("Receipts.findNextToValidate")
                .setParameter("threshold", System.currentTimeMillis() - ONE_DAY_SANDBOX)
                .setParameter("storeCode", storeCode)
                .setMaxResults(1)
                .getResultList()).isEmpty() &&
                !completedTransactionIds.contains(res.get(0).getTransactionId())) {

            final Receipts curr = res.get(0);
            completedTransactionIds.add(curr.getTransactionId());
            Receipts[] validatedReceipts =  validateAndSaveReceipt(curr);
            em.flush();
            for (Receipts r : validatedReceipts) {
                completedTransactionIds.add(r.getTransactionId());
            }

        }
    }
}

That  method  simply  finds  all  of  the  receipts  in  the  database  that  haven’t  been  validated  in  some
period  of  time,  and  validates  it.  Again,  the  magic  happens  inside  the  validateAndSaveReceipt()
method which we cover later.

 In this example we only validate receipts from the iTunes and Play stores because

those are the only ones that we currently support auto-renewing subscriptions on.

9.2.16. The CN1-IAP-Validator Library

For the purpose of this tutorial, I created a library to handle receipt validation in a way that hides

as much of the complexity as possible. It supports both Google Play receipts and iTunes receipts.

The general usage is as follows:

361

IAPValidator validator = IAPValidator.getValidatorForPlatform(receipt.getStoreCode());
if (validator == null) {
   // no validators were found for this store
   // Do custom validation
} else {
    validator.setAppleSecret(APPLE_SECRET);
    validator.setGoogleClientId(GOOGLE_DEVELOPER_API_CLIENT_ID);
    validator.setGooglePrivateKey(GOOGLE_DEVELOPER_PRIVATE_KEY);
    Receipt[] result = validator.validate(receipt);
    ...
}

As you can see from this snippet, the complexity of receipt validation has been reduced to entering

three configuration strings:

1. APPLE_SECRET  -  This  is  a  "secret"  string  that  you  will  get  from  iTunes  connect  when  you  set  up

your in-app products.

2. GOOGLE_DEVELOPER_API_CLIENT_ID  -  A  client  ID  that  you’ll  get  from  the  google  developer  API

console when you set up your API service credentials.

3. GOOGLE_DEVELOPER_PRIVATE_KEY  -  A  PKCS8  encoded  string  with  an  RSA  private  key  that  you’ll

receive at the same time as the GOOGLE_DEVELOPER_API_CLIENT_ID.

I will go through the steps to obtain these values soon.

9.2.17. The validateAndSaveReceipt() Method

You are now ready to see the full magic of the validateAndSaveReceipt() method in all its glory:

/**
 * Validates a given receipt, updating the expiry date,
 * @param receipt The receipt to be validated
 * @param forInsert If true, then an expiry date will be calculated even if there is no validator.
 */
private Receipts[] validateAndSaveReceipt(Receipts receipt) {
    EntityManager em = getEntityManager();
    Receipts managedReceipt = getManagedReceipt(receipt);
        // managedReceipt == receipt if receipt is in database or null otherwise

    if (Receipt.STORE_CODE_SIMULATOR.equals(receipt.getStoreCode())) { ①
        if (receipt.getExpiryDate() == null && managedReceipt == null) {
            //Not inserted yet and no expiry date set yet
            Date dt = calculateExpiryDate(receipt.getSku(), true);
            if (dt != null) {
                receipt.setExpiryDate(dt.getTime());
            }
        }
        if (managedReceipt == null) {
            // Receipt is not in the database yet.  Add it
            em.persist(receipt);
            return new Receipts[]{receipt};

362

        } else {
            // The receipt is already in the database.  Update it.
            em.merge(managedReceipt);
            return new Receipts[]{managedReceipt};
        }
    } else {
        // It's not a simulator receipt
        IAPValidator validator = IAPValidator.getValidatorForPlatform(receipt.getStoreCode());
        if (validator == null) {
            // Receipt must have come from a platform other than iTunes or Play
            // Because there is no validator

            if (receipt.getExpiryDate() == null && managedReceipt == null) {
                // No expiry date.
                // Generate one.
                Date dt = calculateExpiryDate(receipt.getSku(), false);
                if (dt != null) {
                    receipt.setExpiryDate(dt.getTime());
                }

            }
            if (managedReceipt == null) {
                em.persist(receipt);
                return new Receipts[]{receipt};
            } else {
                em.merge(managedReceipt);
                return new Receipts[]{managedReceipt};
            }

        }

        // Set credentials for the validator
        validator.setAppleSecret(APPLE_SECRET);
        validator.setGoogleClientId(GOOGLE_DEVELOPER_API_CLIENT_ID);
        validator.setGooglePrivateKey(GOOGLE_DEVELOPER_PRIVATE_KEY);

        // Create a dummy receipt with only transaction ID and order data to pass
        // to the validator.  Really all it needs is order data to be able to validate
        Receipt r2 = Receipt();
        r2.setTransactionId(receipt.getTransactionId());
        r2.setOrderData(receipt.getOrderData());
        try {
            Receipt[] result = validator.validate(r2);
            // Depending on the platform, result may contain many receipts or a single receipt
            // matching our receipt.  In the case of iTunes, none of the receipt transaction IDs
            // might match the original receipt's transactionId because the validator
            // will set the transaction ID to the *original* receipt's transaction ID.
            // If none match, then we should remove our receipt, and update each of the returned
            // receipts in the database.
             Receipt matchingValidatedReceipt = null;
            for (Receipt r3 : result) {
                if (r3.getTransactionId().equals(receipt.getTransactionId())) {
                    matchingValidatedReceipt = r3;
                    break;
                }
            }

363

            if (matchingValidatedReceipt == null) {
                // Since the validator didn't find our receipt,
                // we should remove the receipt.  The equivalent
                // is stored under the original receipt's transaction ID
                if (managedReceipt != null) {
                    em.remove(managedReceipt);
                    managedReceipt = null;
                }
            }
            List<Receipts> out = new ArrayList<Receipts>();
            // Now go through and
            for (Receipt r3 : result) {
                if (r3.getOrderData() == null) {
                    // No order data found in receipt.  Setting it to the original order data
                    r3.setOrderData(receipt.getOrderData());
                }
                Receipts eReceipt = new Receipts();
                eReceipt.setTransactionId(r3.getTransactionId());
                eReceipt.setStoreCode(receipt.getStoreCode());
                Receipts eManagedReceipt = getManagedReceipt(eReceipt);
                if (eManagedReceipt == null) {
                    copy(eReceipt, r3);
                    eReceipt.setUsername(receipt.getUsername());
                    eReceipt.setLastValidated(System.currentTimeMillis());
                    em.persist(eReceipt);
                    out.add(eReceipt);
                } else {

                    copy(eManagedReceipt, r3);
                    eManagedReceipt.setUsername(receipt.getUsername());
                    eManagedReceipt.setLastValidated(System.currentTimeMillis());
                    em.merge(eManagedReceipt);
                    out.add(eManagedReceipt);
                }
            }

            return out.toArray(new Receipts[out.size()]);

        } catch (Exception ex) {
            // We should probably store some info about the failure in the
            // database to make it easier to find receipts that aren't validating,
            // but for now we'll just log it.
            Log.p("Failed to validate receipt "+r2);
            Log.p("Reason: "+ex.getMessage());
            Log.e(ex);
            return new Receipts[]{receipt};

        }
    }
}

① We need to handle the case where the app is being used in the CN1 simulator. We’ll treat this as
a  non-renewable  receipt,  and  we’ll  calculate  the  expiry  date  using  an  "accelerated"  clock  to

assist in testing.

364



In many of the code snippets for the Server-side code, you’ll see references to both
a Receipts class and a Receipt class. I know this is slightly confusing. The Receipts
class  is  a  JPA  entity  the  encapsulates  a  row  from  the  "receipts"  table  of  our  SQL
database. The Receipt class is com.codename1.payment.Receipt. It’s used to interface
with the IAP validation library.

9.2.18. Google Play Setup

Creating the App in Google Play

In order to test out in-app purchase on an Android device, you’ll need to create an app the Google

Play  Developer  Console  [https://play.google.com/apps/publish/].  I  won’t  describe  the  process  in  this

section,  but  there  is  plenty  of  information  around  the  internet  on  how  to  do  this.  Some  useful

references for this include:

1. Getting  Started  With  Publishing  [https://developer.android.com/distribute/googleplay/start.html]  -  If  you

don’t already have an account with Google to publish your apps.

2. Launch Checklist [https://developer.android.com/distribute/tools/launch-checklist.html]

Graphics, Icons, etc..

You are required to upload some screenshots and feature graphics. Don’t waste time making these

perfect.  For  the  screenshots,  you  can  just  use  the  "Screenshot"  option  in  the  simulator.  (Use  the

Nexus  5  skin).  For  the  feature  graphics,  I  used  this  site  [https://www.norio.be/android-feature-graphic-

generator/] that will generate the graphics in the correct dimensions for Google Play. You can also just

leave the icon as the default Codename One icon.

Creating Test Accounts

 You cannot purchase in-app products from your app using your publisher account.

You need to set up at least one test account for the purpose of testing the app.

In order to test your app, you need to set up a test account. A test account must be associated with a

real gmail email address. If you have a domain that is managed by Google apps, then you can also

use an address from that domain.

The 

full  process 

for 

testing 

in-app  billing  can  be 

found 

in 

this  google  document

[https://developer.android.com/google/play/billing/billing_testing.html].  However,  I  personally  found  this

documentation difficult to follow.

For your purposes, you’ll need to set up a tester list in Google Play. Choose "Settings" > "Tester Lists".

Then create a list with all of the email address that you want to have treated as test accounts. Any

purchases  made  by  these  email  addresses  will  be  treated  as  "Sandbox"  purchases,  and  won’t

require real money to change hands.

Alpha Channel Distribution

In order to test in-app purchase on Android, you must first publish your app. You can’t just build

and  install  your  app  manually.  The  app  needs  to  be  published  on  the  Play  store,  and  it  must  be

365

installed through the play store for in-app purchase to work. Luckily you can publish to an Alpha

channel so that your app won’t be publicly available.

For  more  information  about  setting  up  alpha  testing  on  Google  play  see  this  Google  support

document on the subject [https://support.google.com/googleplay/android-developer/answer/3131213?hl=en].

Once you have set your app up for alpha testing, you can send an invite link to your test accounts.

You can find the link in the Google Play console under the APK section, under the "Alpha" tab (and

assuming you’ve enabled alpha testing.

Figure 327. Alpha testing tab in google play

The format of the link is https://play.google.com/apps/testing/your-app-id in case you can’t find it.
You  can  email  this  to  your  alpha  testers.  Make  sure  that  you  have  added  all  testers  to  your  tester

lists so that their purchases will be made in the sandbox environment.

Also,  before  proceeding  with  testing  in-app  purchases,  you  need  to  add  the  in-app  products  in

Google Play.

Adding In-App Products

After  you  have  published  your  APK  to  the  alpha  channel,  you  can  create  the  products.  For  the

purposes of this tutorial, we’ll just add two products:

1. iapdemo.noads.month.auto - The 1 month subscription.

2. iapdemo.noads.3month.auto - The 3 month subscription.



Since  we  will  be  adding  products  as  "Subscriptions"  in  the  pay  store,  your  app
must  use  the  Purchase.subscribe(sku)  method  for  initiating  a  purchase  on  these
products,  and  not  the  Purchase.purchase(sku)  method.  If  you  accidentally  use
purchase()  to  purchase  a  subscription  on  Android,  the  payment  will  go  through,
but your purchase callback will receive an error.

Adding 1 month Subscription

1. Open Google Play Developer Console, and navigate to your app.

2. Click on "In-app Products" in the menu. Then click the "Add New Product" button.

3. Select  "Subscription",  and  enter  "iapdemo.noads.month.auto"  for  the  Product  ID.  Then  click

"Continue"

366

Figure 328. Add new product dialog

Now fill in the form. You can choose your own price and name for the product. The following is a

screenshot of the options I chose.

Figure 329. Add product to google

Adding 3 month Subscription

Follow the same process as for the 1 month subscription except use "iapdemo.noads.3month.auto"

for the product ID, and select "3 months" for the billing period instead of "Monthly".

Testing The App

At this point we should be ready to test our app. Assuming you’ve installed the app using the invite

link you sent yourself from Google play, as a test account that is listed on your testers list, you

should be good to go.

Open the app, click on "Subscriptions", and try to purchase a 1-month subscription. If all goes well,

it should insert the subscription into your database. But with no expiry date, since we haven’t yet

implemented receipt validation yet. We’ll do that next.

Creating Google Play Receipt Validation Credentials

Google  play  receipt  validation  is  accomplished  via  the  android-publisher  Purchases:  get  API

[https://developers.google.com/android-publisher/api-ref/purchases/subscriptions/get].  The  CN1-IAP-Validation

library  shields  you  from  most  of  the  complexities  of  using  this  API,  but  you  still  need  to  obtain  a

367

"private  key"  and  a  "client  id"  to  access  this  API.  Both  of  these  are  provided  when  you  set  up  an

OAuth2  Service  Account  [https://developers.google.com/identity/protocols/OAuth2ServiceAccount]  for  your

app.



Steps:

The following steps assume that you have already created your app in Google play

and have published it to at least the alpha channel. See my previous post on this

topic here (Link to be provided).

1. Open  the  Google  API  Developer  Console  [https://console.developers.google.com/apis],  and  select  your

App from the the menu.

2. Click  on  the  "Library"  menu  item  in  the  left  menu,  and  then  click  the  "Google  Play  Developer

API" link.

Figure 330. Google Play Developer API Link

3. Click on the button that says "Enable". (If you already have it enabled, then just proceed to the

next step).

Figure 331. Enable API button

4. Click on the "Credentials" menu item in the left menu.

5. In the "Credentials" drop-down menu, select the "Service Account Key" option.

Figure 332. Credentials dropdown

6. You will be presented with a new form. In the "Service Account" drop-down, select "New Service

Account". This will give you some additional options.

Figure 333. Create service account key

7. Enter  anything  you  like  for  the  "Service  account  name".  For  the  role,  we’ll  select  "Project"  >

368

"Owner"  for  now  just  so  we  don’t  run  into  permissions  issues.  You’ll  probably  want  to

investigate further to fine a more limited role that only allows receipt verification, but for now, I

don’t  want  any  unnecessary  road  blocks  for  getting  this  to  work. We’re  probably  going  to  run

into "permission denied" errors at first anyways, so the fewer reasons for this, the better.

8. It will auto-generate an account ID for you.

9. Finally, for the "Key type", select "JSON". Then click the "Create" button.

This should prompt the download of a JSON file that will have contents similar to the following:

{
  "type": "service_account",
  "project_id": "iapdemo-152500",
  "private_key_id": "1b1d39f2bc083026b164b10a444ff7d839826b8a",
  "private_key": "-----BEGIN PRIVATE KEY----- ... some private key string -----END PRIVATE KEY-----\n",
  "client_email": "iapdemo@iapdemo-152500.iam.gserviceaccount.com",
  "client_id": "117601572633333082772",
  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
  "token_uri": "https://accounts.google.com/o/oauth2/token",
  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/iapdemo%40iapdemo-
152500.iam.gserviceaccount.com"
}

This is where we get the information we’re looking for. The "client_email" is what we’ll use for your
googleClientId, and the "private_key" is what we’ll use for the googlePrivateKey.

 Use the "client_email" value as our client ID, not the "client_id" value as you might

be tempted to do.

We’ll set these in our constants:

public static final String GOOGLE_DEVELOPER_API_CLIENT_ID="iapdemo@iapdemo-152500.iam.gserviceaccount.com";
public static final String GOOGLE_DEVELOPER_PRIVATE_KEY="-----BEGIN PRIVATE KEY----- ... -----END PRIVATE KEY-----\n";

...

validator.setGoogleClientId(GOOGLE_DEVELOPER_API_CLIENT_ID);
validator.setGooglePrivateKey(GOOGLE_DEVELOPER_PRIVATE_KEY);

NOT DONE YET

Before we can use these credentials to verify receipts for our app, we need to link our app to this

new service account from within Google Play.

Steps:

1. Open  the  Google  Play  Developer  Console  [https://play.google.com/apps/publish/],  then  click  on

"Settings" > "API Access".

2. You should see your app listed on this page. Click the "Link" button next to your app.

369

Figure 334. Link to API

3. This should reveal some more options on the page. You should see a "Service Accounts" section

with a list of all of the service accounts that you have created. Find the one we just created, and

click the "Grant Access" button in its row.

Figure 335. Grant access

4. This  will  open  a  dialog  titled  "Add  New  User".  Leave  everything  default,  except  change  the

"Role" to "Administrator". This provides "ALL" permissions to this account, which probably isn’t

a good idea for production. Later on, after everything is working, you can circle back and try to

refine  permissions.  For  the  purpose  of  this  tutorial,  I  just  want  to  pull  out  all  of  the  potential

road blocks.

Figure 336. New User

5. Press the "Add User" button.

At this point, the service account should be active so we can try to validate receipts.

Testing Receipt Validation

The  ReceiptsFacadeREST  class  includes  a  flag  to  enable/disable  play  store  validation.  By  default  it’s
disabled. Let’s enable it:

public static final boolean DISABLE_PLAY_STORE_VALIDATION=true;

Change this to false.

Then build and run the server app. The validateSubscriptionsCron() method is set to run once per
minute, so we just need to wait for the timer to come up and it should try to validate all of the play

store receipts.

 I’m  assuming  you’ve  already  added  a  receipt  in  the  previous  test  that  we  did.  If

necessary, you should purchase the subscription again in your app.

After a minute or so, you should see "----------- VALIDATING RECEIPTS ---------" written in the Glassfish

370

log, and it will validate your receipts. If it works, your receipt’s expiry date will get populated in the

database, and you can press "Synchronize Receipts" in your app to see this reflected. If it fails, there

will like be a big ugly stack trace and exception readout with some clues about what went wrong.

Realistically,  your  first  attempt  will  fail  for  some  reason.  Use  the  error  codes  and  stack  traces  to

help lead you to the problem. And feel free to post questions here.

9.2.19. iTunes Connect Setup

The process for setting up and testing your app on iOS is much simpler than on Android (IMHO). It

took me a couple hours to get the iTunes version working, vs a couple days on the Google Play side

of things. One notable difference that makes things simpler is that you don’t need to actually upload

your app to the store to test in-app purchase. You can just use your debug build on your device. It’s

also much easier to roll a bunch of test accounts than on Google Play. You don’t need to set up an

alpha program, you just create a few "test accounts" (and this is easy to do) in your iTunes connect

account, and then make sure to use one of these accounts when making a purchase. You can easily

switch  accounts  on  your  device  from  the  "Settings"  app,  where  you  can  just  log  out  of  the  iTunes

store - which will cause you to be prompted in your app the next time you make a purchase.

Setting up In-App Products

The  process  to  add  products  in  iTunes  connect  is  outlined  in  this  apple  developer  document

[https://developer.apple.com/library/content/documentation/LanguagesUtilities/Conceptual/
iTunesConnectInAppPurchase_Guide/Chapters/CreatingInAppPurchaseProducts.html#//apple_ref/doc/uid/

TP40013727-CH3-SW1]. We’ll add our two SKUs:

1. iapdemo.noads.month.auto - The 1 month subscription.

2. iapdemo.noads.3month.auto - The 3 month subscription.

Just make sure you add them as auto-renewable subscriptions, and that you specify the appropriate

renewal periods. Use the SKU as the product ID. Both of these products will be added to the same

subscription group. Call the group whatever you like.

Creating Test Accounts

In  order  to  test  purchases,  you  need  to  create  some  test  accounts.  See  this  apple  document

[https://developer.apple.com/library/content/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/

Chapters/SettingUpUserAccounts.html#//apple_ref/doc/uid/TP40011225-CH25-SW10] for details on how to create

these test accounts. Don’t worry, the process is much simpler than for Android. It should take you

under 5 minutes.

Once you have the test accounts created, you should be set to test the app.

1. Make sure your server is running.

2. Log out from the app store. The process is described here [https://support.apple.com/en-ca/HT203983].

3. Open your app.

4. Try to purchase a 1-month subscription

371

If  all  went  well,  you  should  see  the  receipt  listed  in  the  RECEIPTS  table  of  your  database.  But  the

expiry date will be null. We need to set up receipt verification in order for this to work.

Setting up Receipt Verification

In  order  for  receipt  verification  to  work  we  simply  need  to  generate  a  shared  secret  in  iTunes

connect.  The  process 
LanguagesUtilities/Conceptual/iTunesConnectInAppPurchase_Guide/Chapters/

is  described  here 

[https://developer.apple.com/library/content/documentation/

CreatingInAppPurchaseProducts.html].

Once you have a shared secret, update the ReceiptsFacadeREST class with the value:

public static final String APPLE_SECRET = "your-shared-secret-here";

And enable iTunes store validation:

public static final boolean DISABLE_ITUNES_STORE_VALIDATION=true;

Change this to false.

If you rebuild and run the server project, and wait for the validateSubscriptionsCron() method to
run,  it  should  validate  the  receipt.  After  about  a  minute  (or  less),  you’ll  see  the  text  "-----------

VALIDATING  RECEIPTS  ---------"  written  to  the  Glassfish  log  file,  followed  by  some  output  from

connecting to the iTunes validation service. If all went well, you should see your receipt expiration

date  updated  in  the  database.  If  not,  you’ll  likely  see  some  exception  stack  traces  in  the  Glassfish

Sandbox receipts in the iTunes store are set to run on an accelerated schedule. A 1

month  subscription  is  actually  5  minutes,  3  months  is  15  minutes  etc…  Also

sandbox  subscriptions  don’t  seem  to  persist  in  perpetuity  until  the  user  has

cancelled it. I have found that they usually renew only 4 or 5 times before they are

allowed to lapse by Apple.

log.



372

10. Graphics, Drawing, Images & Fonts

 Drawing  is  considered  a  low  level  API  that  might  introduce  some  platform

fragmentation.

10.1. Basics - Where & How Do I Draw Manually?

The  Graphics  [https://www.codenameone.com/javadoc/com/codename1/ui/Graphics.html]  class  is  responsible

for drawing basics, shapes, images and text, it is never instantiated by the developer and is always

passed on by the Codename One API.

You can gain access to a Graphics using one of the following methods:

• Derive Component [https://www.codenameone.com/javadoc/com/codename1/ui/Component.html] or a
subclass of Component - within Component there are several methods that allow developers to
modify  the  drawing  behavior.  These  can  be  overridden  to  change  the  way  the  component  is

drawn:

◦ paint(Graphics)  -  invoked  to  draw  the  component,  this  can  be  overridden  to  draw  the

component from scratch.

◦ paintBackground(Graphics) / paintBackgrounds(Graphics) - these allow overriding the way the
component background is painted although you would probably be better off implementing

a painter (see below).

◦ paintBorder(Graphics)  -  allows  overriding  the  process  of  drawing  a  border,  notice  that

border drawing might differ based on the style of the component.

◦ paintComponent(Graphics) - allows painting only the components contents while leaving the

default paint behavior to the style.

◦ paintScrollbars(Graphics),  paintScrollbarX(Graphics),  paintScrollbarY(Graphics)  allows

overriding the behavior of scrollbar painting.

• Implement  the  painter  interface,  this  interface  can  be  used  as  a  GlassPane  or  a  background

painter.

The painter interface is a simple interface that includes 1 paint method, this is a useful way to
allow  developers  to  perform  custom  painting  without  subclassing  Component.  Painters  can  be
the  PainterChain
to  create  elaborate  paint  behavior  by  using 
chained 

together 

[https://www.codenameone.com/javadoc/com/codename1/ui/painter/PainterChain.html] class.

◦ Glass pane - a glass pane allows developers to paint on top of the form painting. This allows

an overlay effect on top of a form.

For a novice it might seem that a glass pane is similar to overriding the Form’s paint method
and drawing after super.paint(g) completed. This isn’t the case. When a component repaints
is  drawn  and  Form
(by 
[https://www.codenameone.com/javadoc/com/codename1/ui/Form.html]’s  paint()  method  wouldn’t  be
invoked. However, the glass pane painter is invoked for such cases and would work exactly

the  repaint()  method)  only 

that  component 

invoking 

as expected.

373

Container [https://www.codenameone.com/javadoc/com/codename1/ui/Container.html] has a glass pane
method called paintGlass(Graphics), which can be overridden to provide a similar effect on
a  Container  level.  This  is  especially  useful  for  complex  containers  such  as  Table
[https://www.codenameone.com/javadoc/com/codename1/ui/table/Table.html]  which  draws  its  lines

using such a methodology.

◦ Background  painter  -  the  background  painter  is  installed  via  the  style,  by  default

Codename  installs  a  custom  background  painter  of  its  own.  Installing  a  custom  painter

allows a developer to completely define how the background of the component is drawn.

Notice that a lot of the background style behaviors can be achieved using styles alone.



A  common  mistake  developers  make  is  overriding  the  paint(Graphics)  method  of
Form.  The  problem  with  that  is  that  form  has  child  components  which  might
request a repaint. To prevent that either place a paintable component in the center
of the Form, override the glasspane or the background painter.

A paint method can be implemented as such:

// hide the title
Form hi = new Form("", new BorderLayout());
hi.add(BorderLayout.CENTER, new Component() {
    @Override
    public void paint(Graphics g) {
        // red color
        g.setColor(0xff0000);

        // paint the screen in red
        g.fillRect(getX(), getY(), getWidth(), getHeight());

        // draw hi world in white text at the top left corner of the screen
        g.setColor(0xffffff);
        g.drawString("Hi World", getX(), getY());
    }
});
hi.show();

Figure 337. Hi world demo code, notice that the blue bar on top is the iOS7+ status bar

374

10.2. Glass Pane

The  GlassPane  `in  Codename  One  is  inspired  by  the  Swing  `GlassPane  &  LayeredPane  with  quite  a
few  twists.  We  tried  to  imagine  how  Swing  developers  would  have  implemented  the  glass  pane

knowing  what  they  do  now  about  painters  and  Swings  learning  curve.  But  first:  what  is  the  glass

pane?

A  typical  Codename  One  application  is  essentially  composed  of  3  layers  (this  is  a  gross

simplification though), the background painters are responsible for drawing the background of all

components including the main form. The component draws its own content (which might overrule

the painter) and the glass pane paints last…

Figure 338. Form layout graphic

Essentially the glass pane is a painter that allows us to draw an overlay on top of the Codename One

application.

Overriding the paint method of a form isn’t a substitute for glasspane as it would appear to work
initially,  when  you  enter  a  Form.  However,  when  modifying  an  element  within  the  form  only  that
element gets repainted not the entire Form!

So  if  we  have  a  form  with  a  Button  [https://www.codenameone.com/javadoc/com/codename1/ui/Button.html]

and text drawn on top using the Form’s paint method it would get erased whenever the button gets

focus.

The  glass  pane  is  called  whenever  a  component  gets  painted,  it  only  paints  within  the  clipping
region of the component hence it won’t break the rest of the components on the Form which weren’t
modified.

You can set a painter on a form using code like this:

hi.setGlassPane(new Painter() {
    @Override
    public void paint(Graphics g, Rectangle rect) {
    }
});

Or you can use Java 8 lambdas to tighten the code a bit:

hi.setGlassPane((g, rect) -> {
});

PainterChain  [https://www.codenameone.com/javadoc/com/codename1/ui/painter/PainterChain.html]  allows  us

375

to  chain  several  painters  together  to  perform  different  logical  tasks  such  as  a  validation  painter

coupled with a fade out painter. The sample below shows a crude validation panel that allows us to

draw error icons next to components while exceeding their physical bounds as is common in many

user interfaces

Form hi = new Form("Glass Pane", new BoxLayout(BoxLayout.Y_AXIS));
Style s = UIManager.getInstance().getComponentStyle("Label");
s.setFgColor(0xff0000);
s.setBgTransparency(0);
Image warningImage = FontImage.createMaterial(FontImage.MATERIAL_WARNING, s).toImage();
TextField tf1 = new TextField("My Field");
tf1.getAllStyles().setMarginUnit(Style.UNIT_TYPE_DIPS);
tf1.getAllStyles().setMargin(5, 5, 5, 5);
hi.add(tf1);
hi.setGlassPane((g, rect) -> {
    int x = tf1.getAbsoluteX() + tf1.getWidth();
    int y = tf1.getAbsoluteY();
    x -= warningImage.getWidth() / 2;
    y += (tf1.getHeight() / 2 - warningImage.getHeight() / 2);
    g.drawImage(warningImage, x, y);
});
hi.show();

Figure 339. The glass pane draws the warning sign on the border of the component partially peeking out

10.3. Shapes & Transforms

The graphics API provides a high performance shape API that allows drawing arbitrary shapes by

defining paths and curves and caching the shape drawn in the GPU.

10.4. Device Support

Shapes  and  transforms  are  available  on  most  smartphone  platforms  with  some  caveats  for  the

current Windows Phone port.

Notice that perspective transform is missing from the desktop/simulator port. Unfortunately there

is no real equivalent to perspective transform in JavaSE that we could use.

10.5. A 2D Drawing App

We can demonstrate shape drawing with a simple example of a drawing app, that allows the user to

tap the screen to draw a contour picture.

The  app  works  by  simply  keeping  a  GeneralPath  [https://www.codenameone.com/javadoc/com/codename1/

376

ui/geom/GeneralPath.html]  in  memory,  and  continually  adding  points  as  bezier  curves.  Whenever  a

point is added, the path is redrawn to the screen.

The 

center  of 

the  app 

is 

the 

DrawingCanvas 

class,  which 

extends  Component

[https://www.codenameone.com/javadoc/com/codename1/ui/Component.html].

public class DrawingCanvas extends Component {
    GeneralPath p = new GeneralPath();
    int strokeColor = 0x0000ff;
    int strokeWidth = 10;

    public void addPoint(float x, float y){
        // To be written
    }

    @Override
    protected void paintBackground(Graphics g) {
        super.paintBackground(g);
            Stroke stroke = new Stroke(
                strokeWidth,
                Stroke.CAP_BUTT,
                Stroke.JOIN_ROUND, 1f
            );
            g.setColor(strokeColor);

            // Draw the shape
            g.drawShape(p, stroke);

    }

    @Override
    public void pointerPressed(int x, int y) {
        addPoint(x-getParent().getAbsoluteX(), y-getParent().getAbsoluteY());
    }
}

Conceptually  this  is  very  basic  component.  We  will  be  overriding  the  paintBackground()
[https://www.codenameone.com/javadoc/com/codename1/ui/Component.html#

paintBackground(com.codename1.ui.Graphics)]  method  to  draw  the  path.  We  keep  a  reference  to  a

GeneralPath [https://www.codenameone.com/javadoc/com/codename1/ui/geom/GeneralPath.html] object (which

is  the  concrete  implementation  of  the  Shape  [https://www.codenameone.com/javadoc/com/codename1/ui/

geom/Shape.html] interface in Codename One) to store each successive point in the drawing. We also

parametrize the stroke width and color.

The  implementation  of  the  paintBackground()  method  (shown  above)  should  be  fairly  straight
forward.  It  creates  a  stroke  of  the  appropriate  width,  and  sets  the  color  on  the  graphics  context.
Then it calls drawShape() to render the path of points.

377

10.5.1. Implementing addPoint()

The addPoint method is designed to allow us to add points to the drawing. A simple implementation

that uses straight lines rather than curves might look like this:

private float lastX = -1;
private float lastY = -1;

public void addPoint(float x, float y) {
    if (lastX == -1) {
        // this is the first point... don't draw a line yet
        p.moveTo(x, y);
    } else {
        p.lineTo(x, y);
    }
    lastX = x;
    lastY = y;

    repaint();
}

We  introduced  a  couple  house-keeping  member  vars  (lastX  and  lastY)  to  store  the  last  point  that
was added so that we know whether this is the first tap or a subsequent tap. The first tap triggers a
moveTo() call, whereas subsequent taps trigger lineTo() calls, which draw lines from the last point
to the current point.

A drawing might look like this:

Figure 340. lineTo example

10.5.2. Using Bezier Curves

Our previous implementation of addPoint() used lines for each segment of the drawing. Let’s make

an adjustment to allow for smoother edges by using quadratic curves instead of lines.

Codename One’s GeneralPath class includes two methods for drawing curves:

378

1. quadTo() 

[https://www.codenameone.com/javadoc/com/codename1/ui/geom/GeneralPath.html#

quadTo(float,%20float,%20float,%20float)]  :  Appends  a  quadratic  bezier  curve.  It  takes  2  points:  a

control point, and an end point.

2. curveTo() 

[https://www.codenameone.com/javadoc/com/codename1/ui/geom/GeneralPath.html#

curveTo(float,%20float,%20float,%20float,%20float,%20float)]  :  Appends  a  cubic  bezier  curve,  taking  3

points: 2 control points, and an end point.

See 

the  General  Path 

javadocs 

[https://www.codenameone.com/javadoc/com/codename1/ui/geom/

GeneralPath.html] for the full API.

We  will  make  use  of  the  quadTo()  [https://www.codenameone.com/javadoc/com/codename1/ui/geom/
GeneralPath.html#quadTo(float,%20float,%20float,%20float)]  method  to  append  curves  to  the  drawing  as

follows:

private boolean odd=true;
public void addPoint(float x, float y){
    if ( lastX == -1 ){
        p.moveTo(x, y);

    } else {
        float controlX = odd ? lastX : x;
        float controlY = odd ? y : lastY;
        p.quadTo(controlX, controlY, x, y);
    }
    odd = !odd;
    lastX = x;
    lastY = y;
    repaint();
}

This  change  should  be  fairly  straight  forward  except,  perhaps,  the  business  with  the  odd  variable.
Since  quadratic  curves  require  two  points  (in  addition  to  the  implied  starting  point),  we  can’t

simply take the last tap point and the current tap point. We need a point between them to act as a

control  point.  This  is  where  we  get  the  curve  from.  The  control  point  works  by  exerting  a  sort  of

"gravity" on the line segment, to pull the line towards it. This results in the line being curved. I use
the odd marker to alternate the control point between positions above the line and below the line.

A drawing from the resulting app looks like:

379

Figure 341. Result of quadTo example

10.5.3. Detecting Platform Support

The DrawingCanvas example is a bit naive in that it assumes that the device supports the shape API. If
I  were  to  run  this  code  on  a  device  that  doesn’t  support  the  Shape  [https://www.codenameone.com/

javadoc/com/codename1/ui/geom/Shape.html] API, it would just draw a blank canvas where I expected my
shape to be drawn. You can fall back gracefully if you make use of the Graphics.isShapeSupported()
[https://www.codenameone.com/javadoc/com/codename1/ui/Graphics.html#isShapeSupported()] method. E.g.

@Override
protected void paintBackground(Graphics g) {
    super.paintBackground(g);
    if ( g.isShapeSupported() ){
       // do my shape drawing code here
    } else {
        // draw an alternate representation for device
        // that doesn't support shapes.
        // E.g. you could defer to the Pisces
        // library in this case
    }

}

10.6. Transforms

The  Graphics  [https://www.codenameone.com/javadoc/com/codename1/ui/Graphics.html]  class  has  included

limited  support  for  2D  transformations  for  some  time  now  including  scaling,  rotation,  and

translation:

• scale(x,y) : Scales drawing operations by a factor in each direction.

• translate(x,y) : Translates drawing operations by an offset in each direction.

• rotate(angle) : Rotates about the origin.

• rotate(angle, px, py) : Rotates about a pivot point.

380

 scale() and rotate() methods are only available on platforms that support Affine

transforms. See table X for a compatibility list.

10.6.1. Device Support

As of this writing, not all devices support transforms (i.e. scale() and rotate()). The following is a
list of platforms and their respective levels of support.

Table 7. Transforms Device Support

Platform

Simulator

iOS

Android

JavaScript

J2ME

BlackBerry (4.2 & 5)

Windows Phone

Affine Supported

Yes

Yes

Yes

Yes

No

No

No (pending)

You  can  check 
Graphics.html] context supports rotation and scaling using the isAffineSupported() method.

if  a  particular  Graphics  [https://www.codenameone.com/javadoc/com/codename1/ui/

e.g.

public void paint(Graphics g){
    if ( g.isAffineSupported() ){
        // Do something that requires rotation and scaling

    } else {
        // Fallback behavior here
    }
}

10.7. Example: Drawing an Analog Clock

In the following sections, I will implement an analog clock component. This will demonstrate three

key concepts in Codename One’s graphics:

1. Using the GeneralPath class for drawing arbitrary shapes.

2. Using Graphics.translate() to translate our drawing position by an offset.

3. Using Graphics.rotate() to rotate our drawing position.

There are three separate things that need to be drawn in a clock:

1. The  tick  marks.  E.g.  most  clocks  will  have  a  tick  mark  for  each  second,  larger  tick  marks  for

381

each hour, and sometimes even larger tick marks for each quarter hour.

2. The numbers. We will draw the clock numbers (1 through 12) in the appropriate positions.

3. The  hands.  We  will  draw  the  clock  hands  to  point  at  the  appropriate  points  to  display  the

current time.

10.7.1. The AnalogClock Component

Our  clock  will  extend 
Component.html] class, and override the paintBackground() method to draw the clock as follows:

[https://www.codenameone.com/javadoc/com/codename1/ui/

the  Component 

public class AnalogClock extends Component {
    Date currentTime = new Date();

    @Override
    public void paintBackground(Graphics g) {
        // Draw the clock in this method
    }
}

10.7.2. Setting up the Parameters

Before we actually draw anything, let’s take a moment to figure out what values we need to know

in order to draw an effective clock. Minimally, we need two values:

1. The center point of the clock.

2. The radius of the clock.

In addition, I am adding the following parameters to to help customize how the clock is rendered:

1. The padding (i.e. the space between the edge of the component and the edge of the clock circle.

2. The tick lengths. I will be using 3 different lengths of tick marks on this clock. The longest ticks

will be displayed at quarter points (i.e. 12, 3, 6, and 9). Slightly shorter ticks will be displayed at

the  five-minute  marks  (i.e.  where  the  numbers  appear),  and  the  remaining  marks

(corresponding with seconds) will be quite short.

382

// Hard code the padding at 10 pixels for now
double padding = 10;

// Clock radius
double r = Math.min(getWidth(), getHeight())/2-padding;

// Center point.
double cX = getX()+getWidth()/2;
double cY = getY()+getHeight()/2;

//Tick Styles
int tickLen = 10;  // short tick
int medTickLen = 30;  // at 5-minute intervals
int longTickLen = 50; // at the quarters
int tickColor = 0xCCCCCC;
Stroke tickStroke = new Stroke(2f, Stroke.CAP_BUTT, Stroke.JOIN_ROUND, 1f);

10.7.3. Drawing the Tick Marks

For  the  tick  marks,  we  will  use  a  single  GeneralPath  [https://www.codenameone.com/javadoc/com/
codename1/ui/geom/GeneralPath.html] object, making use of the moveTo() and lineTo() methods to draw
each individual tick.

383

// Draw a tick for each "second" (1 through 60)
for ( int i=1; i<= 60; i++){
    // default tick length is short
    int len = tickLen;
    if ( i % 15 == 0 ){
        // Longest tick on quarters (every 15 ticks)
        len = longTickLen;
    } else if ( i % 5 == 0 ){
        // Medium ticks on the '5's (every 5 ticks)
        len = medTickLen;
    }

    double di = (double)i; // tick num as double for easier math

    // Get the angle from 12 O'Clock to this tick (radians)
    double angleFrom12 = di/60.0*2.0*Math.PI;

    // Get the angle from 3 O'Clock to this tick
        // Note: 3 O'Clock corresponds with zero angle in unit circle
        // Makes it easier to do the math.
    double angleFrom3 = Math.PI/2.0-angleFrom12;

    // Move to the outer edge of the circle at correct position
    // for this tick.
    ticksPath.moveTo(
            (float)(cX+Math.cos(angleFrom3)*r),
            (float)(cY-Math.sin(angleFrom3)*r)
    );

    // Draw line inward along radius for length of tick mark
    ticksPath.lineTo(
            (float)(cX+Math.cos(angleFrom3)*(r-len)),
            (float)(cY-Math.sin(angleFrom3)*(r-len))
    );
}

// Draw the full shape onto the graphics context.
g.setColor(tickColor);
g.drawShape(ticksPath, tickStroke);



This example uses a little bit of trigonometry to calculate the (x,y) coordinates of
the  tick  marks  based  on  the  angle  and  the  radius.  If  math  isn’t  your  thing,  don’t
worry. This example just makes use of the identities: x=r*cosθ and y=r*sinθ.

At this point our clock should include a series of tick marks orbiting a blank center as shown below:

384

Figure 342. Drawing tick marks on the watch face

10.7.4. Drawing the Numbers

The Graphics.drawString(str, x, y) method allows you to draw text at any point of a component.
The  tricky  part  here  is  calculating  the  correct  x  and  y  values  for  each  string  so  that  the  number
appears in the correct location.

For the purposes of this tutorial, we will use the following strategy. For each number (1 through 12):

1. Use the Graphics.translate(x,y) method to apply a translation from the clock’s center point to

the point where the number should appear.

2. Draw  number  (using  drawString())  at  the  clock’s  center.  It  should  be  rendered  at  the  correct

point due to our translation.

3. Invert the translation performed in step 1.

385

for ( int i=1; i<=12; i++){
    // Calculate the string width and height so we can center it properly
    String numStr = ""+i;
    int charWidth = g.getFont().stringWidth(numStr);
    int charHeight = g.getFont().getHeight();

    double di = (double)i;  // number as double for easier math

    // Calculate the position along the edge of the clock where the number should
    // be drawn
     // Get the angle from 12 O'Clock to this tick (radians)
    double angleFrom12 = di/12.0*2.0*Math.PI;

    // Get the angle from 3 O'Clock to this tick
        // Note: 3 O'Clock corresponds with zero angle in unit circle
        // Makes it easier to do the math.
    double angleFrom3 = Math.PI/2.0-angleFrom12;

    // Get diff between number position and clock center
    int tx = (int)(Math.cos(angleFrom3)*(r-longTickLen));
    int ty = (int)(-Math.sin(angleFrom3)*(r-longTickLen));

    // For 6 and 12 we will shift number slightly so they are more even
    if ( i == 6 ){
        ty -= charHeight/2;
    } else if ( i == 12 ){
        ty += charHeight/2;
    }

    // Translate the graphics context by delta between clock center and
    // number position
    g.translate(
            tx,
            ty
    );

    // Draw number at clock center.
    g.drawString(numStr, (int)cX-charWidth/2, (int)cY-charHeight/2);

    // Undo translation
    g.translate(-tx, -ty);

}



386

This  example  is,  admittedly,  a  little  contrived  to  allow  for  a  demonstration  of  the
Graphics.translate()  method.  We  could  have  just  as  easily  passed  the  exact
location  of  the  number  to  drawString()  rather  than  draw  at  the  clock  center  and
translate to the correct location.

Now, we should have a clock with tick marks and numbers as shown below:

Figure 343. Drawing the numbers on the watch face

10.7.5. Drawing the Hands

The clock will include three hands: Hour, Minute, and Second. We will use a separate GeneralPath

[https://www.codenameone.com/javadoc/com/codename1/ui/geom/GeneralPath.html]  object  for  each  hand.  For

the positioning/angle of each, I will employ the following strategy:

1. Draw the hand at the clock center pointing toward 12 (straight up).

2. Translate the hand slightly down so that it overlaps the center.

3. Rotate the hand at the appropriate angle for the current time, using the clock center as a pivot

point.

Drawing the Second Hand:

For the "second" hand, we will just use a simple line from the clock center to the inside edge of the

medium tick mark at the 12 o’clock position.

GeneralPath secondHand = new GeneralPath();
secondHand.moveTo((float)cX, (float)cY);
secondHand.lineTo((float)cX, (float)(cY-(r-medTickLen)));

And  we  will  translate  it  down  slightly  so  that  it  overlaps  the  center.  This  translation  will  be
performed on the GeneralPath object directly rather than through the Graphics context:

Shape translatedSecondHand = secondHand.createTransformedShape(
    Transform.makeTranslation(0f, 5)
);

Rotating the Second Hand::

The rotation of the second hand will be performed in the Graphics context via the rotate(angle, px,
py)  method.  This  requires  us  to  calculate  the  angle.  The  px  and  py  arguments  constitute  the  pivot

387

point of the rotation, which, in our case will be the clock center.



The  rotation  pivot  point  is  expected  to  be  in  absolute  screen  coordinates  rather

than relative coordinates of the component. Therefore we need to get the absolute

clock center position in order to perform the rotation.

// Calculate the angle of the second hand
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
double second = (double)(calendar.get(Calendar.SECOND));
double secondAngle = second/60.0*2.0*Math.PI;

// Get absolute center position of the clock
double absCX = getAbsoluteX()+cX-getX();
double absCY = getAbsoluteY()+cY-getY();

g.rotate((float)secondAngle, (int)absCX, (int)absCY);
g.setColor(0xff0000);
g.drawShape(
        translatedSecondHand,
        new Stroke(2f, Stroke.CAP_BUTT, Stroke.JOIN_BEVEL, 1f)
);
g.resetAffine();

 Remember to call resetAffine() after you’re done with the rotation, or you will see

some unexpected results on your form.

Drawing the Minute And Hour Hands:

The mechanism for drawing the hour and minute hands is largely the same as for the minute hand.

There are a couple of added complexities though:

1. We’ll make these hands trapezoidal, and almost triangular rather than just using a simple line.

Therefore the GeneralPath construction will be slightly more complex.

2. Calculation of the angles will be slightly more complex because they need to take into account

multiple parameters. E.g. The hour hand angle is informed by both the hour of the day and the

minute of the hour.

The remaining drawing code is as follows:

388

// Draw the minute hand
GeneralPath minuteHand = new GeneralPath();
minuteHand.moveTo((float)cX, (float)cY);
minuteHand.lineTo((float)cX+6, (float)cY);
minuteHand.lineTo((float)cX+2, (float)(cY-(r-tickLen)));
minuteHand.lineTo((float)cX-2, (float)(cY-(r-tickLen)));
minuteHand.lineTo((float)cX-6, (float)cY);
minuteHand.closePath();

// Translate the minute hand slightly down so it overlaps the center
Shape translatedMinuteHand = minuteHand.createTransformedShape(
    Transform.makeTranslation(0f, 5)
);

double minute = (double)(calendar.get(Calendar.MINUTE)) +
        (double)(calendar.get(Calendar.SECOND))/60.0;

double minuteAngle = minute/60.0*2.0*Math.PI;

// Rotate and draw the minute hand
g.rotate((float)minuteAngle, (int)absCX, (int)absCY);
g.setColor(0x000000);
g.fillShape(translatedMinuteHand);
g.resetAffine();

// Draw the hour hand
GeneralPath hourHand = new GeneralPath();
hourHand.moveTo((float)cX, (float)cY);
hourHand.lineTo((float)cX+4, (float)cY);
hourHand.lineTo((float)cX+1, (float)(cY-(r-longTickLen)*0.75));
hourHand.lineTo((float)cX-1, (float)(cY-(r-longTickLen)*0.75));
hourHand.lineTo((float)cX-4, (float)cY);
hourHand.closePath();

Shape translatedHourHand = hourHand.createTransformedShape(
    Transform.makeTranslation(0f, 5)
);

//Calendar cal = Calendar.getInstance().get
double hour = (double)(calendar.get(Calendar.HOUR_OF_DAY)%12) +
        (double)(calendar.get(Calendar.MINUTE))/60.0;

double angle = hour/12.0*2.0*Math.PI;
g.rotate((float)angle, (int)absCX, (int)absCY);
g.setColor(0x000000);
g.fillShape(translatedHourHand);
g.resetAffine();

389

10.7.6. The Final Result

At this point, we have a complete clock as shown below:

Figure 344. The final result - fully rendered watch face

10.7.7. Animating the Clock

The current clock component is cool, but it is static. It just displays the time at the point the clock

was created. We discussed low level animations in the animation section of the guide, here we will

show a somewhat more elaborate example.

In order to animate our clock so that it updates once per second, we only need to do two things:

1. Implement the animate() method to indicate when the clock needs to be updated/re-drawn.

2. Register the component with the form so that it will receive animation "pulses".

The animate() method in the AnalogClock class:

Date currentTime = new Date();
long lastRenderedTime = 0;

@Override
public boolean animate() {
    if ( System.currentTimeMillis()/1000 != lastRenderedTime/1000){
        currentTime.setTime(System.currentTimeMillis());
        return true;
    }
    return false;
}

This  method  will  be  invoked  on  each  "pulse"  of  the  EDT.  It  checks  the  last  time  the  clock  was
rendered  and  returns  true  only  if  the  clock  hasn’t  been  rendered  in  the  current  "time  second"
interval. Otherwise it returns false. This ensures that the clock will only be redrawn when the time

changes.

390

10.8. Starting and Stopping the Animation

the  Form.registerAnimated(component)  and
Animations  can  be  started  and  stopped  via 
Form.deregisterAnimated(component)  methods.  We  chose  to  encapsulate  these  calls  in  start()  and
stop() methods in the component as follows:

public void start(){
    getComponentForm().registerAnimated(this);
}

public void stop(){
    getComponentForm().deregisterAnimated(this);
}

So the code to instantiate the clock, and start the animation would be something like:

AnalogClock clock = new AnalogClock();
parent.addComponent(clock);
clock.start();

10.9. Shape Clipping

Clipping is one of the core tenants of graphics programming, you define the boundaries for drawing

and when you exceed said boundaries things aren’t drawn. Shape clipping allows us to clip based
on  any  arbitrary  Shape  and  not  just  a  rectangle,  this  allows  some  unique  effects  generated  in
runtime.

E.g. this code allows us to draw a rather complex image of duke:

391

Image duke = null;
try {
    // duke.png is just the default Codename One icon copied into place
    duke = Image.createImage("/duke.png");
} catch(IOException err) {
    Log.e(err);
}
final Image finalDuke = duke;

Form hi = new Form("Shape Clip");

// We create a 50 x 100 shape, this is arbitrary since we can scale it easily
GeneralPath path = new GeneralPath();
path.moveTo(20,0);
path.lineTo(30, 0);
path.lineTo(30, 100);
path.lineTo(20, 100);
path.lineTo(20, 15);
path.lineTo(5, 40);
path.lineTo(5, 25);
path.lineTo(20,0);

Stroke stroke = new Stroke(0.5f, Stroke.CAP_ROUND, Stroke.JOIN_ROUND, 4);
hi.getContentPane().getUnselectedStyle().setBgPainter((Graphics g, Rectangle rect) -> {
    g.setColor(0xff);
    float widthRatio = ((float)rect.getWidth()) / 50f;
    float heightRatio = ((float)rect.getHeight()) / 100f;
    g.scale(widthRatio, heightRatio);
    g.translate((int)(((float)rect.getX()) / widthRatio), (int)(((float)rect.getY()) / heightRatio));
    g.setClip(path);
    g.setAntiAliased(true);
    g.drawImage(finalDuke, 0, 0, 50, 100);
    g.setClip(path.getBounds());
    g.drawShape(path, stroke);
    g.translate(-(int)(((float)rect.getX()) / widthRatio), -(int)(((float)rect.getY()) / heightRatio));
    g.resetAffine();
});

hi.show();

Figure 345. Shape Clipping used to clip the image of duke within the given shape



Notice that this functionality isn’t available on all platforms so you normally need

to 

test 

if 

shaped  clipping 

is 

supported  using 

isShapeClipSupported()

[https://www.codenameone.com/javadoc/com/codename1/ui/Graphics.html#

isShapeClipSupported--].

392

10.10. The Coordinate System

The Codename One coordinate system follows the example of Swing (and many other - but not all-

graphics libraries) and places the origin in the upper left corner of the screen. X-values grow to the

right, and Y-values grow downward as illustrated below:

Figure 346. The Codename One graphics coordinate space

Therefore the screen origin is at the top left corner of the screen. Given this information, consider

the  method  call  on  the  Graphics  [https://www.codenameone.com/javadoc/com/codename1/ui/Graphics.html]
context g:

g.drawRect(10,10, 100, 100);

Where would this rectangle be drawn on the screen?

If you answered something something like "10 pixels from the top, and 10 pixels from the left of the

screen",  you  might  be  right.  It  depends  on  whether  the  graphics  has  a  translation  or  transform
applied  to  it.  If  there  is  currently  a  translation  of  (20,20)  (i.e.  20  pixels  to  the  right,  and  20  pixels
down), then the rectangle would be rendered at (30, 30).

You  can  always  find  out 
Graphics.getTranslateX() and Graphics.getTranslateY() methods:

translation  of 

the  current 

the  graphics  context  using 

// Find out the current translation
int currX = g.getTranslateX();
int currY = g.getTranslateY();

// Reset the translation to zeroes
g.translate(-currX, -currY);

// Now we are working in absolute screen coordinates
g.drawRect(10, 10, 100, 100);

// This rectangle should now be drawn at the exact screen
// coordinates (10,10).

//Restore the translation
g.translate(currX, currY);

the

393



This example glosses over issues such as clipping and transforms which may cause
it  to  not  work  as  you  expect.  E.g.  When  painting  a  component  inside  its  paint()
method,  there  is  a  clip  applied  to  the  context  so  that  only  the  content  you  draw

within the bounds of the component will be seen.

If, in addition, there is a transform applied that rotates the context 45 degrees clockwise, then the

rectangle will be drawn at a 45 degree angle with its top left corner somewhere on the left edge of

the screen.

Luckily you usually don’t have to worry about the exact screen coordinates for the things you paint.

Most of the time, you will only be concerned with relative coordinates.

10.10.1. Relative Coordinates

Usually,  when  you  are  drawing  onto  a  Graphics  context,  you  are  doing  so  within  the  context  of  a
Component’s paint() method (or one of its variants). In this case, you generally don’t care what the
exact screen coordinates are of your drawing. You are only concerned with their relative location

within  the  coordinate.  You  can  leave  the  positioning  (and  even  sizing)  of  the  coordinate  up  to

Codename One. Thank you for reading.

To  demonstrate  this,  let’s  create  a  simple  component  called  Rectangle  [https://www.codenameone.com/

javadoc/com/codename1/ui/geom/Rectangle.html] component, that simply draws a rectangle on the screen.

We will use the component’s position and size to dictate the size of the rectangle to be drawn. And

we will keep a 5 pixel padding between the edge of the component and the edge of our rectangle.

class RectangleComponent extends Component {
    public void paint(Graphics g){
        g.setColor(0x0000ff);
        g.drawRect(getX()+5, getY()+5, getWidth()-10, getHeight()-10);
    }
}

The result is as follows:

Figure 347. The rectangle component



The  x  and  y  coordinates  that  are  passed  to  the  drawRect(x,y,w,h)  method  are
relative  to  the  component’s  parent’s  origin — not  the  component  itself  ..  its
parent. This is why we the x position is getX()+5 and not just 5.

394

10.10.2. Transforms and Rotations

Unlike  the  Graphics  drawXXX  primitives,  methods  for  setting  transformations,  including  scale(x,y)
and rotate(angle), are always applied in terms of screen coordinates. This can be confusing at first,
because you may be unsure whether to provide a relative coordinate or an absolute coordinate for

a given method.

The general rule is:

1. All  coordinates  passed  to  the  drawXXX()  and  fillXXX()  methods  will  be  subject  to  the

graphics context’s transform and translation settings.

2. All  coordinates  passed  to  the  context’s  transformation  settings  are  considered  to  be

screen coordinates, and are not subject to current transform and translation settings.

Let’s  take  our  RectangleComponent  as  an  example.  Suppose  we  want  to  rotate  the  rectangle  by  45
degrees, our first attempt might look something like:

    class RectangleComponent extends Component {

        @Override
        protected Dimension calcPreferredSize() {
            return new Dimension(250,250);
        }

        public void paint(Graphics g) {
            g.setColor(0x0000ff);
            g.rotate((float) (Math.PI / 4.0));
            g.drawRect(getX() + 5, getY() + 5, getWidth() - 10, getHeight() - 10);
            g.rotate(-(float) (Math.PI / 4.0));
        }
    }



When performing rotations and transformations inside a paint() method, always
remember  to  revert  your  transformations  at  the  end  of  the  method  so  that  it

doesn’t pollute the rendering pipeline for subsequent components.

The behavior of this rotation will vary based on where the component is rendered on the screen. To

demonstrate  this,  let’s  try  to  place  five  of  these  components  on  a  form  inside  a  BorderLayout

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/BorderLayout.html] and see how it looks:

395

    class MyForm extends Form {

        public MyForm() {
            super("Rectangle Rotations");
            for ( int i=0; i< 10; i++ ){
                this.addComponent(new RectangleComponent());
            }
        }
    }

The result is as follows:

Figure 348. Rotating the rectangle

This  may  not  be  an  intuitive  outcome  since  we  drew  10  rectangle  components,  be  we  only  see  a
portion of one rectangle. The reason is that the rotate(angle) method uses the screen origin as the
pivot point for the rotation. Components nearer to this pivot point will experience a less dramatic

effect than components farther from it. In our case, the rotation has caused all rectangles except the

first one to be rotated outside the bounds of their containing component - so they are being clipped.

A more sensible solution for our component would be to place the rotation pivot point somewhere

inside  the  component.  That  way  all  of  the  components  would  look  the  same.  Some  possibilities

would be:

Top Left Corner:

        public void paint(Graphics g) {
            g.setColor(0x0000ff);
            g.rotate((float)(Math.PI/4.0), getAbsoluteX(), getAbsoluteY());
            g.drawRect(getX() + 5, getY() + 5, getWidth() - 10, getHeight() - 10);
            g.rotate(-(float) (Math.PI / 4.0), getAbsoluteX(), getAbsoluteY());
        }

396

Figure 349. Rotating the rectangle with wrong pivot point

Center:

public void paint(Graphics g) {
    g.setColor(0x0000ff);
    g.rotate(
        (float)(Math.PI/4.0),
        getAbsoluteX()+getWidth()/2,
        getAbsoluteY()+getHeight()/2
    );
    g.drawRect(getX() + 5, getY() + 5, getWidth() - 10, getHeight() - 10);
    g.rotate(
        -(float)(Math.PI/4.0),
        getAbsoluteX()+getWidth()/2,
        getAbsoluteY()+getHeight()/2
    );
}

Figure 350. Rotating the rectangle with the center pivot point

You  could  also  use  the  Graphics.setTransform()  class  to  apply  rotations  and  other  complex
transformations (including 3D perspective transforms), but I’ll leave that for its own topic as it is a

397

little bit more complex.

10.10.3. Event Coordinates

The  coordinate  system  and  event  handling  are  closely  tied.  You  can  listen  for  touch  events  on  a
component by overriding the pointerPressed(x,y) method. The coordinates received in this method
will  be  absolute  screen  coordinates,  so  you  may  need  to  do  some  conversions  on  these
coordinates before using them in your drawXXX() methods.

E.g. a pointerPressed() callback method can look like this:

public void pointerPressed(int x, int y) {
    addPoint(x-getParent().getAbsoluteX(), y-getParent().getAbsoluteY());
}

In  this  case  we  translated  these  points  so  that  they  would  be  relative  to  the  origin  of  the  parent
component. This is because the drawXXX() methods for this component take coordinates relative to
the parent component.

10.11. Images

Codename One has quite a few image types: loaded, RGB (builtin), RGB (Codename One), Mutable,

EncodedImage,  SVG,  MultiImage,  FontImage  &  Timeline.  There  are  also  URLImage,
FileEncodedImage, FileEncodedImageAsync, StorageEncodedImage/Async that will be covered in the
IO section.

All  image  types  are  mostly  seamless  to  use  and  will  just  work  with  drawImage  and  various  image
related image API’s for the most part with caveats on performance etc.



For  animation  images  the  code  must  invoke  the  animate()  method  on  the  image
(this  is  done  automatically  by  Codename  One  when  placing  the  image  as  a

background or as an icon!
You  only  need  to  do  it  if  you  invoke  drawImage  in  code  rather  than  use  a  builtin
component).

Performance  and  memory  wise  you  should  read  the  section  below  carefully  and  be  aware  of  the

image  types  you  use.  The  Codename  One  designer  tries  to  conserve  memory  and  be  "clever"  by
using  only  EncodedImage.  While  these  are  great  for  low  memory  you  need  to  understand  the
complexities of image locking and be aware that you might pay a penalty if you don’t.

Here are the pros/cons and logic behind every image type. This covers the logic of how it’s created:

10.11.1. Loaded Image

This  is  the  basic  image  you  get  when  loading  an  image  from  the  jar  or  network  using

Image.createImage(String) 

[https://www.codenameone.com/javadoc/com/codename1/ui/Image.html#

createImage-java.lang.String-], Image.createImage(InputStream) [https://www.codenameone.com/javadoc/com/

codename1/ui/Image.html#createImage-java.io.InputStream-]  & 

Image.createImage(byte 

array,int,int)

398

[https://www.codenameone.com/javadoc/com/codename1/ui/Image.html#createImage-byte:A-int-int-], …



Some other API’s might return this image type but those API’s do so explicitly!

In  some  platforms  calling  getGraphics()  on  an  image  like  this  will  throw  an  exception  as  it’s
immutable). This is true for almost all other images as well.

This restriction might not apply for all platforms.

The  image  is  stored  in  RAM  based  on  device  logic  and  should  be  reasonably  efficient  in  terms  of

drawing speed. However, it usually takes up a lot of RAM.

To calculate the amount of RAM taken by a loaded image we use the following formula:

Image Width * Image Height * 4 = Size In RAM in Bytes

E.g. a 50x100 image will take up 20,000 bytes of RAM.

The  logic  behind  this  is  simple,  every  pixel  contains  3  color  channels  and  an  alpha  component

hence 3 bytes for color and one for alpha.



This  isn’t  the  case  for  all  images  but  it’s  very  common  and  we  prefer  calculating

for the worst case scenario. Even with JPEG’s that don’t include an alpha channel

some OS’s might reuire that additional byte.

10.11.2. The RGB Image’s

There are two types of RGB constructed images that are very different from one another but since

they are both technically "RGB image’s" we are bundling them under the same subsection.

Internal

This  is  a  close  cousin  of  the  loaded  image.  This  image  is  created  using  the  method

Image.createImage(int array, int, int) [https://www.codenameone.com/javadoc/com/codename1/ui/Image.html#

createImage-int:A-int-int-] and receives the AARRGGBB data to form the image. It’s more efficient than

the Codename One RGB image but can’t be modified, at least not on the pixel level.

The  goal  of  this  image  type  is  to  provide  an  easy  way  to  render  RGB  data  that  isn’t  modified

efficiently at platform native speeds. It’s technically a standard "Loaded Image" internally.

RGBImage class

RGBImage 

[https://www.codenameone.com/javadoc/com/codename1/ui/RGBImage.html] 

is  effectively  an

AARRGGBB array that can be drawn by Codename One.

On  most  platforms  this  is  quite  inefficient  but  for  some  pixel  level  manipulations  there  is  just  no

other way.

An  RGBImage  is  constructed  with  an  int  array  (int[])  that  includes  width*height  elements.  You  can

399

then  modify  the  colors  and  alpha  channel  directly  within  the  array  and  draw  the  image  to  any

source using standard image drawing API’s.



This  is  very  inefficient  in  terms  of  rendering  speed  and  memory  overhead.  Only

use this technique if there is absolutely no other way!

10.11.3. EncodedImage

[https://www.codenameone.com/javadoc/com/codename1/ui/EncodedImage.html] 

the
EncodedImage 
workhorse of Codename One. Images returned from resource files are EncodedImage and many API’s
expect it.

is 

The EncodedImage is effectively a loaded image that is "hidden" and extracted as needed to remove
the memory overhead associated with loaded image. When creating an EncodedImage only the PNG
(or JPEG etc.) is loaded to an array in RAM. Normally such images are very small (relatively) so they

can be kept in memory without much overhead.

When image information is needed (pixels) the image is decoded into RAM and kept in a weak/sort

reference. This allows the image to be cached for performance and allows the garbage collector to

reclaim it when the memory becomes scarce.

Since  the  fully  decoded  image  can  be  pretty  big  (width  X  height  X  4)  the  ability  to  store  just  the
encoded  image  can  be  pretty  stark.  E.g.  taking  our  example  above  a  50x100  image  will  take  up
20,000 bytes of RAM for a loaded image but an EncodedImage can reduce that to 1kb-2kb of RAM.



An  EncodedImage  might  be  more  expensive  than  a  loaded  image  as  it  will  take  up
both  the  encoded  size  and  the  loaded  size.  So  the  cost  might  be  slightly  bigger  in

some cases. It’s main value is its ability to shrink.

When drawing an EncodedImage it checks the weak reference cache and if the image is cached then
it is shown otherwise the image is loaded the encoded image cache it then drawn.

EncodedImage is not final and can be derived to produce complex image fetching strategies e.g. the
can
URLImage 

[https://www.codenameone.com/javadoc/com/codename1/ui/URLImage.html] 

class 

that 

dynamically download its content from the web.

EncodedImage can be instantiated via the create methods in the EncodedImage class. Pretty much any
image  can  be  converted  into  an  EncodedImage  via  the  createFromImage(Image,  boolean)
[https://www.codenameone.com/javadoc/com/codename1/ui/EncodedImage.html#createFromImage-

com.codename1.ui.Image-boolean-] method.

400

EncodedImage Locking

Naturally loading the image is more expensive so we want the images that are on the current
form to remain in cache (otherwise GC will thrash a lot). That’s where lock() kicks in, when
lock() is active we keep a hard reference to the actual native image so it won’t get GC’d. This
significantly improves performance!

Internally this is invoked automatically for background images, icons etc. which results in a

huge  performance  boost.  This  makes  sense  since  these  images  are  currently  showing  and

they will be in RAM anyway. However, if you use a complex renderer or custom drawing UI
you should lock() your images where possible!

To  verify  that  locking  might  be  a  problem  you  can  launch  the  performance  monitor  tool

(accessible from the simulator menu), if you get log messages that indicate that an unlocked

image was drawn you might have a problem.

10.11.4. MultiImage

Multi images don’t physically exist as a concept within the Codename One API so there is no way to
actually create them and they are in no way distinguishable from EnclodedImage.

The only builtin support for multi images is in the resource file loading logic where a MultiImage is

decoded and only the version that matches the current DPI is physically loaded. From that point on
user code can treat it like any other EnclodedImage.

9-image borders use multi images by default to keep their appearance more refined on the different

DPI’s.

10.11.5. FontImage & Material Design Icons

FontImage  [https://www.codenameone.com/javadoc/com/codename1/ui/FontImage.html]  allows  using  an  icon
font as if it was an image. You can specify the character, color and size and then treat the FontImage
as  if  its  a  regular  image.  The  huge  benefits  are  that  the  font  image  can  adapt  to  platform

conventions in terms of color and easily scale to adapt to DPI.

You  can  generate  icon  fonts  using  free  tools  on  the  internet  such  as  this  [http://fontello.com/].  Icon

fonts are a remarkably simple and powerful technique to create a small, modern applications.

Icon fonts can be created in 2 basic ways the first is explicitly by defining all of the elements within

the font.

Form hi = new Form("Icon Font");
Font materialFont = FontImage.getMaterialDesignFont();
int w = Display.getInstance().getDisplayWidth();
FontImage fntImage = FontImage.createFixed("\uE161", materialFont, 0xff0000, w, w);
hi.add(fntImage);
hi.show();

401

Figure 351. Icon font from material design icons created with the fixed size of display width



The  samples  use  the  builtin  material  design  icon  font.  This  is  for  convenience  so

the sample will work out of the box, for everyone. However you should be able to

do this with any arbitrary icon font off the internet as long as its a valid TTF file.

A  more  common  and  arguably  "correct"  way  to  construct  such  an  icon  would  be  thru  the  Style
[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/Style.html]  object.  The  Style  object  can
provide the color, size and background information needed by FontImage.

There are two versions of this method, the first one expects the Style object to have the correct icon
font set to its font attribute. The second accepts a Font object as an argument. The latter is useful for
a case where you want to reuse the same Style object that you defined for a general UI element e.g.
we can set an icon for a Button like this and it will take up the style of the Button:

Form hi = new Form("Icon Font");
Font materialFont = FontImage.getMaterialDesignFont();
int size = Display.getInstance().convertToPixels(6, true);
materialFont = materialFont.derive(size, Font.STYLE_PLAIN);
Button myButton = new Button("Save");
myButton.setIcon(FontImage.create("\uE161", myButton.getUnselectedStyle(), materialFont));
hi.add(myButton);
hi.show();

Figure 352. An image created from the Style object



Notice  that  for  this  specific  version  of  the  method  the  size  of  the  font  is  used  to
determine the icon size. In the other methods for FontImage creation the size of the
font is ignored!

Material Design Icons

There are many icon fonts in the web, the field is rather volatile and constantly changing. However,

we  wanted  to  have  builtin  icons  that  would  allow  us  to  create  better  looking  demos  and  builtin

components.

402

That’s why we picked the material design icon font for inclusion in the Codename One distribution.

It features a relatively stable core set of icons, that aren’t IP encumbered.

You can use the builtin font directly as demonstrated above but there are far better ways to create a

material design icon. To find the icon you want you can check out the material design icon gallery

[https://design.google.com/icons/]. E.g. we used the save icon in the samples above.

To recreate the save icon from above we can do something like:

Form hi = new Form("Icon Font");
Button myButton = new Button("Save");
myButton.setIcon(FontImage.createMaterial(FontImage.MATERIAL_SAVE, myButton.getUnselectedStyle()));
hi.add(myButton);

Figure 353. Material save icon

 Notice that the icon is smaller now as it’s calculated based on the font size of the

Button UIID.

We can even write the code in a more terse style using:

Form hi = new Form("Icon Font");
Button myButton = new Button("Save");
FontImage.setMaterialIcon(myButton, FontImage.MATERIAL_SAVE);
hi.add(myButton);

This will produce the same result for slightly shorter syntax.



FontImage  can  conflict  with  some  complex  API’s  that  expect  a  "real"  image
underneath.  Some  odd  issues  can  often  be  resolved  by  using  the  toImage()  or
toEncodedImage() methods to convert the scaled FontImage to a loaded image.

10.11.6. Timeline

Timeline’s  allow  rudimentary  animation  and  enable  GIF  importing  using  the  Codename  One

Designer.  Effectively  a  timeline  is  a  set  of  images  that  can  be  moved  rotated,  scaled  &  blended  to

provide 

interesting  animation  effects.  It  can  be  created  manually  using  the  Timeline

[https://www.codenameone.com/javadoc/com/codename1/ui/animations/Timeline.html] class.

10.11.7. Image Masking

Image masking allows us to manipulate images by changing the opacity of an image according to a

mask image. The mask image can be hardcoded or generated dynamically, it is then converted to a

Mask object that can be applied to any image. Notice that the masking process is computationally

intensive, it should be done once and cached/saved.

403

The code below can convert an image to a rounded image:

Toolbar.setGlobalToolbar(true);
Form hi = new Form("Rounder", new BorderLayout());
Label picture = new Label("", "Container");
hi.add(BorderLayout.CENTER, picture);
hi.getUnselectedStyle().setBgColor(0xff0000);
hi.getUnselectedStyle().setBgTransparency(255);
Style s = UIManager.getInstance().getComponentStyle("TitleCommand");
Image camera = FontImage.createMaterial(FontImage.MATERIAL_CAMERA, s);
hi.getToolbar().addCommandToRightBar("", camera, (ev) -> {
    try {
        int width = Display.getInstance().getDisplayWidth();
        Image capturedImage = Image.createImage(Capture.capturePhoto(width, -1));
        Image roundMask = Image.createImage(width, capturedImage.getHeight(), 0xff000000);
        Graphics gr = roundMask.getGraphics();
        gr.setColor(0xffffff);
        gr.fillArc(0, 0, width, width, 0, 360);
        Object mask = roundMask.createMask();
        capturedImage = capturedImage.applyMask(mask);
        picture.setIcon(capturedImage);
        hi.revalidate();
    } catch(IOException err) {
        Log.e(err);
    }
});

Figure 354. Picture after the capture was complete and the resulted image was rounded. The background

was set to red so the rounding effect will be more noticeable

Notice  that  this  example  is  simplistic  in  order  to  be  self  contained.  We  often  recommend  that

developers  ship  "ready  made"  mask  images  with  their  application  which  can  allow  very  complex

effects on the images.

10.11.8. URLImage

URLImage  [https://www.codenameone.com/javadoc/com/codename1/ui/URLImage.html]  is  an  image  created

with a URL, it implicitly downloads and adapts the image in the given URL while caching it locally.

The  typical  adapt  process  scales  the  image  or  crops  it  to  fit  into  the  same  size  which  is  a  hard
restriction because of the way URLImage is implemented.

404

How Does URLImage Work?

The  reason  for  the  size  restriction  lies  in  the  implementation  of  URLImage.  URLImage  is
physically  an  animated  image  and  so  the  UI  thread  tries  to  invoke  its  animate()  method  to
refresh.  The  URLImage  uses  that  call  to  check  if  the  image  was  fetched  and  if  not  fetches  it
asynchronously.

Once the image was fetched the animate() method returns true to refresh the UI. During the
loading process the placeholder is shown, the reason for the restriction in size is that image

animations  can’t  "grow"  the  image.  They  are  assumed  to  be  fixed  so  the  placeholder  must

match the dimensions of the resulting image.

The simple use case is pretty trivial:

Image i = URLImage.createToStorage(placeholder, "fileNameInStorage", "http://xxx/myurl.jpg", URLImage.RESIZE_SCALE);

Alternatively  you  can  use  the  similar  URLImage.createToFileSystem  method  instead  of  the  Storage
[https://www.codenameone.com/javadoc/com/codename1/io/Storage.html] version.

This  image  can  now  be  used  anywhere  a  regular  image  will  appear,  it  will  initially  show  the

placeholder image and then seamlessly replace it with the file after it was downloaded and stored.
Notice that if you make changes to the image itself (e.g. the scaled method) it will generate a new
image which won’t be able to fetch the actual image.



Since  ImageIO  [https://www.codenameone.com/javadoc/com/codename1/ui/util/ImageIO.html]
is used to perform the operations of the adapter interface its required that ImageIO
will  work.  It  is  currently  working  in  JavaSE,  Android,  iOS  &  Windows  Phone.  It

doesn’t  work  on  J2ME/Blackberry  devices  so  if  you  pass  an  adapter  instance  on

those platforms it will probably fail to perform its task.

If  the  file  in  the  URL  contains  an  image  that  is  too  big  it  will  scale  it  to  match  the  size  of  the

placeholder precisely!

There is also an option to fail if the sizes don’t match. Notice that the image that will be saved is the

scaled  image,  this  means  you  will  have  very  little  overhead  in  downloading  images  that  are  the

wrong size although you will get some artifacts.

The  last  argument  is  really  quite  powerful,  its  an  interface  called  URLImage.ImageAdapter

[https://www.codenameone.com/javadoc/com/codename1/ui/URLImage.ImageAdapter.html] 

and 

you 

can

implement it to adapt the downloaded image in any way you like. E.g. you can use an image mask

to automatically create a rounded version of the downloaded image.

To do this you can just override:

public EncodedImage adaptImage(EncodedImage downloadedImage, Image placeholderImage)

In the adapter interface and just return the processed encoded image. If you do heavy processing

405

(e.g.  rounded  edge  images)  you  would  need  to  convert  the  processed  image  back  to  an  encoded

image  so  it  can  be  saved.  You  would  then  also  want  to  indicate  that  this  operation  should  run

asynchronously via the appropriate method in the class.

If  you  need  to  download  the  file  instantly  and  not  wait  for  the  image  to  appear  before  download
initiates  you  can  explicitly  invoke  the  fetch()  method  which  will  asynchronously  fetch  the  image
from  the  network.  Notice  that  the  downloading  will  still  take  time  so  the  placeholder  is  still

required.

Mask Adapter

A  URLImage  can  be  created  with  a  mask  adapter  to  apply  an  effect  to  an  image.  This  allows  us  to
round  downloaded  images  or  apply  any  sort  of  masking  e.g.  we  can  adapt  the  round  mask  code

above as such:

Image roundMask = Image.createImage(placeholder.getWidth(), placeholder.getHeight(), 0xff000000);
Graphics gr = roundMask.getGraphics();
gr.setColor(0xffffff);
gr.fillArc(0, 0, placeholder.getWidth(), placeholder.getHeight(), 0, 360);

URLImage.ImageAdapter ada = URLImage.createMaskAdapter(roundMask);
Image i = URLImage.createToStorage(placeholder, "fileNameInStorage", "http://xxx/myurl.jpg", ada);

URLImage In Lists

The  biggest  problem  with  image  download  service  is  with  lists.  We  decided  to  attack  this  issue  at

the core by integrating URLImage [https://www.codenameone.com/javadoc/com/codename1/ui/URLImage.html]

support  directly  into  GenericListCellRenderer  [https://www.codenameone.com/javadoc/com/codename1/ui/

list/GenericListCellRenderer.html] which means it will work with MultiList [https://www.codenameone.com/

javadoc/com/codename1/ui/list/MultiList.html],  List  [https://www.codenameone.com/javadoc/java/util/List.html]  &

ContainerList  [https://www.codenameone.com/javadoc/com/codename1/ui/list/ContainerList.html].  To  use  this
support just define the name of the component (name not UIID) to end with _URLImage and give it an
icon  to  use  as  the  placeholder.  This  is  easy  to  do  in  the  multilist  by  changing  the  name  of  icon  to
icon_URLImage then using this in the data:

map.put("icon_URLImage", urlToActualImage);

Make sure you also set a "real" icon to the entry in the GUI builder or in handcoded applications.

This  is  important  since  the  icon  will  be  implicitly  extracted  and  used  as  the  placeholder  value.
Everything  else  should  be  handled  automatically.  You  can  use  setDefaultAdapter  &  setAdapter  on
the  generic  list  cell  renderer  to  install  adapters  for  the  images.  The  default  is  a  scale  adapter

although we might change that to scale fill in the future.

406

Style s = UIManager.getInstance().getComponentStyle("Button");
FontImage p = FontImage.createMaterial(FontImage.MATERIAL_PORTRAIT, s);
EncodedImage placeholder = EncodedImage.createFromImage(p.scaled(p.getWidth() * 3, p.getHeight() * 4), false);

Form hi = new Form("MultiList", new BorderLayout());

ArrayList<Map<String, Object>> data = new ArrayList<>();

data.add(createListEntry("A Game of Thrones", "1996", "http://www.georgerrmartin.com/wp-
content/uploads/2013/03/GOTMTI2.jpg"));
data.add(createListEntry("A Clash Of Kings", "1998", "http://www.georgerrmartin.com/wp-
content/uploads/2012/08/clashofkings.jpg"));
data.add(createListEntry("A Storm Of Swords", "2000", "http://www.georgerrmartin.com/wp-
content/uploads/2013/03/stormswordsMTI.jpg"));
data.add(createListEntry("A Feast For Crows", "2005", "http://www.georgerrmartin.com/wp-
content/uploads/2012/08/feastforcrows.jpg"));
data.add(createListEntry("A Dance With Dragons", "2011", "http://georgerrmartin.com/gallery/art/dragons05.jpg"));
data.add(createListEntry("The Winds of Winter", "2016 (please, please, please)", "http://www.georgerrmartin.com/wp-
content/uploads/2013/03/GOTMTI2.jpg"));
data.add(createListEntry("A Dream of Spring", "Ugh", "http://www.georgerrmartin.com/wp-
content/uploads/2013/03/GOTMTI2.jpg"));

DefaultListModel<Map<String, Object>> model = new DefaultListModel<>(data);
MultiList ml = new MultiList(model);
ml.getUnselectedButton().setIconName("icon_URLImage");
ml.getSelectedButton().setIconName("icon_URLImage");
ml.getUnselectedButton().setIcon(placeholder);
ml.getSelectedButton().setIcon(placeholder);
hi.add(BorderLayout.CENTER, ml);

The createListEntry method then looks like this:

private Map<String, Object> createListEntry(String name, String date, String coverURL) {
    Map<String, Object> entry = new HashMap<>();
    entry.put("Line1", name);
    entry.put("Line2", date);
    entry.put("icon_URLImage", coverURL);
    entry.put("icon_URLImageName", name);
    return entry;
}

Figure 355. A URL image fetched dynamically into the list model

407

408

11. Events

Most  events  in  Codename  One  are  routed  via  the  high  level  events  (e.g.  action  listener)  but

sometimes we need access to low level events (e.g. when drawing via Graphics) that provide more

fine  grained  access.  Typically  working  with  the  higher  level  events  is  far  more  potable  since  it

might map to different functionality on different devices.

11.1. High Level Events

High level events are broadcast using an addListener/setListener - publish/subscribe system. Most
of them are channeled via the EventDispatcher [https://www.codenameone.com/javadoc/com/codename1/ui/

util/EventDispatcher.html]  class  which  further  simplifies  that  and  makes  sending  events  correctly  far

easier.



All events are fired on the Event Dispatch Thread, the EventDispatcher makes sure
of that.

11.1.1. Chain Of Events

Since all events fire on the EDT some complexities occur. E.g.:

We have two listeners monitoring the same event (or related events e.g. pointer event and button

click event both of which will fire when the button is touched).

When the event occurs we can run into a scenario like this:

1. First event fires

2. It shows a blocking dialog or invokes an "AndWait" API

3. Second event fires only after the dialog was dismissed!

This  happens  because  events  are  processed  in-order  per  cycle.  Since  the  old  EDT  cycle  is  stuck
(because of the Dialog) the rest of the events within the cycle can’t complete. New events are in a
new EDT cycle so they can finish just fine!

A workaround to this issue is to wrap the code in a callSerially, you shouldn’t do this universally
as this can create a case of shifting the problem to the next EDT cycle. However, using callSerially

will allow the current cycle to flush which should help.

Another workaround for the issue is avoiding blocking calls within an event chain.

11.1.2. Action Events

The  most  common  high  level  event  is  the  ActionListener  [https://www.codenameone.com/javadoc/com/

codename1/ui/events/ActionListener.html]  which  allows  binding  a  generic  action  event  to  pretty  much

anything.  This  is  so  ubiquitous  in  Codename  One  that  it  is  even  used  for  networking  (as  a  base

class) and for some of the low level event options.

E.g. we can bind an event callback for a Button [https://www.codenameone.com/javadoc/com/codename1/ui/

409

Button.html] by using:

Button b = new Button("Click Me");
b.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent ev) {
        // button was clicked, you can do anything you want here...
    }
});

Or thanks to the Java 8 lambdas we can write it as:

Button b = new Button("Click Me");
b.addActionListener((ev) ->
    // button was clicked, you can do anything you want here...
});

Notice  that  the  click  will  work  whether  the  button  was  touched  using  a  mouse,  finger  or  keypad

shortcut seamlessly with an action listener. Many components work with action events e.g. buttons,

text components, slider etc.

There are quite a few types of high level event types that are more specific to requirements.

Types Of Action Events

When  an  action  event  is  fired  it  is  given  a  type,  however  this  type  might  change  as  the  event

evolves  e.g.  a  command  triggered  by  a  pointer  event  won’t  include  details  of  the  original  pointer

event.

You can get the event type from getEventType() [https://www.codenameone.com/javadoc/com/codename1/ui/

events/ActionEvent.html#getEventType--], this also gives you a rather exhaustive list of the possible event

types for the action event.

Source Of Event

ActionEvent  has  a  source  object,  what  that  source  is  depends  heavily  on  the  event  type.  For  most
component based events this is the component but there are some nuances.

The getComponent() method might not get the actual component. In case of a lead component such
the
as  MultiButton 

[https://www.codenameone.com/javadoc/com/codename1/components/MultiButton.html] 

underlying  Button  [https://www.codenameone.com/javadoc/com/codename1/ui/Button.html]  will  be  returned
and not the MultiButton itself.

To  get  the  component  that  you  would  logically  think  of  as  the  source  component  use  the
getActualComponent() method.

Event Consumption

An ActionEvent can be consumed, once consumed it will no longer proceed down the chain of event

410

processing. This is useful for some cases where we would like to block behavior from proceeding

down the path.

E.g. the event dispatch thread allows us to listen to errors on the EDT using:

Display.getInstance().addEdtErrorHandler((e) -> {
    Exception err = (Exception)e.getSource();
    // ...
});

This  will  work  great  but  you  will  still  get  the  default  error  message  from  the  EDT  over  that

exception. To prevent the event from proceeding to the default error handling you can just do this:

Display.getInstance().addEdtErrorHandler((e) -> {
    e.consume();
    Exception err = (Exception)e.getSource();
    // ...
});

Notice that you can check if an event was already consumed using the isConsumed() method but it’s
pretty unlikely that you will receive a consumed event as the system will usually stop sending it.

NetworkEvent

NetworkEvent [https://www.codenameone.com/javadoc/com/codename1/io/NetworkEvent.html] is a subclass of
ActionEvent  that  is  passed  to  actionPerformed  callbacks  made  in  relation  to  generic  network  code.
E.g.

NetworkManager.getInstance().addErrorListener(new ActionListener<NetworkEvent>() {
    public void actionPerformed(NetworkEvent ev) {
        // now we have access to the methods on NetworkEvent that provide more information about the network specific
flags
    }
});

Or with Java 8 lambdas:

NetworkManager.getInstance().addErrorListener((ev) -> {
    // now we have access to the methods on NetworkEvent that provide more information about the network specific flags
});

The  NetworkEvent  allows  the  networking  code  to  reuse  the  EventDispatcher  infrastructure  and  to
simplify  event  firing  thru  the  EDT.  But  you  should  notice  that  some  code  might  not  be  equivalent

e.g. we could do this to read the input stream:

411

ConnectionRequest r = new ConnectionRequest() {
    @Override
    protected void readResponse(InputStream input) throws IOException {
        // read the input stream
    }
};

or we can do something similar using this code:

ConnectionRequest r = new ConnectionRequest();
r.addResponseListener((e) -> {
    byte[] data = (byte[])e.getMetaData();
    // work with the byte data
});

These seem very similar but they have one important distinction. The latter code is invoked on the
EDT, so if data is big it might slow down processing significantly. The ConnectionRequest is invoked
on  the  network  thread  and  so  can  process  any  amount  of  data  without  slowing  down  the  UI

significantly.

11.1.3. DataChangeListener

The 

DataChangedListener 

[https://www.codenameone.com/javadoc/com/codename1/ui/events/

DataChangedListener.html]  is  used  in  several  places  to  indicate  that  the  underlying  model  data  has

changed:

• TextField  [https://www.codenameone.com/javadoc/com/codename1/ui/TextField.html] 

-  the  text  field

provides  an  action  listener  but  that  only  "fires"  when  the  data  input  is  complete.
DataChangeListener  fires  with  every  key  entered  and  thus  allows  functionality  such  as  "auto
complete" and is indeed used internally in the Codename One AutoCompleteTextField.

• TableModel 

[https://www.codenameone.com/javadoc/com/codename1/ui/table/TableModel.html] 

&

ListModel  [https://www.codenameone.com/javadoc/com/codename1/ui/list/ListModel.html]  -  the  model  for

the  Table  [https://www.codenameone.com/javadoc/com/codename1/ui/table/Table.html]  class  notifies  the

view that its content has changed via this event, thus allowing the UI to refresh properly.

There is a very exhaustive example of search that is implemented using the DataChangedListener in
the Toolbar section [https://www.codenameone.com/manual/components.html#Advanced-search-code].

11.1.4. FocusListener

The  focus  listener  allows  us  to  track  the  currently  "selected"  or  focused  component.  It’s  not  as

useful as it used to be in feature phones.

You can bind a focus listener to the Component itself and receive an event when it gained focus, or
you  can  bind  the  listener  to  the  Form  and  receive  events  for  every  focus  change  event  within  the
hierarchy.

412

11.1.5. ScrollListener

ScrollListener 

[https://www.codenameone.com/javadoc/com/codename1/ui/events/ScrollListener.html]  allows

tracking scroll events so UI elements can be adapted if necessary.

Normally  scrolling  is  seamless  and  this  event  isn’t  necessary,  however  if  developers  wish  to

"shrink" or "fade" an element on scrolling this interface can be used to achieve that. Notice that you

should  bind  the  scroll  listener  to  the  actual  scrollable  component  and  not  to  an  arbitrary

component.

E.g. in this code from the Flickr demo the Toolbar [https://www.codenameone.com/javadoc/com/codename1/
ui/Toolbar.html] is faded based on scroll position:

public class CustomToolbar extends Toolbar implements ScrollListener {
    private int alpha;

    public CustomToolbar() {
    }

    public void paintComponentBackground(Graphics g) {
        int a = g.getAlpha();
        g.setAlpha(alpha);
        super.paintComponentBackground(g);
        g.setAlpha(a);
    }

    public void scrollChanged(int scrollX, int scrollY, int oldscrollX, int oldscrollY) {
        alpha = scrollY;
        alpha = Math.max(alpha, 0);
        alpha = Math.min(alpha, 255);
    }
}



There  is  a  better  way  of  implementing  this  exact  effect  using  title  animations

illustrated  here  [https://www.codenameone.com/manual/components.html#title-animations-

section].

11.1.6. SelectionListener

The SelectionListener [https://www.codenameone.com/javadoc/com/codename1/ui/events/SelectionListener.html]

event is mostly used to broadcast list model selection changes to the list view. Since list supports the
ActionListener event callback its usually the better option since it’s more coarse grained.

SelectionListener  gets  fired  too  often  for  events  and  that  might  result  in  a  performance  penalty.
When  running  on  non-touch  devices  list  selection  could  be  changed  with  the  keypad  and  only  a
specific fire button click would fire the action event, for those cases SelectionListener made a lot of
sense. However, in touch devices this API isn’t as useful.

413

11.1.7. StyleListener

StyleListener 

[https://www.codenameone.com/javadoc/com/codename1/ui/events/StyleListener.html] 

allows

components to track changes to the style objects. E.g. if the developer does something like:

cmp.getUnselectedStyle().setFgColor(0xffffff);

This  will  trigger  a  style  event  that  will  eventually  lead  to  the  component  being  repainted.  This  is

quite important for the component class but not a very important event for general user code. It is

recommended that developers don’t bind a style listener.

11.1.8. Event Dispatcher

When  creating  your  own  components  and  objects  you  sometimes  want  to  broadcast  your  own

events,  for  that  purpose  Codename  One  has  the  EventDispatcher  [https://www.codenameone.com/

javadoc/com/codename1/ui/util/EventDispatcher.html] class which saves a lot of coding effort in this regard.

E.g.  if  you  wish  to  provide  an  ActionListener  [https://www.codenameone.com/javadoc/com/codename1/ui/

events/ActionListener.html] event for components you can just add this to your class:

private final EventDispatcher listeners = new EventDispatcher();

public void addActionListener(ActionListener a) {
    listeners.addListener(a);
}
public void removeActionListener(ActionListener a) {
    listeners.removeListener(a);
}

Then when you need to broadcast the event just use:

private void fireEvent(ActionEvent ev) {
    listeners.fireActionEvent(ev);
}

11.2. Low Level Events

Low level events map to "system" events directly. Touch events are considered low level since they

might expose platform specific nuances to your code.

E.g. one platform might send a very large number of events during drag while another might send

only  a  few.  Normally  the  high  level  event  handling  hides  those  complexities  but  some  of  them

trickle down into the low level event handling.



Codename One tries to hide some of the complexities from the low level events as

well. However, due to the nature of the event types it’s a more challenging task.

414

Low level events can be bound in one of 3 ways:

• Use  one  of  the  add  listener  methods  in  Form  [https://www.codenameone.com/javadoc/com/codename1/

ui/Form.html] e.g. addPointerPressedListener.

• Override one of the event callbacks on Form

• Override  one  of  the  event  callbacks  on  a  Component  [https://www.codenameone.com/javadoc/com/

codename1/ui/Component.html].



When you override event callbacks on a Component the Component in question must
be focusable and have focus at that point. This can be an advantage for some use

cases as it will save you the need of handling unrelated events.

Each of those has advantages and disadvantages, specifically:

• 'Form' based events and callbacks deliver pointer events in the 'Form' coordinate space.

• 'Component' based events require focus

• 'Form' based events can block existing functionality from proceeding thru the event chain e.g.

you can avoid calling super in a form event and thus block other events from happening (e.g.

block a listener or component event from triggering).

Table 8. Event type map

Listener

Override Form

Override Component

Coordinate System

Form

Form

Component

Block current

functionality

Yes, just avoid super

Partially (event

No

consume)

11.2.1. Low Level Event Types

There are two basic types of low level events: Key and Pointer.



Key  events  are  only  relevant  to  physical  keys  and  will  not  trigger  on  virtual

keyboard  keys,  to  track  those  use  a  TextField  [https://www.codenameone.com/javadoc/
com/codename1/ui/TextField.html] with a DataChangeListener as mentioned above.

The pointer events (touch events) can be intercepted by overriding one or more of these methods in
Component  or  Form.  Notice  that  unless  you  want  to  block  functionality  you  should  probably  invoke
super when overriding:

415

public void pointerDragged(int[] x, int[] y)
public void pointerDragged(final int x, final int y)
public void pointerPressed(int[] x, int[] y)
public void pointerPressed(int x, int y)
public void pointerReleased(int[] x, int[] y)
public void pointerReleased(int x, int y)
public void longPointerPress(int x, int y)
public void keyPressed(int keyCode)
public void keyReleased(int keyCode)
public void keyRepeated(int keyCode)

Notice that most pointer events have a version that accepts an array as an argument, this allows for

multi-touch event handling by sending all the currently touched coordinates.

11.2.2. Drag Event Sanitation

Drag  events  are  quite  difficult  to  handle  properly  across  devices.  Some  devices  send  a  ridiculous

number  of  events  for  even  the  lightest  touch  while  others  send  too  little.  It  seems  like  too  many

drag  events  wouldn’t  be  a  problem,  however  if  we  drag  over  a  button  then  it  might  disable  the

buttons action event (since this might be the user trying to scroll).

Drag  sensitivity  is  really  about  the  component  being  dragged  which  is  why  we  have  the  method
getDragRegionStatus  that  allows  us  to  "hint"  to  the  drag  API  whether  we  are  interested  in  drag
events or not and if so in which directional bias.

E.g. if our component is a painting app where we are trying to draw using drag gestures we would

use code such as:

public class MyComponent extends Component {
    protected int getDragRegionStatus(int x, int y) {
        return DRAG_REGION_LIKELY_DRAG_XY;
    }
}

This indicates that we want all drag events on both AXIS to be sent as soon as possible. Notice that

this doesn’t completely disable event sanitation.

11.3. BrowserNavigationCallback

The 

BrowserNavigationCallback 

[https://www.codenameone.com/javadoc/com/codename1/ui/events/

BrowserNavigationCallback.html] isn’t quite an "event" but there is no real "proper" classification for it.



The  callback  method  of  this  interface  is  invoked  off  the  EDT!  You  must  NEVER

block this method and must not access UI or Codename One sensitive elements in

this method!

The browser navigation callback is invoked directly from the native web component as it navigates

416

to  a  new  page.  Because  of  that  it  is  invoked  on  the  native  OS  thread  and  gives  us  a  unique

opportunity to handle the navigation ourselves as we see fit. That is why it MUST be invoked on the

native  thread,  since  the  native  browser  is  pending  on  our  response  to  that  method,  spanning  an

invokeAndBlock/callSerially would be to slow and would bog down the browser.

You  can  use  the  browser  navigation  callback  to  change  the  UI  or  even  to  invoke  Java  code  from

JavaScript code e.g.:

bc.setBrowserNavigationCallback((url) -> {
    if(url.startsWith("http://click")) {
        Display.getInstance().callSerially(() -> bc.execute("fnc('<p>You clicked!</p>')"));
        return false;
    }
    return true;
});

417

418

12. File System, Storage, Network & Parsing

12.1. Jar Resources

Resources  that  are  packaged  within  the  "JAR"  don’t  really  belong  in  this  section  of  the  developer
guide but since they are often confused with Storage/FileSystemStorage this might be the best place
to clarify what they are.

You can place arbitrary files within the src directory of a Codename One project. This file will get
packaged into the final distribution. In standard Java SE you can usually do something like:

InputStream i = getClass().getResourceAsStream("/myFile");

This isn’t guaranteed to work on all platforms and will probably fail on some. Instead you should

use something such as:

InputStream i = Display.getInstance().getResourceAsStream(getClass(), "/myFile");

This isn’t the only limitation though, you can use hierarchies so something like this would fail:

InputStream i = Display.getInstance().getResourceAsStream(getClass(), "/res/myFile");

You can’t use relative paths either so this will fail as well (notice the lack of the first slash):

InputStream i = Display.getInstance().getResourceAsStream(getClass(), "myFile");

The  reason  for  those  limitations  is  portability,  on  iOS  and  Android  resources  behave  quite

differently so supporting the full Java SE semantics is unrealistic.



This is even worse in some regards. Because of the way iOS works with resources
some unique file names might fail e.g. if you use the @ character or have a . more
than once (e.g. file.ext.act)

Notice that just like in Java SE, the entries within the "JAR" are read only and can’t be modified. You

can’t gain access to the actual file, only to the stream!

12.2. Storage

Storage  [https://www.codenameone.com/javadoc/com/codename1/io/Storage.html]  is  accessed  via  the  Storage
class. It is a flat filesystem like interface and contains the ability to list/delete and write to named

storage entries.

The Storage API also provides convenient methods to write objects to Storage and read them from

419

Storage specifically readObject & writeObject.

The  objects  in  Storage  are  usually  deleted  when  an  app  is  uninstalled  but  are



retained  between  application  updates.  A  notable  exception  is  Android  which,  on

some  devices,  keeps  by  default  objects  in  Storage  after  app  uninstalling.  To  force

Android 
android.allowBackup=false

to  remove 

them  on  app  uninstalling,  use 

the  build  hint

The sample code below demonstrates listing the content of the storage, adding/viewing and deleting

entries within the storage:

420

Toolbar.setGlobalToolbar(true);
Form hi = new Form("Storage", new BoxLayout(BoxLayout.Y_AXIS));
hi.getToolbar().addCommandToRightBar("+", null, e -> {
    TextField tf = new TextField("", "File Name", 20, TextField.ANY);
    TextArea body = new TextArea(5, 20);
    body.setHint("File Body");
    Command ok = new Command("OK");
    Command cancel = new Command("Cancel");
    Command result = Dialog.show("File Name", BorderLayout.north(tf).add(BorderLayout.CENTER, body), ok, cancel);
    if(ok == result) {
        try(OutputStream os = Storage.getInstance().createOutputStream(tf.getText());) {
            os.write(body.getText().getBytes("UTF-8"));
            createFileEntry(hi, tf.getText());
            hi.getContentPane().animateLayout(250);
        } catch(IOException err) {
            Log.e(err);
        }
    }
});
for(String file : Storage.getInstance().listEntries()) {
    createFileEntry(hi, file);
}
hi.show();

private void createFileEntry(Form hi, String file) {
   Label fileField = new Label(file);
   Button delete = new Button();
   Button view = new Button();
   FontImage.setMaterialIcon(delete, FontImage.MATERIAL_DELETE);
   FontImage.setMaterialIcon(view, FontImage.MATERIAL_OPEN_IN_NEW);
   Container content = BorderLayout.center(fileField);
   int size = Storage.getInstance().entrySize(file);
   content.add(BorderLayout.EAST, BoxLayout.encloseX(new Label(size + "bytes"), delete, view));
   delete.addActionListener(e -> {
       Storage.getInstance().deleteStorageFile(file);
       content.setY(hi.getWidth());
       hi.getContentPane().animateUnlayoutAndWait(150, 255);
       hi.removeComponent(content);
       hi.getContentPane().animateLayout(150);
   });
   view.addActionListener(e -> {
       try(InputStream is = Storage.getInstance().createInputStream(file);) {
           String s = Util.readToString(is, "UTF-8");
           Dialog.show(file, s, "OK", null);
       } catch(IOException err) {
           Log.e(err);
       }
   });
   hi.add(content);
}

421

Figure 356. List of files within the storage

Figure 357. Content of a file added to the storage

12.2.1. The Preferences API

Storage  also  offers  a  very  simple  API  in  the  form  of  the  Preferences  [https://www.codenameone.com/
javadoc/com/codename1/io/Preferences.html]  class.  The  Preferences  class  allows  developers  to  store
simple variables, strings, numbers, booleans etc. in storage without writing any storage code. This is

a common use case within applications e.g. you have a server token that you need to store you can

store it like this:

Preferences.set("token", myToken);

You can then read the token like this:

String token = Preferences.get("token", null);

This  gets  somewhat  confusing  with  primitive  numbers  e.g. 
Preferences.set("primitiveLongValue", 
then 
Preferences.get("primitiveLongValue", 0) you might get an exception!
This would happen because the value is physically a Long object but you are trying
to  get  an  Integer.  The  workaround  is  to  remain  consistent  and  use  code  like  this
Preferences.get("primitiveLongValue", (long)0).

myLongNumber) 

if  you  use

invoke



422

12.3. File System

FileSystemStorage 

[https://www.codenameone.com/javadoc/com/codename1/io/FileSystemStorage.html]

provides  file  system  access.  It  maps  to  the  underlying  OS’s  file  system  API  providing  most  of  the
common  operations  expected  from  a  file  API  somewhat  in  the  vain  of  java.io.File  &
java.io.FileInputStream e.g. opening, renaming, deleting etc.

Notice that the file system API is somewhat platform specific in its behavior. All paths used the API

should be absolute otherwise they are not guaranteed to work.

The main reason java.io.File & java.io.FileInputStream weren’t supported directly has a lot to do
with the richness of those two API’s. They effectively allow saving a file anywhere, however mobile

devices  are  far  more  restrictive  and  don’t  allow  apps  to  see/modify  files  that  are  owned  by  other

apps.

12.3.1. File Paths & App Home

All paths in FileSystemStorage are absolute, this simplifies the issue of portability significantly since
the concept of relativity and current working directory aren’t very portable.

All URL’s use the / as their path separator we try to enforce this behavior even in Windows.

Directories end with the / character and thus can be easily distinguished by their name.

The  FileSystemStorage  API  provides  a  getRoots()  call  to  list  the  root  directories  of  the  file  system
(you  can  then  "dig  in"  via  the  listFiles  API).  However,  this  is  confusing  and  unintuitive  for
developers.

To  simplify  the  process  of  creating/reading  files  we  added  the  getAppHomePath()  method.  This
method allows us to obtain the path to a directory where files can be stored/read.

We  can  use  this  directory  to  place  an  image  to  share  as  we  did  in  the  share  sample

[https://www.codenameone.com/manual/components.html#sharebutton-section].



A  common  Android  hack  is  to  write  files  to  the  SDCard  storage  to  share  them

among  apps.  Android  4.x  disabled  the  ability  to  write  to  arbitrary  directories  on

the SDCard even when the appropriate permission was requested.

A more advanced usage of the FileSystemStorage API can be a FileSystemStorage Tree:

423

Form hi = new Form("FileSystemTree", new BorderLayout());
TreeModel tm = new TreeModel() {
    @Override
    public Vector getChildren(Object parent) {
        String[] files;
        if(parent == null) {
            files = FileSystemStorage.getInstance().getRoots();
            return new Vector<Object>(Arrays.asList(files));
        } else {
            try {
                files = FileSystemStorage.getInstance().listFiles((String)parent);
            } catch(IOException err) {
                Log.e(err);
                files = new String[0];
            }
        }
        String p = (String)parent;
        Vector result = new Vector();
        for(String s : files) {
            result.add(p + s);
        }
        return result;
    }

    @Override
    public boolean isLeaf(Object node) {
        return !FileSystemStorage.getInstance().isDirectory((String)node);
    }
};
Tree t = new Tree(tm) {
    @Override
    protected String childToDisplayLabel(Object child) {
        String n = (String)child;
        int pos = n.lastIndexOf("/");
        if(pos < 0) {
            return n;
        }
        return n.substring(pos);
    }
};
hi.add(BorderLayout.CENTER, t);
hi.show();

424

Figure 358. Simple sample of a tree for the FileSystemStorage API

12.3.2. Storage vs. File System

The question of storage vs. file system is often confusing for novice mobile developers. This embeds

two separate questions:

• Why are there 2 API’s where one would have worked?

• Which one should I pick?

The main reasons for the 2 API’s are technical. Many OS’s provide 2 ways of accessing data specific
to the app and this is reflected within the API. E.g. on Android the FileSystemStorage maps to API’s
such as java.io.FileInputStream whereas the Storage maps to Context.openFileInput().

The secondary reason for the two API’s is conceptual. FileSystemStorage is more powerful and in a
sense provides more ways to fail, this is compounded by the complex on-device behavior of the API.
Storage is designed to be friendlier to the uninitiated and more portable.

You should pick Storage unless you have a specific requirement that prevents it. Some API’s such as
Capture expect a FileSystemStorage URI so in those cases this would also be a requirement.

Another case where FileSystemStorage is beneficial is the case of hierarchy or native API usage. If
you need a a directory structure or need to communicate with a native API the FileSystemStorage
approach is usually easier.



In some OS’s the FileSystemStorage API can find the content of the Storage API. As
one  is  implemented  on  top  of  the  other.  This  is  undocumented  behavior  that  can

change at any moment!

To summarize the differences between the 3 file storage options:

Table 9. Compare Storage, FileSystem & Jar Resources

Option

Storage

File System

JAR Resource

Main Use Case

General application

Low level access

Ship data within the

Initial State

Data

Blank

Blank

app

As defined by

developer

425

Option

Storage

File System

JAR Resource

Modifiable

Yes

Supports Hierarchies No

Yes

Yes

No

No

12.4. SQL

Most new devices contain one version of sqlite or another; sqlite is a very lightweight SQL database

designed for embedding into devices. For portability we recommend avoiding SQL altogether since

it is both fragmented between devices (different sqlite versions) and isn’t supported on all devices.

In general SQL seems overly complex for most embedded device programming tasks.

Portability Of SQLite

SQLite  is  supported  on  iOS,  Android,  RIM,  Desktop  &  JavaScript  builds.  However,  the

JavaScript version of SQL has been deprecated and isn’t supported on all platforms.

You will notice that at this time support is still missing from the Windows builds.

The  biggest  issue  with  SQLite  portability  is  in  iOS.  The  SQLite  version  for  most  platforms  is

threadsafe and as a result very stable. However, the iOS version is not!

This might not seem like a big deal normally, however if you forget to close a connection the

GC  might  close  it  for  you  thus  producing  a  crash.  This  is  such  a  common  occurrence  that

Codename One logs a warning when the GC collects a database resource on the simulator.

SQL is pretty powerful and very well suited for common tabular data. The Codename One SQL API

is similar in spirit to JDBC but considerably simpler since many of the abstractions of JDBC designed

for pluggable database architecture make no sense for a local database.

The  Database  [https://www.codenameone.com/javadoc/com/codename1/db/Database.html]  API  is  a  high  level

abstraction that allows you to open an arbitrary database file using syntax such as:

Database db = Display.getInstance().openOrCreate(“databaseName”);

Some SQLite apps ship with a "ready made" database. We allow you to replace the DB file by using

the code:

String path = Display.getInstance().getDatabasePath(“databaseName”);

You  can  then  use  the  FileSystemStorage  class  to  write  the  content  of  your  DB  file  into  the  path.
Notice that it must be a valid SQLite file!

 getDatabasePath() is not supported in the Javascript port. It will always return null.

426

This  is  very  useful  for  applications  that  need  to  synchronize  with  a  central  server  or  applications

that ship with a large database as part of their core product.

Working with a database is pretty trivial, the application logic below can send arbitrary queries to
the database and present the results in a Table. You can probably integrate this code into your app
as a debugging tool:

Toolbar.setGlobalToolbar(true);
Style s = UIManager.getInstance().getComponentStyle("TitleCommand");
FontImage icon = FontImage.createMaterial(FontImage.MATERIAL_QUERY_BUILDER, s);
Form hi = new Form("SQL Explorer", new BorderLayout());
hi.getToolbar().addCommandToRightBar("", icon, (e) -> {
    TextArea query = new TextArea(3, 80);
    Command ok = new Command("Execute");
    Command cancel = new Command("Cancel");
    if(Dialog.show("Query", query, ok, cancel) == ok) {
        Database db = null;
        Cursor cur = null;
        try {
            db = Display.getInstance().openOrCreate("MyDB.db");
            if(query.getText().startsWith("select")) {
                cur = db.executeQuery(query.getText());
                int columns = cur.getColumnCount();
                hi.removeAll();
                if(columns > 0) {
                    boolean next = cur.next();
                    if(next) {
                        ArrayList<String[]> data = new ArrayList<>();
                        String[] columnNames = new String[columns];
                        for(int iter = 0 ; iter < columns ; iter++) {
                            columnNames[iter] = cur.getColumnName(iter);
                        }
                        while(next) {
                            Row currentRow = cur.getRow();
                            String[] currentRowArray = new String[columns];
                            for(int iter = 0 ; iter < columns ; iter++) {
                                currentRowArray[iter] = currentRow.getString(iter);
                            }
                            data.add(currentRowArray);
                            next = cur.next();
                        }
                        Object[][] arr = new Object[data.size()][];
                        data.toArray(arr);
                        hi.add(BorderLayout.CENTER, new Table(new DefaultTableModel(columnNames, arr)));
                    } else {
                        hi.add(BorderLayout.CENTER, "Query returned no results");
                    }
                } else {
                    hi.add(BorderLayout.CENTER, "Query returned no results");
                }
            } else {
                db.execute(query.getText());
                hi.add(BorderLayout.CENTER, "Query completed successfully");
            }
            hi.revalidate();
        } catch(IOException err) {
            Log.e(err);

427

            hi.removeAll();
            hi.add(BorderLayout.CENTER, "Error: " + err);
            hi.revalidate();
        } finally {
            Util.cleanup(db);
            Util.cleanup(cur);
        }
    }
});
hi.show();

Figure 359. Querying the temp demo generated by the SQLDemo application

Figure 360. Issuing a query

12.5. Network Manager & Connection Request

One of the more common problems in Network programming is spawning a new thread to handle

the network operations. In Codename One this is done seamlessly and becomes unessential thanks

to the NetworkManager [http://www.codenameone.com/javadoc/com/codename1/io/NetworkManager.html].

NetworkManager  effectively  alleviates  the  need  for  managing  network  threads  by  managing  the
complexity of network threading. The connection request class can be used to facilitate web service

requests when coupled with the JSON/XML parsing capabilities.

To open a connection one needs to use a ConnectionRequest [http://www.codenameone.com/javadoc/com/

codename1/io/ConnectionRequest.html]  object,  which  has  some  similarities 

to 

the  networking

mechanism in JavaScript but is obviously somewhat more elaborate.

You can send a get request to a URL using something like:

428

ConnectionRequest request = new ConnectionRequest(url, false);
request.addResponseListener((e) -> {
    // process the response
});

// request will be handled asynchronously
NetworkManager.getInstance().addToQueue(request);

Notice  that  you  can  also  implement  the  same  thing  and  much  more  by  avoiding  the  response
listener  code  and  instead  overriding  the  methods  of  the  ConnectionRequest  class  which  offers
multiple points to override e.g.

ConnectionRequest request = new ConnectionRequest(url, false) {
   protected void readResponse(InputStream input) {
        // just read from the response input stream
   }

   protected void postResponse() {
        // invoked on the EDT after processing is complete to allow the networking code
        // to update the UI
   }

   protected void buildRequestBody(OutputStream os) {
        // writes post data, by default this “just works” but if you want to write this
       // manually then override this
   }
};
NetworkManager.getInstance().addToQueue(request);



Notice  that  overriding  buildRequestBody(OutputStream)  will  only  work  for  POST
requests and will replace writing the arguments

 You  don’t  need  to  close  the  output/input  streams  passed  to  the  request  methods.

They are implicitly cleaned up.

NetworkManager  also  supports  synchronous  requests  which  work  in  a  similar  way  to  Dialog  via  the
invokeAndBlock call and thus don’t block the EDT [9] illegally. E.g. you can do something like this:

ConnectionRequest request = new ConnectionRequest(url, false);
// request will be handled synchronously
NetworkManager.getInstance().addToQueueAndWait(request);
byte[] resultOfRequest = request.getData();

Notice that in this case the addToQueueAndWait method returned after the connection completed. Also
notice that this was totally legal to do on the EDT!

429

12.5.1. Threading

By  default  the  NetworkManager  launches  with  a  single  network  thread.  This  is  sufficient  for  very
simple  applications  that  don’t  do  too  much  networking  but  if  you  need  to  fetch  many  images

concurrently and perform web services in parallel this might be an issue.



Once  you  increase  the  thread  count  there  is  no  guarantee  of  order  for  your

requests. Requests might not execute in the order with which you added them to

the queue!

To update the number of threads use:

NetworkManager.getInstance().updateThreadCount(4);

All the callbacks in the ConnectionRequest occur on the network thread and not on the EDT!

There  is  one  exception  to  this  rule  which  is  the  postResponse()  method  designed  to  update  the  UI
after the networking code completes.



Never  change  the  UI  from  a  ConnectionRequest  callback.  You  can  either  use  a
listener on the ConnectionRequest, use postResponse() (which is the only exception
to this rule) or wrap your UI code with callSerially.

12.5.2. Arguments, Headers & Methods

HTTP/S  is  a  complex  protocol  that  expects  complex  encoded  data  for  its  requests.  Codename  One

tries  to  simplify  and  abstract  most  of  these  complexities  behind  common  sense  API’s  while  still

providing the full low level access you would expect from such an API.

Arguments

HTTP supports several "request methods", most commonly GET & POST but also a few others such as
HEAD, PUT, DELETE etc.

Arguments in HTTP are passed differently between GET and POST methods. That is what the setPost
method in Codename One determines, whether arguments added to the request should be placed
using the GET semantics or the POST semantics.

So if we continue our example from above we can do something like this:

ConnectionRequest request = new ConnectionRequest(url, false);
request.addArgument("MyArgName", value);

This  will  implicitly  add  a  get  argument  with  the  content  of  value.  Notice  that  we  don’t  really  care
what value is. It’s implicitly HTTP encoded based on the get/post semantics. In this case it will use
the get encoding since we passed false to the constructor.

430

A simpler implementation could do something like this:

ConnectionRequest request = new ConnectionRequest(url +
    "MyArgName=" + Util.encodeUrl(value), false);

This  would  be  almost  identical  but  doesn’t  provide  the  convenience  for  switching  back  and  forth
between GET/POST and it isn’t as fluent.

We can skip the encoding in complex cases where server code expects illegal HTTP characters (this
happens)  using  the  addArgumentNoEncoding  method.  We  can  also  add  multiple  arguments  with  the
same key using addArgumentArray.

Methods

As  we  explained  above,  the  setPost()  method  allows  us  to  manipulate  the  get/post  semantics  of  a
request. This implicitly changes the POST or GET method submitted to the server.

However, if you wish to have finer grained control over the submission process e.g. for making a
HEAD request you can do this with code like:

ConnectionRequest request = new ConnectionRequest(url, false);
request.setHttpMethod("HEAD");

Headers

When  communicating  with  HTTP  servers  we  often  pass  data  within  headers  mostly  for

authentication/authorization but also to convey various properties.

Some headers are builtin as direct API’s e.g. content type is directly exposed within the API since it’s

a pretty common use case. We can set the content type of a post request using:

ConnectionRequest request = new ConnectionRequest(url, true);
request.setContentType("text/xml");

We  can  also  add  any  arbitrary  header  type  we  want,  e.g.  a  very  common  use  case  is  basic

authorization  where  the  authorization  header  includes  the  Base64  encoded  user/password

combination as such:

String authCode = user + ":" + password;
String authHeader = "Basic " + Base64.encode(authCode.getBytes());
request.addRequestHeader("Authorization", authHeader);

This can be quite tedious to do if you want all requests from your app to use this header. For this

use case you can just use:

431

String authCode = user + ":" + password;
String authHeader = "Basic " + Base64.encode(authCode.getBytes());
NetworkManager.getInstance().addDefaultHeader("Authorization", authHeader);

Server Headers

Server returned headers are a bit trickier to read. We need to subclass the connection request and
override the readHeaders method e.g.:

ConnectionRequest request = new ConnectionRequest(url, false) {
    protected void readHeaders(Object connection) throws IOException {
        String[] headerNames = getHeaderFieldNames(connection);
        for(String headerName : headerNames) {
            String headerValue = getHeader(headerName);
            //....
        }
    }
    protected void readResponse(InputStream input) {
        // just read from the response input stream
    }
};
NetworkManager.getInstance().addToQueue(request);

Here  we  can  extract  the  headers  one  by  one  to  handle  complex  headers  such  as  cookies,

authentication etc.

Error Handling

As you noticed above practically all of the methods in the ConectionRequest throw IOException. This
allows you to avoid the try/catch semantics and just let the error propagate up the chain so it can be
handled uniformly by the application.

There are two distinct placed where you can handle a networking error:

• The ConnectionRequest - by overriding callback methods

• The NetworkManager error handler

Notice that the NetworkManager error handler takes precedence thus allowing you to define a global
policy for network error handling by consuming errors.

E.g.  if  I  would  like  to  block  all  network  errors  from  showing  anything  to  the  user  I  could  do

something like this:

NetworkManager.getInstance().addToQueue(request);
NetworkManager.getInstance().addErrorListener((e) -> e.consume());

The  error  listener  is  invoked  first  with  the  NetworkEvent  [https://www.codenameone.com/javadoc/com/

432

codename1/io/NetworkEvent.html]  matching  the  error.  Consuming  the  event  prevents  it  from
propagating further down the chain into the ConnectionRequest callbacks.

We  can  also  override  the  error  callbacks  of  the  various  types  in  the  request  e.g.  in  the  case  of  a

server error code we can do:

ConnectionRequest request = new ConnectionRequest(url, false) {
    protected void handleErrorResponseCode(int code, String message) {
        if(code == 444) {
            // do something
        }
    }
    protected void readResponse(InputStream input) {
        // just read from the response input stream
    }
};
NetworkManager.getInstance().addToQueue(request);

 The error callback callback is triggered in the network thread!

As a result it can’t access the UI to show a Dialog or anything like that.

Another  approach  is  to  use  the  setFailSilently(true)  method  on  the  ConnectionRequest.  This  will
prevent the ConnectionRequest from displaying any errors to the user. It’s a very powerful strategy if
you use the synchronous version of the API’s e.g.:

ConnectionRequest request = new ConnectionRequest(url, false);
request.setFailSilently(true);
NetworkManager.getInstance().addToQueueAndWait(request);
if(request.getResponseCode() != 200) {
    // probably an error...
}



This  code  will  only  work  with  the  synchronous  "AndWait"  version  of  the  method

since the response code will take a while to return for the non-wait version.

Error Stream

When we get an error code that isn’t 200/300 we ignore the result. This is problematic as the result

might contain information we need. E.g. many webservices provide further XML/JSON based details

describing the reason for the error code.

Calling  setReadResponseForErrors(true)  will  trigger  a  mode  where  even  errors  will  receive  the
readResponse callback with the error stream. This also means that API’s like getData and the listener
API’s will also work correctly in case of error.

433

12.5.3. GZIP

Gzip  is  a  very  common  compression  format  based  on  the  lz  algorithm,  it’s  used  by  web  servers

around the world to compress data.

Codename  One  supports  GZipInputStream  [https://www.codenameone.com/javadoc/com/codename1/io/gzip/

GZIPInputStream.html]  and  GZipOutputStream  [https://www.codenameone.com/javadoc/com/codename1/io/

gzip/GZIPOutputStream.html], which allow you to compress data seamlessly into a stream and extract

compressed data from a stream. This is very useful and can be applied to every arbitrary stream.

Codename  One  also  features  a  GZConnectionRequest  [https://www.codenameone.com/javadoc/com/

codename1/io/gzip/GZConnectionRequest.html],  which  will  automatically  unzip  an  HTTP  response  if  it  is

indeed gzipped. Notice that some devices (iOS) always request gzip’ed data and always decompress
it for us, however in the case of iOS it doesn’t remove the gziped header. The GZConnectionRequest is
aware of such behaviors so it’s better to use that when connecting to the network (if applicable).

By default GZConnectionRequest doesn’t request gzipped data (only unzips it when its received) but
its pretty easy to do so just add the HTTP header Accept-Encoding: gzip e.g.:

GZConnectionRequest con = new GZConnectionRequest();
con.addRequestHeader("Accept-Encoding", "gzip");

Do the rest as usual and you should have smaller responses from the servers.

12.5.4. File Upload

MultipartRequest  [https://www.codenameone.com/javadoc/com/codename1/io/MultipartRequest.html]  tries  to

simplify the process of uploading a file from the local device to a remote server.

You  can  always  submit  data  in  the  buildRequestBody  but  this  is  flaky  and  has  some  limitations  in
terms of devices/size allowed. HTTP standardized file upload capabilities thru the multipart request

protocol, this is implemented by countless servers and is well documented. Codename One supports

this out of the box:

MultipartRequest request = new MultipartRequest();
request.setUrl(url);
request.addData("myFileName", fullPathToFile, "text/plain")
NetworkManager.getInstance().addToQueue(request);



MultipartRequest  is  a  ConnectionRequest  most  stuff  you  expect  from  there  should
work. Even addArgument etc.

Since  we  assume  most  developers  reading  this  will  be  familiar  with  Java  here  is  the  way  to

implement the multipart upload in the servlet API:

434

@WebServlet(name = "UploadServlet", urlPatterns = {"/upload"})
@MultipartConfig(fileSizeThreshold = 1024 * 1024 * 100, // 10 MB
        maxFileSize = 1024 * 1024 * 150, // 50 MB
        maxRequestSize = 1024 * 1024 * 200)      // 100 MB
public class UploadServlet extends HttpServlet {

    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {
        Collection<Part> parts = req.getParts();
        Part data = parts.iterator().next();
        try(InputStream is = data.getInputStream();) {}
            // store or do something with the input stream
        }
    }
}

12.5.5. Parsing

Codename One has several built in parsers for JSON, XML, CSV & Properties formats. You can use

those parsers to read data from the Internet or data that is shipping with your product. E.g. use the

CSV data to setup default values for your application.

All our parsers are designed with simplicity and small distribution size; they don’t validate and will

fail in odd ways when faced with broken data. The main logic behind this is that validation takes up

CPU time on the device where CPU is a precious resource.

Parsing CSV

CSV  is  probably  the  easiest  to  use,  the  "Comma  Separated  Values"  format  is  just  a  list  of  values

separated by commas (or some other character) with new lines to indicate another row in the table.

These usually map well to an Excel spreadsheet or database table and are supported by default in

all spreadsheets.

To  parse  a  CSV 

just  use  the  CSVParser  [https://www.codenameone.com/javadoc/com/codename1/io/

CSVParser.html] class as such:

435

Form hi = new Form("CSV Parsing", new BorderLayout());
CSVParser parser = new CSVParser();
try(Reader r = new CharArrayReader("1997,Ford,E350,\"Super, \"\"luxurious\"\" truck\"".toCharArray());) {
    String[][] data = parser.parse(r);
    String[] columnNames = new String[data[0].length];
    for(int iter=  0 ; iter < columnNames.length ; iter++) {
        columnNames[iter] = "Col " + (iter + 1);
    }
    TableModel tm = new DefaultTableModel(columnNames, data);
    hi.add(BorderLayout.CENTER, new Table(tm));
} catch(IOException err) {
    Log.e(err);
}
hi.show();

Figure 361. CSV parsing results, notice the properly escaped parentheses and comma

The  data  contains  a  two  dimensional  array  of  the  CSV  content.  You  can  change  the  delimiter
character by using the CSVParser constructor that accepts a character.



Notice  that  we  used  CharArrayReader  from  the  com.codename1.io  package  for  this
sample.  Normally  you  would  want  to  use  java.util.InputStreamReader  for  real
world data.

JSON

The  JSON  ("Java  Script  Object  Notation")  format  is  popular  on  the  web  for  passing  values  to/from

webservices since it works so well with JavaScript. Parsing JSON is just as easy but has two different

variations.  You  can  use  the  JSONParser  [https://www.codenameone.com/javadoc/com/codename1/io/

JSONParser.html] class to build a tree of the JSON data as such:

JSONParser parser = new JSONParser();
Hashtable response = parser.parse(reader);

The  response  is  a  Map  containing  a  nested  hierarchy  of  Collection  (java.util.List),  Strings  and
numbers  to  represent  the  content  of  the  submitted  JSON.  To  extract  the  data  from  a  specific  path
just iterate the Map keys and recurs into it.

The sample below uses results from an API of ice and fire [https://anapioficeandfire.com/] that queries

structured data about the "Song Of Ice & Fire" book series. Here is a sample result returned from

the API for the query http://www.anapioficeandfire.com/api/characters?page=5&pageSize=3 :

[
  {
    "url": "http://www.anapioficeandfire.com/api/characters/13",

436

    "name": "Chayle",
    "culture": "",
    "born": "",
    "died": "In 299 AC, at Winterfell",
    "titles": [
      "Septon"
    ],
    "aliases": [],
    "father": "",
    "mother": "",
    "spouse": "",
    "allegiances": [],
    "books": [
      "http://www.anapioficeandfire.com/api/books/1",
      "http://www.anapioficeandfire.com/api/books/2",
      "http://www.anapioficeandfire.com/api/books/3"
    ],
    "povBooks": [],
    "tvSeries": [],
    "playedBy": []
  },
  {
    "url": "http://www.anapioficeandfire.com/api/characters/14",
    "name": "Gillam",
    "culture": "",
    "born": "",
    "died": "",
    "titles": [
      "Brother"
    ],
    "aliases": [],
    "father": "",
    "mother": "",
    "spouse": "",
    "allegiances": [],
    "books": [
      "http://www.anapioficeandfire.com/api/books/5"
    ],
    "povBooks": [],
    "tvSeries": [],
    "playedBy": []
  },
  {
    "url": "http://www.anapioficeandfire.com/api/characters/15",
    "name": "High Septon",
    "culture": "",
    "born": "",
    "died": "",
    "titles": [
      "High Septon",
      "His High Holiness",

437

      "Father of the Faithful",
      "Voice of the Seven on Earth"
    ],
    "aliases": [
      "The High Sparrow"
    ],
    "father": "",
    "mother": "",
    "spouse": "",
    "allegiances": [],
    "books": [
      "http://www.anapioficeandfire.com/api/books/5",
      "http://www.anapioficeandfire.com/api/books/8"
    ],
    "povBooks": [],
    "tvSeries": [
      "Season 5"
    ],
    "playedBy": [
      "Jonathan Pryce"
    ]
  }
]

We will place that into a file named "anapioficeandfire.json" in the src directory to make the next

sample simpler:

Form hi = new Form("JSON Parsing", new BoxLayout(BoxLayout.Y_AXIS));
JSONParser json = new JSONParser();
try(Reader r = new InputStreamReader(Display.getInstance().getResourceAsStream(getClass(), "/anapioficeandfire.json"),
"UTF-8");) {
    Map<String, Object> data = json.parseJSON(r);
    java.util.List<Map<String, Object>> content = (java.util.List<Map<String, Object>>)data.get("root"); ①
    for(Map<String, Object> obj : content) { ②
        String url = (String)obj.get("url");
        String name = (String)obj.get("name");
        java.util.List<String> titles =  (java.util.List<String>)obj.get("titles"); ③
        if(name == null || name.length() == 0) {
            java.util.List<String> aliases = (java.util.List<String>)obj.get("aliases");
            if(aliases != null && aliases.size() > 0) {
                name = aliases.get(0);
            }
        }
        MultiButton mb = new MultiButton(name);
        if(titles != null && titles.size() > 0) {
            mb.setTextLine2(titles.get(0));
        }
        mb.addActionListener((e) -> Display.getInstance().execute(url));
        hi.add(mb);
    }
} catch(IOException err) {
    Log.e(err);
}
hi.show();

① The JSONParser returns a Map which is great if the root object is a Map but in some cases its a list of

438

elements (as is the case above). In this case a special case "root" element is created to contain the

actual list of elements.

② We rely that the entries are all maps, this might not be the case for every API type.

③ Notice that the "titles" and "aliases" entries are both lists of elements. We use java.util.List to

avoid a clash with com.codename1.ui.List.

Figure 362. Parsed JSON result, clicking the elements opens the URL from the JSON

The  structure  of  the  returned  map  is  sometimes  unintuitive  when  looking  at  the



raw  JSON.  The  easiest  thing  to  do  is  set  a  breakpoint  on  the  method  and  use  the

inspect variables capability of your IDE to inspect the returned element hierarchy

while writing the code to extract that data

An  alternative  approach  is  to  use  the  static  data  parse()  method  of  the  JSONParser  class  and
implement a callback parser e.g.:

JSONParser.parse(reader, callback);

Notice  that  a  static  version  of  the  method  is  used!  The  callback  object  is  an  instance  of  the
JSONParseCallback  interface,  which  includes  multiple  methods.  These  methods  are  invoked  by  the
parser  to  indicate  internal  parser  states,  this  is  similar  to  the  way  traditional  XML  SAX  event

parsers work.

XML Parsing

The  XMLParser  [https://www.codenameone.com/javadoc/com/codename1/xml/XMLParser.html]  started  its  life

as an HTML parser built for displaying mobile HTML. That usage has since been deprecated but the

parser  can  still  parse  many  HTML  pages  and  is  very  "loose"  in  terms  of  verification.  This  is  both

good and bad as the parser will work with invalid data without complaining.

The simplest usage of XMLParser looks a bit like this:

XMLParser parser = new XMLParser();
Element elem = parser.parse(reader);

The  Element  [https://www.codenameone.com/javadoc/com/codename1/xml/Element.html]  contains  children

and attributes. It represents a tag within the XML document and even the root document itself. You

can iterate over the XML tree to extract the data from within the XML file.

439

We’ve  had 

a 

great 

sample  of  working  with 

XMLParser 

in 

the  Tree 

Section

[https://www.codenameone.com/manual/components.html#tree-section] of this guide.

XMLParser  has  the  complimentary  XMLWriter  [https://www.codenameone.com/javadoc/com/codename1/xml/
XMLWriter.html] class which can generate XML from the Element hierarchy. This allows a developers
to mutate (modify) the elements and save them to a writer stream.

XPath Processing

The  Result  [https://www.codenameone.com/javadoc/com/codename1/processing/Result.html]  class  provides  a

subset  of  XPath  [https://www.w3schools.com/xml/xpath_intro.asp],  but  it  is  not  limited  to  just  XML
documents, it can also work with JSON documents, and even with raw Map objects.

Lets  start  by  demonstrating  how  to  process  a  response  from  the  Google  Reverse  Geocoder  API

[https://developers.google.com/maps/documentation/geocoding/]. Lets start with this XML snippet:

<?xml version="1.0" encoding="UTF-8"?>
<GeocodeResponse>
  <status>OK</status>
  <result> <!-- (irrelevant content removed) -->
      <address_component>
          <long_name>London</long_name>
          <short_name>London</short_name>
          <type>locality</type>
          <type>political</type>
      </address_component>
      <!-- (irrelevant content removed) -->
     <address_component>
          <long_name>Ontario</long_name>
          <short_name>ON</short_name>
          <type>administrative_area_level_1</type>
          <type>political</type>
      </address_component>
      <address_component>
         <long_name>Canada</long_name>
         <short_name>CA</short_name>
         <type>country</type>
         <type>political</type>
      </address_component>
  </result>
</GeocodeResponse>

We want to extract some of the data above into simpler string results. We can do this using:

Result result = Result.fromContent(input, Result.XML);
String country = result.getAsString("/result/address_component[type='country']/long_name");
String region = result.getAsString("/result/address_component[type='administrative_area_level_1']/long_name");
String city = result.getAsString("/result/address_component[type='locality']/long_name");

440

If  you  are  at  all  familiar  with  processing  responses  from  webservices,  you  will  notice  that  what

would normally require several lines of code of selecting and testing nodes in regular java can now

be done in a single line using the new path expressions.

In the code above, input can be any of:

• InputStream directly from ConnectionRequest.readResponse(java.io.InputStream).

• XML or JSON document in the form of a {@code String}</li>

• XML  DOM  Element  [https://www.codenameone.com/javadoc/com/codename1/xml/Element.html]  returned

from XMLParser [https://www.codenameone.com/javadoc/com/codename1/xml/XMLParser.html]

• JSON  DOM  Map  returned  from  JSONParser  [https://www.codenameone.com/javadoc/com/codename1/io/

JSONParser.html]

To  use  the  expression  processor  when  calling  a  webservice,  you  could  use  something  like  the

following to parse JSON (notice this is interchangeable between JSON and XML):

Form hi = new Form("Location", new BoxLayout(BoxLayout.Y_AXIS));
hi.add("Pinpointing Location");
Display.getInstance().callSerially(() -> {
    Location l = Display.getInstance().getLocationManager().getCurrentLocationSync();
    ConnectionRequest request = new ConnectionRequest("http://maps.googleapis.com/maps/api/geocode/json", false) {
        private String country;
        private String region;
        private String city;
        private String json;

        @Override
        protected void readResponse(InputStream input) throws IOException {
                Result result = Result.fromContent(input, Result.JSON);
                country = result.getAsString("/results/address_components[types='country']/long_name");
                region =
result.getAsString("/results/address_components[types='administrative_area_level_1']/long_name");
                city = result.getAsString("/results/address_components[types='locality']/long_name");
                json = result.toString();
        }

        @Override
        protected void postResponse() {
            hi.removeAll();
            hi.add(country);
            hi.add(region);
            hi.add(city);
            hi.add(new SpanLabel(json));
            hi.revalidate();
        }
    };
    request.setContentType("application/json");
    request.addRequestHeader("Accept", "application/json");
    request.addArgument("sensor", "true");
    request.addArgument("latlng", l.getLatitude() + "," + l.getLongitude());

    NetworkManager.getInstance().addToQueue(request);
});
hi.show();
[source,java]

The returned JSON looks something like this (notice it’s snipped because the data is too long):

441

{
  "status": "OK",
  "results": [
    {
      "place_id": "ChIJJ5T9-iFawokRTPGaOginEO4",
      "formatted_address": "280 Broadway, New York, NY 10007, USA",
      "address_components": [
        {
          "short_name": "280",
          "types": ["street_number"],
          "long_name": "280"
        },
        {
          "short_name": "Broadway",
          "types": ["route"],
          "long_name": "Broadway"
        },
        {
          "short_name": "Lower Manhattan",
          "types": [
            "neighborhood",
            "political"
          ],
          "long_name": "Lower Manhattan"
        },
        {
          "short_name": "Manhattan",
          "types": [
            "sublocality_level_1",
            "sublocality",
            "political"
          ],
          "long_name": "Manhattan"
        },
        {
          "short_name": "New York",
          "types": [
            "locality",
            "political"
          ],
          "long_name": "New York"
        },
        {
          "short_name": "New York County",
          "types": [
            "administrative_area_level_2",
            "political"
          ],
          "long_name": "New York County"
        },

442

        {
          "short_name": "NY",
          "types": [
            "administrative_area_level_1",
            "political"
          ],
          "long_name": "New York"
        },
        {
          "short_name": "US",
          "types": [
            "country",
            "political"
          ],
          "long_name": "United States"
        },
        {
          "short_name": "10007",
          "types": ["postal_code"],
          "long_name": "10007"
        },
        {
          "short_name": "1868",
          "types": ["postal_code_suffix"],
          "long_name": "1868"
        }
      ],
      "types": ["street_address"],
      "geometry": {
        "viewport": {
          "northeast": {
            "lng": -74.0044642197085,
            "lat": 40.7156470802915
          },
          "southwest": {
            "lng": -74.0071621802915,
            "lat": 40.7129491197085
          }
        },
        "location_type": "ROOFTOP",
        "location": {
          "lng": -74.00581319999999,
          "lat": 40.7142981
        }
      }
    }
    /* SNIPED the rest */
  ]
}

443

Figure 363. Running the geocode sample above in the simulator

The XML processor currently handles global selections by using a double slash anywhere within the

expression, for example:

// get all address_component names anywhere in the document with a type "political"
String array[] = result.getAsStringArray("//address_component[type='political']/long_name");

// get all types anywhere under the second result (dimension is 0-based)
String array[] = result.getAsStringArray("/result[1]//type");



Notice that Google’s JSON webservice uses plural form for each of the node names

in  that  API  (ie.  results,  address_components,  and  types)  where  they  don’t  in  the

XML services (ie result, address_component etc.)

Second Example

It also possible to do some more complex expressions. We’ll use the following XML fragment for the

next batch of examples:

444

<rankings type="aus" gender="male" date="2011-12-31">
    <player id="1036" coretennisid="6752" rank="1"
       delta="0" singlespoints="485000" doublespoints="675"
       deductedpoints="0" totalpoints="485675">
        <firstname>Bernard</firstname>
        <lastname>Tomic</lastname>
        <town>SOUTHPORT</town>
        <state>QLD</state>
        <dob>1992-10-21</dob>
    </player>
    <player id="2585" coretennisid="1500" rank="2"
       delta="0" singlespoints="313500" doublespoints="12630"
       deductedpoints="0" totalpoints="326130">
        <firstname>Mathew</firstname>
        <lastname>Ebden</lastname>
        <town>CHURCHLANDS</town>
        <state>WA</state>
        <dob>1987-11-26</dob>
    </player>
    <player id="6457" coretennisid="287" rank="3"
        delta="0" singlespoints="132500" doublespoints="1500"
        deductedpoints="0" totalpoints="134000">
       <firstname>Lleyton</firstname>
       <lastname>Hewitt</lastname>
       <town>EXETER</town>
       <state>SA</state>
       <dob>1981-02-24</dob>
    </player>
    <!-- ... etc ... -->
</rankings>

Above,  if  you  want  to  select  the  IDs  of  all  players  that  are  ranked  in  the  top  2,  you  can  use  an

expression like:

int top2[] = result.getAsIntegerArray("//player[@rank < 3]/@id");



Notice above that the expression is using an attribute for selecting both rank and

id. In JSON documents, if you attempt to select an attribute, it will look for a child

node under the attribute name you ask for)

If a document is ordered, you might want to select nodes by their position, for example:

String first2[] = result.getAsStringArray("//player[position() < 3]/firstname");

String secondLast = result.getAsString("//player[last() - 1]/firstName");

It is also possible to select parent nodes, by using the ‘..’ expression. For example:

445

int id = result.getAsInteger("//lastname[text()='Hewitt']/../@id");

Above, we globally find a lastname element with a value of ‘Hewitt’, then grab the parent node of

lastname  which  happens  to  be  the  player  node,  then  grab  the  id  attribute  from  the  player  node.

Alternatively, you could get the same result from the following simpler statement:

int id = result.getAsInteger("//player[lastname='Hewitt']/@id");

It is also possible to nest expressions, for example:

String id=result.getAsInteger("//player[//address[country/isocode='CA']]/@id");

In the above example, if the player node had an address object, we’d be selecting all players from

Canada.  This  is  a  simple  example  of  a  nested  expression,  but  they  can  get  much  more  complex,

which will be required as the documents themselves get more complex.

Moving on, to select a node based on the existence of an attribute:

int id[] = result.getAsIntegerArray("//player[@rank]/@id");

Above, we selected the IDs of all ranked players. Conversely, we can select the non-ranked players

like this:

int id[] = result.getAsIntegerArray("//player[@rank=null]/@id");

 Logical not (!) operators currently are not implemented)

You can also select by the existence of a child node

int id[] = result.getAsIntegerArray("//player[middlename]/@id");

Above, we selected all players that have a middle name.<br/> Keep in mind that the Codename One

path expression language is not a full implementation of XPath 1.0, but does already handle many

of the most useful features of the specification.

Properties Files

Properties  [https://www.codenameone.com/javadoc/com/codename1/io/Properties.html]  files  are  standard

key/value pairs encoded into a text file. This file format is very familiar to Java developers and the

Codename One specific version tries to be as close as possible to the original Java implementation.

Notice  that  properties  file  both  in  Java  proper  and  in  Codename  One  don’t  support  non-ascii

characters.  In  order  to  encode  unicode  values  into  the  properties  file  format  you  should  use  the
native2ascii tool that ships with the JDK.

446

One  major  difference  between  standard  Java  properties  and  the  ones  in  Codename  One  is  that

Codename One sorts properties alphabetically when saving. Java uses random order based on the
Hashtable natural ordering.

This was done to provide consistency for saved files.

12.6. Debugging Network Connections

Figure 364. Debugging Network Connections

Codename  One  includes  a  Network  Monitor  tool  which  you  can  access  via  the  simulator  menu

option. This tool reflects all the requests made through the connection requests and displays them

in the left pane. This allows you to track issues in your code/web service and see everything the is

"going through the wire".

This is a remarkably useful tool for optimizing and for figuring out what exactly is happening with

your server connection logic.

12.6.1. Simpler Downloads

A very common task is file download to storage or filesystem.

The  Util  [https://www.codenameone.com/javadoc/com/codename1/io/Util.html]  class  has  simple  utility

methods:

downloadUrlToFileSystemInBackground, 
downloadUrlToStorage.

downloadUrlToStorageInBackground, 

downloadUrlToFile  &

These  all  delegate  to  a  feature  in  ConnectionRequest  [https://www.codenameone.com/javadoc/com/

codename1/io/ConnectionRequest.html]:

ConnectionRequest.setDestinationStorage(fileName) 
ConnectionRequest.setDestinationFile(fileName);

Both of which simplify the whole process of downloading a file.

Downloading Images

&

Codename  One  has  multiple  ways  to  download  an  image  and  the  general  recommendation  is  the

[https://www.codenameone.com/javadoc/com/codename1/ui/URLImage.html].  However, 

URLImage 
the
URLImage assumes that you know the size of the image in advance or that you are willing to resize it.
In that regard it works great for some use cases but not so much for others.

The  download  methods  mentioned  above  are  great  alternatives  but  they  are  a  bit  verbose  when
working with images and don’t provide fine grained control over the ConnectionRequest e.g. making

447

a POST request to get an image.



Adding  global  headers  is  another  use  case  but  you  can  use  addDefaultHeader

[https://www.codenameone.com/javadoc/com/codename1/io/NetworkManager.html#

addDefaultHeader-java.lang.String-java.lang.String-] to add those.

To make this process simpler there is a set of helper methods in ConnectionRequest that downloads

images 

directly 

[https://www.codenameone.com/javadoc/com/codename1/io/ConnectionRequest.html#

downloadImageToStorage-java.lang.String-com.codename1.util.SuccessCallback-].

These methods complement the Util methods but go a bit further and feature very terse syntax e.g.
you can just download a ConnectionRequest to Storage using code like this:

request.downloadImageToStorage(url, (img) -> theImageIsHereDoSomethingWithIt(img));

This 

effectively  maps 

ConnectionRequest 
[https://www.codenameone.com/javadoc/com/codename1/util/SuccessCallback.html] for further processing.

directly 

the 

SuccessCallback

to 

a 

URLImage Caching

URLImage is great. It changed the way we do some things in Codename One.

However,  when  we  introduced  it  we  didn’t  have  support  for  the  cache  filesystem  or  for  the
JavaScript port. The cache filesystem is probably the best place for images of URLImage so supporting
that as a target is a "no brainer" but JavaScript seems to work so why would it need a special case?

JavaScript already knows how to download and cache images from the web. URLImage is actually a
step back from the things a good browser can do so why not use the native abilities of the browser

when we are running there and fallback to using the cache filesystem if it’s available and as a last

resort go to storage…

That’s exactly what the new method of URLImage does:

public static Image createCachedImage(String imageName, String url, Image placeholder, int resizeRule);

There are a few important things you need to notice about this method:

• It returns Image and not URLImage. This is crucial. Down casting to `URLImage* will work on

the simulator but might fail in some platforms (e.g. JavaScript) so don’t do that!

Since  this  is  implemented  natively  in  JavaScript  we  need  a  different  abstraction  for  that

platform.

• It  doesn’t  support  image  adapters  and  instead  uses  a  simplified  resize  rule.  Image  adapters
work  on  URLImage  since  we  have  a  lot  of  control  in  that  class.  However,  in  the  browser  our
control is limited and so an adapter won’t work.

If you do use this approach it would be far more efficient when running in the JavaScript port and

will make better use of caching in most OS’s.

448

12.7. Rest API

The  Rest  API  makes  it  easy  to  invoke  a  restfull  webservice  without  many  of  the  nuances  of
ConnectionRequest. You can use it to define the HTTP method and start building based on that. So if I
want to get a parsed JSON result from a URL you could do:

Map<String, Object> jsonData = Rest.get(myUrl).getAsJsonMap();

For a lot of REST requests this will fail because we need to add an HTTP header indicating that we

accept JSON results. We have a special case support for that:

Map<String, Object> jsonData = Rest.get(myUrl).acceptJson().getAsJsonMap();

We can also do POST requests just as easily:

Map<String, Object> jsonData = Rest.post(myUrl).body(bodyValueAsString).getAsJsonMap();

Notice the usage of post and the body builder method. There are MANY methods in the builder class

that cover pretty much everything you would expect and then some when it comes to the needs of

rest services.

I  changed  the  code  in  the  kitchen  sink  webservice  sample  to  use  this  API.  I  was  able  to  make  it

shorter and more readable without sacrificing anything.

12.7.1. Rest in Practice - Twilio

The best way to explain the usage of this API is via a concrete "real world" example. Twilio provides

many  great  telephony  oriented  webservices  to  developers.  One  of  those  is  an  SMS  sending

webservice which can be useful for things such as "device activation".

To get started you would need to signup to Twilio [http://twillo.com/] and have the following 3 variable

values:

String accountSID = "----------------";
String authToken = "---------------";
String fromPhone = "your Twilio phone number here";



You  can  open  a  trial  Twilio  account  and  it  just  tags  all  of  your  SMS’s.  Notice  you

would need to use a US based number if you don’t want to pay

We can now send hello world as an SMS to the end user. Once this is in place sending an SMS via
REST is just a matter of using the Rest API:

449

Response<Map> result = Rest.post("https://api.twilio.com/2010-04-01/Accounts/" + accountSID + "/Messages.json").
        queryParam("To", destinationPhone).
        queryParam("From", fromPhone).
        queryParam("Body", "Hello World").
        basicAuth(accountSID, authToken)).
        getAsJsonMap();

Notice that this is equivalent of this "curl" command:

curl 'https://api.twilio.com/2010-04-01/Accounts/[accountSID]/Messages.json' -X POST \
--data-urlencode 'To=[destinationPhone]' \
--data-urlencode 'From=[fromPhone]' \
--data-urlencode 'Body=Hello World' \
-u [accountSID]:[AuthToken]

That’s pretty cool as the curl command maps almost directly to the Rest API call!

What we do here is actually pretty trivial, we open a connection the the api messages URL. We add

arguments to the body of the post request and define the basic authentication data.

The result is in JSON form we mostly ignore it since it isn’t that important but it might be useful for

error handling. This is a sample response (redacted keys):

{
    "sid": "[sid value]",
    "date_created": "Sat, 09 Sep 2017 19:47:30 +0000",
    "date_updated": "Sat, 09 Sep 2017 19:47:30 +0000",
    "date_sent": null,
    "account_sid": "[sid value]",
    "to": "[to phone number]",
    "from": "[from phone number]",
    "messaging_service_sid": null,
    "body": "Sent from your Twilio trial account - Hello World",
    "status": "queued",
    "num_segments": "1",
    "num_media": "0",
    "direction": "outbound-api",
    "api_version": "2010-04-01",
    "price": null,
    "price_unit": "USD",
    "error_code": null,
    "error_message": null,
    "uri": "/2010-04-01/Accounts/[sid value]/Messages/SMe802d86b9f2246989c7c66e74b2d84ef.json",
    "subresource_uris": {
        "media": "/2010-04-01/Accounts/[sid value]/Messages/[message value]/Media.json"
    }
}

Notice  the  error  message  entry  which  is  null  meaning  there  was  no  error,  if  there  was  an  error

we’d have a message there or an error code that isn’t in the 200-210 range.

450

This should display an error message to the user if there was a problem sending the SMS:

if(result.getResponseData() != null) {
    String error = (String)result.getResponseData().get("error_message");
    if(error != null) {
        ToastBar.showErrorMessage(error);
    }
} else {
    ToastBar.showErrorMessage("Error sending SMS: " + result.getResponseCode());
}

12.8. Webservice Wizard

The  Webservice  Wizard  can  be  invoked  directly  from  the  plugin.  It  generates  stubs  for  the  client

side that allow performing simple method invocations on the server. It also generates a servlet that

can be installed on any servlet container to intercept client side calls.

There are limits to the types of values that can be passed via the webservice wizard protocol but it

is  highly  efficient  since  it  is  a  binary  protocol  and  very  extensible  thru  object  externalization.  All

methods  are  provided  both  as  asynchronous  and  synchronous  calls  for  the  convenience  of  the

developer.

Figure 365. The first step in creating a client/server connection using the webservice wizard is to create a

web application

Figure 366. Any name will do

Normally  you  should  have  a  server  setup  locally.  I  use  Tomcat  since  it’s  really  trivial  and  I  don’t

really need much but there are many great Java webservers out there and this should work with all

of them!

451

Figure 367. Setup your webserver in the IDE

Figure 368. Configure the application server to the newly created app, notice the application context value

which we will use later

Figure 369. In the main Codename One project right click and select the WebService Wizard option

Figure 370. Set the package and class name for the webservice abstraction (notice this isn’t your main class

name) and then add the methods you want in the webservice

Figure 371. Add the methods and their arguments/return types. Once you finished adding all of those press

the "Generate" button

452



The  types  of  arguments  are  pretty  limited  however  you  can  pass  an  arbitrary
Externalizable object which can be "anything"

Figure 372. Pick the directory in the server project to which the source files will be generated by default this

is the src/java directory under the project we created in the first step

Figure 373. If you saved to the right location the server project directory should look like this

We can now open the GameOfThronesServiceServer.java file in the server and it looks like this:

public class GameOfThronesServiceServer {
    public static String[] getBookNames() {
        // your code goes here...
        return null;
    }

    public static String[] getBookPovCharacters(String bookName) {
        // your code goes here...
        return null;
    }
}

All  we  need  to  do  is  fill  in  the  code,  for  this  example  we’ll  only  implement  the  first  method  for

simplicity:

453

public class GameOfThronesServiceServer {
    public static String[] getBookNames() {
        return new String[] {
            "A Game of Thrones", "A Clash Of Kings", "A Storm Of Swords", "A Feast For Crows",
            "A Dance With Dragons", "The Winds of Winter", "A Dream of Spring"
        };
    }

    public static String[] getBookPovCharacters(String bookName) {
        // your code goes here...
        return null;
    }
}

Now lets open the client side code, in the GameOfThronesService.java file we see this

public class GameOfThronesService {
    private static final String DESTINATION_URL = "http://localhost:8080/cn1proxy";

//...
}

The destination URL needs to point at the actual server which you will recall from the new project

creation should include "HelloWebServiceWizard". So we can fix the URL to:

private static final String DESTINATION_URL = "http://localhost:8080/HelloWebServiceWizard/cn1proxy";

You would naturally need to update the host name of the server for running on a device otherwise

the device would need to reside within your internal network and point to your IP address.

It is now time to write the actual client code that calls this. Every method we defined above is now
defined  as  a  static  method  within  the  GameOfThronesService  class  with  two  permutations.  One  is  a
synchronous  permutation  that  behaves  exactly  as  expected.  It  blocks  the  calling  thread  while
calling the server and might throw an IOException if something failed.

This type of method (synchronous method) is very easy to work with since it’s completely legal to

call it from the event dispatch thread and it’s very easy to map it to application logic flow.

The  second  type  of  method  uses  the  async  JavaScript  style  callbacks  and  accepts  the  callback

interface.  It  returns  immediately  and  doesn’t  throw  any  exception.  It  will  call  onSuccess/onError

based on the server result.

You  can  pick  either  one  of  these  approaches  based  on  your  personal  preferences.  Here  we

demonstrate both uses with the server API:

454

Form hi = new Form("WebService Wizard", new BoxLayout(BoxLayout.Y_AXIS));
Button getNamesSync = new Button("Get Names - Sync");
Button getNamesASync = new Button("Get Names - ASync");
hi.add(getNamesSync).add(getNamesASync);

getNamesSync.addActionListener((e) -> {
    try {
        String[] books = GameOfThronesService.getBookNames();
        hi.add("--- SYNC");
        for(String b : books) {
            hi.add(b);
        }
        hi.revalidate();
    } catch(IOException err) {
        Log.e(err);
    }
});

getNamesASync.addActionListener((e) -> {
    GameOfThronesService.getBookNamesAsync(new Callback<String[]>() {
        @Override
        public void onSucess(String[] value) {
            hi.add("--- ASYNC");
            for(String b : value) {
                hi.add(b);
            }
            hi.revalidate();
        }

        @Override
        public void onError(Object sender, Throwable err, int errorCode, String errorMessage) {
            Log.e(err);
        }
    });
});

Figure 374. The final result of the WebService Wizard code

12.9. Connection Request Caching

Caching  server  data  locally  is  a  huge  part  of  the  advantage  a  native  app  has  over  a  web  app.

455

Normally this is non-trivial as it requires a delicate balance especially if you want to test the server

resource for changes.

HTTP provides two ways to do that the ETag [https://en.wikipedia.org/wiki/HTTP_ETag] and Last-Modified

[https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified].  While  both  are  great  they  are

non-trivial to use and by no definition seamless.

We  just  added  an  experimental  feature  to  connection  request  that  allows  you  to  set  the  caching

mode to one of 4 states either globally or per connection request:

• OFF is the default meaning no caching.

• SMART means all get requests are cached intelligently and caching is "mostly" seamless

• MANUAL means that the developer is responsible for the actual caching but the system will not

do a request on a resource that’s already "fresh"

• OFFLINE will fetch data from the cache and wont try to go to the server. It will generate a 404

error if data isn’t available

You  can  toggle  these  in  the  specific  request  by  using  setCacheMode(CachingMode)  and  set  the  global
default using setDefaultCacheMode(CachingMode).

 Caching only applies to GET operations, it will not work for POST or other methods

There are several methods of interest to keep an eye for:

protected InputStream getCachedData() throws IOException;
protected void cacheUnmodified() throws IOException;
public void purgeCache();
public static void purgeCacheDirectory() throws IOException;

12.9.1. getCachedData()

This  returns  the  cached  data.  This  is  invoked  to  implement  readResponse(InputStream)  when
running offline or when we detect that the local cache isn’t stale.

The smart mode implements this properly and will fetch the right data. However, the manual mode

doesn’t store the data and relies on you to do so. In that case you need to return the data you stored

at this point and must implement this method for manual mode.

12.9.2. cacheUnmodified()

This is a callback that’s invoked to indicate a cache hit, meaning that we already have the data.

The  default  implementation  still  tries  to  call  all  the  pieces  for  compatibility  (e.g.  readResponse).
However,  if  this  is  unnecessary  you  can  override  that  method  with  a  custom  implementation  or

even a blank implementation to block such a case.

456

12.9.3. purgeCache & purgeCacheDirectory

These methods are pretty self explanatory. Notice one caveat though…

When  you  download  a  file  or  a  storage  element  we  don’t  cache  them  and  rely  on  the  file/storage

element to be present and serve as "cache". When purging we won’t delete a file or storage element

you downloaded and thus these might remain.

However,  we  do  remove  the  ETag  and  Last-Modified  data  so  the  files  might  get  refreshed  the  next
time around.

12.10. Cached Data Service

The 

CachedDataService 

[https://www.codenameone.com/javadoc/com/codename1/io/services/

CachedDataService.html]  allows  caching  data  and  only  updating  it  if  the  data  changed  on  the  server.

Normally  the  download  API’s  won’t  check  for  update  if  there  is  a  local  cache  of  the  data  (e.g.
URLImage always uses the local copy). This isn’t a bad thing, it’s pretty efficient.

However, it might be important to update the image if it changed but we still want caching.

The  CachedDataService  will  fetch  data  if  it  isn’t  cached  locally  and  cache  it.  When  you  "refresh"  it
will send a special HTTP request that will only send back the data if it has been updated since the

last refresh:

CachedDataService.register();
CachedData d = (CachedData)Storage.getInstance().readObject("LocallyCachedData");

if(d == null) {
  d = new CachedData();
  d.setUrl("http://....");
}
// check if there is a new version of this on the server
CachedDataService.updateData(d, new ActionListener() {
    public void actionPerformed(ActionEvent ev) {
        // invoked when/if the data arrives, we now have a fresh cache
        Storage.getInstance().writeObject("LocallyCachedData", d);
    }
});

12.11. Externalizable Objects

Codename  One  provides  the  Externalizable  [https://www.codenameone.com/javadoc/com/codename1/io/
Externalizable.html] interface, which is similar to the Java SE Externalizable interface. This interface
allows an object to declare itself as Externalizable for serialization (so an object can be stored in a
file/storage or sent over the network). However, due to the lack of reflection and use of obfuscation

these  objects  must  be  registered  with  the  Util  [https://www.codenameone.com/javadoc/com/codename1/io/

Util.html] class.

457

Codename One doesn’t support the Java SE Serialization API due to the size issues and complexities

related to obfuscation.

The  major  objects  that  are  supported  by  default  in  the  Codename  One  Externalizable  are:  String,
Collection,  Map,  ArrayList,  HashMap,  Vector,  Hashtable,  Integer,  Double,  Float,  Byte,  Short,  Long,
Character, Boolean, Object[], byte[], int[], float[], long[], double[].

Externalizing an object such as h below should work just fine:

Map<String, Object> h = new HashMap<>();
h.put("Hi","World");
h.put("data", new byte[] {(byte)1});
Storage.getInstance().writeObject("Test", h);

However, notice that some things aren’t polymorphic e.g. if we will externalize a String[] we will
get back an Object[] since String arrays aren’t detected by the implementation.

 The externalization process caches objects so the app will seem to work and only

fail on restart!

Implementing the Externalizable interface is only important when we want to store a proprietary
object.  In  this  case  we  must  register  the  object  with  the  com.codename1.io.Util  class  so  the
externalization algorithm will be able to recognize it by name by invoking:

Util.register("MyClass", MyClass.class);

 You should do this early on in the app e.g. in the init(Object) but you shouldn’t do

it in a static initializer within the object as that might never be invoked!

An  Externalizable  object  must  have  a  default  public  constructor  and  must  implement  the
following 4 methods:

public int getVersion();
public void externalize(DataOutputStream out) throws IOException;
public void internalize(int version, DataInputStream in) throws IOException;
public String getObjectId();

The  getVersion()  method  returns  the  current  version  of  the  object  allowing  the  stored  data  to
change  its  structure  in  the  future  (the  version  is  then  passed  when  internalizing  the  object).  The
object id is a String uniquely representing the object; it usually corresponds to the class name (in
the example above the Unique Name should be MyClass).

458



It’s a common mistake to use getClass().getName() to implement getObjectId() and
it would seem to work in the simulator. This isn’t the case though!

Since devices obfuscate the class names this becomes a problem as data is stored

in a random name that changes with every release.

Developers need to write the data of the object in the externalize method using the methods in the

data output stream and read the data of the object in the internalize method e.g.:

public void externalize(DataOutputStream out) throws IOException {
    out.writeUTF(name);
    if(value != null) {
        out.writeBoolean(true);
        out.writeUTF(value);
    } else {
        out.writeBoolean(false);
    }
    if(domain != null) {
        out.writeBoolean(true);
        out.writeUTF(domain);
    } else {
        out.writeBoolean(false);
    }
    out.writeLong(expires);
}

public void internalize(int version, DataInputStream in) throws IOException {
    name = in.readUTF();
    if(in.readBoolean()) {
        value = in.readUTF();
    }
    if(in.readBoolean()) {
        domain = in.readUTF();
    }
    expires = in.readLong();
}

Since  strings  might  be  null  sometimes  we  also  included  convenience  methods  to  implement  such

externalization.  This  effectively  writes  a  boolean  before  writing  the  UTF  to  indicate  whether  the

string is null:

459

public void externalize(DataOutputStream out) throws IOException {
    Util.writeUTF(name, out);
    Util.writeUTF(value, out);
    Util.writeUTF(domain, out);
    out.writeLong(expires);
}

public void internalize(int version, DataInputStream in) throws IOException {
    name = Util.readUTF(in);
    value = Util.readUTF(in);
    domain = Util.readUTF(in);
    expires = in.readLong();
}

Assuming  we  added  a  new  date  field  to  the  object  we  can  do  the  following.  Notice  that  a  Date  is
really a long value in Java that can be null. For completeness the full class is presented below:

460

public class MyClass implements Externalizable {
    private static final int VERSION = 2;
    private String name;
    private String value;
    private String domain;
    private Date date;
    private long expires;

    public MyClass() {}

    public int getVersion() {
        return VERSION;
    }

    public String getObjectId() {
        return "MyClass";
    }

    public void externalize(DataOutputStream out) throws IOException {
        Util.writeUTF(name, out);
        Util.writeUTF(value, out);
        Util.writeUTF(domain, out);
        if(date != null) {
            out.writeBoolean(true);
            out.writeLong(date.getTime());
        } else {
            out.writeBoolean(false);
        }
        out.writeLong(expires);
    }

    public void internalize(int version, DataInputStream in) throws IOException {
        name = Util.readUTF(in);
        value = Util.readUTF(in);
        domain = Util.readUTF(in);
        if(version > 1) {
            boolean hasDate = in.readBoolean();
            if(hasDate) {
                date = new Date(in.readLong());
            }
        }
        expires = in.readLong();
    }
}

Notice  that  we  only  need  to  check  for  compatibility  during  the  reading  process  as  the  writing

process always writes the latest version of the data.

461

12.12. UI Bindings & Utilities

Codename  One  provides  several  tools  to  simplify  the  path  between  networking/IO  &  GUI.  A

common task of showing a wait dialog or progress indication while fetching network data can be

simplified  by  using 

the 

InfiniteProgress 

[https://www.codenameone.com/javadoc/com/codename1/

components/InfiniteProgress.html] class e.g.:

InfiniteProgress ip = new InfiniteProgress();
Dialog dlg = ip.showInifiniteBlocking();
request.setDisposeOnCompletion(dlg);

The process of showing a progress bar for a long IO operation such as downloading is automatically

mapped  to  the  IO  stream  in  Codename  One  using  the  SliderBridge  [https://www.codenameone.com/

javadoc/com/codename1/components/SliderBridge.html] class.



You  can  simulate  network  delays  and  disconnected  network  in  the  Simulator

menu

The SliderBridge class can bind a ConnectionRequest to a Slider and effectively indicate the progress
of the download. E.g.:

Form hi = new Form("Download Progress", new BorderLayout());
Slider progress = new Slider();
Button download = new Button("Download");
download.addActionListener((e) -> {
    ConnectionRequest cr = new ConnectionRequest("https://www.codenameone.com/img/blog/new_icon.png", false);
    SliderBridge.bindProgress(cr, progress);
    NetworkManager.getInstance().addToQueueAndWait(cr);
    if(cr.getResponseCode() == 200) {
        hi.add(BorderLayout.CENTER, new ScaleImageLabel(EncodedImage.create(cr.getResponseData())));
        hi.revalidate();
    }
});
hi.add(BorderLayout.SOUTH, progress).add(BorderLayout.NORTH, download);
hi.show();

Figure 375. SliderBridge progress for downloading the image in the slow network mode

462

12.13. Logging & Crash Protection

Codename One includes a Log [https://www.codenameone.com/javadoc/com/codename1/io/Log.html] API that
allows developers to just invoke Log.p(String) or Log.e(Throwable) to log information to storage.

As part of the premium cloud features it is possible to invoke Log.sendLog() in order to email a log

directly to the developer account. Codename One can do that seamlessly based on changes printed

into the log or based on exceptions that are uncaught or logged e.g.:

Log.setReportingLevel(Log.REPORTING_DEBUG);
DefaultCrashReporter.init(true, 2);

This code will send a log every 2 minutes to your email if anything was changed. You can place it

within the init(Object) method of your application.

For a production application you can use Log.REPORTING_PRODUCTION which will only email the log on
exception.

12.14. Sockets

At  this  moment  Codename  One  only  supports  TCP  sockets.  Server  socket  (listen/accept)  is  only

available on Android and the simulator but not on iOS.

You  can  check  if  Sockets  are  supported  using  the  Socket.isSupported().  You  can  test  for  server
socket support using Socket.isServerSocketSupported().

To  use  sockets  you  can  use  the  Socket.connect(String  host,  int  port,  SocketConnection
eventCallback) method.

To  listen  on  sockets  you  can  use  the  Socket.listen(int  port,  Class  scClass)  method  which  will
instantiate a SocketConnection instance (scClass is expected to be a subclass of SocketConnection) for
every incoming connection.

This simple example allows you to create a server and a client assuming the device supports both:

public class MyApplication {
    private Form current;

    public void init(Object context) {
        try {
            Resources theme = Resources.openLayered("/theme");
            UIManager.getInstance().setThemeProps(theme.getTheme(theme.getThemeResourceNames()[0]));
        } catch(IOException e){
            e.printStackTrace();
        }
    }

    public void start() {
        if(current != null){
            current.show();

463

            return;
        }
        final Form soc = new Form("Socket Test");
        Button btn = new Button("Create Server");
        Button connect = new Button("Connect");
        final TextField host = new TextField("127.0.0.1");
        btn.addActionListener((evt) -> {
            soc.addComponent(new Label("Listening: " + Socket.getIP()));
            soc.revalidate();
            Socket.listen(5557, SocketListenerCallback.class);
        });
        connect.addActionListener((evt) -> {
            Socket.connect(host.getText(), 5557, new SocketConnection() {
                @Override
                public void connectionError(int errorCode, String message) {
                    System.out.println("Error");
                }

                @Override
                public void connectionEstablished(InputStream is, OutputStream os) {
                    try {
                        int counter = 1;
                        while(isConnected()) {
                            os.write(("Hi: " + counter).getBytes());
                            counter++;
                            Thread.sleep(2000);
                        }
                    } catch(Exception err) {
                        err.printStackTrace();
                    }
                }
            });
        });
        soc.setLayout(new BoxLayout(BoxLayout.Y_AXIS));
        soc.addComponent(btn);
        soc.addComponent(connect);
        soc.addComponent(host);
        soc.show();
    }

    public static class SocketListenerCallback extends SocketConnection {
        private Label connectionLabel;

        @Override
        public void connectionError(int errorCode, String message) {
            System.out.println("Error");
        }

        private void updateLabel(final String t) {
            Display.getInstance().callSerially(new Runnable() {
                public void run() {
                    if(connectionLabel == null) {
                        connectionLabel = new Label(t);
                        Display.getInstance().getCurrent().addComponent(connectionLabel);
                    } else {
                        connectionLabel.setText(t);
                    }

464

                    Display.getInstance().getCurrent().revalidate();
                }
            });
        }

        @Override
        public void connectionEstablished(InputStream is, OutputStream os) {
            try {
                byte[] buffer = new byte[8192];
                while(isConnected()) {
                    int pending = is.available();
                    if(pending > 0) {
                        int size = is.read(buffer, 0, 8192);
                        if(size == -1) {
                            return;
                        }
                        if(size > 0) {
                            updateLabel(new String(buffer, 0, size));
                        }
                    } else {
                        Thread.sleep(50);
                    }
                }
            } catch(Exception err) {
                err.printStackTrace();
            }
        }
    }

    public void stop() {
        current = Display.getInstance().getCurrent();
    }

    public void destroy() {
    }
}

12.15. Properties

In  standard  Java  we  usually  have  a  POJO  (Plain  Old  Java  Object)  which  has  getters/setters  e.g.  we
can have a simple Meeting class like this:

465

public class Meeting {
     private Date when;
     private String subject;
     private int attendance;

     public Date getWhen() {
        return when;
    }

     public String getSubject() {
        return subject;
     }

     public int getAttendance() {
        return attendance;
     }

     public void setWhen(Date when) {
        this.when = when;
    }

     public void setSubject(String subject) {
        this.subject  = subject;
     }

     public void setAttendance(int attendance) {
        this.attendance = attendance;
     }
}

That’s a classic POJO and it is the force that underlies JavaBeans and quite a few tools in Java.

The  properties  are  effectively  the  getters/setters  e.g.  subject,  when  etc.  but  properties  have  several
features that are crucial:

• They can be manipulated in runtime by a tool that had no knowledge of them during compile

time

• They are observable - a tool can monitor changes to a value of a property

• They can have meta-data associated with them

These  features  are  crucial  since  properties  allow  us  all  kinds  of  magic  e.g.  hibernate/ORM  uses

properties to bind Java objects to a database representation, jaxb does it to parse XML directly into

Java objects and GUI builders use them to let us customize UI’s visually.

POJO’s  don’t  support  most  of  that  so  pretty  much  all  Java  based  tools  use  a  lot  of  reflection  &

bytecode manipulation. This works but has a lot of downsides e.g. say I want to map an object both

to the Database and to XML/JSON.

Would the bytecode manipulation collide?

466

Would it result in duplicate efforts?

And how do I write custom generic code that uses such abilities? Do I need to manipulate the VM?

12.15.1. Properties in Java

These are all very abstract ideas, lets look at how we think properties should look in Java and how

we can benefit from this moving forward.

This is the same class as the one above written with properties:

public class Meeting implements PropertyBusinessObject {
     public final Property<Date,Meeting> when = new Property<>("when");
     public final Property<String,Meeting> subject = new Property<>("subject");
     public final Property<Integer,Meeting>  attendance = new Property<>("attendance");
     private final PropertyIndex idx = new PropertyIndex(this, "Meeting", when, subject, attendance);

    @Override
    public PropertyIndex getPropertyIndex() {
        return idx;
    }
}

This looks a bit like a handful so let’s start with usage which might clarify a few things then dig into

the class itself.

When we used a POJO we did this:

Meeting meet = new Meeting();
meet.setSubject("My Subject");
Log.p(meet.getSubject());

With properties we do this:

Meeting meet = new Meeting();
meet.subject.set("My Subject");
Log.p(meet.subject.get());

Encapsulation

At first glance it looks like we just created public fields (which we did) but if you will look closely at
the declaration you will notice the final keyword:

public final Property<String,Meeting> subject = new Property<>("subject");

This means that this code will not compile:

467

meet.subject = otherValue;

So  all  setting/getting  must  happen  thru  the  set/get  methods  and  they  can  be  replaced.  E.g.  this  is

valid syntax that prevents setting the property to null and defaults it to an empty string:

public final Property<String,Meeting> subject = new Property<>("subject", "") {
     public Meeting set(String value) {
         if(value == null) {
            return Meeting.this;
         }
         return super.set(value);
     }
};

 We’ll discuss the reason for returning the Meeting instance below

Introspection & Observability

Since  Property  is  a  common  class  it’s  pretty  easy  for  introspective  code  to  manipulate  properties.
However, it can’t detect properties in an object without reflection.

That’s  why  we  have  the  index  object  and  the  PropertyBusinessObject  interface  (which  defines
getPropertyIndex).

The  PropertyIndex  class  provides  meta  data  for  the  surrounding  class  including  the  list  of  the
properties  within.  It  allows  enumerating  the  properties  and  iterating  over  them  making  them

accessible to all tools.

Furthermore all properties are observable with the property change listener. I can just write this to

instantly print out any change made to the property:

meet.subject.addChangeListener((p) -> Log.p("New property value is: " + p.get()));

12.15.2. The Cool Stuff

That’s the simple stuff that can be done with properties, but they can do much more!

For starters all the common methods of Object can be implemented with almost no code:

468

public class Meeting implements PropertyBusinessObject {
     public final Property<Date,Meeting> when = new Property<>("when");
     public final Property<String,Meeting> subject = new Property<>("subject");
     public final Property<Integer,Meeting>  attendance = new Property<>("attendance");
     private final PropertyIndex idx = new PropertyIndex(this, "Meeting", when, subject, attendance);

    @Override
    public PropertyIndex getPropertyIndex() {
        return idx;
    }

    public String toString() {
        return idx.toString();
    }

    @Override
    public boolean equals(Object obj) {
        return obj.getClass() == getClass() && idx.equals(((TodoTask)obj).getPropertyIndex());
    }

    @Override
    public int hashCode() {
        return idx.hashCode();
    }
}

This is easy thanks to introspection…

We already have some simple code that can convert an object to/from JSON Maps e.g. this can fill

the property values from parsed JSON:

meet.getPropertyIndex().populateFromMap(jsonParsedData);

And visa versa:

String jsonString = meet.toJSON();

We also have a very simple ORM solution that maps values to table columns and can create tables.

It’s no hibernate but sqlite isn’t exactly big iron so it might be good enough.

Constructors

One of the problematic issues with constructors is that any change starts propagating everywhere.

If I have fields in the constructor and I add a new field later I need to keep the old constructor for

compatibility.

So we added a new syntax:

469

Meeting meet = new Meeting().
        subject.set("My Subject").
        when.set(new Date());

That is why every property in the definition needed the Meeting generic and the set method returns
the Meeting instance…

We are pretty conflicted on this feature and are thinking about removing it.

Without this feature the code would look like this:

Meeting meet = new Meeting();
meet.subject.set("My Subject");
meet.when.set(new Date());

Seamless Serialization

Lets assume I have an object called Contacts which includes contact information of contact e.g.:

public class Contact implements PropertyBusinessObject {
    public final IntProperty<Contact> id  = new IntProperty<>("id");
    public final Property<String, Contact> name = new Property<>("name");
    public final Property<String, Contact> email = new Property<>("email");
    public final Property<String, Contact> phone = new Property<>("phone");
    public final Property<Date, Contact> dateOfBirth = new Property<>("dateOfBirth", Date.class);
    public final Property<String, Contact> gender  = new Property<>("gender");
    public final IntProperty<Contact> rank  = new IntProperty<>("rank");
    public final PropertyIndex idx = new PropertyIndex(this, "Contact", id, name, email, phone, dateOfBirth, gender,
rank);

    @Override
    public PropertyIndex getPropertyIndex() {
        return idx;
    }

    public Contact() {
        name.setLabel("Name");
        email.setLabel("E-Mail");
        phone.setLabel("Phone");
        dateOfBirth.setLabel("Date Of Birth");
        gender.setLabel("Gender");
        rank.setLabel("Rank");
    }
}

Standard  Java  Objects  can  be  serialized  in  Codename  One  by  implementing  the  Codename  One
Externalizable interface. You also need to register the Externalizable object so the implementation
will be aware of it. Codename One business objects are seamlessly Externalizable and you just need
to register them.

E.g. you can do something like this in your init(Object) method:

470

new Contact().getPropertyIndex().registerExternalizable();

After you do that once you can write/read contacts from storage if you so desire:

Storage.getInstance().writeObject("MyContact", contact);

Contact readContact = (Contact)Storage.getInstance().readObject("MyContact");

This will obviously also work for things like List<Contact> etc…

Seamless SQL Storage

Writing  SQL  code  can  be  tedious.  Which  is  why  SQLMap  is  such  an  important  API  for  some  of  us.
SQLMap allows CRUD (Create, Read, Update, Delete) operations on the builtin SQLite database using
property objects.

If  we  continue  the  example  from  above  to  show  persistence  to  the  SQL  database  we  can  just  do

something like this:

private Database db;
private SQLMap sm;
public void init(Object context) {
    theme = UIManager.initFirstTheme("/theme");
    Toolbar.setGlobalToolbar(true);
    Log.bindCrashProtection(true);

    try {
        Contact c = new Contact();
        db = Display.getInstance().openOrCreate("propertiesdemo.db"); ①
        sm = SQLMap.create(db); ②
        sm.setPrimaryKeyAutoIncrement(c, c.id); ③
        sm.createTable(c); ④
    } catch(IOException err) {
        Log.e(err);
    }
}

In the above code we do the following:

① Create or open an SQLite database using the standard syntax

② Create a properties binding instance

③ Define the primary key for contact as id and set it to auto increment which will give it a unique

value from the database

④ Call SQL’s createTable if the table doesn’t exist yet!

471



Notice  that  at  this  time  altering  a  created  table  isn’t  possible  so  if  you  add  a  new
property you might need to detect that and do an alter call manually

We can then add entries to the contact table using:

sm.insert(myContact);

We can update an entry using:

sm.update(myContact);

And delete an entry using:

sm.delete(myContact);

Listing the entries is more interesting:

List<PropertyBusinessObject> contacts = sm.select(c, c.name, true, 1000, 0);

for(PropertyBusinessObject cc : contacts) {
    Contact currentContact = (Contact)cc;

   // ...
}

The arguments for the select method are:

• The object type

• The attribute by which we want to sort the result (can be null)

• Whether sort is ascending

• Number of elements to fetch

• Page to start with - in this case if we have more than 1000 elements we can fetch the next page

using sm.select(c, c.name, true, 1000, 1)

There are many additional configurations where we can fine tune how a specific property maps to

a column etc.

What’s Still Missing

The  SQLMap  API  is  very  simplistic  and  doesn’t  try  to  be  Hibernate/JPA  for  mobile.  So  basic  things
aren’t  available  at  this  time  and  just  won’t  work.  This  isn’t  necessarily  a  problem  as  mobile

databases don’t need to be as powerful as server databases.

472

Relational Mappings/JOIN

Right now we can’t map an object to another object in the database with the typical one-many, one-
one  etc.  relationships  that  would  could  do  with  JPA.  The  SQLMap  API  is  really  simplistic  and  isn’t
suited for that level of mapping at this time.

If  there  is  demand  for  this  it’s  something  we  might  add  moving  forward  but  our  goal  isn’t  to  re-

invent hibernate.

Threading

SQLite is sensitive to threading issues especially on iOS. We mostly ignored the issue of threading

and issue all calls in process. This can be a problem for larger data sets as the calls would usually go

on the EDT.

This  is  something  we  might  want  to  fix  for  the  generic  SQLite  API  so  low  level  SQL  queries  will

work with our mapping in a sensible way.

Alter

Right now we don’t support table altering to support updated schemas. This is doable and shouldn’t

be too hard to implement correctly so if there is demand for doing it we’ll probably add support for

this.

Complex SQL/Transactions

We ignored functions, joins, transactions and a lot of other SQL capabilities.

You  can  use  SQL  directly  to  use  all  of  these  capabilities  e.g.  if  you  begin  a  transaction  before

inserting/updating  or  deleting  this  will  work  as  advertised  however  if  a  rollback  occurs  our

mapping will be unaware of that so you will need to re-fetch the data.

You will notice we mapped auto-increment so we will generally try to map things that make sense

for various use cases, if you have such a use case we’d appreciate pull requests and feedback on the

implementation.

Caching/Collision

As mentioned above, we don’t cache anything and there might be a collision if you select the same

object  twice  you  will  get  two  separate  instances  that  might  collide  if  you  update  both  (one  will

"win").

That  means  you  need  to  pay  attention  to  the  way  you  cache  objects  to  avoid  a  case  of  a  modified

version of an object kept with an older version.

Preferences Binding

Some  objects  make  sense  as  global  objects,  we  can  just  use  the  Preferences  API  to  store  that  data
directly but then we don’t have the type safety that property objects bring to the table. That’s where
the  binding  of  property  objects  to  preferences  makes  sense.  E.g.  say  we  have  a  global  Settings
property object we can just bind it to preferences using:

473

PreferencesObject.create(settingsInstance).bind();

So  if  settings  has  a  property  called  companyName  it  would  bind  into  Preferences  under  the
Settings.companyName entry.

We can do some more elaborate bindings such as:

PreferencesObject.create(settingsInstance).
    setPrefix("MySettings-").
    setName(settingsInstance.companyName, "company").
    bind();

This would customize all entry keys to start with MySettings- instead of Settings.. This would also
set  the  company  name  entry  to  company  so  in  this  case  instead  of  Settings.companyName  we’d  have
MySettings-company.

UI Binding

One of the bigger features of properties are their ability to bind UI to a property. E.g. if we continue
the sample above with the Contact class let’s say we have a text field on the form and we want the
property  (which  we  mapped  to  the  database)  to  have  the  value  of  the  text  field.  We  could  do

something like this:

myNameTextField.setText(myNameTextField.getText());
myNameTextField.addActionListener(e -> myContact.name.set(myNameTextField.getText()));

That would work nicely but what if we changed the property value, that wouldn’t be reflected back

into the text field?

Also that works nicely for text field but what about other types e.g. numbers, check boxes, pickers

etc. this becomes a bit more tedious with those.

Binding makes this all seamless. E.g. the code above can be written as:

UiBinding uib = new UiBinding();
uib.bind(myNameTextField, myContact.name);

The  cool  thing  is  that  this  works  with  multiple  component  types  and  property  types  almost

magically. Binding works by using an adapter class to convert the data to/from the component. The

adapter itself works with a generic converter e.g. this code:

uib.bind(myRankTextField, myContact.rank);

Seems similar to the one above but it takes a String that is returned by the text field and seamlessly

474

converts it to the integer needed by rank. This also works in the other direction…

We can easily build a UI that would allow us to edit the Contact property in memory:

Container resp = new Container(BoxLayout.y());
UiBinding uib = new UiBinding();

TextField nameTf = new TextField();
uib.bind(c.name, nameTf);
resp.add(c.name.getLabel()). ①
        add(nameTf);

TextField emailTf = new TextField();
emailTf.setConstraint(TextField.EMAILADDR);
uib.bind(c.email, emailTf);
resp.add(c.email.getLabel()).
        add(emailTf);

TextField phoneTf = new TextField();
phoneTf.setConstraint(TextField.PHONENUMBER);
uib.bind(c.phone, phoneTf);
resp.add(c.phone.getLabel()).
        add(phoneTf);

Picker dateOfBirth = new Picker();
dateOfBirth.setType(Display.PICKER_TYPE_DATE); ②
uib.bind(c.dateOfBirth, dateOfBirth);
resp.add(c.dateOfBirth.getLabel()).
        add(dateOfBirth);

ButtonGroup genderGroup = new ButtonGroup();
RadioButton male = RadioButton.createToggle("Male", genderGroup);
RadioButton female = RadioButton.createToggle("Female", genderGroup);
RadioButton undefined = RadioButton.createToggle("Undefined", genderGroup);
uib.bindGroup(c.gender, new String[] {"M", "F", "U"}, male, female, undefined); ③
resp.add(c.gender.getLabel()).
        add(GridLayout.encloseIn(3, male, female, undefined));

TextField rankTf = new TextField();
rankTf.setConstraint(TextField.NUMERIC);
uib.bind(c.rank, rankTf); ④
resp.add(c.rank.getLabel()).
        add(rankTf);

① Notice I use the label of the property which allows better encapsulation

② We can bind picker seamlessly

③ We can bind multiple radio buttons to a single property to allow the user to select the gender,
notice  that  labels  and  values  can  be  different  e.g.  "Male"  selection  will  translate  to  "M"  as  the

value

475

④ Numeric bindings "just work"

Figure 376. Properties form for the contact

Binding Object & Auto Commit

We  skipped  a  couple  of  fact  about  the  bind()  method.  It  has  an  additional  version  that  accepts  a
ComponentAdapter which allows you to adapt the binding to any custom 3rd party component. That’s
a bit advanced for now but I might discuss this later.

However,  the  big  thing  I  "skipped"  was  the  return  value…  bind  returns  a  UiBinding.Binding  object
when performing the bind. This object allows us to manipulate aspects of the binding specifically

unbind a component and also manipulate auto commit for a specific binding.

Auto  commit  determines  if  a  property  is  changed  instantly  or  on  commit.  This  is  useful  for  a  case
where we have an "OK" button and want the changes to the UI to update the properties only when

"OK"  is  pressed  (this  might  not  matter  if  you  keep  different  instances  of  the  object).  When  auto-
commit is on (the default which you can change via setAutoCommit in the UiBinding) changes reflect
instantly, when it’s off you need to explicitly call commit() or rollback() on the Binding class.

commit()  applies  the  changes  in  the  UI  to  the  properties,  rollback()  restores  the  UI  to  the  values
from the properties object (useful for a "reset changes" button).

Binding  also  includes  the  ability  to  "unbind"  this  is  important  if  you  have  a  global  object  that’s

bound  to  a  UI  that’s  discarded.  Binding  might  hold  a  hard  reference  to  the  UI  and  the  property

object might create a memory leak.

By using the disconnect() method in Binding we can separate the UI from the object and allow the
GC to cleanup.

UI Generation

Up until now this was pretty cool but if you looked at the UI construction code above you would see

that  it’s  pretty  full  of  boilerplate  code.  The  thing  about  boilerplate  is  that  it  shows  where

automation  can  be  applied,  that’s  the  exact  idea  behind  the  magical  "InstantUI"  class.  This  means

that the UI above can be generated using this code:

476

InstantUI iui = new InstantUI();
iui.excludeProperty(myContact.id); ①
iui.setMultiChoiceLabels(myContact.gender, "Male", "Female", "Undefined"); ②
iui.setMultiChoiceValues(myContact.gender, "M", "F", "U");
Container cnt = iui.createEditUI(myContact, true); ③

① The id property is useful for database storage but we want to exclude it from the UI

② This  implements  the  gender  toggle  button  selection,  we  provide  a  hint  to  the  UI  so  labels  and

values differ

③ We  create  the  UI  from  the  screenshot  above  with  one  line  and  it’s  seamlessly  bound  to  the

properties of myContact. The second argument indicates the "auto commit" status.

This  still  carries  most  of  the  flexibilities  of  the  regular  binding  e.g.  I  can  still  get  a  binding  object

using:

UiBinding.Binding b = iui.getBindings(cnt);

You might not have noticed this but in the previous vebose code we had lines like:

emailTf.setConstraint(TextField.EMAILADDR);

You  might  be  surprised  to  know  that  this  will  still  work  seamlessly  without  doing  anything,  as

would the picker component used to pick a date…

The picker component implicitly works for date type properties, numeric constraints and numbers

are implicitly used for number properties and check boxes are used for booleans.

But how do we know to use an email constraint for the email property?

We  have  some  special  case  defaults  for  some  common  property  names,  so  if  your  property  is

named email it will use an email constraint by default. If it’s named url or password etc. it will do

the  "right  thing"  unless  you  explicitly  state  otherwise.  You  can  customize  the  constraint  for  a

specific property using something like:

iui.setTextFieldConstraint(contact.email, TextArea.ANY);

This will override the defaults we have in place. The goal of this tool is to have sensible "magical"

defaults that "just work".

[9] Event Dispatch Thread

477

478

13. Push Notifications

This chapter discusses push support in Codename One applications. It covers how to set up push on

the  various  platforms,  how  to  respond  to  push  notifications  in  your  app,  and  how  to  send  push

notifications to your app.

 Push  notifications  require  a  Codename  One  Pro  account  or  higher.  You  must

notification 

receive 

push 

using

register 
Display.getInstance().registerPush();

your 

app 

to 



For  a  quick  reference  on  setting  up  Push  notifications,  check  out  the  Push

Cheatsheet [https://www.codenameone.com/files/push-cheatsheet.pdf].

13.1. Understanding Push Notifications

Push  notifications  provide  a  way  to  inform  users  that  something  of  interest  has  taken  place.  It  is

one of the few mechanisms available to interact with the user even when the app isn’t running. If

your app is registered to receive push notifications, then you can send messages to the user’s device

via REST API either from another device, or, as is usually the case, from a web server.

Messages may contain a short title and text body that will be displayed to the user in their device’s

messages stream. They may also specify a badge to display on the app’s icon (e.g. that red circle on

your mail app icon that indicates how many unread messages you have), a sound to play then the

message arrives, an image attachment, and a set of "actions" that the user can perform directly in

the push notification.

In addition to messages that the user sees, a push notification can contain non-visual information

that is silently sent to your app.

13.2. Implementing Push Support

Enabling  push  support  in  your  application  is  just  a  matter  of  implementing  the  PushCallback
interface  in  your  application’s  main  class  (i.e.  the  class  that  includes  your  start(),  init(),  etc…
methods.

479

public class MyApplication implements PushCallback {

    // ....

    /**
     * Invoked when the push notification occurs
     *
     * @param value the value of the push notification
     */
    public void push(String value) {
        System.out.println("Received push message: "+value);
    }

    /**
     * Invoked when push registration is complete to pass the device ID to the application.
     *
     * @param deviceId OS native push id you should not use this value and instead use <code>Push.getPushKey()</code>
     * @see Push#getPushKey()
     */
    public void registeredForPush(String deviceId) {
        System.out.println("The Push ID for this device is "+Push.getPushKey());
    }

    /**
     * Invoked to indicate an error occurred during registration for push notification
     * @param error descriptive error string
     * @param errorCode an error code
     */
    public void pushRegistrationError(String error, int errorCode) {
        System.out.println("An error occurred during push registration.");
    }
}

There will be additional steps required to deploy to each platform (e.g. iOS requires you to generate

push certificates, Android needs you to register your app ID with their cloud messaging platform,

etc…), but, fundamentally, this is all that is required to enable push support in your app.

13.3. The Push Lifecycle

Let’s take minute to go over the three callbacks in our application.

13.3.1. Registration

When your application first opens, it needs to register with the platform’s central cloud messaging

infrastructure. On Android this involves a call to their GCM/FCM server; on iOS, the call will be to

the APNS server, on Windows (UWP) the call will be to the WNS server. And so on. That server will

return a unique device ID that can be used to send push notifications to the device. This device ID
will then be passed to your registeredForPush() method as the deviceId parameter so that you can
save  it  somewhere.  Typically  you  would  send  this  value  to  your  own  web  service  so  that  you  can

use it to send notifications to the device later on. The device ID will generally not change unless you

uninstall and reinstall the app, but you will receive the callback every time the app starts.

480



The deviceId parameter cannot be used directly when sending push messages via
the Codename One push service. It needs to be prefixed with a platform identifier

so  the  that  push  server  knows  which  messaging  service  to  route  the  message

through. You can obtain the complete device ID, including the platform prefix, by
calling Push.getPushKey()

If  the  registration  failed  for  some  reason,  the  the  pushRegistrationError()  callback  will  be  fired
instead.

Notice that all of this happens seamlessly behind the scenes when your app loads. You don’t need to

initiate any of this workflow.

13.3.2. Sending a Push Notification

Codename  One  provides  a  secure  REST  API  for  sending  push  notifications.  As  an  HTTP  API,  it  is

language  agnostic.  You  can  send  push  notifications  to  your  app  using  Java,  PHP,  Python,  Ruby,  or

even by hand using something like curl. Each HTTP request can contain a push message and a list

of device IDs to which the message should be sent. You don’t need to worry about whether your app

is  running  on  Android,  iOS,  Windows,  or  the  web.  A  single  HTTP  request  can  send  a  message  to

many devices at once.

13.3.3. Receiving a Push Notification

There are two different scenarios to be aware of when it comes to receiving push notifications. If

your app is running in the foreground when the message arrives, then it will be passed directly to
your push() callback. If your app is either in the background, or not running, then the notification
will  be  displayed  in  your  device’s  notifications.  If  the  user  then  taps  the  notification,  it  will  open
your app, and the push() callback will be run with the contents of the message.

Some  push  message  types  include  hidden  content  that  will  not  be  displayed  in  your  device’s
notifications.  These  hidden  messages  (or  portions  of  messages)  are  passed  directly  to  the  push()
callback of your app for processing.

 On iOS, hidden push messages (push type 2) will not be delivered when the app is

in the background.



You  can  set  the  android.background_push_handling  build  hint  to  "true"  to  deliver
push  messages  on  Android  when  the  app  is  minimized  (running  in  the

background). There is no equivalent setting on other platforms currently.

13.4. Testing Push Support

The easiest way to test push notifications in your app is to use the push simulation feature of the

Codename One Simulator.

481

Figure 377. The "Push Simulation" menu item in the simulator opens the push simulator tool.

The  "Registered  Successfully"  button  will  trigger  your  app’s  registeredForPush()  method,  and  the
"Registration Error" button will trigger your app’s pushRegistrationError() method.

The "Send" button will trigger the push() callback with the message body that you place in the "Send
Message" field.

The "Push Type" drop-down allows you to select the "type" of the push message. This dictates how

the  message  body  (i.e.  the  contents  of  the  "Send  Message"  field)  is  interpreted.  Some  push  types

simply  pass  the  message  to  the  device  verbatim,  while  others  assume  that  the  message  contains

structure that is meant to be parsed by the client to extract such things as badges, sounds, images,

and  actions  that  are  associated  with  the  message.  We’ll  go  over  the  available  push  types  in  a

moment,  but  for  now,  we’ll  keep  it  simple  by  just  using  a  push  type  of  "1"  -  which  just  sends  the

message verbatim.

Figure 378. Sending a basic hello world push from the push simulator

Let’s  try  a  simple  "hello  world"  push  message.  Select  "1"  from  the  "Push  Type"  drop-down  menu,

and enter "Hello World" into the "Send Message" field as shown above. Then press "send".

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Assuming your push() method looks like:

public void push(String value) {
    System.out.println("Received push message: "+value);
}

You should see the following output in your console:

Received push message: Hello World

This experiment simulated a push notification while the app is running in the foreground. Now let’s

simulate the case where the app is not running, or running in the background. We can simulate this

by pausing the app. Return to the Codename One simulator window, and select "Pause App" from

the "Simulate" menu as shown below.

Figure 379. Pausing the app in the simulator so we can simulate push notifications while app is in the

background.

When the app is paused it will simply display a white screen in the simulator with the text "Paused"

in the middle.

Now return to the push simulator again, and press "Send" again with same values in the other fields
(Push type 1, and Message "Hello World"). Rather than running the push() callback this time, it will
display a popup dialog outside the app, as shown below.

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Figure 380. Push message causes a popup dialog in the simulator when the app is paused.

While  this  popup  dialog  doesn’t  replicate  what  a  push  notification  will  look  like  in  a  device’s

notifications stream when the app is closed, it does simulate the conceptual workflow. The process

whereby  the  user  is  notified  of  the  message  outside  of  the  app,  and  the  app  is  not  notified

until/unless the user taps on the notification.

If  you  monitor  the  console  for  your  app,  you  should  notice  that  the  push()  callback  hasn’t  been
called yet for this notification, but if you click "OK" in the dialog, your push() callback will be run.
Clicking OK is analogous to the user tapping on the notification. If you simply close the dialog box

(by clicking the "x" in the corner), this would be analogous to the user dismissing the notification. In
this case the push() callback would not be called at all.

13.5. Push Types and Message Structure

The  example  above  sends  a  simple  message  to  be  displayed  to  the  user.  Push  notifications  can

include more data than just an alert message, though. When the selected "push type" is 0 or 1, the

push  server  will  interpret  the  message  body  a  simple  alert  string.  Selecting  a  different  push  type

will affect how the message body is interpreted. The following push types are supported:

• 0, 1 - The default push types, they work everywhere and present the string as the push alert to

the user

• 2 - hidden, non-visual push. This won’t show any visual indicator on any OS!

In  Android  this  will  trigger  the  push(String)  call  with  the  message  body.  In  iOS  this  will  only

happen if the application is in the foreground otherwise the push will be lost

• 3 - 1 + 2 = 3 allows combining a visual push with a non-visual portion. Expects a message in the
form:  This  is  what  the  user  won’t  see;This  is  something  he  will  see.  E.g.  you  can  bundle  a
special  ID  or  even  a  JSON  string  in  the  hidden  part  while  including  a  friendly  message  in  the

visual part.

When active this will trigger the push(String) method twice, once with the visual and once with

the hidden data.

• 4 - Allows splitting a visual push request based on the format title;body to provide better visual

representation in some OS’s.

• 5 - Sends a regular push message but doesn’t play a sound when the push arrives

• 99 - The message body is expected to be XML, where the root element contains at least type and
body  attributes  which  correspond  to  one  of  the  other  push  push  types  and  message  body
respectively.  This  push  type  supports  additional  information  such  as  image  attachments  and
push actions. E.g. <push type="1" body="Hello World"/>

• 100 - Applicable only to iOS and Windows. Allows setting the numeric badge on the icon to the

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given number. The body of the message must be a number e.g. unread count.

• 101 - identical to 100 with an added message payload separated with a space. E.g. 30 You have 30
unread messages will set the badge to "30" and present the push notification text of "You have 30
unread messages". Supported on Android, iOS, and Windows.

The  following  sections  will  show  examples  of  the  various  kinds  of  pushes.  You  can  try  them  out

yourself by opening the push simulator.

13.5.1. Example Push Type 1

Push Type 1; Message Body: "Hello World"

Figure 381. Push type 1 "Hello World" message in simulator.

Figure 382. Push type 1 "Hello World" message in Android when app is in background.

Figure 383. Push type 1 "Hello World" message in iOS when app is in background.

Figure 384. Push type 1 "Hello World" message in Chrome desktop.

In all cases, if the user taps/clicks the notification, it will bring the app to the foreground and call
the push() callback with "Hello World" as the argument.

13.5.2. Example Push Type 2

Push Type 2; Message Body: "Hello World"

Push type 2 is a hidden push so it will behave differently on different platforms. On Android, the
push() callback will be fired even if the app is in the background. On iOS, it will simply be ignored if
the app is in the background.

If  the  app  is  in  the  foreground,  this  will  trigger  the  push()  callback  with  "Hello  World"  as  the
argument.

485



You  can  determine  the  the  type  of  push  that  has  been  received  in  your  push()
callback by calling Display.getInstance().getProperty("pushType"). This will return
case
a 
Display.getInstance().getProperty("pushType") will return "2".

String 

push 

type. 

this 

E.g. 

the 

in 

of 

13.5.3. Example Push Type 3

Push Type 3; Message Body Hello World;{"from":"Jim", "content":"Hello World"}

Push  type  3  combines  an  alert  message  with  some  hidden  content  that  the  user  won’t  see.  In  the

example above, the alert message is "Hello World" and the hidden content is a JSON string that will

be passed to our app to be parsed.

If the app is in the background, then the alert message will be posted to the user’s notifications. See

"Example Push Type 1" above as this message will be identical.

Figure 385. Push type 3 shows only the alert message (the portion before the first ";").

the 

This push will result in our push() callback being fired twice; once with the alert message, and once
with 
alert  message,
it 
Display.getInstance().getProperty("pushType")  will  report  a  type  of  "1".  When  it  is  fired  with  the
JSON hidden content, it will report a push type of "2".

content.  When 

fired  with 

hidden 

the 

is 

13.5.4. Example Push Type 4

Push Type 4; Message Body "Hello World;I’m just saying hello"

Push type 4 specifies a title and a message body. In this example, alert title will be "Hello World",

and the body will by "I’m just saying hello".

Figure 386. Push type 4 "Hello World" message in simulator.

Figure 387. Push type 4 "Hello World" message in Android when app is in background.

Figure 388. Push type 4 "Hello World" message in iOS when app is in background.

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Figure 389. Push type 4 "Hello World" message in Firefox desktop.

With this push type, the push() callback will be fired only if the user taps/opens the notification, and
the argument will contain the entire message ("Title;Body").



On  some  platforms,  the  argument  of  the  push()  callback  will  only  include  the
"body"  portion  of  the  payload,  and  in  other  platforms  it  will  include  the  full

"Title;Body" payload.

13.5.5. Example Push Type 5

Push Type 5; Message Body "Hello World"

Push  type  5  will  behave  identically  to  push  type  1,  except  that  the  notification  won’t  make  any
sound on the device. On some platforms, Display.getInstance().getProperty("pushType") will report
a push type of "1", when it receives a push of type 5.

13.5.6. Example Push Type 100

Push Type 100; Message Body "5"

Push  type  100  just  expects  an  integer  in  the  message  body.  This  is  interpreted  as  the  badge  that

should be set on the app. This is currently only supported on Windows and iOS.

Figure 390. Push type 100 on iOS, setting the badge to "5"

Push type 100 should not trigger the push() callback.

13.5.7. Example Push Type 101

Push Type 101; Message Body "5 Hello World"

Push type 101 combines a badge with an alert message. The badge number should be the first thing

in the payload, followed by a space, and the remainder is the alert message.

On platforms that do not support badges, Push type 101 will behave exactly as push type 1, except

that the badge prefix will be stripped from the message.

487

push() 

The 
Display.getInstance().getProperty("pushType") will return "1" for this type.

callback  will  be 

the  user 

called 

only 

if 

taps 

the  notification.

Badging on iOS

The  badge  number  can  be  set  thru  code  as  well,  this  is  useful  if  you  want  the  badge  to

represent the unread count within your application.

To  do  this  we  have  two  methods  in  the  Display  [https://www.codenameone.com/javadoc/com/
codename1/ui/Display.html] class: isBadgingSupported() and setBadgeNumber(int). Notice that even
if isBadgingSupported will return true, it will not work unless you activate push support!

To truly utilize this you might need to disable the clearing of the badges on startup which you
can do with the build hint ios.enableBadgeClear=false.

13.6. Rich Push Notifications

Rich  push  notifications  refer  to  push  notifications  that  include  functionality  above  and  beyond

simply  displaying  an  alert  message  to  the  user.  Codename  One’s  support  for  rich  notifications

includes image attachments and push actions.

13.6.1. Image Attachment Support

When  you  attach  an  image  to  a  push  notification,  it  will  appear  as  a  large  image  in  the  push

notification  on  the  user’s  device  if  that  device  supports  it.  iOS  supports  image  attachments  in  iOS

10,  Android  supports  them  in  API  26.  The  Javascript  port,  and  Windows  (UWP)  port  do  not

currently  support  image  attachments.  If  a  platform  that  doesn’t  support  image  attachments

receives a push notification with an image attachment, it will just ignore it.

Push  type  "99"  is  used  to  send  rich  push  notifications.  It  is  sort  of  a  "meta"  push  type,  or  a

"container", as it can be used to send any of the other push types, but to attach additional content,

such as image attachments.

The  message  body  should  be  an  XML  string.  A  minimal  example  of  a  push  type  99  that  actually

sends a push type 1, which message "Hello World", but with an attached image is:

<push type="1" body="Hello World"><img src="https://exmaple.com/myimage.jpg"/></push>

 The  image  URL  must  be  a  secure  URL  (i.e.  start  with  "https:"  and  not  "http:",

otherwise, iOS will simply ignore it.

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Figure 391. Push type 99 with attached image in simulator.

Figure 392. Push type 99 with attached image in Android when app is in background.

489

Figure 393. Push type 99 with attached image in iOS when app is in background.



The  image  will  only  be  shown  if  you  press  and  pull  down  on  the  notification.

When the notification initially appears in the user’s notifications it will appear like

a normal alert - but possibly with the image shown as a small thumbnail.

push() 

The 
its 
Display.getInstance().getProperty("pushType") will return "1" in this example.

"Hello  World" 

callback  will 

receive 

as 

argument 

and

can 

You 
com.codename1.push.PushContent class, as follows:

additional 

information 

access 

about 

the 

push 

content 

using 

the

public void push(String message) {
    PushContent content = PushContent.get();
    if (content != null) {
        String imageUrl = content.getImageUrl();
            // The image attachment URL in the push notification
            // or `null` if there was no image attachment.
    }
}



Make  sure  to  only  call  PushContent.get()  once  inside  your  push()  callback,  and
store the return value. PushContent.get() works like a queue of size=1, and it pops
off the item from the front of the queue when it is called. If you call it twice, the
second time will return null.

13.6.2. Notification Actions

When you include actions in a push notification, the user will be presented with buttons as part of

the notification on supported platforms. E.g. if the notification is intended to invite the user to an

490

event, you might want to include buttons/actions like "Attending", "Not Attending", "Maybe", so that

the user can respond quickly to the notification and not necessarily have to open your app.

You can determine whether the user has pressed a particular button on the notification using the
`PushContent.getActionId()` method inside your `push()` callback.

How it works

Your  app  defines  which  action  categories  it  supports,  and  associates  a  set  of  actions  with  each

category.  If  a  push  notification  includes  a  "category"  attribute,  then  the  notification  will  be

presented with the associated actions manifested as buttons.

Defining the Categories and Actions

You  can  specify  the  available  categories  and  actions  for  your  app  by  implementing  the
com.codename1.push.PushActionsProvider interface in your app’s main class.

E.g.

import com.codename1.push.PushAction;
import com.codename1.push.PushActionCategory;
import com.codename1.push.PushActionsProvider;
...

public class MyApplication implements PushCallback, PushActionsProvider {

    ...

    @Override
    public PushActionCategory[] getPushActionCategories() {
        return new PushActionCategory[]{
            new PushActionCategory("invite", new PushAction[]{
                new PushAction("yes", "Yes"),
                new PushAction("no", "No"),
                new PushAction("maybe", "Maybe")
            })

        };
    }
}

In  the  above  example,  we  create  only  a  single  category,  "invite"  that  has  actions  "yes",  "no",  and

"maybe".

Sending a Push Notification with "invite" Category

Now we can test our new category. In the push simulator, you can select Push Type "99", with the

message body:

491

<push type="1" body="Would you like to come to a party?" category="invite"/>

Figure 394. Push notification with "invite" category on the simulator will show dialog with buttons to select

between the actions defined in the "invite" category.

Figure 395. Push notification with "invite" category on the android will show dialog with buttons to select

between the actions defined in the "invite" category.

Figure 396. Push notification with "invite" category on the android will show dialog with buttons to select

between the actions defined in the "invite" category.

Figure 397. Push notification with "invite" category on the Chrome desktop includes a "More" dropdown

where user can select the action.

The push() callback will be fired after the user taps on the notification, or one of its actions. If the

492

user taps the notification itself, and not one of the actions, then your PushContent.getActionId() will
return  null.  If  they  selected  one  of  the  actions,  then  the  action  ID  of  that  action  can  be  obtained
from getActionId().

The  category  of  the  notification  will  be  made  available  via  the  getCategory()  method  of
PushContent.

E.g.

public void push(String message) {
    PushContent content = PushContent.get();
    if (content != null) {
        if ("invite".equals(content.getCategory())) {
            if (content.getActionId() != null) {
                System.out.println("The user selected the "+content.getActionid()+" action");
            } else {
                System.out.println("The user clicked on the invite notification, but didn't select an action.");
            }
        }
    }
}

13.7. Deploying Push-Enabled Apps to Device

So,  you’ve  implemented  the  Push  callback  in  your  app,  and  tested  it  in  the  push  simulator  and  it

works. If you try to deploy your app to a device, you may be disappointed to discover that your app

doesn’t seem to be receiving push notifications when installed on the device. This is because each

platform has its own bureaucracy and hoops that you have to jump through before they will deliver

notifications to your app. Read on to find out how to satisfy their requirements.

13.7.1. The Push Bureaucracy - Android



To  set  the  push  icon  place  a  24x24  icon  named  ic_stat_notify.png  under  the
native/android folder of the app. The icon can be white with transparency areas

Android Push goes thru Google servers and to do that we need to register with Google to get keys

for server usage. Google uses Firebase for its cloud messaging, so we’ll begin by creating a Firebase

project.

Go to https://console.firebase.google.com/ and click Add project:

493

Figure 398. Click "Add project"

This will open a form as shown here:

Figure 399. Enter project name

Enter the project name, select your country, read/accept their terms, and press "Create Project".

Once  the  project  has  been  created  (should  take  only  a  few  seconds),  you’ll  be  sent  to  your  new

project’s dashboard.

Figure 400. Firebase Project Dashboard

Expand the "Grow" section of the left menu bar, then click on the "Cloud Messaging" link.

494

Figure 401. Expand "Grow" Section and select "Cloud Messaging"

On the next screen, click on the Android icon where is says "Add an app to get started".

Figure 402. Click on the "Android" icon to add an Android App to the project

This  will  bring  us  to  the  "Add  Application  Form",  which  visually  shows  us  the  remainder  of  the

steps.

Fill  in  the  Android  package  name  with  the  package  name  of  your  project,  and  the  app  nickname

with your app’s name.

The  Debug  signing  certificate  SHA-1  is  optional,  but  you  can  paste  the  SHA-1  from  your  app’s

certificate here if you like.

Figure 403. Fill in the package name

Press "Register app" once you have filled in the required fields.

This will expand "Step 2" of this form: "Download config file".

495

Figure 404. Download the google-services.json file

All we need to do here is press the "Download google-services.json" file, then copy the file into your

project’s native/android directory.

Firebase  console  directs  you  to  copy  the  google-services.json  file  into  the  "app"



directory of your project. Ignore this direction as it only applies for Android studio

projects. For Codename One, this file goes into the native/android directory of your

project.

There is one last piece of information that we need so that we can send push notifications to our
app: The FCM_SERVER_API_KEY value.

Go to your project dashboard in Firebase console. Then click the "Settings" menu (the "Gear" icon

next to "Project Overview" in the upper left):

Figure 405. Select "Project settings"

Then select the "Cloud Messaging" tab.

The  "Server  Key"  displayed  here  is  the  FCM_SERVER_API_KEY  that  we  refer  to  throughout  this
document.  It  will  be  used  to  send  push  notifications  to  your  app  from  a  server,  or  from  another

device.  You  can  copy  and  paste  this  value  now,  or  you  can  retrieve  it  later  by  logging  into  the

Firebase console.

Figure 406. Save the Server key for later use.



The Sender ID shown in the above is not required for our Android app, however it

it is helpful/required to support Push notifications in Javascript builds (in Chrome).
This value is referred to elsewhere in this document as GCM_SENDER_ID.

13.7.2. The Push Bureaucracy - iOS

Push  on  iOS  is  much  harder  to  handle  than  the  Android  version,  however  we  simplified  this

496

significantly with the certificate wizard.

iOS push needs two additional P12 certificates.



Please notice that these are NOT the signing certificates!

They are completely different certificates that have nothing to do with the build

process!

The  certificate  wizard  can  generate  these  additional  push  certificates  and  do  quite  a  few  other

things if you just check this flag in the end of the wizard:

Figure 407. Enable Push in the certificate wizard

 If  you  already  have  signing  certificated  defined  for  your  app  just  skip  the

certificate generation phase (answer no) the rest will work as usual.

You can then install the push certificates locally and use them later on but there is an easier way.

You  need  to  host  the  push  certificates  in  the  cloud  so  they  will  be  reachable  by  the  push  servers,

Codename One that for you seamlessly.

Once  you  go  thru  the  wizard  you  should  get  an  automated  email  containing  information  about

push and the location of the push certificates, it should start like this:

iOS Push certificates have been created for your app with bundle ID com.mycompany.myapp.mypushdemo.  Please file this
email away for safe keeping as you will need the details about the certificate locations and passwords to use Push
successfully in your apps.

Development Push Certificate URL:
https://codename-one-push-
certificates.s3.amazonaws.com/com.mycompany.myapp.mypushdemo_DevelopmentPush_LONG_UNIQUE_KEY.p12

Development Push Certificate Password: ssDfdsfer324

Production Push Certificate URL:
https://codename-one-push-certificates.s3.amazonaws.com/com.mycompany.myapp.mypushdemo_ProductionPush_LONG_UNIQUE_KEY.p12

Production Push Certificate Password: ssDfdsfer324

The  URL’s  and  passwords  are  everything  that  you  will  need  later  on  to  get  push  working  on  iOS.

497

Notice that the wizard also performs a couple of other tasks specifically it sets the ios.includePush
build hint to true & adds push to the provisioning profile etc.

You  can  read  more  about  the  certificate  wizard  in  the  signing  section  [https://www.codenameone.com/

manual/signing.html].

13.7.3. The Push Bureaucracy - UWP (Windows 10)

Push on UWP requires only that you register your app in the Windows Store Dashboard. You will

then be provided with credentials (Package Security Identifier (SID) and a secret key) that you can

use  to  send  push  notifications  to  your  app.  To  begin  this  process,  go  to  the  Windows  Dev  Center

[https://developer.microsoft.com/en-us/windows] and select "Dashboard".

You  can  read  more  about 

the  registering  your  app 

in 

the  Windows  store  here

[https://www.codenameone.com/manual/appendix-uwp.html#building-for-the-windows-store].

Once you have registered your app in the Windows Store, and completed the corresponding setup

in Codename One settings (e.g. generated a certificate), you should proceed to configure your app

for push notifications.

Navigate  to  the  App  overview  page  for  your  app  inside  the  Windows  store  dashboard.  Under  the

"Services" menu (left side), select "Push notifications".

Figure 408. Push notifications menu item in Windows Store dashboard

Then, select the "WNS/MPNS" option that appears in the left menu under "Push notifications"

Figure 409. WNS menu item in Windows Store dashboard

This will bring you to a page with information about WNS push notifications. You’ll be interested in

the paragraph shown here:

Figure 410. Live services link

Click on the "Live Services Site" link.

You’ll be prompted to log in using your Windows Store account. Then you’ll be taken to a page that

contains  the  push  credentials  that  you  can  use  for  sending  push  messages  to  your  app.  You’ll  be

interested in two values:

Package SID. (It will be of the form "ms-app://XXXXXXXXXXX…")

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Figure 411. WNS Package SID

Client Secret. This will be listed in a section called "Application Secrets"

Figure 412. WNS Client secret

You will use these two values for sending push notifications to your app.

Microsoft  provides  full  instructions  on  setting  up  WNS  notifications  here  [https://msdn.microsoft.com/

library/windows/apps/hh465407]  but  much  of  this  is  not  relevant  for  Codename  One  apps.  For

Codename One apps, one need only obtain Package Security ID and client secret values for the app.

13.7.4. The Push Bureaucracy - Javascript

Codename  One  apps  support  push  in  browsers  that  implement  the  Web  Push  API.  At  time  of

writing, this list includes:

• Firefox (Version 50)

• Chrome (Version 49)

• Opera (Version 42)

• Chrome for Android (Version 56)

• MS Edge

Firefox doesn’t require any special setup for Push. If your main class implements the PushCallback
interface, it should just work.

Chrome uses FCM for its push notifications - the same system that Android uses. The directions for
setting up a FCM account are the same as provided here, and you can reuse the same GCM_SENDER_ID
and FCM_API_SERVER_KEY values. For Chrome push support you will need to add the GCM_SENDER_ID in
the gcm.sender_id build hint so that the GCM_SENDER_ID will be added to the app’s manifest file:

gcm.sender_id=GCM_SENDER_ID

Where GCM_SENDER_ID is your GCM_SENDER_ID.



Push  support  requires  that  your  app  be  served  over  https  with  a  valid  SSL

certificate. It will not work with the "preview" version of your app. You’ll need to

download the .zip or .war file and host the file on your own site - with a valid SSL

certificate.

499

13.8. Sending Push Messages

You can send a push message in many ways e.g. from another device or any type of server but there

are some values that you will need regardless of the way in which you send the push message.

private static final String PUSH_TOKEN = "********-****-****-****-*************";

The push token is a unique "key" that you can use to send push thru your Codename One account. It

allows  you  to  send  push  messages  without  placing  your  Codename  One  email  or  password  into

your source files.

You 

can  get 

it  by  going 

to 

the  Codename  One  build 

server  dashboard  at

https://www.codenameone.com/build-server.html and selecting the Account tab.

The token should appear at the bottom as such:

Figure 413. Push Token from the build server

The instructions for extracting the API key for Google are listed above.

private static final String FCM_SERVER_API_KEY = "******************-********************";

The instructions for extracting the SID and Client Secret for Windows are listed above.

private static final String WNS_SID = "ms-app://**************************************";
private static final String WNS_CLIENT_SECRET = "*************************";

When sending push to iOS devices we have two modes: - Production - Distribution

This allows you to debug the push related functionality without risking the possibility of sending a

push  into  a  production  app.  Its  important  to  send  the  values  to  the  right  server  during

development/production.

private static final boolean ITUNES_PRODUCTION_PUSH = false;

iOS needs a certificate in order to send a push, this allows you to prove to Apples push servers that

you are who you claim to be (the author of the app).

500

 These are not the signing certificates and are completely separate from them!

You  can  obtain  these  two  certificates  (for  development/appstore)  via  the  certificate  wizard  as

explained above.

private static final String ITUNES_PRODUCTION_PUSH_CERT = "https://domain.com/linkToP12Prod.p12";
private static final String ITUNES_PRODUCTION_PUSH_CERT_PASSWORD = "ProdPassword";
private static final String ITUNES_DEVELOPMENT_PUSH_CERT = "https://domain.com/linkToP12Dev.p12";
private static final String ITUNES_DEVELOPMENT_PUSH_CERT_PASSWORD = "DevPassword";

13.8.1. Sending a Push Message From Codename One

While  normally  sending  a  push  message  to  a  device  should  involve  a  server  code  there  might  be

cases (e.g. instant messaging/social) where initiating a push from one client to another makes sense.

To  simplify  these  use  cases  we  added  the  Push  [https://www.codenameone.com/javadoc/com/codename1/
push/Push.html] API. To use the Push API you need the device key of the destination device to which
you  want  to  send  the  message.  You  can  get  that  value  from  the  Push.getPushKey()  method.  Notice
that you need that value from the destination device and not the local device!

To send a message to another device just use:

String cert = ITUNES_DEVELOPMENT_PUSH_CERT;
String pass = ITUNES_DEVELOPMENT_PUSH_CERT_PASSWORD;
if(ITUNES_PRODUCTION_PUSH) {
    cert = ITUNES_PRODUCTION_PUSH_CERT;
    pass = ITUNES_PRODUCTION_PUSH_CERT_PASSWORD;
}
new Push(PUSH_TOKEN, "Hello World", deviceKey)
    .apnsAuth(cert, pass, ITUNES_PRODUCTION_PUSH)
    .gcmAuth(FCM_SERVER_API_KEY)
    .wnsAuth(WNS_SID, WNS_CLIENT_SECRET)
    .send();

The "builder" style API used in the above sample was added post Codename One 3.6 to facilitate the

addition of new Push services. If you are building against Codename one 3.6 or earlier, you should
use the static Push.sendPushMessage() instead as shown below:

Push.sendPushMessage(PUSH_TOKEN, "Hello World",
         ITUNES_PRODUCTION_PUSH, FCM_SERVER_API_KEY, cert, pass, 1, deviceKey));

This will send the push message "Hello World" to the device with the key deviceKey. The 1 argument
represents the standard push message type, which we discussed previously.

501

13.8.2. Sending Push Message From A Java or Generic Server

Sending a push message from the server is a more elaborate affair and might require sending push

messages to many devices in a single batch.

We can send a push message as an HTTP POST request to https://push.codenameone.com/push/push
[https://push.codenameone.com/push/push]. That URL accepts the following arguments:

• token - your developer token to identify the account sending the push - PUSH_TOKEN

• device - one or more device keys to send the push to. You can send push to up to 500 devices

with a single request -

• type - the message type identical to the old set of supported types in the old push servers

• body - the body of the message

• auth  -  the  Google  push  auth  key  -  FCM_SERVER_API_KEY  (also  used  for  sending  to  Chrome

Javascript Apps)

• production  -  true/false  whether  to  push  to  production  or  sandbox  environment  in  iOS  -

ITUNES_PRODUCTION_PUSH

• certPassword 

- 

password 

for 

the 

push 

certificate 

in 

iOS 

push 

ITUNES_DEVELOPMENT_PUSH_CERT_PASSWORD or ITUNES_PRODUCTION_PUSH_CERT_PASSWORD

• cert 

-  http  or  https  URL  containing 

the  push  certificate 

for  an 

iOS  push 

ITUNES_DEVELOPMENT_PUSH_CERT or ITUNES_PRODUCTION_PUSH_CERT

-

-

• sid - The package security ID (SID) for UWP apps.

• client_secret - The client secret for UWP apps.

We can thus send a push from Java EE using code like this:

502

HttpURLConnection connection = (HttpURLConnection)new URL("https://push.codenameone.com/push/push").openConnection();
connection.setDoOutput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8");
String cert = ITUNES_DEVELOPMENT_PUSH_CERT;
String pass = ITUNES_DEVELOPMENT_PUSH_CERT_PASSWORD;
if(ITUNES_PRODUCTION_PUSH) {
    cert = ITUNES_PRODUCTION_PUSH_CERT;
    pass = ITUNES_PRODUCTION_PUSH_CERT_PASSWORD;
}
String query = "token="  + PUSH_TOKEN +
    "&device=" + URLEncoder.encode(deviceId1, "UTF-8") +
    "&device=" + URLEncoder.encode(deviceId2, "UTF-8") +
    "&device=" + URLEncoder.encode(deviceId3, "UTF-8") +
    "&type=1" +
    "&auth=" + URLEncoder.encode(FCM_SERVER_API_KEY, "UTF-8") +
    "&certPassword=" + URLEncoder.encode(pass, "UTF-8") +
    "&cert=" + URLEncoder.encode(cert, "UTF-8") +
    "&body=" + URLEncoder.encode(MESSAGE_BODY, "UTF-8") +
    "&production=" + ITUNES_PRODUCTION_PUSH +
    "&sid=" + URLEncoder.encode(WNS_SID, "UTF-8") +
    "&client_secret=" + URLEncoder.encode(WNS_CLIENT_SECRET, "UTF-8");
try (OutputStream output = connection.getOutputStream()) {
    output.write(query.getBytes("UTF-8"));
}
int c = connection.getResponseCode();
// read response JSON

Notice that you can send a push to 500 devices. To send in larger batches you need to split the push

requests into 500 device batches.

Server JSON Responses

The push servers send responses in JSON form. It’s crucial to parse and manage those as they might

contain important information.

If  there  is  an  error  that  isn’t  fatal  such  as  quota  exceeded  etc.  you  will  get  an  error  message  like

this:

{"error":"Error message"}

A normal response, will be an array with results:

[
   {"id"="deviceId","status"="error","message"="Invalid Device ID"},
   {"id"="cn1-gcm-nativegcmkey","status"="updateId", "newId"="cn1-gcm-newgcmkey"},
   {"id"="cn1-gcm-okgcmkey","status"="OK"},
   {"id"="cn1-gcm-errorkey","status"="error","message"="Server error message"},
   {"id"="cn1-ios-iphonekey","status"="inactive"},
]

There are several things to notice in the responses above:

503

• If the response contains status=updateId it means that the GCM server wants you to update the
device id to a new device id. You should do that in the database and avoid sending pushes to the

old key

• iOS  doesn’t  acknowledge  device  receipt  but  it  does  send  a  status=inactive  result  which  you

should use to remove the device from the list of devices

 APNS  (Apple’s  push  service)  returns  uppercase  key  results.  This  means  that  code

for managing the keys in your database must be case insensitive



Apple doesn’t always send back a result for a device being inactive and might fail

silently

504

14. Miscellaneous Features

14.1. Phone Functions

Most  of  the  low  level  phone  functionality  is  accessible  in  the  Display  [https://www.codenameone.com/

javadoc/com/codename1/ui/Display.html] class. Think of it as a global central class covering your access to

the "system".

14.1.1. SMS

Codename  One  supports  sending  SMS  messages  but  not  receiving  them  as  this  functionality  isn’t

portable. You can send an SMS using:

Display.getInstance().setSMS("+999999999", "My SMS Message");

Android/Blackberry support sending SMS’s in the background without showing the user anything.

iOS & Windows Phone just don’t have that ability, the best they can offer is to launch the native SMS

app with your message already in that app. Android supports that capability as well (launching the

OS native SMS app).

The  default  sendSMS  API  ignores  that  difference  and  simply  works  interactively  on  iOS/Windows
Phone while sending in the background for the other platforms.

The getSMSSupport API returns one of the following options:

• SMS_NOT_SUPPORTED - for desktop, tablet etc.

• SMS_SEAMLESS - sendSMS will not show a UI and will just send in the background

• SMS_INTERACTIVE - sendSMS will show an SMS sending UI

• SMS_BOTH - sendSMS can support both seamless and interactive mode, this currently only works

on Android

The  sendSMS  can  accept  an  interactive  argument:  sendSMS(String  phoneNumber,  String  message,
boolean interactive)

The  last  argument  will  be  ignored  unless  SMS_BOTH  is  returned  from  getSMSSupport  at  which  point
you would be able to choose one way or the other. The default behavior (when not using that flag)

is the background sending which is the current behavior on Android.

A typical use of this API would be something like this:

505

switch(Display.getInstance().getSMSSupport()) {
    case Display.SMS_NOT_SUPPORTED:
        return;
    case Display.SMS_SEAMLESS:
        showUIDialogToEditMessageData();
        Display.getInstance().sendSMS(phone, data);
        return;
    default:
        Display.getInstance().sendSMS(phone, data);
        return;
}

14.1.2. Dialing

Dialog  the  phone  is  pretty  trivial,  this  should  open  the  dialer  UI  without  physically  dialing  the

phone as that is discouraged by device vendors.

You can dial the phone by using:

Display.getInstance().dial("+999999999");

14.1.3. E-Mail

You can send an email via the platforms native email client with code such as this:

Message m = new Message("Body of message");
Display.getInstance().sendMessage(new String[] {"someone@gmail.com"}, "Subject of message", m);

You can add one attachment by using setAttachment and setAttachmentMimeType.

 You need to use files from FileSystemStorage and NOT Storage files!

You can add more than one attachment by putting them directly into the attachment map e.g.:

Message m = new Message("Body of message");
m.getAttachments().put(textAttachmentUri, "text/plain");
m.getAttachments().put(imageAttachmentUri, "image/png");
Display.getInstance().sendMessage(new String[] {"someone@gmail.com"}, "Subject of message", m);

 Some  features  such  as  attachments  etc.  don’t  work  correctly  in  the  simulator  but

should work on iOS/Android

The email messaging API has an additional ability within the Message [https://www.codenameone.com/
javadoc/com/codename1/messaging/Message.html] class. The sendMessageViaCloud method allows you to use
the Codename One cloud to send an email without end user interaction. This feature is available to

506

pro users only since it makes use of the Codename One cloud:

Message m = new Message("<html><body>Check out <a href=\"https://www.codenameone.com/\">Codename One</a></body></html>");
m.setMimeType(Message.MIME_HTML);

// notice that we provide a plain text alternative as well in the send method
boolean success = m.sendMessageViaCloudSync("Codename One", "destination@domain.com", "Name Of User", "Message Subject",
                            "Check out Codename One at https://www.codenameone.com/");

14.2. Contacts API

The  contacts  API  provides  us  with  the  means  to  query  the  phone’s  address  book,  delete  elements

from  it  and  create  new  entries  into  it.  To  get  the  platform  specific  list  of  contacts  you  can  use
String[] contacts = ContactsManager.getAllContacts();

Notice that on some platforms this will prompt the user for permissions and the user might choose

to  grant 

that  permission.  To  detect  whether 

invoke
not 
isContactsPermissionGranted() after invoking getAllContacts(). This can help you adapt your error
message to the user.

the  case  you  can 

this 

is 

Once  you  have  a  Contact  [https://www.codenameone.com/javadoc/com/codename1/contacts/Contact.html]  you
can use the getContactById method, however the default method is a bit slow if you want to pull a
large batch of contacts. The solution for this is to only extract the data that you need via

getContactById(String id, boolean includesFullName,
            boolean includesPicture, boolean includesNumbers, boolean includesEmail,
            boolean includeAddress)

Here you can specify true only for the attributes that actually matter to you.

Another capability of the contacts API is the ability to extract all of the contacts very quickly. This

isn’t supported on all platforms but platforms such as Android can really get a boost from this API

as extracting the contacts one by one is remarkably slow on Android.

You  can  check  if  a  platform  supports  the  extraction  of  all  the  contacts  quickly  thru
ContactsManager.isGetAllContactsFast().

 When  retrieving  all  the  contacts,  notice  that  you  should  probably  not  retrieve  all

the data and should set some fields to false to perform a more efficient query

You can then extract all the contacts using code that looks a bit like this, notice that we use a thread

so the UI won’t be blocked!

507

Form hi = new Form("Contacts", new BoxLayout(BoxLayout.Y_AXIS));
hi.add(new InfiniteProgress());
Display.getInstance().scheduleBackgroundTask(() -> {
    Contact[] contacts = ContactsManager.getAllContacts(true, true, false, true, false, false);
    Display.getInstance().callSerially(() -> {
        hi.removeAll();
        for(Contact c : contacts) {
            MultiButton mb = new MultiButton(c.getDisplayName());
            mb.setTextLine2(c.getPrimaryPhoneNumber());
            hi.add(mb);
            mb.putClientProperty("id", c.getId());
        }
        hi.getContentPane().animateLayout(150);
    });
});
hi.show();

Figure 414. List of contacts

Notice  that  we  didn’t  fetch  the  image  of  the  contact  as  the  performance  of  loading  these  images

might  be  prohibitive.  We  can  enhance  the  code  above  to  include  images  by  using  slightly  more

complex code such as this:



The  scheduleBackgroundTask  method  is  similar  to  new  Thread()  in  some  regards.  It
places elements in a queue instead of opening too many threads so it can be good

for non-urgent tasks

508

Form hi = new Form("Contacts", new BoxLayout(BoxLayout.Y_AXIS));
hi.add(new InfiniteProgress());
int size = Display.getInstance().convertToPixels(5, true);
FontImage fi = FontImage.createFixed("" + FontImage.MATERIAL_PERSON, FontImage.getMaterialDesignFont(), 0xff, size,
size);

Display.getInstance().scheduleBackgroundTask(() -> {
    Contact[] contacts = ContactsManager.getContacts(true, true, false, true, false, false);
    Display.getInstance().callSerially(() -> {
        hi.removeAll();
        for(Contact c : contacts) {
            MultiButton mb = new MultiButton(c.getDisplayName());
            mb.setIcon(fi);
            mb.setTextLine2(c.getPrimaryPhoneNumber());
            hi.add(mb);
            mb.putClientProperty("id", c.getId());
            Display.getInstance().scheduleBackgroundTask(() -> {
                Contact cc = ContactsManager.getContactById(c.getId(), false, true, false, false, false);
                Display.getInstance().callSerially(() -> {
                    Image photo = cc.getPhoto();
                    if(photo != null) {
                        mb.setIcon(photo.fill(size, size));
                        mb.revalidate();
                    }
                });
            });
        }
        hi.getContentPane().animateLayout(150);
    });
});

Figure 415. Contacts with the default photos on the simulator, on device these will use actual user photos

when available



Notice that the code above uses callSerially & scheduleBackgroundTask in a liberal
nested way. This is important to avoid an EDT violation

You  can  use  createContact(String  firstName,  String  familyName,  String  officePhone,  String
homePhone,  String  cellPhone,  String  email)  to  add  a  new  contact  and  deleteContact(String  id)  to
delete a contact.

509

14.3. Localization & Internationalization (L10N & I18N)

Localization  (l10n)  means  adapting  to  a  locale  which  is  more  than  just  translating  to  a  specific
language  within  environment  e.g.  en_US  !=  en_UK.
Internationalization (i18n) is the process of creating one application that adapts to all locales and

language  but  also 

to  a  specific 

regional requirements.

Codename One supports automatic localization and seamless internationalization of an application

using the Codename One design tool.



Although localization is performed in the design tool most features apply to hand

coded  applications  as  well.  The  only  exception  is  the  tool  that  automatically

extracts localizable strings from the GUI.

Figure 416. Localization tool in the Designer

To translate an application you need to use the localization section of the Codename One Designer.

This section features a handy tool to extract localization called Sync With UI, it’s a great tool to get

you started assuming you used the old GUI builder.

Some fields on some components (e.g. Commands) are not added when using "Sync With UI" button.
But you can add them manually on the localization bundle and they will be automatically localized.

You  can  just  use  the  Property Key  used  in  the  localization  bundle  in  the  Command  name  of  the

form.

You can add additional languages by pressing the Add Locale button.

This generates “bundles” in the resource file which are really just key/value pairs mapping a string

in one language to another language. You can install the bundle using code like this:

UIManager.getInstance().setBundle(res.getL10N("l10n", local));

The device language (as an ISO 639 two letter code) could be retrieved with this:

String local = L10NManager.getInstance().getLanguage();

Once  installed  a  resource  bundle  takes  over  the  UI  and  every  string  set  to  a  label  (and  label  like

510

components)  will  be  automatically  localized  based  on  the  bundle.  You  can  also  use  the  localize

method  of  UIManager  [https://www.codenameone.com/javadoc/com/codename1/ui/plaf/UIManager.html]  to

perform localization on your own:

UIManager.getInstance().localize( "KeyInBundle", "DefaultValue");

The list of available languages in the resource bundle could be retrieved like this. Notice that this a

list that was set by you and doesn’t need to confirm to the ISO language code standards:

Resources res = fetchResourceFile();
Enumeration locales = res.listL10NLocales( "l10n" );

An exception for localization is the TextField/TextArea components both of which contain user data,
in those cases the text will not be localized to avoid accidental localization of user input.

You  can  preview  localization  in  the  theme  mode  within  the  Codename  One  designer  by  selecting

Advanced, picking your locale then clicking the theme again.

You can export and import resource bundles as standard Java properties files, CSV



and  XML.  The  formats  are  pretty  standard  for  most  localization  shops,  the  XML

format Codename One supports is the one used by Android’s string bundles which

means most localization specialists should easily localize it

The resource bundle is just a map between keys and values e.g. the code below displays "This Label
is  localized"  on  the  Label  with  the  hardcoded  resource  bundle.  It  would  work  the  same  with  a
resource bundle loaded from a resource file:

Form hi = new Form("L10N", new BoxLayout(BoxLayout.Y_AXIS));
HashMap<String, String> resourceBudle = new HashMap<String, String>();
resourceBudle.put("Localize", "This Label is localized");
UIManager.getInstance().setBundle(resourceBudle);
hi.add(new Label("Localize"));
hi.show();

Figure 417. Localized label

14.3.1. Localization Manager

The  L10NManager 

[https://www.codenameone.com/javadoc/com/codename1/l10n/L10NManager.html]  class

includes a multitude of features useful for common localization tasks.

It allows formatting numbers/dates & time based on platform locale. It also provides a great deal of

the  information  you  need  such  as  the  language/locale  information  you  need  to  pick  the  proper

511

resource bundle.

Form hi = new Form("L10N", new TableLayout(16, 2));
L10NManager l10n = L10NManager.getInstance();
hi.add("format(double)").add(l10n.format(11.11)).
    add("format(int)").add(l10n.format(33)).
    add("formatCurrency").add(l10n.formatCurrency(53.267)).
    add("formatDateLongStyle").add(l10n.formatDateLongStyle(new Date())).
    add("formatDateShortStyle").add(l10n.formatDateShortStyle(new Date())).
    add("formatDateTime").add(l10n.formatDateTime(new Date())).
    add("formatDateTimeMedium").add(l10n.formatDateTimeMedium(new Date())).
    add("formatDateTimeShort").add(l10n.formatDateTimeShort(new Date())).
    add("getCurrencySymbol").add(l10n.getCurrencySymbol()).
    add("getLanguage").add(l10n.getLanguage()).
    add("getLocale").add(l10n.getLocale()).
    add("isRTLLocale").add("" + l10n.isRTLLocale()).
    add("parseCurrency").add(l10n.formatCurrency(l10n.parseCurrency("33.77$"))).
    add("parseDouble").add(l10n.format(l10n.parseDouble("34.35"))).
    add("parseInt").add(l10n.format(l10n.parseInt("56"))).
    add("parseLong").add("" + l10n.parseLong("4444444"));
hi.show();

Figure 418. Localization formatting/parsing and information

14.3.2. RTL/Bidi

RTL  stands  for  right  to  left,  in  the  world  of  internationalization  it  refers  to  languages  that  are

written from right to left (Arabic, Hebrew, Syriac, Thaana).

Most western languages are written from left to right (LTR), however some languages are written

from right to left (RTL) speakers of these languages expect the UI to flow in the opposite direction

otherwise it seems weird just like reading this word would be to most English speakers: "drieW".

The  problem  posed  by  RTL  languages  is  known  as  BiDi  (Bi-directional)  and  not  as  RTL  since  the

"true" problem isn’t the reversal of the writing/UI but rather the mixing of RTL and LTR together.

E.g. numbers are always written from left to right (just like in English) so in an RTL language the

direction is from right to left and once we reach a number or English text embedded in the middle

of the sentence (such as a name) the direction switches for a duration and is later restored.

512

The  main  issue  in  the  Codename  One  world  is  in  the  layouts,  which  need  to  reverse  on  the  fly.
Codename One supports this via an RTL flag on all components that is derived from the global RTL
flag in UIManager [https://www.codenameone.com/javadoc/com/codename1/ui/plaf/UIManager.html].

Resource  bundles  can  also  include  special  case  constant  @rtl,  which  indicates  if  a  language  is

written from right to left. This allows everything to automatically reverse.

When in RTL mode the UI will be the exact mirror so WEST will become EAST, RIGHT will become LEFT
and this would be true for paddings/margins as well.

If you have a special case where you don’t want this behavior you will need to wrap it with an isRTL
check.  You  can  also  use  setRTL  on  a  per  Component  basis  to  disable  RTL  behavior  for  a  specific
Component.



Most  UI  API’s  have  special  cases  for  BiDi  instead  of  applying  it  globally  e.g.  AWT
introduced  constants  such  as  LEADING  instead  of  making  WEST  mean  the  opposite
direction.  We  think  that  was  a  mistake  since  the  cases  where  you  wouldn’t  want

the behavior of automatic reversal are quite rare.

Codename One’s support for bidi includes the following components:

• Bidi algorithm - allows converting between logical to visual representation for rendering

• Global RTL flag - default flag for the entire application indicating the UI should flow from right

to left

• Individual RTL flag - flag indicating that the specific component/container should be presented

as an RTL/LTR component (e.g. for displaying English elements within a RTL UI).

• RTL text field input

Most  of  Codename  One’s  RTL 

support 

is  under 

the  hood, 

the  LookAndFeel

[https://www.codenameone.com/javadoc/com/codename1/ui/plaf/LookAndFeel.html]  global  RTL  flag  can  be

enabled using:

UIManager.getInstance().getLookAndFeel().setRTL(true);

Once RTL is activated all positions in Codename One become reversed and the UI becomes a mirror
of  itself.  E.g.  Adding  a  Toolbar  command  to  the  left  will  actually  make  it  appear  on  the  right.
Padding on the left becomes padding on the right. The scroll moves to the left etc.

This applies to the layout managers (except for group layout) and most components. Bidi is mostly

seamless in Codename One but a developer still needs to be aware that his UI might be mirrored for

these cases.

14.4. Location - GPS

The Location [https://www.codenameone.com/javadoc/com/codename1/location/Location.html] API allows us to

track changes in device location or the current user position.

513



The  Simulator  includes  a  Location Simulation  tool  that  you  can  launch  to

determine the current position of the simulator and debug location events

The  most  basic  usage  for  the  API  allows  us  to  just  fetch  a  device  Location,  notice  that  this  API  is

blocking and can take a while to return:

Location position = LocationManager.getLocationManager().getCurrentLocationSync();



In  order  for  location  to  work  on  iOS  you  MUST  define  the  build  hint
ios.locationUsageDescription  and  describe  why  your  application  needs  access  to
location. Otherwise you won’t get location updates!

The getCurrentLocationSync() method is very good for cases where you only need to fetch a current
location  once  and  not  repeatedly  query  location.  It  activates  the  GPS  then  turns  it  off  to  avoid

excessive battery usage. However, if an application needs to track motion or position over time it

should use the location listener API to track location as such:



Notice  that  there  is  a  method  called  getCurrentLocation()  which  will  return  the
current state immediately and might not be accurate for some cases.

public MyListener implements LocationListener {
    public void locationUpdated(Location location) {
        // update UI etc.
    }

    public void providerStateChanged(int newState) {
        // handle status changes/errors appropriately
    }
}
LocationManager.getLocationManager().setLocationListener(new MyListener());



On Android location maps to low level API’s if you disable the usage of Google Play

Services.  By  default  location  should  perform  well  if  you  leave  the  Google  Play

Services on

14.4.1. Location In The Background - Geofencing

Polling  location  is  generally  expensive  and  requires  a  special  permission  on  iOS.  Its  also

implemented  rather  differently  both  in  iOS  and  Android.  Both  platforms  place  restrictions  on  the

location API usage in the background.

Because  of  the  nature  of  background  location  the  API  is  non-trivial.  It  starts  with  the  venerable
LocationManager 
setBackgroundLocationListener.

standard  API 

instead 

using 

need 

you 

but 

the 

use

of 

to 

Instead  of  passing  a  LocationListener  instance  you  need  to  pass  a  Class  object  instance.  This  is

514

important because background location might be invoked when the app isn’t running and an object

would need to be allocated.

Notice that you should NOT perform long operations in the background listener callback. IOS wake-

up time is limited to approximately 10 seconds and the app could get killed if it exceeds that time

slice.

Notice  that  the  listener  can  also  send  events  when  the  app  is  in  the  foreground,  therefore  it  is

recommended  to  check  the  app  state  before  deciding  how  to  process  this  event.  You  can  use
Display.isMinimized() to determine if the app is currently running or in the background.

When implementing this make sure that:

• The class passed to the API is a public class in the global scope. Not an inner class or anything

like that!

• The class has a public no-argument constructor

• You  need 

to  pass 

it 

as 

a 

class 

literal 

e.g. 

MyClassName.class.  Don’t  use

Class.forName("my.package.MyClassName")!
Class  names  are  problematic  since  device  builds  are  obfuscated,  you  should  only  use  literals

which the obfuscator detects and handles correctly.

The following code demonstrates usage of the GeoFence API:

Geofence gf = new Geofence("test", loc, 100, 100000);

LocationManager.getLocationManager()
        .addGeoFencing(GeofenceListenerImpl.class, gf);

public class GeofenceListenerImpl implements GeofenceListener {
    @Override
    public void onExit(String id) {
    }

    @Override
    public void onEntered(String id) {
        if(Display.getInstance().isMinimized()) {
            Display.getInstance().callSerially(() -> {
                Dialog.show("Welcome", "Thanks for arriving", "OK", null);
            });
        } else {
            LocalNotification ln = new LocalNotification();
            ln.setAlertTitle("Welcome");
            ln.setAlertBody("Thanks for arriving!");
            Display.getInstance().scheduleLocalNotification(ln, 10, false);
        }
    }
}

515

14.5. Background Music Playback

Codename One supports playing music in the background (e.g. when the app is minimized) which is

quite useful for developers building a music player style application.

This  support  isn’t  totally  portable  since  the  Android  and  iOS  approaches  for  background  music

playback  differ  a  great  deal.  To  get  this  to  work  on  Android  you  need  to  use  the  API:
MediaManager.createBackgroundMedia().

You should use that API when you want to create a media stream that will work even when your

app is minimized.

For iOS you will need to use a special build hint: ios.background_modes=music.

Which  should  allow  background  playback  of  music  on  iOS  and  would  work  with  the
createBackgroundMedia() method.

14.6. Capture - Photos, Video, Audio

The capture API allows us to use the camera to capture photographs or the microphone to capture

audio. It even includes an API for video capture.

The API itself couldn’t be simpler:

String filePath = Capture.capturePhoto();

Just  captures  and  returns  a  path  to  a  photo  you  can  either  open  it  using  the  Image

[https://www.codenameone.com/javadoc/com/codename1/ui/Image.html] class or save it somewhere.

 The  returned  file  is  a  temporary  file,  you  shouldn’t  store  a  reference  to  it  and

instead copy it locally or work with the Image object

E.g. you can copy the Image to Storage using:

String filePath = Capture.capturePhoto();
if(filePath != null) {
    Util.copy(FileSystemStorage.getInstance().openInputStream(filePath),
Storage.getInstance().createOutputStream(myImageFileName));
}



When running on the simulator the Capture API opens a file chooser API instead of
physically  capturing  the  data.  This  makes  debugging  device  or  situation  specific

issues simpler

We can capture an image from the camera using an API like this:

516

Form hi = new Form("Capture", new BorderLayout());
hi.setToolbar(new Toolbar());
Style s = UIManager.getInstance().getComponentStyle("Title");
FontImage icon = FontImage.createMaterial(FontImage.MATERIAL_CAMERA, s);

ImageViewer iv = new ImageViewer(icon);

hi.getToolbar().addCommandToRightBar("", icon, (ev) -> {
    String filePath = Capture.capturePhoto();
    if(filePath != null) {
        try {
            DefaultListModel<Image> m = (DefaultListModel<Image>)iv.getImageList();
            Image img = Image.createImage(filePath);
            if(m == null) {
                m = new DefaultListModel<>(img);
                iv.setImageList(m);
                iv.setImage(img);
            } else {
                m.addItem(img);
            }
            m.setSelectedIndex(m.getSize() - 1);
        } catch(IOException err) {
            Log.e(err);
        }
    }
});

hi.add(BorderLayout.CENTER, iv);
hi.show();

Figure 419. Captured photos previewed in the ImageViewer

We  demonstrate  video  capture  in  the  MediaManager  section  [https://www.codenameone.com/manual/

components.html#mediamanager-section].

The  sample  below  captures  audio  recordings  (using  the  'Capture'  API)  and  copies  them  locally

under unique names. It also demonstrates the storage and organization of captured audio:

517

Form hi = new Form("Capture", BoxLayout.y());
hi.setToolbar(new Toolbar());
Style s = UIManager.getInstance().getComponentStyle("Title");
FontImage icon = FontImage.createMaterial(FontImage.MATERIAL_MIC, s);

FileSystemStorage fs = FileSystemStorage.getInstance();
String recordingsDir = fs.getAppHomePath() + "recordings/";
fs.mkdir(recordingsDir);
try {
    for(String file : fs.listFiles(recordingsDir)) {
        MultiButton mb = new MultiButton(file.substring(file.lastIndexOf("/") + 1));
        mb.addActionListener((e) -> {
            try {
                Media m = MediaManager.createMedia(recordingsDir + file, false);
                m.play();
            } catch(IOException err) {
                Log.e(err);
            }
        });
        hi.add(mb);
    }

    hi.getToolbar().addCommandToRightBar("", icon, (ev) -> {
        try {
            String file = Capture.captureAudio();
            if(file != null) {
                SimpleDateFormat sd = new SimpleDateFormat("yyyy-MMM-dd-kk-mm");
                String fileName =sd.format(new Date());
                String filePath = recordingsDir + fileName;
                Util.copy(fs.openInputStream(file), fs.openOutputStream(filePath));
                MultiButton mb = new MultiButton(fileName);
                mb.addActionListener((e) -> {
                    try {
                        Media m = MediaManager.createMedia(filePath, false);
                        m.play();
                    } catch(IOException err) {
                        Log.e(err);
                    }
                });
                hi.add(mb);
                hi.revalidate();
            }
        } catch(IOException err) {
            Log.e(err);
        }
    });
} catch(IOException err) {
    Log.e(err);
}
hi.show();

518

Figure 420. Captured recordings in the demo

Alternatively, you can use the Media, MediaManager and MediaRecorderBuilder APIs to capture audio,
as a more customizable approach than using the Capture API:

    private static final EasyThread countTime = EasyThread.start("countTime");

    public void start() {
        if (current != null) {
            current.show();
            return;
        }
        Form hi = new Form("Recording audio", BoxLayout.y());
        hi.add(new SpanLabel("Example of recording and playback audio using the Media, MediaManager and
MediaRecorderBuilder APIs"));
        hi.add(recordAudio((String filePath) -> {
            ToastBar.showInfoMessage("Do something with the recorded audio file: " + filePath);
        }));
        hi.show();
    }

    public static Component recordAudio(OnComplete<String> callback) {
        try {
            // mime types supported by Android: audio/amr, audio/aac, audio/mp4
            // mime types supported by iOS: audio/mp4, audio/aac, audio/m4a
            // mime type supported by Simulator: audio/wav
            // more info: https://www.iana.org/assignments/media-types/media-types.xhtml

            List<String> availableMimetypes = Arrays.asList(MediaManager.getAvailableRecordingMimeTypes());
            String mimetype;
            if (availableMimetypes.contains("audio/aac")) {
                // Android and iOS
                mimetype = "audio/aac";
            } else if (availableMimetypes.contains("audio/wav")) {
                // Simulator
                mimetype = "audio/wav";
            } else {
                // others
                mimetype = availableMimetypes.get(0);
            }
            String fileName = "audioExample." + mimetype.substring(mimetype.indexOf("/") + 1);
            String output = FileSystemStorage.getInstance().getAppHomePath() + "/" + fileName;
            // https://tritondigitalcommunity.force.com/s/article/Choosing-Audio-Bitrate-Settings
            MediaRecorderBuilder options = new MediaRecorderBuilder()
                    .mimeType(mimetype)
                    .path(output)
                    .bitRate(64000)
                    .samplingRate(44100);
            Media[] microphone = {MediaManager.createMediaRecorder(options)};
            Media[] speaker = {null};

519

            Container recordingUI = new Container(BoxLayout.y());
            Label time = new Label("0:00");
            Button recordBtn = new Button("", FontImage.MATERIAL_FIBER_MANUAL_RECORD, "Button");
            Button playBtn = new Button("", FontImage.MATERIAL_PLAY_ARROW, "Button");
            Button stopBtn = new Button("", FontImage.MATERIAL_STOP, "Button");
            Button sendBtn = new Button("Send");
            sendBtn.setEnabled(false);
            Container buttons = GridLayout.encloseIn(3, recordBtn, stopBtn, sendBtn);
            recordingUI.addAll(FlowLayout.encloseCenter(time), FlowLayout.encloseCenter(buttons));

            recordBtn.addActionListener(l -> {
                try {
                    // every time we have to create a new instance of Media to make it working correctly (as reported in
the Javadoc)
                    microphone[0] = MediaManager.createMediaRecorder(options);
                    if (speaker[0] != null && speaker[0].isPlaying()) {
                        return; // do nothing if the audio is currently recorded or played
                    }
                    recordBtn.setEnabled(false);
                    sendBtn.setEnabled(true);
                    Log.p("Audio recording started", Log.DEBUG);
                    if (buttons.contains(playBtn)) {
                        buttons.replace(playBtn, stopBtn, CommonTransitions.createEmpty());
                        buttons.revalidateWithAnimationSafety();
                    }
                    if (speaker[0] != null) {
                        speaker[0].pause();
                    }

                    microphone[0].play();
                    startWatch(time);
                } catch (IOException ex) {
                    Log.p("ERROR recording audio", Log.ERROR);
                    Log.e(ex);
                }
            });

            stopBtn.addActionListener(l -> {
                if (!microphone[0].isPlaying() && (speaker[0] == null || !speaker[0].isPlaying())) {
                    return; // do nothing if the audio is NOT currently recorded or played
                }
                recordBtn.setEnabled(true);
                sendBtn.setEnabled(true);
                Log.p("Audio recording stopped");
                if (microphone[0].isPlaying()) {
                    microphone[0].pause();
                } else if (speaker[0] != null) {
                    speaker[0].pause();
                } else {
                    return;
                }
                stopWatch(time);
                if (buttons.contains(stopBtn)) {
                    buttons.replace(stopBtn, playBtn, CommonTransitions.createEmpty());
                    buttons.revalidateWithAnimationSafety();
                }
                if (FileSystemStorage.getInstance().exists(output)) {
                    Log.p("Audio saved to: " + output);
                } else {
                    ToastBar.showErrorMessage("Error recording audio", 5000);
                    Log.p("ERROR SAVING AUDIO");
                }
            });

            playBtn.addActionListener(l -> {
                // every time we have to create a new instance of Media to make it working correctly (as reported in the
Javadoc)

520

                if (microphone[0].isPlaying() || (speaker[0] != null && speaker[0].isPlaying())) {
                    return; // do nothing if the audio is currently recorded or played
                }
                recordBtn.setEnabled(false);
                sendBtn.setEnabled(true);
                if (buttons.contains(playBtn)) {
                    buttons.replace(playBtn, stopBtn, CommonTransitions.createEmpty());
                    buttons.revalidateWithAnimationSafety();
                }
                if (FileSystemStorage.getInstance().exists(output)) {
                    try {
                        speaker[0] = MediaManager.createMedia(output, false, () -> {
                            // callback on completation
                            recordBtn.setEnabled(true);
                            if (speaker[0].isPlaying()) {
                                speaker[0].pause();
                            }
                            stopWatch(time);
                            if (buttons.contains(stopBtn)) {
                                buttons.replace(stopBtn, playBtn, CommonTransitions.createEmpty());
                                buttons.revalidateWithAnimationSafety();
                            }
                        });
                        speaker[0].play();
                        startWatch(time);
                    } catch (IOException ex) {
                        Log.p("ERROR playing audio", Log.ERROR);
                        Log.e(ex);
                    }
                }
            });

            sendBtn.addActionListener(l -> {
                if (microphone[0].isPlaying()) {
                    microphone[0].pause();
                }
                if (speaker[0] != null && speaker[0].isPlaying()) {
                    speaker[0].pause();
                }
                if (buttons.contains(stopBtn)) {
                    buttons.replace(stopBtn, playBtn, CommonTransitions.createEmpty());
                    buttons.revalidateWithAnimationSafety();
                }
                stopWatch(time);
                recordBtn.setEnabled(true);

                callback.completed(output);
            });

            return FlowLayout.encloseCenter(recordingUI);

        } catch (IOException ex) {
            Log.p("ERROR recording audio", Log.ERROR);
            Log.e(ex);
            return new Label("Error recording audio");
        }

    }

    private static void startWatch(Label label) {
        label.putClientProperty("stopTime", Boolean.FALSE);
        countTime.run(() -> {
            long startTime = System.currentTimeMillis();
            while (label.getClientProperty("stopTime") == Boolean.FALSE) {
                // the sleep is every 200ms instead of 1000ms to make the app more reactive when stop is tapped
                Util.sleep(200);
                int seconds = (int) ((System.currentTimeMillis() - startTime) / 1000);

521

                String min = (seconds / 60) + "";
                String sec = (seconds % 60) + "";
                if (sec.length() == 1) {
                    sec = "0" + sec;
                }
                String newTime = min + ":" + sec;
                if (!label.getText().equals(newTime)) {
                    CN.callSerially(() -> {
                        label.setText(newTime);
                        if (label.getParent() != null) {
                            label.getParent().revalidateWithAnimationSafety();
                        }
                    });
                }
            }
        });
    }

    private static void stopWatch(Label label) {
        label.putClientProperty("stopTime", Boolean.TRUE);
    }

[Example of recording and playback audio using Media API] | https://user-

522

images.githubusercontent.com/1997316/78480286-02131b00-7735-11ea-8a70-5ca5512e7d92.png

14.6.1. Capture Asynchronous API

The  Capture  API  also  includes  a  callback  based  API  that  uses  the  ActionListener  interface  to
implement capture. E.g. we can adapt the previous sample to use this API as such:

hi.getToolbar().addCommandToRightBar("", icon, (ev) -> {
    Capture.capturePhoto((e) -> {
        if(e != null && e.getSource() != null) {
            try {
                DefaultListModel<Image> m = (DefaultListModel<Image>)iv.getImageList();
                Image img = Image.createImage((String)e.getSource());
                if(m == null) {
                    m = new DefaultListModel<>(img);
                    iv.setImageList(m);
                    iv.setImage(img);
                } else {
                    m.addItem(img);
                }
                m.setSelectedIndex(m.getSize() - 1);
            } catch(IOException err) {
                Log.e(err);
            }
        }
    });
});

14.7. Gallery

The gallery API allows picking an image and/or video from the cameras gallery (camera roll).



Like  the  Capture  API  the  image  returned  is  a  temporary  image  that  should  be
copied  locally,  this  is  due  to  device  restrictions  that  don’t  allow  direct

modifications of the gallery

We can adapt the Capture sample above to use the gallery as such:

523

Form hi = new Form("Capture", new BorderLayout());
hi.setToolbar(new Toolbar());
Style s = UIManager.getInstance().getComponentStyle("Title");
FontImage icon = FontImage.createMaterial(FontImage.MATERIAL_CAMERA, s);

ImageViewer iv = new ImageViewer(icon);

hi.getToolbar().addCommandToRightBar("", icon, (ev) -> {
    Display.getInstance().openGallery((e) -> {
        if(e != null && e.getSource() != null) {
            try {
                DefaultListModel<Image> m = (DefaultListModel<Image>)iv.getImageList();
                Image img = Image.createImage((String)e.getSource());
                if(m == null) {
                    m = new DefaultListModel<>(img);
                    iv.setImageList(m);
                    iv.setImage(img);
                } else {
                    m.addItem(img);
                }
                m.setSelectedIndex(m.getSize() - 1);
            } catch(IOException err) {
                Log.e(err);
            }
        }
    }, Display.GALLERY_IMAGE);
});

hi.add(BorderLayout.CENTER, iv);



There  is  no  need  for  a  screenshot  as  it  will  look  identical  to  the  capture  image

screenshot above

The  last  value  is  the  type  of  content  picked  which  can  be  one  of:  Display.GALLERY_ALL,
Display.GALLERY_VIDEO or Display.GALLERY_IMAGE.

14.8. Analytics Integration

One  of  the  features  in  Codename  One  is  builtin  support  for  analytic  instrumentation.  Currently

Codename  One  has  builtin  support  for  Google  Analytics  [https://www.google.com/analytics/],  which

provides reasonable enough statistics of application usage.

Analytics is pretty seamless for the old GUI builder since navigation occurs via the Codename One

API  and  can  be  logged  without  developer  interaction.  However,  to  begin  the  instrumentation  one

needs to add the line:

524

AnalyticsService.setAppsMode(true);
AnalyticsService.init(agent, domain);

To get the value for the agent value just create a Google Analytics account and add a domain, then

copy  and  paste  the  string  that  looks  something  like  UA-99999999-8  from  the  console  to  the  agent

string. Once this is in place you should start receiving statistic events for the application.

If  your  application  is  not  a  GUI  builder  application  or  you  would  like  to  send  more  detailed  data
you can use the Analytics.visit() method to indicate that you are entering a specific page.

14.8.1. Application Level Analytics

In 2013 Google introduced an improved application level analytics API that is specifically built for

mobile apps. However, it requires a slightly different API usage. You can activate this specific mode
by invoking setAppsMode(true).

When using this mode you can also report errors and crashes to the Google analytics server using
the sendCrashReport(Throwable, String message, boolean fatal) method.

We generally recommend using this mode and setting up an apps analytics account as the results

are more refined.

14.8.2. Overriding The Analytics Implementation

The Analytics API can also be enhanced to support any other form of analytics solution of your own
choosing by deriving the AnalyticsService class.

This  allows  you  to  integrate  with  any  3rd  party  via  native  or  otherwise  by  overriding  methods  in
the AnalyticsService class then invoking:

AnalyticsService.init(new MyAnalyticsServiceSubclass());

Notice that this removes the need to invoke the other init method or setAppsMode(boolean).

14.9. Native Facebook Support



Check 

out 

the 

ShareButton 

section 

[https://www.codenameone.com/manual/

components.html#sharebutton-section] it might be enough for most of your needs.

Codename  One  supports  Facebooks  Oauth2  [https://www.codenameone.com/javadoc/com/codename1/io/

Oauth2.html] login and Facebooks single sign on for iOS and Android.

14.9.1. Getting Started - Web Setup

To  get  started  first  you  will  need  to  create  a  facebook  app  on  the  Facebook  developer  portal  at

https://developers.facebook.com/apps/

525

Figure 421. Create New App

You need to repeat the process for web, Android & iOS (web is used by the simulator):

Figure 422. Pick Platform

For the first platform you need to enter the app name:

Figure 423. Pick app name

And provide some basic details:

Figure 424. Basic details for the app

For  iOS  we  need  the  bundle  ID  which  is  the  exact  same  thing  we  used  in  the  Google+  login  to

identify the iOS app its effectively your package name:

Figure 425. iOS specific basic details

You should end up with something that looks like this:

526

Figure 426. Finished Facebook app

The Android process is pretty similar but in this case we need the activity name too.



The  activity  name  should  match  the  main  class  name  followed  by  the  word  Stub
(uppercase  s).  E.g.  for  the  main  class  SociallChat  we  would  use  SocialChatStub  as
the activity name

Figure 427. Android Activity definition

To  build  the  native  Android  app  we  must  make  sure  that  we  setup  the  keystore  correctly  for  our

application. If you don’t have an Android certificate you can use the visual wizard (in the Android

section in the project preferences the button labeled Generate) or use the command line:

keytool -genkey -keystore Keystore.ks -alias [alias_name] -keyalg RSA -keysize 2048 -validity 15000 -dname "CN=[full
name], OU=[ou], O=[comp], L=[City], S=[State], C=[Country Code]" -storepass [password] -keypass [password]



You  can  reuse  the  certificate  in  all  your  apps,  some  developers  like  having  a

different certificate for every app. This is like having one master key for all your

doors, or a huge keyring filled with keys.

With  the  certificate  we  need  an  SHA1  key  to  further  authenticate  us  to  Facebook  and  we  do  this

using the keytool command line on Linux/Mac:

keytool -exportcert -alias (your_keystore_alias) -keystore (path_to_your_keystore) | openssl sha1 -binary | openssl
base64

And on Windows:

keytool -exportcert -alias androiddebugkey -keystore %HOMEPATH%\.android\debug.keystore | openssl sha1 -binary | openssl
base64

You  can  read  more  about  it  on  the  Facebook  guide  here  [https://developers.facebook.com/docs/android/

527

getting-started].

Figure 428. Hash generation process, notice the command lines are listed as part of the web wizard

Lastly you need to publish the Facebook app by flipping the switch in the apps "Status & Review"

page as such:

Figure 429. Without flipping the switch the app won’t "appear"

14.9.2. IDE Setup

We now need to set some important build hints in the project so it will work correctly. To set the

build  hints  just  right  click  the  project  select  project  properties  and  in  the  Codename  One  section

pick the second tab. Add this entry into the table:

facebook.appId=...

The app ID will be visible in your Facebook app page in the top left position.

14.9.3. The Code

To bind your mobile app into the Facebook app you can use the following code:

528

Login fb = FacebookConnect.getInstance();

fb.setClientId("9999999");
fb.setRedirectURI("http://www.youruri.com/");
fb.setClientSecret("-------");

// Sets a LoginCallback listener
fb.setCallback(new LoginCallback() {
    public void loginSuccessful() {
        // we can now start fetching stuff from Facebook!
    }

    public void loginFailed(String errorMessage) {}
});

// trigger the login if not already logged in
if(!fb.isUserLoggedIn()){
    fb.doLogin();
} else {
    // get the token and now you can query the Facebook API
    String token = fb.getAccessToken().getToken();
    // ...
}



All of these values are from the web version of the app!

They are only used in the simulator and on "unsupported" platforms as a fallback.

Android and iOS will use the native login

14.9.4. Facebook Publish Permissions

In  order  to  post  something  to  Facebook  you  need  to  request  a  write  permission,  you  can  only  do

write operations within the callback which is invoked when the user approves the permission.

You can prompt the user for publish permissions by using this code on a logged in FacebookConnect

[https://www.codenameone.com/javadoc/com/codename1/social/FacebookConnect.html]:

FacebookConnect.getInstance()askPublishPermissions(new LoginCallback() {
    public void loginSuccessful() {
         // do something...
    }
    public void loginFailed(String errorMessage) {
        // show error or just ignore
    }
});



Notice that this won’t always prompt the user, but its required to verify that your

token is valid for writing.

529

14.10. Google Sign-In

Google  Login  is  a  bit  of  a  moving  target,  as  they  are  regularly  creating  new  APIs  and  deprecating

old ones. Codename One 3.7 and earlier used the Google+ API for sign-in, which is now deprecated.

While this API still works, it is no longer useful on iOS as it redirects to Safari to perform login, and

Apple no longer allows this practice.

The new, approved API is called Google Sign-In. Rather than using Safari to handle login (on iOS), it

uses an embedded web view, which is permitted by Apple.

The process involves four parts:

1. Section 14.10.1, “iOS Setup Instructions”

2. Section 14.10.2, “Android Setup Instructions”

3. Section 14.10.3, “OAuth Setup (Simulator and REST API Access)”

4. Section 14.10.5, “The Code”

OAuth Setup is required for using Google Sign-In in the simulator, and for accessing other Google

APIs in Android.

14.10.1. iOS Setup Instructions

Short Version

Go  to  the  Google  Developer  Portal  [https://developers.google.com/mobile/add],  follow  the  steps  to  create

an App, and enable Google Sign-In, and download the GoogleService-Info.plist file. Then copy this

file into your project’s native/ios directory.

Long Version

Point your browser to this page [https://developers.google.com/mobile/add].

Figure 430. Set up mobile app form on Google

Click on the "Getting Started" button.

530

Figure 431. Getting started button

Then click "iOS App"

Figure 432. Pick a platform

Now enter an app name and the bundle ID for your app on the form below. The app name doesn’t

necessary  need  to  match  your  app’s  name,  but  the  bundle  ID  should  match  the  package  name  of

your app.

Figure 433. Create or Choose App

Select your country, and then click the "Choose and Configure Services" button.

Figure 434. Choose and Configure Services

You’ll be presented with the following screen

531

Figure 435. Choose and Configure Services form

Click on "Google Sign-In".

Then press the "Enable Google Sign-In" button that appears.

Figure 436. Enable Google Sign-In

You  should  then  be  presented  with  another  button  to  "Generate  Configuration  Files"  as  shown

below

Figure 437. Generate Configuration Files

Finally you will be presented with a button to "Download GoogleServices-Info.plist".

Figure 438. Download GoogleService-Info.plist file

Press this button to download the GoogleService-Info.plist file. Then copy this into the "native/ios"

directory of your Codename One project.

Figure 439. Project file structure after placing the GoogleService-Info.plist into the native/ios directory

At this point, your app should be able to use Google Sign-In. Notice that we don’t require any build

hints. Only that the GoogleService-Info.plist file is added to the project’s native/ios directory.

532

14.10.2. Android Setup Instructions

Short Version

Go  to  the  Google  Developer  Portal  [https://developers.google.com/mobile/add],  follow  the  steps  to  create

an App, and enable Google Sign-In, and download the google-services.json file. Then copy this file

into your project’s native/android directory.

Long Version

Point your browser to this page [https://developers.google.com/mobile/add].

Figure 440. Set up mobile app form on Google

Click on the "Getting Started" button.

Then click "Android App"

Now enter an app name and the platform for your app on the form below. The app name doesn’t

necessary need to match your app’s name, but the package name should match the package name

of your app.

Figure 441. Create or Choose App

Select your country, and then click the "Choose and Configure Services" button.

533

Figure 442. Choose and Configure Services

Click on "Google Sign-In"

Then you’ll be presented with a field to enter the Android Signing Certificate SHA-1.

Figure 443. Android Signing Certifiate SHA-1

The  value  that  you  enter  here  should  be  obtained  from  the  certificate  that  you  are  using  to  build

your app. You an use the keytool app that is distributed with the JDK to extract this value

$ keytool -exportcert -alias myAlias -keystore /path/to/my-keystore.keystore -list -v

The snippet above assumes that your keystore is located at /path/to/my-keystore.keystore, and the
certificate alias is "myAlias". You’ll be prompted to enter the password for your keystore, then the

output will look something like:

534

Alias name: myAlias
Creation date: 22-Jan-2014
Entry type: PrivateKeyEntry
Certificate chain length: 1
Certificate[1]:
Owner: CN=My Own Company Corp., OU=, O=, L=Vancouver, ST=British Columbia, C=CA
Issuer: CN=My Own Company Corp., OU=, O=, L=Vancouver, ST=British Columbia, C=CA
Serial number: 56b2fd42
Valid from: Wed Jan 22 12:23:50 PST 2014 until: Tue Feb 16 12:23:50 PST 2055
Certificate fingerprints:
     MD5:  98:F9:34:5B:B5:1A:14:2D:3C:5D:F4:92:D2:73:30:6B
     SHA1: 76:BA:AA:11:A9:22:42:24:93:82:6D:33:7E:48:BC:AF:45:4D:79:B0
     SHA256: 3D:04:33:67:6A:13:FF:4F:EE:E8:C9:7D:D2:CC:DF:70:33:E1:90:44:BF:22:B6:96:11:C7:00:67:8D:CD:53:BC
     Signature algorithm name: SHA256withRSA
     Version: 3

Extensions:

#1: ObjectId: 2.5.29.14 Criticality=false
SubjectKeyIdentifier [
KeyIdentifier [
0000: C2 A0 48 AA 60 BA DD E3   0C 3F 00 B4 2C D5 92 A5  ..H.`.......D...
0010: 31 16 EF A2                                        1...
]
]

You will be interested in SHA1 fingerprint. In the snippet above, the SHA1 fingerprint is:

76:BA:AA:11:A9:22:42:24:93:82:6D:33:7E:48:BC:AF:45:4D:79:B0

You would paste this value into the "Android Signing Certificate SHA-1" field in the web form.

After pasting that in, you’ll see a new button with label "Enable Google Sign-in"

Figure 444. Enable Google Sign-In

Press this button and you’ll be presented with another button to "Generate Configuration Files" as

shown below

Figure 445. Generate Configuration Files

Finally you will be presented with a button to "Download google-services.json".

Figure 446. Download google-services.json file

535

Press this button to download the google-services.json file. Then copy this into the "native/android"

directory of your Codename One project.

Figure 447. Project file structure after placing the GoogleService-Info.plist into the native/android directory

At this point, your app should be able to use Google Sign-In. Notice that we don’t require any build

hints. Only that the google-services.json file is added to the project’s native/android directory.

If  you  want  to  access  additional  information  about  the  logged  in  user  using



Google’s REST APIs, you will require an OAuth2.0 client ID of type Web Application

for this project as well. See Section 14.10.3, “OAuth Setup (Simulator and REST API

Access)” for details.

14.10.3. OAuth Setup (Simulator and REST API Access)

Getting  Google  Sign-In  to  work  in  the  Codename  One  simulator  requires  an  additional  step  after

you’ve set up iOS and/or Android apps. The Simulator can’t use the native Google Sign-In APIs, so it

uses  the  standard  Web  Application  OAuth2.0  API.  In  addition,  the  Android  App  requires  a  Web

Application OAuth2.0 client ID to access additional Google REST APIs.

If  you’ve  set  up  the  Google  Sign-In  API  for  either  Android  or  iOS,  then  Google  will  have  already

automatically generated a Web Application OAuth2.0 client ID for you. You just need to provide the
ClientID and ClientSecret to the GoogleConnect instance (in your java code).

Client ID, Client Secret and Redirect URL

1. Log into the Google Cloud Platform API console [https://console.cloud.google.com/apis].

2. Select your app from the drop-down-menu in the top bar

3. Click on "Credentials" in the left menu. You’ll see a screen like this

4. Under the "OAuth2.0 Client IDs", find the row with "Web application" listed in the type column

5. Click the "Edit icon for that row.

6. Make note of the "Client ID" and "Client Secret" on this page, as you’ll need to add them to your

Java source in the next step.

7. In  the  "Authorized  redirect  URIs"  section,  you  will  need  to  enter  the  URL  to  the  page  that  the

user  will  be  sent  to  after  a  successful  login.  This  page  will  only  appear  in  the  simulator  for  a

split  second,  as  Codename  One’s  BrowserComponent  will  intercept  this  request  to  obtain  the

access  token  upon  successful  login.  You  can  use  any  URL  you  like  here,  but  it  must  match  the
value you give to GoogleConnect.setRedirectURL() in Section 14.10.5, “The Code”.

536

14.10.4. Javascript Setup Instructions

The Javascript port can use the same OAuth2.0 credentials as the simulator does. It doesn’t require

your Client Secret or redirect URL. It only requires your Client ID, which you can specify using the
GoogleConnect.setClientID() method.

14.10.5. The Code

Login gc = GoogleConnect.getInstance();
gc.setClientId("*****************.apps.googleusercontent.com");
gc.setRedirectURI("https://yourURL.com/");
gc.setClientSecret("-------------------");

// Sets a LoginCallback listener
gc.setCallback(new LoginCallback() {
    public void loginSuccessful() {
        // we can now start fetching stuff from Google+!
    }

    public void loginFailed(String errorMessage) {}
});

// trigger the login if not already logged in
if(!gc.isUserLoggedIn()){
    gc.doLogin();
} else {
    // get the token and now you can query the Google API
    String token = gc.getAccessToken().getToken();
      // NOTE: On Android, this token will be null unless you provide valid
      // client ID and secrets.
}

 The client ID and client secret values here are the ones from your OAuth2.0 Web

Application.



The  Client  ID  and  Client  Secret  values  are  used  on  both  the  Simulator  and  on

Android.  On  simulator  these  values  are  required  for  login  to  work  at  all.  On

Android  these  values  are  required  to  obtain  an  access  token  to  query  the  Google

API  further  using  its  various  REST  APIs.  If  you  do  not  include  these  values  on
Android, login will still work, but gc.getAccessToken().getToken() will return null.

537

14.11. Lead Component

Codename One has two basic ways to create new components:

1. Subclass a Component override paint, implement event callbacks etc.

2. Compose multiple components into a new component, usually by subclassing a Container.

Components  such  as  Tabs  [https://www.codenameone.com/javadoc/com/codename1/ui/Tabs.html]  subclass
Container which make a lot of sense for that component since it is physically a Container.

However, 

components 

like  MultiButton 

[https://www.codenameone.com/javadoc/com/codename1/

components/MultiButton.html], 

SpanButton 

[https://www.codenameone.com/javadoc/com/codename1/

components/SpanButton.html] 

& 

SpanLabel 

[https://www.codenameone.com/javadoc/com/codename1/

components/SpanLabel.html]  don’t  necessarily  seem  like  the  right  candidate  for  compositing  but  they
are all Container subclasses.

Using  a  Container  provides  us  a  lot  of  flexibility  in  terms  of  layout  &  functionality  for  a  specific
component. MultiButton is a great example of that. It’s a Container internally that is composed of 5
labels and a Button.

Codename  One  makes 
setLeadComponent(Component) which turns the button into the "leader" of the component.

like  a  single  button 

the  MultiButton  "feel" 

thru 

the  use  of

When a Container hierarchy is placed under a leader all events within the hierarchy are sent to the
leader,  so  if  a  label  within  the  lead  component  receives  a  pointer  pressed  event  this  event  will

really be sent to the leader.

E.g.  in  the  case  of  the  MultiButton  the  internal  button  will  receive  that  event  and  send  the  action
performed event, change the state etc.

This creates some potential issues for instance in MultiButton:

myMultiButton.addActionListener((e) -> {
    if(e.getComponent() == myMultiButton) {
        // this won't occur since the source component is really a button!
    }
    if(e.getActualComponent() == myMultiButton) {
        // this will happen...
    }
});

The leader also determines the style state, so all the elements being lead are in the same state. E.g. if

the  the  button  is  pressed  all  elements  will  display  their  pressed  states,  notice  that  they  will  do  so
with their own styles but they will each pick the pressed version of that style so a Label UIID within
a lead component in the pressed state would return the Pressed state for a Label not for the Button.

This is very convenient when you need to construct more elaborate UI’s and the cool thing about it

is that you can do this entirely in the designer which allows assembling containers and defining the

lead component inside the hierarchy.

538

E.g. the SpanButton class is very similar to this code:

public class SpanButton extends Container {
    private Button actualButton;
    private TextArea text;

    public SpanButton(String txt) {
        setUIID("Button");
        setLayout(new BorderLayout());
        text = new TextArea(getUIManager().localize(txt, txt));
        text.setUIID("Button");
        text.setEditable(false);
        text.setFocusable(false);
        actualButton = new Button();
        addComponent(BorderLayout.WEST, actualButton);
        addComponent(BorderLayout.CENTER, text);
        setLeadComponent(actualButton);
    }

    public void setText(String t) {
        text.setText(getUIManager().localize(t, t));
    }

    public void setIcon(Image i) {
        actualButton.setIcon(i);
    }

    public String getText() {
        return text.getText();
    }

    public Image getIcon() {
        return actualButton.getIcon();
    }

    public void addActionListener(ActionListener l) {
        actualButton.addActionListener(l);
    }

    public void removeActionListener(ActionListener l) {
        actualButton.removeActionListener(l);
    }

}

14.11.1. Blocking Lead Behavior

The  Component  class  has  two  methods  that  allow  us  to  exclude  a  component  from  lead  behavior:

539

setBlockLead(boolean) & isBlockLead().

Effectively  when  you  have  a  Component  within  the  lead  hierarchy  that  you  would  like  to  treat
differently from the rest you can use this method to exclude it from the lead component behavior

while keeping the rest in line…

This should have no effect if the component isn’t a part of a lead component.

The sample below is based on the Accordion component which uses a lead component internally.

Form f = new Form("Accordion", new BorderLayout());
Accordion accr = new Accordion();
f.getToolbar().addMaterialCommandToRightBar("", FontImage.MATERIAL_ADD, e -> addEntry(accr));
addEntry(accr);
f.add(BorderLayout.CENTER, accr);
f.show();

void addEntry(Accordion accr) {
    TextArea t = new TextArea("New Entry");
    Button delete = new Button();
    FontImage.setMaterialIcon(delete, FontImage.MATERIAL_DELETE);
    Label title = new Label(t.getText());
    t.addActionListener(ee -> title.setText(t.getText()));
    delete.addActionListener(ee -> {
        accr.removeContent(t);
        accr.animateLayout(200);
    });
    delete.setBlockLead(true);
    delete.setUIID("Label");
    Container header = BorderLayout.center(title).
            add(BorderLayout.EAST, delete);
    accr.addContent(header, t);
    accr.animateLayout(200);
}

This  allows  us  to  add/edit  entries  but  it  also  allows  the  delete  button  above  to  actually  work
separately.  Without  a  call  to  setBlockLead(true)  the  delete  button  would  cat  as  the  rest  of  the
accordion title.

Figure 448. Accordion with delete button entries that work despite the surrounding lead

540

14.12. Pull To Refresh

Pull to refresh is the common UI paradigm that Twitter popularized where the user can pull down

the form/container to receive an update. Adding this to Codename One couldn’t be simpler!

Just  invoke  addPullToRefresh(Runnable)  on  a  scrollable  container  (or  form)  and  the  runnable
method will be invoked when the refresh operation occurs.



Pull to refresh is implicitly implements in the InifiniteContainer

Form hi = new Form("Pull To Refresh", BoxLayout.y());
hi.getContentPane().addPullToRefresh(() -> {
    hi.add("Pulled at " + L10NManager.getInstance().formatDateTimeShort(new Date()));
});
hi.show();

Figure 449. Pull to refresh demo

14.13. Running 3rd Party Apps Using Display’s execute

The  Display  [https://www.codenameone.com/javadoc/com/codename1/ui/Display.html]  class’s  execute  method
allows us to invoke a URL which is bound to a particular application.

This  works  rather  well  assuming  the  application  is  installed.  E.g.  this  list  [http://wiki.akosma.com/

IPhone_URL_Schemes]  contains  a  set  of  valid  URL’s  that  can  be  used  on  iOS  to  run  common

applications and use builtin functionality.

Some URL’s might not be supported if an app isn’t installed, on Android there isn’t much that can be
done but iOS has a canOpenURL method for Objective-C.

On iOS you can use the Display.canExecute() method which returns a Boolean instead of a boolean
which allows us to support 3 result states:

1. Boolean.TRUE - the URL can be executed

2. Boolean.FALSE - the URL isn’t supported or the app is missing

3. null - we have no idea whether the URL will work on this platform.

541

The sample below launches a "godfather" search on IMDB only when this is sure to work (only on

iOS currently). We can actually try to search in the case of null as well but this sample plays it safe

by using the http link which is sure to work:

Boolean can = Display.getInstance().canExecute("imdb:///find?q=godfather");
if(can != null && can) {
    Display.getInstance().execute("imdb:///find?q=godfather");
} else {
    Display.getInstance().execute("http://www.imdb.com");
}

14.14. Automatic Build Hint Configuration

We  try  to  make  Codename  One  "seamless",  this  expresses  itself  in  small  details  such  as  the

automatic  detection  of  permissions  on  Android  etc.  The  build  servers  go  a  long  way  in  setting  up

the environment as intuitive. But it’s not enough, build hints are often confusing and obscure. It’s

hard to abstract the mess that is native mobile OS’s and the odd policies from Apple/Google…

A good example for a common problem developers face is location code that doesn’t work in iOS.
This is due to the ios.locationUsageDescription build hint that’s required. The reason that build hint
was added is a requirement by Apple to provide a description for every app that uses the location

service.

To solve this sort of used case we have two API’s in Display:

/**
 * Returns the build hints for the simulator, this will only work in the debug environment and it's
 * designed to allow extensions/API's to verify user settings/build hints exist
 * @return map of the build hints that isn't modified without the codename1.arg. prefix
 */
public Map<String, String> getProjectBuildHints() {}

/**
 * Sets a build hint into the settings while overwriting any previous value. This will only work in the
 * debug environment and it's designed to allow extensions/API's to verify user settings/build hints exist.
 * Important: this will throw an exception outside of the simulator!
 * @param key the build hint without the codename1.arg. prefix
 * @param value the value for the hint
 */
public void setProjectBuildHint(String key, String value) {}

Both  of  these  allow  you  to  detect  if  a  build  hint  is  set  and  if  not  (or  if  it’s  set  incorrectly)  set  its

value…

if  you  will  use 

So 
the  simulator  and  you  didn’t  define
from 
ios.locationUsageDescription Codename One will implicitly define a string there. The cool thing is
that you will now see that string in your settings and you would be able to customize it easily.

location  API 

the 

However, this gets way better than just that trivial example!

542

The real value is for 3rd party cn1lib authors. E.g. Google Maps or Parse. They can inspect the build

hints in the simulator and show an error in case of a misconfiguration. They can even show a setup

UI.  Demos  that  need  special  keys  in  place  can  force  the  developer  to  set  them  up  properly  before

continuing.

14.15. Easy Thread

Working  with  threads  is  usually  ranked  as  one  of  the  least  intuitive  and  painful  tasks  in

programming.  This  is  such  an  error  prone  task  that  some  platforms/languages  took  the  route  of

avoiding  threads  entirely.  I  needed  to  convert  some  code  to  work  on  a  separate  thread  but  I  still

wanted the ability to communicate and transfer data from that thread.

This is possible in Java but non-trivial, the thing is that this is relatively easy to do in Codename One
with tools such as callSerially I can let arbitrary code run on the EDT. Why not offer that to any
random thread?

That’s why I created EasyThread which takes some of the concepts of Codeame One’s threading and
makes  them  more  accessible  to  an  arbitrary  thread.  This  way  you  can  move  things  like  resource

loading into a separate thread and easily synchronize the data back into the EDT as needed…

Easy thread can be created like this:

EasyThread e = EasyThread.start("ThreadName");

You can just send a task to the thread using:

e.run(() -> doThisOnTheThread());

But it gets better, say you want to return a value:

e.run((success) -> success.onSuccess(doThisOnTheThread()), (myResult) -> onEDTGotResult(myRsult));

Lets  break  that  down…  We  ran  the  thread  with  the  success  callback  on  the  new  thread  then  the
→
callback 
success.onSuccess(doThisOnTheThread())  ran  off  the  EDT  in  the  thread  and  when  we  invoked  the
onSuccess callback it sent it asynchronously to the EDT here: (myResult) → onEDTGotResult(myRsult).

the  EDT 

(success) 

invoked 

result. 

code 

this 

got 

on 

So 

as 

a 

These asynchronous calls make things a bit painful to wade thru so instead I chose to wrap them in

a simplified synchronous version:

EasyThread e = EasyThread.start("Hi");
int result = e.run(() -> {
    System.out.println("This is a thread");
    return 3;
});

543

There  are  a  few  other  variants  like  runAndWait  and  there  is  a  kill()  method  which  stops  a  thread
and releases its resources.

14.16. Mouse Cursor

Codename  one  can  change  the  mouse  cursor  when  hovering  over  specific  areas  to  indicate

resizability,  movability  etc.  For  obvious  reasons  this  feature  is  only  available  in  the  desktop  and

JavaScript ports as the other ports rely mostly on touch interaction. The feature is off by default and
needs  to  be  enabled  on  a  Form  by  using  Form.setEnableCursors(true);.  If  you  are  writing  a  custom
component that can use cursors such as SplitPane you can use:

@Override
protected void initComponent() {
    super.initComponent();
    getComponentForm().setEnableCursors(true);
}

Once  this  is  enabled  you  can  set  the  cursor  over  a  specific  region  using  cmp.setCursor()  which
accepts one of the cursor constants defined in Component.

14.17. Working With GIT

Working  with  GIT  for  storing  Codename  One  projects  isn’t  exactly  a  feature  but  since  it  is  so

ubiquitous we think it’s important to have a common guideline.

When we first started committing to git we used something like this for netbeans projects:

*.jar
nbproject/private/
build/
dist/
lib/CodenameOne_SRC.zip

Removing the jars, build, private folder etc. makes a lot of sense but there are a few nuances that

are missing here…

14.17.1. cn1lib’s

You will notice we excluded the jars which are stored under lib and we exclude the Codename One

source  zip.  But  I  didn’t  exclude  cn1libs…  That  was  an  omission  since  the  original  project  we

committed didn’t have cn1libs. But should we commit a binary file to git?

I don’t know. Generally git isn’t very good with binaries but cn1libs make sense. In another project

that did have a cn1lib I did this:

544

*.jar
nbproject/private/
build/
dist/
lib/CodenameOne_SRC.zip
lib/impl/
native/internal_tmp/

The important lines are lib/impl/ and native/internal_tmp/. Technically cn1libs are just zips. When
you do a refresh libs they unzip into the right directories under lib/impl and native/internal_tmp.
By excluding these directories we can remove duplicates that can result in conflicts.

14.17.2. Resource Files

Committing the res file is a matter of personal choice. It is committed in the git ignore files above

but you can remove it. The res file is at risk of corruption and in that case having a history we can

refer to, matters a lot.

But the resource file is a bit of a problematic file. As a binary file if we have a team working with it

the conflicts can be a major blocker. This was far worse with the old GUI builder, that was one of

the big motivations of moving into the new GUI builder which works better for teams.

Still, if you want to keep an eye of every change in the resource file you can switch on the  File →
XML Team Mode which should be on by default. This mode creates a file hierarchy under the res
directory to match the res file you opened. E.g. if you have a file named src/theme.res it will create
a matching res/theme.xml and also nest all the images and resources you use in the res directory.

That’s very useful as you can edit the files directly and keep track of every file in git. However, this

has two big drawbacks:

• It’s flaky - while this mode works it never reached the stability of the regular res file mode

• It conflicts - the simulator/device are oblivious to this mode. So if you fetch an update you also

need to update the res file and you might still have conflicts related to that file

Ultimately both of these issues shouldn’t be a deal breaker. Even though this mode is a bit flaky it’s

better than the alternative as you can literally "see" the content of the resource file. You can easily

revert and reapply your changes to the res file when merging from git, it’s tedious but again not a

deal breaker.

14.17.3. Eclipse Version

Building on the gitignore we have for NetBeans the eclipse version should look like this:

545

.DS_Store
*.jar
build/
dist/
lib/impl/
native/internal_tmp/
.metadata
bin/
tmp/
*.tmp
*.bak
*.swp
*.zip
*~.nib
local.properties
.settings/
.loadpath
.recommenders
.externalToolBuilders/
*.launch
*.pydevproject
.cproject
.factorypath
.buildpath
.project
.classpath

14.17.4. IntelliJ/IDEA

546

.DS_Store
*.jar
build/
dist/
lib/impl/
native/internal_tmp/
*.zip
.idea/**/workspace.xml
.idea/**/tasks.xml
.idea/dictionaries
.idea/**/dataSources/
.idea/**/dataSources.ids
.idea/**/dataSources.xml
.idea/**/dataSources.local.xml
.idea/**/sqlDataSources.xml
.idea/**/dynamic.xml
.idea/**/uiDesigner.xml
.idea/**/gradle.xml
.idea/**/libraries
*.iws
/out/
atlassian-ide-plugin.xml

547

548

15. Performance, Size & Debugging

15.1. Reducing Resource File Size

It’s  easy  to  lose  track  of  size/performance  when  you  are  working  within  the  comforts  of  a  visual

tool like the Codename One Designer. When optimizing resource files you need to keep in mind one

thing: it’s all about image sizes.



Images  will  take  up  95-99%  of  the  resource  file  size;  everything  else  pales  in

comparison.

Like every optimization the first rule is to reduce the size of the biggest images which will provide

your  biggest  improvements,  for  this  purpose  we  introduced  the  ability  to  see  image  sizes  in

kilobytes. To launch that feature use the menu item Images → Image Sizes (KB) in the designer.

Figure 450. Image sizes window that allows us to find the biggest impact on our RAM/Storage

This  produces  a  list  of  images  sorted  by  size  with  their  sizes.  Often  the  top  entries  will  be  multi-

images,  which  include  HD  resolution  values  that  can  be  pretty  large.  These  very  high-resolution

images take up a significant amount of space!

Just  going  to  the  multi-images,  selecting  the  unnecessary  resolutions  &  deleting  these  images  can

saves significant amounts of space:

Figure 451. Removing unused DPI’s



You can see the size in KB at the top right side in the designers image viewer

Applications using the old GUI builder can use the  Images →  Delete Unused Images menu option

(it’s  also  under  the  Images  menu).  This  tool  allows  detecting  and  deleting  images  that  aren’t  used

549

within the theme/GUI.

If you have a very large image that is opaque you might want to consider converting it to JPEG and

replacing  the  built  in  PNG’s.  Notice  that  JPEG’s  work  on  all  supported  devices  and  are  typically

smaller.

Figure 452. Convert a MultiImage to use JPEGs instead of PNGs

You  can  use  the  excellent  OptiPng  [http://optipng.sourceforge.net/]  tool  to  optimize  image  files  right

from the Codename One designer. To use this feature you need to install OptiPng then select Images

→  Launch OptiPng from the menu. Once you do that the tool will automatically optimize all your

PNG’s.

When  faced  with  size  issues  make  sure  to  check  the  size  of  your  res  file,  if  your  JAR  file  is  large

open it with a tool such as 7-zip and sort elements by size. Start reviewing which element justifies

the size overhead.

15.2. Improving Performance

There are quite a few things you can do as a developer in order to improve the performance and

memory  footprint  of  a  Codename  One  application.  This  sometimes  depends  on  specific  device

behaviors but some of the tips here are true for all devices.

The simulator contains some tools to measure performance overhead of a specific component and

also detect EDT blocking logic. Other than that follow these guidelines to create more performance

code:

• Avoid  round  rect  borders  -  they  have  a  huge  overhead  on  all  platforms.  Use  image  borders

instead (counter intuitively they are MUCH faster)

• Avoid Gradients - they perform poorly on most OS’s. Use a background image instead

• Use larger images when tiling or building image borders, using a 1 pixel (or event a few pixels)

wide or high image and tiling it repeatedly can be very expensive

• Shrink  resource  file  sizes  -  Otherwise  data  might  get  collected  by  the  garbage  collector  and

reloading data might be expensive

• Check  that  you  don’t  have  too  many  image  lock  misses  -  this  is  discussed  in  the  graphics

section

• On some platforms mutable images are slow - mutable images are images you can draw on
(using  getGraphics()).  On  some  platforms  they  perform  quite  badly  (e.g.  iOS)  and  should

550

generally  be  avoided.  You  can  check  if  mutable  images  are  fast  in  a  platform  using
Display.areMutableImagesFast()

• *  Make  components  either  transparent  or  opaque  *  -  a  translucent  component  must  paint  it’s

parent  every  time.  This  can  be  expensive.  An  opaque  component  might  have  margins  that

would  require  that  we  paint  the  parent  so  there  is  often  overdraw  in  such  cases  (overdraw

means the same pixel being painted twice).

15.3. Performance Monitor

The Performance Monitor tool can be accessible via the  Simulator →  Performance Monitor menu

option  in  the  simulator.  This  launches  the  following  UI  that  can  help  you  improve  application

performance:

Figure 453. Main tab of the performance monitor: Logs and timings

The  first  tab  of  the  performance  monitor  includes  a  table  of  the  drawn  components.  Each  entry

includes the number of times it was drawn and the slowest/fastest and average drawing time.

This is useful if a Form is slow. You might be able to pinpoint it to a specific component using this
tool.

The Log on the bottom includes debug related information. E.g. it warns about the usage of mutable

images  which  might  be  slow  on  some  platforms.  This  also  displays  warnings  when  an  unlocked

image is drawn etc.

551

Figure 454. Rendering tree

The  rendering  tree  view  allows  us  to  inspect  the  hierarchy  painting.  You  can  press  the  refresh
button which will trigger the painting of the current Form. Every graphics operation is logged and so
is the stack to it.

You can then inspect the hierarchy and see what was drawn by the various components. You can

click the "stack" buttons to see the specific stack trace that lead to that specific drawing operation.

This is a remarkably powerful debugging tool as you can literally see "overdraw" within this tool.
E.g  if  you  see  fillRect  or  similar  API’s  invoked  in  the  parent  and  then  again  and  again  in  the
children this could indicate a problem.



Android devices have a very nice overdraw debugging tool

15.4. Network Speed

Figure 455. Network speed tool

This  feature  is  actually  more  useful  for  general  debugging  however  it’s  sometimes  useful  to

simulate a slow/disconnected network to see how this affects performance.

For this purpose the Codename One simulator allows you to slow down networking or even fake a

disconnected network to see how your application handles such cases.

552

15.5. Debugging Codename One Sources

When you debug your app with our source code you can place breakpoints deep within Codename

One and gain unique insight. You can also use the profilers and profile into Codename One to gain

similar performance specific insight.

When you run into a bug or a missing feature you can push that feature/fix back to Codename One

[https://www.codenameone.com/] using a pull request. Github makes that process trivial and in this new

video and slides below we show you how. The steps to use the code are:

1. Signup for Github

2. Fork  http://github.com/codenameone/CodenameOne  and  http://github.com/codenameone/

codenameone-skins (also star and watch the projects for good measure).

3. Clone the git URL’s from the projects into the IDE using the  Team →  Git →  Clone menu option.

Notice that you must deselect projects in the IDE for the menu to appear.

4. Download  the  cn1-binaries  project  from  github  here  [https://github.com/codenameone/cn1-binaries/

archive/master.zip].

5. Unzip  the  cn1-binaries  project  and  make  sure  the  directory  has  the  name  cn1-binaries.  Verify

that cn1-binaries, CodenameOne and codenameone-skins are within the same parent directory.

.In your own project remove the jars both in the build & run libraries section. Replace the build
libraries  with  the  CodenameOne/CodenameOne  project.  Replace  the  runtime  libraries  with  the
CodenameOne/Ports/JavaSEPort project.

This allows you to run the existing Codename One project with the Codename One source code and

debug  into  Codename  One.  You  can  now  also  commit,  push  and  send  a  pull  request  with  the

changes.

15.6. Device Testing Framework/Unit Testing

Codename One includes a built in testing framework and test recorder tool as part of the simulator.

This allows developers to build both functional and unit test execution on top of Codename One. It

even enables sending tests for execution on the device (pro-only feature).

To get started with the testing framework, launch the application and open the test recorder in the

simulator menu.

553

Figure 456. The test recorder tool in the simulator

Once you press record a test will be generate for you as you use the application.

Figure 457. Test recording in progress, when done just press the save icon

You can build tests using the Codename One testing package to manipulate the Codename One UI

programmatically and perform various assertions.

Unlike  frameworks  such  as  JUnit  which  assign  a  method  per  test,  the  Codename  One  test

framework uses a class per test. This allows the framework to avoid reflection and thus allows it to

work properly on the device.

15.7. EDT Error Handler and sendLog

Handling errors or exceptions in a deployed product is pretty difficult, most users would just throw

away  your  app  and  some  would  give  it  a  negative  rating  without  providing  you  with  the

opportunity to actually fix the bug that might have happened.

Figure 458. Default error dialog

554

Google  improved  on  this  a  bit  by  allowing  users  to  submit  stack  traces  for  failures  on  Android

devices but this requires the users approval for sending personal data which you might not need if

you only want to receive the stack trace and maybe some basic application state (without violating

user privacy).

For quite some time Codename One had a very powerful feature that allows you to both catch and

report such errors, the error reporting feature uses the Codename One cloud which is exclusive for

pro/enterprise  users.  Normally  in  Codename  One  we  catch  all  exceptions  on  the  EDT  (which  is

where  most  exceptions  occur)  and  just  display  an  error  to  the  user  as  you  can  see  in  the  picture.

Unfortunately  this  isn’t  very  helpful  to  us  as  developers  who  really  want  to  see  the  stack;

furthermore we might prefer the user doesn’t see an error message at all!

Codename One allows us to grab all exceptions that occur on the EDT and handle them using the
method  addEdtErrorHandler  in  the  Display  [https://www.codenameone.com/javadoc/com/codename1/ui/
Display.html]  class.  Adding  this  to  the  Log’s  ability  to  report  errors  directly  to  us  and  we  can  get  a

very powerful tool that will send us an email with information when a crash occurs!

This can be accomplished with a single line of code:

Log.bindCrashProtection(true);

We  normally  place  this  in  the  init(Object)  method  so  all  future  on-device  errors  are  emailed  to
you. Internally this method uses the Display.getInstance().addEdtErrorHandler() API to bind error
listeners 
(using
ActionEvent.consume()). The Log data is then sent using Log.sendLog().

the  EDT.  When  an  exception 

is  swallowed 

thrown 

there 

to 

is 

it 

To truly benefit from this feature we need to use the Log class for all logging and exception handling
instead of API’s such as System.out.

To  log  standard  printouts  you  can  use  the  Log.p(String)  method  and  to  log  exceptions  with  their
stack trace you can use Log.e(Throwable).

15.8. Kitchen Sink Case Study

Performance is one of those vague subjects that is often taught by example.

During our debugging of the contacts demo that is a part of the new kitchen sink demo we noticed
its performance was sub par. We assumed this was due to the implementation of getAllContacts &
that  there  is  nothing  to  do.  While  debugging  another  issue  we  noticed  an  anomaly  during  the

loading of the contacts.

This led to the discovery that we are loading the same resource file over and over again for every

single contact in the list!

In  the  new  Contacts  demo  we  have  a  share  button  for  each  contact,  the  code  for  constructing  a
ShareButton looks like this:

555

public ShareButton() {
    setUIID("ShareButton");
    FontImage.setMaterialIcon(this, FontImage.MATERIAL_SHARE);
    addActionListener(this);
    shareServices.addElement(new SMSShare());
    shareServices.addElement(new EmailShare());
    shareServices.addElement(new FacebookShare());
}

This  seems  reasonable  until  you  realize  that  the  constructors  for  SMSShare,  EmailShare  &
FacebookShare load the icons for each of those…

These  icons  are  in  a  shared  resource  file  that  we  load  and  don’t  properly  cache.  The  initial

workaround was to cache this resource but a better solution was to convert this code:

public SMSShare() {
    super("SMS", Resources.getSystemResource().getImage("sms.png"));
}

Into this code:

public SMSShare() {
    super("SMS", null);
}

@Override
public Image getIcon() {
    Image i = super.getIcon();
    if(i == null) {
        i = Resources.getSystemResource().getImage("sms.png");
        setIcon(i);
    }
    return i;
}

This way the resource uses lazy loading as needed.

This small change boosted the loading performance and probably the general performance due to

less memory fragmentation.

The lesson that we should learn every day is to never assume about performance…

15.8.1. Scroll Performance - Threads aren’t magic

Another  performance  pitfall  in  this  same  demo  came  during  scrolling.  Scrolling  was  janky

(uneven/unsmooth) right after loading finished would recover after a couple of minutes.

556

This relates to the images of the contacts.

To  hasten  the  loading  of  contacts  we  load  them  all  without  images.  We  then  launch  a  thread  that

iterates the contacts and loads an individual image for a contact. Then sets that image to the contact

and replaces the placeholder image.

This performed well in the simulator but didn’t do too well even on powerful mobile phones. We
assumed  this  wouldn’t  be  a  problem  because  we  used  Util.sleep()  to  yield  CPU  time  but  that
wasn’t enough.

Often  when  we  see  performance  penalty  the  response  is:  "move  it  to  a  separate  thread".  The

problem is that this separate thread needs to compete for the same system resources and merge its

changes back into the EDT. When we perform something intensive we need to make sure that the

CPU isn’t needed right now…

In this and past cases we solved this using a class member indicating the last time a user interacted

with the UI.

Here we defined:

private long lastScroll;

Then we did this within the background loading thread:

// don't do anything while we are scrolling or animating
long idle = System.currentTimeMillis() - lastScroll;
while(idle < 1500 || contactsDemo.getAnimationManager().isAnimating() || scrollY != contactsDemo.getScrollY()) {
    scrollY = contactsDemo.getScrollY();
    Util.sleep(Math.min(1500, Math.max(100, 2000 - ((int)idle))));
    idle = System.currentTimeMillis() - lastScroll;
}

This  effectively  sleeps  when  the  user  interacts  with  the  UI  and  only  loads  the  images  if  the  user

hasn’t touched the UI in a while.

Notice that we also check if the scroll changes, this allows us to notice cases like the animation of

scroll winding down.

All we need to do now is update the lastScroll variable whenever user interaction is in place. This
works for user touches:

parentForm.addPointerDraggedListener(e -> lastScroll = System.currentTimeMillis());

This works for general scrolling:

557

contactsDemo.addScrollListener(new ScrollListener() {
    int initial = -1;
    @Override
    public void scrollChanged(int scrollX, int scrollY, int oldscrollX, int oldscrollY) {
        // scrolling is sensitive on devices...
        if(initial < 0) {
            initial = scrollY;
        }
        lastScroll = System.currentTimeMillis();
        ...
    }
});

 Due to technical constraints we can’t use a lambda in this specific case…

558

16. Advanced Topics/Under the Hood

16.1. Sending Arguments To The Build Server

When sending a build to the server we can provide additional parameters to the build, which are

incorporated into the build process on the server to "hint" on multiple different build time options.

These  hints  are  often  referred  to  as  "build  hints"  or  "build  arguments",  they  are  effectively  very

much  like  souped  up  compiler  flags  that  you  can  use  to  tune  the  build  server’s  behavior.  This  is

useful  for  fast  iteration  on  new  functionality  without  building  plugin  UI  for  every  change.  This  is

also useful for exposing very low level behavior such as customizing the Android manifest XML or

the iOS plist.

You  can  set  these  hints  by  right  clicking  the  project  in  the  IDE  and  selecting  Codename One  →
Codename One Settings → Build Hints. The hints use the key=value style of data.

Figure 459. The build hints UI in Codename One Settings

You can set the build hints in the codenameone_settings.properties file directly notice that when you
do  that  all  settings  need  to  start  with  the  codename1.arg.  prefix.  When  editing  the  properties  file
directly  we  would 
as
need 
codename1.arg.android.debug=true.

android.debug=true 

something 

define 

like 

to 

Here  is  the  current  list  of  supported  arguments,  notice  that  build  hints  are  added  all  the  time  so

consult the discussion forum if you don’t find what you need here:

Table 10. Build hints

Name

android.debug

android.release

android.installLocation

Description

true/false defaults to true - indicates whether to

include the debug version in the build

true/false defaults to true - indicates whether to

include the release version in the build

Maps to android:installLocation manifest entry

defaults to auto. Can also be set to internalOnly

or preferExternal.

559

Name

android.gradle

Description

Deprecated, this mode is no longer supported.

true/false defaults to false prior to 3.3 and true

after. Uses Gradle instead of Ant to build the

Android app

android.xapplication

defaults to an empty string. Allows developers of

native Android code to add text within the

application block to define things such as

widgets, services etc.

android.permission.PERMISSION_NAME

true/false Whether to include a particular

permission. Use of these build hints is preferred
to android.xpermissions since they avoid possible
conflicts with libraries. See Android’s

Manifest.permission docs

[https://developer.android.com/reference/android/

Manifest.permission.html] for a full list of

permissions.

Will be translated to the maxSdkVersion attribute
of the <uses-permission> tag for the
corresponding
android.permission.PERMISSION_NAME build hint.
(Optional)

true/false Will be translated to the required
attribute of the <uses-permission> tag for the
corresponding
android.permission.PERMISSION_NAME build hint.
(Optional)

additional permissions for the Android manifest

Allows adding an intent filter to the main

android activity

Allows explicitly setting the android:launchMode
attribute of the main activity in android. Default

is "singleTop", but for some applications you

may need to change this behaviour. In

particular, apps that are meant to open a file

type will need to set this to "singleTask". See

Android docs for the activity element

[https://developer.android.com/guide/topics/manifest/

activity-element.html] for more information about
the android:launchMode attribute.

The license key for the Android app, this is

required if you use in-app-purchase on Android

android.permission.PERMISSION_NAME.maxSd

kVersion

android.permission.PERMISSION_NAME.require

d

android.xpermissions

android.xintent_filter

android.activity.launchMode

android.licenseKey

android.stack_size

Size in bytes for the Android stack thread

560

Name

Description

android.statusbar_hidden

true/false defaults to false. When set to true

hides the status bar on Android devices.

android.facebook_permissions

Permissions for Facebook used in the Android

android.googleAdUnitId

build target, applicable only if Facebook native

integration is used.

Allows integrating admob/google play ads, this is

effectively identical to google.adUnitId but only

applies to Android

android.googleAdUnitTestDevice

Device key used to mark a specific Android

device as a test device for Google Play ads

defaults to

C6783E2486F0931D9D09FABC65094FDF

android.includeGPlayServices

Deprecated, please android.playService.*!

android.playService.plus,

android.playService.auth,

android.playService.base,

android.playService.identity,

android.playService.indexing,

android.playService.appInvite,

android.playService.analytics,

android.playService.cast,

android.playService.gcm,

android.playService.drive,

android.playService.fitness,

android.playService.location,

android.playService.maps,

android.playService.ads,

android.playService.vision,

android.playService.nearby,

android.playService.panorama,

android.playService.games,

android.playService.safetynet,

android.playService.wallet,

android.playService.wearable

Indicates whether Goolge Play Services should

be included into the build, defaults to false but

that might change based on the functionality of

the application and other build hints. Adding

Google Play Services support allows us to use a

more refined location implementation and

invoke some Google specific functionality from

native code.

Allows including only a specific play services

library portion. Notice that this setting conflicts

with the deprecated
android.includeGPlayServices and only works
with the gradle build (which is on by default but
can be toggled using android.gradle).

If none of the services are defined to true then

plus, auth, base, analytics, gcm, location, maps &

ads will be set to true. If one or more of the
android.playService entries are defined to
something then all entries will default to false.

561

Name

Description

android.playServicesVersion

The version number of play services to build

against. Experimental. Use with caution as

building against versions other than the server

default may introduce incompatibilities with

some Codename One APIs.

xxx.minPlayServicesVersion

This is a special case build hint. You can use any

prefix to the build hint and the convention is to

use your cn1lib name. It’s identical to
android.minPlayServicesVersion with the
exception that the "highest version wins". That

way if your cn1lib requires play services 9+ and
uses: myLib.minPlayServicesVersion=9.0.0 and
another library has
otherLib.minPlayServicesVersion=10.0.0 then
play services will be 10.0.0

Boolean true/false defaults to false. Multidex

allows Android binaries to reference more than

65536 methods. This slows builds a bit so we

have it off by default but if you get a build error

mentioning this limit you should turn this on.

android.multidex

android.headphoneCallback

Boolean true/false defaults to false. When set to

true it assumes the main class has two methods:
headphonesConnected & headphonesDisconnected
which it invokes appropriately as needed

Indicates whether the GPS permission should be

requested, it is auto-detected by default if you

use the location API. However, some code might

want to explicitly define it

Boolean true/false defaults to true. Toggles the

Android pipeline between the legacy pipeline

(false) and new pipeline (true)

Allows injecting additional entries into the

strings.xml file using a value that includes

something like this`<string

name="key1">value1</string><string

name="key2">value2</string>`

Boolean true/false defaults to false but that can

change based on usage (e.g. push implicitly

activates this). Indicates whether the android

support v4 library should be included in the

build

android.gpsPermission

android.asyncPaint

android.stringsXml

android.supportV4

562

Name

android.style

Description

Allows injecting additional data into the
styles.xml file right before the closing resources
tag

android.cusom_layout1

Applies to any number of layouts as long as they

are in sequence (e.g. android.cusom_layout2,

android.cusom_layout3 etc.). Will write the

content of the argument as a layout xml file and
give it the name cusom_layout1.xml onwards.
This can be used by native code to work with

XML files

android.keyboardOpen

Boolean true/false defaults to true. Toggles the

android.versionCode

android.captureRecord

new async keyboard mode that leaves the

keyboard open while we move between text

components

Allows overriding the auto generated version

number with a custom internal version number

specifically used for the xml attribute
android:versionCode

Indicates whether the RECORD_AUDIO permission
should be requested. Can be enabled or any other
value to disable this option

android.nonconsumable

Comma delimited string of items that are non-

android.removeBasePermissions

consumable in the in-app-purchase API

Boolean true/false defaults to false. Disables the
builtin permissions specifically INTERNET
permission (i.e. no networking…)

android.blockExternalStoragePermission

Boolean true/false defaults to false. Disables the

external storage (SD card) permission

android.min_sdk_version

The minimum SDK required to run this app, the

default value changes based on functionality but

can be as low as 7. This corresponds to the XML
attribute android:minSdkVersion.

android.mockLocation

Boolean true/false defaults to true. Toggles the

android.smallScreens

android.xapplication_attr

mock location permission which is on by

default, this allows easier debugging of Android

device location based services

Boolean true/false defaults to true. Corresponds
to the android:smallScreens XML attribute and
allows disabling the support for very small

phones

Allows injecting additional attributes into the
application` tag in the Android XML

563

Name

android.xactivity

android.streamMode

android.pushVibratePattern

android.enableProguard

android.proguardKeep

Description

Allows injecting additional attributes into the
activity tag in the Android XML

The mode in which the volume key should

behave, defaults to OS default. Allows setting it
to music for music playback apps

Comma delimited long values to describe the
push pattern of vibrate used for the setVibrate
native method

Boolean true/false defaults to true. Allows

disabling the proguard obfuscation even on

release builds, notice that this isn’t

recommended

Arguments for the keep option in proguard
allowing us to keep a pattern of files e.g. -keep
class com.mypackage.ProblemClass { *; }

android.shrinkResources

Boolean true/false defaults to false. Used only in

conjunction with android.enableProguard.

Strips out unused resources to reduce apk size.

Since 7.0

android.sharedUserId

Allows adding a manifest attribute for the

sharedUserId option

android.sharedUserLabel

Allows adding a manifest attribute for the

sharedUserLabel option

android.targetSDKVersion

Indicates the Android SDK used to compile the

android.useAndroidX

android.theme

Android build currently defaults to 21. Notice

that not all targets will work since the source

might have some limitations and not all SDK

targets are installed on the build servers.

Use Android X instead of support libraries. This

will also run a find/replace on all source files to

replace support libraries and artifacts with

AndroidX equivalents.

Light or Dark defaults to Light. On Android 4+

the default Holo theme is used to render the

native widgets in some cases and this indicates

whether holo light or holo dark is used.

Currently this doesn’t affect the Codename One

theme but that might change in the future.

android.web_loading_hidden

true/false defaults to false - set to true to hide the

progress indicator that appears when loading a

web page on Android.

564

Name

Description

block_server_registration

true/false flag defaults to false. By default

facebook.appId

Codename One applications register with our

server, setting this to true blocks them from

sending information to our cloud. We keep this

data for statistical purposes and intend to

provide additional installation stats in the

future.

The application ID for an app that requires

native Facebook login integration, this defaults

to null which means native Facebook support

shouldn’t be in the app

gcm.sender_id

The Android/chrome push identifier, see the

push section for more details

android.background_push_handling

Deliver push messages on Android when the app

ios.associatedDomains

is minimized by setting this to "true". Default

behaviour is to deliver the message only if the

app is in the foreground when received, or after

the user taps on the notification to open the app,

if the app was in the background when the

message was received.

Comma-delimited list of domains associated

with this app. Since 6.0. Note that each domain

should be prefixed by a supported prefix. E.g.

"applinks:" or "webcredentials:". See Apple’s

documentation on Associated domains

[https://developer.apple.com/documentation/security/
password_autofill/

setting_up_an_app_s_associated_domains?

language=objc] for more information.

ios.bitcode

true/false defaults to false. Enables bitcode

ios.debug.archs

support for the build.

Can be set to "arm64" to force iOS debug builds

to be 64 bit. By default, debug builds are 32 bit in

order to shorten build-times and maintain

compatibility with older devices.

ios.distributionMethod

Specifies distribution type for debug iOS builds.

This is generally used for enterprise or ad-hoc

builds (using values "enterprise" and "ad-hoc"

respectively).

ios.debug.distributionMethod

Specifies distribution type for debug iOS builds

only. This is generally used for enterprise or ad-

hoc builds (using values "enterprise" and "ad-

hoc" respectively).

565

Name

Description

ios.release.distributionMethod

Specifies distribution type for release iOS builds

ios.keyboardOpen

ios.urlScheme

ios.useAVKit

ios.teamId

ios.debug.teamId

ios.release.teamId

ios.project_type

ios.rpmalloc

only. This is generally used for enterprise or ad-

hoc builds (using values "enterprise" and "ad-

hoc" respectively).

Flips between iOS keyboard open mode and

auto-fold keyboard mode. Defaults to true which

means the keyboard will remain open and not

fold automatically when editing moves to

another field.

Allows intercepting a URL call using the syntax
<string>urlPrefix<string>

Use AVKit for video components on iOS rather
than MPMoviePlayerController on iOS versions 8
through 12. iOS 13 will always use AVKit, and

iOS 7 and lower will always use
MPMoviePlayerController. Default value false

Specifies the team ID associated with the iOS

provisioning profile and certificate. Use
ios.debug.teamId and ios.release.teamId to
specify different team IDs for debug and release

builds respectively.

Specifies the team ID associated with the iOS

debug provisioning profile and certificate.

Specifies the team ID associated with the iOS

release provisioning profile and certificate.

one of ios, ipad, iphone (defaults to ios).

Indicates whether the resulting binary is

targeted to the iphone only or ipad only. Notice

that the IDE plugin has a "Project Type" combo

box you should use under the iOS section.

true/false Use rpmalloc [https://github.com/
rampantpixels/rpmalloc] instead of malloc/free for

memory allocation in ParparVM. This will cause

the deployment target to be changed to a

minimum of iOS 8.0.

ios.statusbar_hidden

true/false defaults to false. Hides the iOS status

bar if set to true.

566

Name

ios.newStorageLocation

ios.prerendered_icon

Description

true/false defaults to false but defined on new

projects as true by default. This changes the

storage directory on iOS from using caches to

using the documents directory which is more

correct but might break compatibility. This is

described in this issue [https://github.com/

codenameone/CodenameOne/issues/1480]

true/false defaults to false. The iOS build process

adapts the submitted icon for iOS conventions

(adding an overlay) that might not be

appropriate on some icons. Setting this to true

leaves the icon unchanged (only scaled).

ios.app_groups

Space-delimited list of app groups that this app

belongs to as described in Apple’s

documentation [https://developer.apple.com/library/
content/documentation/Miscellaneous/Reference/

EntitlementKeyReference/Chapters/

EnablingAppSandbox.html#//apple_ref/doc/uid/

TP40011195-CH4-SW19]. These are added to the

entitlements file with key
com.apple.security.application-groups.

ios.keychainAccessGroup

Space-delimited list of keychain access groups

ios.application_exits

that this app has access to as described in

Apple’s documentation [https://developer.apple.com/
library/content/documentation/Security/Conceptual/

keychainServConcepts/02concepts/concepts.html#//

apple_ref/doc/uid/TP30000897-CH204-SW11]. These are

added to the entitlements file with the key
keychain-access-groups.

true/false (defaults to false). Indicates whether

the application should exit immediately on

home button press. The default is to exit, leaving

the application running is only partially tested at

the moment.

ios.blockScreenshotsOnEnterBackground

true/false (defaults to false). Indicates that app

should prevent iOS from taking screenshots

when app enters background. Described here

[https://shannah.github.io/cn1-recipes/#

_hiding_sensitive_data_when_entering_background].

567

Name

Description

ios.applicationQueriesSchemes

ios.themeMode

ios.interface_orientation

Comma separated list of url schemes that
canExecute will respect on iOS. If the url scheme
isn’t mentioned here canExecute will return false
starting with iOS 9. Notice that this collides with
ios.plistInject when used with the
<key>LSApplicationQueriesSchemes</key>… value
so you should use one or the other. E.g. to enable
canExecute for a url like myurl://xys you can use:
myurl,myotherurl

default/legacy/modern/auto (defaults to default).

Default means you don’t define a theme mode.

Currently this is equivalent to legacy. In the

future we will switch this to be equivalent to

auto. legacy - this will behave like iOS 6

regardless of the device you are running on.

modern - this will behave like iOS 7 regardless of

the device you are running on. auto - this will

behave like iOS 6 on older devices and iOS 7 on

newer devices.

UIInterfaceOrientationPortrait by default.

Indicates the orientation, one or more of

(separated by colon :):

UIInterfaceOrientationPortrait,

UIInterfaceOrientationPortraitUpsideDown,

UIInterfaceOrientationLandscapeLeft,

UIInterfaceOrientationLandscapeRight. Notice

that the IDE plugin has an "Interface

Orientation" combo box you should use under

the iOS section.

ios.xcode_version

The version of xcode used on the server.

Defaults to 4.5; currently accepts 5.0 as an option

and nothing else.

ios.multitasking

Set to true to enable iOS multitasking and split-

screen support. This only works if
ios.xcode_verson=9.2.

Valid values include 5 or 8. Indicates the JVM

version that should be used for server

compilation, this is defined by default for newly

created apps based on the Java 8 mode selection

java.version

568

Name

javascript.inject_proxy

javascript.inject.beforeHead

javascript.inject.afterHead

javascript.minifying

Description

true/false (defaults to true) By default, the build
server will configure the .war version of your

app to use the bundled proxy servlet for HTTP

requests (to get around same-origin restrictions
on network requests). Setting this to false
prevents this, causing the application to make

network requests without a proxy.

Content to be injected into the index.html file at
the beginning of the <head> tag.

Content to be injected into the index.html file at
the end of the <head> tag.

true/false (defaults to true). By default the
javascript code is minified to reduce file size.

You may optionally disable minification by
setting javascript.minifying to false.

javascript.proxy.url

The URL to the proxy servlet that should be used

javascript.sourceFilesCopied

javascript.stopOnErrors

for making network requests. If this is omitted,

the .war version of the app will be set to use the

bundled proxy servlet, and the .zip version of

the app will be set to use no proxy. If
javascript.inject_proxy is false, this build-hint
will be ignored.

true/false (defaults to false). Setting this flag to
true will cause available java source files to be
included in the resulting .zip and .war files.

These may be used by Chrome during

debugging.

true/false (defaults to true). Cause javascript
build to fail if there are warnings during the

build. In some cases build warnings won’t affect

the running of the app. E.g. if the Javascript port

is missing a method that the app depends on, but

it isn’t used in most of the app. Or if there is

multithreaded code detected in static initializers,

but that code-path isn’t used by the app. Setting
this to false may allow you to get past some
build errors, but it might just result in runtime

errors later on, which are much more difficult to

debug. *This build hint is only available in

Codename One 3.4 and later.

javascript.teavm.version

(Optional) The version of TeaVM to use for the

build. Use caution, only use this property if you

know what you are doing!

569

Name

rim.askPermissions

Description

true/false defaults to true. Indicates whether the

user is prompted for permissions on Blackberry

devices.

google.adUnitId

Allows integrating Admob/Google Play ads into

rim.ignor_legacy

rim.obfuscation

the application see this

[https://www.codenameone.com/blog/adding-google-play-

ads.html]

true/false defaults to false. When set to true the

Blackberry build targets only 5.0 devices and

newer and doesn’t build the 4.x version.

rim.nativeBrowser true/false defaults to false.

Enables the native blackberry browser on OS 5

or higher. It is disabled by default since it might

casue crashes on some cases.

true/false defaults to false. Obfuscate the JAR

before invoking the rimc compiler.

ios.plistInject

entries to inject into the iOS plist file during

ios.includePush

ios.newPipeline

ios.headphoneCallback

build.

true/false (defaults to false). Whether to include

the push capabilities in the iOS build. Notice that

the IDE plugin has an "Include Push" check box

you should use under the iOS section.

Boolean true/false defaults to true. Allows

toggling the OpenGL ES 2.0 drawing pipeline off

to the older OGL ES 1.0 pipeline.

Boolean true/false defaults to false. When set to

true it assumes the main class has two methods:
headphonesConnected & headphonesDisconnected
which it invokes appropriately as needed

ios.facebook_permissions

Permissions for Facebook used in the Android

build target, applicable only if Facebook native

integration is used.

ios.applicationDidEnterBackground

Objective-C code that can be injected into the iOS

callback method (message)
applicationDidEnterBackground.

ios.enableAutoplayVideo

Boolean true/false defaults to false. Makes videos

"auto-play" when loaded on iOS

Allows integrating admob/google play ads, this is

effectively identical to google.adUnitId but only

applies to iOS

ios.googleAdUnitId

570

Name

ios.viewDidLoad

Description

Objective-C code that can be injected into the iOS
callback method (message) viewDidLoad

ios.googleAdUnitIdPadding

Indicates the amount of padding to pass to the

ios.enableBadgeClear

Google ads placed at the bottom of the screen
with google.adUnitId

Boolean true/false defaults to true. Clears the

badge value with every load of the app, this is

useful if the app doesn’t manually keep track of

number values for the badge

ios.glAppDelegateHeader

Objective-C code that can be injected into the iOS

ios.glAppDelegateBody

app delegate at the top of the file. E.g. if you

need to include headers or make special imports

for other injected code

Objective-C code that can be injected into the iOS

app delegate within the body of the file before

the end. This only makes sence for methods that

aren’t already declared in the class

ios.beforeFinishLaunching

Objective-C code that can be injected into the iOS

app delegate at the top of the body of the

didFinishLaunchingWithOptions callback

method

ios.afterFinishLaunching

Objective-C code that can be injected into the iOS

app delegate at the bottom of the body of the

didFinishLaunchingWithOptions callback

method

ios.locationUsageDescription

This flag is required for iOS 8 and newer if you

are using the location API. It needs to include a

description of the reason for which you need

access to the users location

571

Name

Description

ios.NSXXXUsageDescription

iOS privacy flags for using certain APIs. Starting

with Xcode 8, you are required to add usage

description strings for certain APIs. Find a full

list of the available keys in Apple’s docs

[https://developer.apple.com/library/content/
documentation/General/Reference/

InfoPlistKeyReference/Articles/CocoaKeys.html]. Some

relevant ones include
ios.NSCameraUsageDescription,
ios.NSContactsUsageDescription,
ios.NSLocationAlwaysUsageDescription,
NSLocationUsageDescription,
ios.NSMicrophoneUsageDescription,
ios.NSPhotoLibraryAddUsageDescription,
ios.NSSpeechRecognitionUsageDescription,
ios.NSSiriUsageDescription

A semicolon separated list of libraries that

should be linked to the app in order to build it

A comma separated list of Cocoa Pods

[https://cocoapods.org/] that should be linked to the
app in order to build it. E.g. AFNetworking ~> 2.6,
ORStackView ~> 3.0, SwiftyJSON ~> 2.3

Sets the Cocoapods 'platform' for the Cocoapods.

Some Cocoapods require a minimum platform
level. E.g. ios.pods.platform=7.0.

ios.add_libs

ios.pods

ios.pods.platform

ios.deployment_target

Sets the deployment target for iOS builds. This is

the minimum version of iOS required by a

device to install the app. E.g.
ios.deployment_target=8.0. Default is '6.0'. Note:
This build hint interacts with the ios.rpmalloc
build hint. If ios.deployment_target is 8.0 or
higher, ParparVM will use rpmalloc

[https://github.com/rampantpixels/rpmalloc] by

default. You can disable this default and revert

back to using malloc/free by setting the
ios.rpmalloc=false build hint.

Indicates the version number of the bundle, this

is useful if you want to create a minor version

number change for the beta testing support

Added the -ObjC compile flag to the project files
which some native libraries require

ios.bundleVersion

ios.objC

572

Name

ios.testFlight

Description

Boolean true/false defaults to false and works

only for pro accounts. Enables the testflight

support in the release binaries for easy beta

testing. Notice that the IDE plugin has a "Test

Flight" check box you should use under the iOS

section.

ios.generateSplashScreens

Boolean true/false defaults to false as of 5.0.

desktop.width

desktop.height

desktop.adaptToRetina

desktop.resizable

Enable legacy generation of splash screen

images for use when launching the app. These

have been replaced now by the new launch

storyboards.

Width in pixels for the form in desktop builds,

will be doubled for retina grade displays.

Defaults to 800.

Height in pixels for the form in desktop builds,

will be doubled for retina grade displays.

Defaults to 600.

Boolean true/false defaults to true. When set to

true some values will ve implicitly doubled to

deal with retina displays and icons etc. will use

higher DPI’s

Boolean true/false defaults to true. Indicates

whether the UI in the desktop build is resizable

desktop.fontSizes

Indicates the sizes in pixels for the system fonts

desktop.theme

desktop.themeMac

desktop.themeWin

as a comma delimited string containing 3

numbers for small,medium,large fonts.

Name of the theme res file to use as the "native"

theme. By default this is native indicating iOS

theme on Mac and Windows Metro on Windows.

If its something else then the app will try to load

the file /themeName.res.

Same as desktop.theme but specific to Mac OS

Same as desktop.theme but specific to Windows

desktop.windowsOutput

Can be exe or msi depending on desired results

windows.extensions

Content to be embedded into the <Extensions>
section of the Package.appxmanifest file for

windows (UWP) builds.

573

Name

win.vm32bit

noExtraResources

j2me.iconSize

Description

true/false (defaults to false). Forces windows

desktop builds to use the Win32 JVM instead of

the 64 bit VM making them compatible with

older Windows Machines. This is off by default

at the moment because of a bug in JDK 8 update

112 that might cause this to fail for some cases

true/false (defaults to false). Blocks codename

one from injecting its own resources when set to

true, the only effect this has is in slightly

reducing archive size. This might have adverse

effects on some features of Codename One so it

isn’t recommended.

Defaults to 48x48. The size of the icon in the

format of width x height (without the spacing).

16.2. Offline Build

 Offline build is an enterprise feature

At  this  time  Codename  One  supports  iOS  &  Android  targets  for  offline  builds.  We  require  an

Enterprise grade subscription as explained in the sidebar.

 If you signup for Enterprise and cancel you can still do the offline build. You won’t

be able to update the builder though

Why only Enterprise?

There are several reasons, the technical one is that offline builds are no panacea. Things fail.

The support effort for offline builds is huge, as evidence despite the fact that all of our code is

open source very few people bothered trying to compile it because of the complexities.

We don’t think building offline is convenient and we always recommended avoiding it. When

we  build  our  own  apps  we  use  the  cloud  just  like  everyone  else  because  it’s  surprisingly

faster and more convenient…

However,  some  government  and  regulated  industries  have  issues  with  SaaS  delivered

solutions and thus must use offline build. These organizations also require enterprise grade

support for most cases and so it makes sense to bundle as an enterprise only solution.

16.2.1. Prerequisites for iOS Builds

You need the following installed tools/versions for Codename One’s offline build process:

• Mac ideally with El Capitan, newer should work

574

• Xcode 7+ (but not 8+ at this time)

• Oracle’s JDK 8

• Cocoapods - in the terminal type sudo gem install cocoapods --pre.

• xcodeproj - in the terminal type sudo gem install xcodeproj

16.2.2. Prerequisites for Android Builds

Android builds need the following:

• Android Studio

• Oracle’s JDK 8

• Gradle version 2.11

16.2.3. Installation

To build offline you need to install the offline builder code which is a stripped down version of the

build  servers.  When  you  install  a  version  of  the  offline  builder  it  maps  to  the  time  in  which  you

downloaded it…

That means that features like versioned builds won’t work. You can download/keep multiple offline

builders and toggle between them which is similar in scope.

E.g. if you installed an offline builder then installed a newer version and the newer version has a

bug  you  can  revert  to  the  old  version.  Notice  that  the  older  version  might  not  have  features  that

exist in a newer version.



Since installation requires an enterprise account, you might need to re-login in the

Codename One Settings UI

To  install  an  offline  builder  open  the  Codename  One  Settings  UI  by  right  clicking  the  project  and

selecting Codename One → Codname One Settings.

Figure 460. Open Codename One settings



Even though the settings are a part of a project, the offline build settings are global

and apply to all the projects…

Once the Codename One settings UI launches select the Offline Builds entry:

575

Figure 461. Offline build entry

This should launch the settings UI which would be blank the first time around:

Figure 462. Offline builds setting UI

When  you  are  in  this  form  you  can  press  the  download  button  to  download  the  current  version

from the build server. If there is no update nothing will happen. If there is the latest version will

download and tag with a version number/date.

You  can  see/change  the  selected  version  in  this  UI.  This  allows  building  against  an  older  version.

You can also delete older builds to save space.

16.2.4. Building

Offline building is almost like building with the cloud. In the right click menu you can select one of

the offline build targets as such:

Figure 463. The offline build targets

Once selected build generates a project under the build/and or build/iphone respectively.

Open  these  directories  in  Android  Studio  or  xcode  to  run/build  in  the  native  IDE  to  the  device  or

native emulator/simulator.

 Build deletes previous offline builds, if you want to keep the sources of a build you

need to move it to a different directory!

To  get  this  to  work  with  Android  Studio  you  will  need  one  more  step.  You  will  need  to  configure

Android studio to use your local version of gradle 2.11 by following these steps:

• Open the Android Studio preferences

576

Figure 464. Android Studio Preferences

• Select Build, Execution, Deployment → Build Tools → Gradle

• Select the Use Local gradle distribution

• Press the … and pick your local gradle 2.11 install

Figure 465. Local gradle config

16.2.5. FAQ

Should I use the Offline Builder?

Probably not.

Cloud build is far more convenient, simple. Doesn’t require any installs (other than the plugin) and

is much faster.

We built this tool for developers who work in situations that prohibit cloud build. E.g. government,

banking etc. where regulation is restrictive.

Can I Move/Backup my Builders?

No.

We protect all the builders to avoid abuse. If you backup and restore on a new system the builders

might stop working even if you are a paying enterprise customer.

Can I install the builders for all our developers?

Our  licensing  terms  require  a  parallel  developer  seat  for  the  Codename  One  developers  in  your

company.  If  you  have  5  Codename  One  developers  they  must  all  have  an  enterprise  developer

577

account to comply.

E.g. You can’t have one enterprise account and 4 basic accounts.

The reason behind this is simple, in the past we saw a lot of funneling from developers who built

such a licensing structure.

What Happens if I Cancel?

If you cancel your enterprise subscription all your existing installed offline builders should work as

before but you won’t be able to update them or get support for this.

When are Versions Released?

We will try to keep this in the same release pace as library updates i.e. once a week typically on a

Friday.

Are Version Numbers Sequential?

They  grow  but  we  sometimes  skip  versions.  Versions  map  to  our  cloud  deployment  versioning

scheme and we might skip versions in some cases.

Why is this Feature Limited to Enterprise Subscribers?

This is a complex tool to support & maintain. SaaS has a well defined business model where we can

reduce prices and maintenance costs.

Offline builds are more like a shrinkwrap business model in which case our pricing needs to align

itself to shrinkwrap pricing models for long term sustainability.

The main use case this product tries to address is government and highly regulated industries who

are in effect enterprise users.

How Different is the Code From Cloud Builds?

We use the same code as we do in the cloud build process with minor modifications in the process.

Since the cloud servers are setup by us they work differently but should align reasonably well.

16.3. Android Permissions

One  of  the  annoying  tasks  when  programming  native  Android  applications  is  tuning  all  the

required permissions to match your codes requirements, Codename One aims to simplify this. The

build server automatically introspects the classes sent to it as part of the build and injects the right

set of permissions required by the app.

However, sometimes developers might find the permissions that come up a bit confusing and might

not  understand  why  a  specific  permission  came  up.  This  maps  Android  permissions  to  the

methods/classes in Codename One that would trigger them. Notice that this list isn’t exhaustive as

the API is rather large:

578

android.permission.WRITE_EXTERNAL_STORAGE - this permission appears by default for Codename One
applications,  since  the  FileSystemStorage  API  (which  is  used  extensively)  might  have  some
hint
dependencies 
android.blockExternalStoragePermission=true,  notice  that  this  is  something  we  don’t  test  and  it
might fail on devices.

explicitly 

disable 

using 

build 

You 

can 

the 

on 

it. 

it 

android.permission.INTERNET  -  this  is  a  hardcoded  permission  in  Codename  One,  the  ability  to
connect to the network is coded into all Codename One applications.

android.hardware.camera 
com.codename1.Capture

& 

android.permission.RECORD_AUDIO 

- 

are 

triggered 

by

android.permission.RECORD_AUDIO  -  is  triggered  by  usage  of  MediaManager.createMediaRecorder()  &
Display.createMediaRecorder()

android.permission.READ_PHONE_STATE 
package,
com.codename1.media,
com.codename1.components.Ads, 
com.codename1.push, Display.getUdid() & Display.getMsisdn(). This permission is required for media
in order to suspend audio playback when you get a phone call.

triggered 
com.codename1.components.ShareButton, 

com.codename1.ads 

by 

is 

- 

android.hardware.location, 
android.permission.ACCESS_FINE_LOCATION, 
android.permission.ACCESS_COARSE_LOCATION - map to com.codename1.maps & com.codename1.location.

android.hardware.location.gps,
&

android.permission.ACCESS_MOCK_LOCATION 

package.permission.C2D_MESSAGE, 
android.permission.RECEIVE_BOOT_COMPLETED - are requested by the com.codename1.push package

com.google.android.c2dm.permission.RECEIVE,

android.permission.READ_CONTACTS 
Display.getAllContacts().

- 

triggers  by 

the  package 

com.codename1.contacts  &

android.permission.VIBRATE - is triggered by Display.vibrate() and Display.notifyStatusBar()

android.permission.SEND_SMS - is triggered by Display.sendSMS()

android.permission.WAKE_LOCK 
Display.setScreenSaverEnabled()

- 

is 

triggered 

by 

Display.lockScreen() 

&

android.permission.WRITE_CONTACTS 
is 
Display.deleteContact(), ContactsManager.createContact() & ContactsManager.deleteContact()

Display.createContact(),

triggered 

by 

- 

16.3.1. Permissions Under Marshmallow (Android 6+)

Starting with Marshmallow (Android 6+ API level 23) Android shifted to a permissions system that

prompts users for permission the first time an API is used e.g. when accessing contacts the user will

receive a prompt whether to allow contacts access.

 Permission  can  be  denied  and  a  user  can  later  on  revoke/grant  a  permission  via

external settings UI

This  is  really  great  as  it  allows  apps  to  be  installed  with  a  single  click  and  no  permission  prompt

during install which can increase conversion rates!

579

Enabling Permissions

Codenmae One compiles Android targets with SDK level 23 but not with target level 23!

This means that by default the new permission mode is still off and you won’t see any of the effects

mentioned below.

 This will probably change to the default in the future but at the moment the target

SDK defaults to 21

To  activate  this  functionality  you  will  need  to  set  the  target  SDK  to  level  23  by  using  the
android.targetSDKVersion=23 build hint.

Permission Prompts

To test this API see the following simple contacts app:

Form f = new Form("Contacts", BoxLayout.y());
f.add(new InfiniteProgress());
Display.getInstance().invokeAndBlock(() -> {
    Contact[] ct = Display.getInstance().getAllContacts(true, true, false, true, true, false);
    Display.getInstance().callSerially(() -> {
        f.removeAll();
        for(Contact c : ct) {
            MultiButton mb = new MultiButton(c.getDisplayName());
            mb.setTextLine2(c.getPrimaryPhoneNumber());
            f.add(mb);
        }
        f.revalidate();
    });
});

f.show();

When we try to install this app without changing anything on an Android 6 device we see this UI:

Figure 466. Install UI when using the old permissions system

When we set android.targetSDKVersion=23 in the build hints and try to install again the UI looks like

580

this:

Figure 467. Install UI when using the new permissions system

When we launch the UI under the old permissions system we see the contacts instantly. In the new

system we are presented with this UI:

Figure 468. Native permission prompt first time

If  we  accept  and  allow  all  is  good  and  the  app  loads  as  usual  but  if  we  deny  then  Codename  One

gives the user another chance to request the permission. Notice that in this case you can customize

the prompt string as explained below.

Figure 469. Codename One permission prompt

581

If we select don’t ask then you will get a blank screen since the contacts will return as a 0 length

array. This makes sense as the user is aware he denied permission and the app will still function as

expected on a device where no contacts are available. However, if the user realizes his mistake he

can double back and ask to re-prompt for permission in which case he will see this native prompt:

Figure 470. Native permission prompt second time

Notice that denying this second request will not trigger another Codename One prompt.

Code Changes

There are no explicit code changes needed for this functionality to "just work". The respective API’s

will work just like they always worked and will prompt the user seamlessly for permissions.



Some  behaviors  that  never  occurred  on  Android  but  were  perfectly  legal  in  the

past  might  start  occurring  with  the  switch  to  the  new  API.  E.g.  the  location

manager  might  be  null  and  your  app  must  always  be  ready  to  deal  with  such  a

situation

When  permission  is  requested  a  user  will  be  seamlessly  prompted/warned,  Codename  One  has

builtin text to control such prompts but you might want to customize the text. You can customize
permission text via the Display properties e.g. to customize the text of the contacts permission we
can do something such as:

Display.getInstance().setProperty("android.permission.READ_CONTACTS", "MyCoolChatApp needs access to your contacts so we
can show you which of your friends already have MyCoolChatApp installed");

This  is  optional  as  there  is  a  default  value  defined.  You  can  define  this  once  in  the  init(Object)
method but for some extreme cases permission might be needed for different things e.g. you might

ask  for  this  permission  with  one  reason  at  one  point  in  the  app  and  with  a  different  reason  at

another point in the app.

following  permission  keys  are  supported: 

The 
"android.permission.READ_PHONE_STATE"
android.permission.ACCESS_FINE_LOCATION,
android.permission.WRITE_EXTERNAL_STORAGE, 
android.permission.SEND_SMS,  android.permission.READ_CONTACTS,  android.permission.WRITE_CONTACTS,
android.permission.RECORD_AUDIO.

582

Simulating Prompts

You can simulate permission prompts by checking that option in the simulator menu.

Figure 471. Simulate permission prompts menu item in the simulator

This  will  produce  a  dialog  to  the  user  whenever  this  happens  in  Android  and  will  try  to  act  in  a

similar way to the device. Notice that you can test it in the iOS simulator too.

AndroidNativeUtil’s checkForPermission

If  you  write  Android  native  code  using  native  interfaces  you  are  probably  familiar  with  the
AndroidNativeUtil class from the com.codename1.impl.android package.

This  class  provides  access  to  many  low  level  capabilities  you  would  need  as  a  developer  writing

native  code.  Since  native  code  might  need  to  request  a  permission  we  introduced  the  same
underlying logic we used namely: checkForPermission.

To get a permission you can use this code as such:

if(!AndroidNativeUtil.checkForPermission(
    Manifest.permission.READ_PHONE_STATE, "
    This should be the description shown to the user...")){
    // you didn't get the permission, you might want to return here
}
// you have the permission, do what you need

This  will  prompt  the  user  with  the  native  UI  and  later  on  with  the  fallback  option  as  described
above.  Notice  that  the  checkForPermission  method  is  a  blocking  method  and  it  will  return  when
there  is  a  final  conclusion  on  the  subject.  It  uses  invokeAndBlock  and  can  be  safely  invoked  on  the
event dispatch thread without concern.

16.4. On Device Debugging

Codename One supports debugging applications on devices by using the natively generated project.

All paid subscription levels include the ability to check an  Include Source flag in the settings that

returns a native OS project. You can debug that project in the respective native IDE.

In iOS this is usually strait forward, just open the project with xcode and run it optionally disabling
bitcode.  Unzip  the  .bz2  file  and  open  the  .xcworkspace  file  if  it’s  available  otherwise  open  the
.xcodeproj file inside the dist directory.

583

 Only the .xcworkspace if it is there, it is activated by the CocoaPods build pipeline

so it won’t always be there

With Android Studio this is sometimes as very easy task as it is possible to actually open the gradle

project in Android Studio and just run it. However, due to the fragile nature of the gradle project

this stopped working for some builds and has been "flaky".

16.4.1. Android Studio Debugging (Easy Way)

By  default  you  should  be  able  to  open  the  gradle  project  in  Android  Studio  and  just  run  it.  To  get

this to work open the Android Studio Setting and select gradle 2.11.

Figure 472. Gradle settings UI in Android Studio (notice you need gradle 2.11 and not 2.8 as pictured here)

If this works for you then you can ignore the section below.

16.4.2. Android Studio Debugging the Hard Way

In some cases the gradle project might not work or this might fail with a change from Google.

Here are steps that should work for everyone:

1. Check the include source flag in the IDE and send a build

2. Download the sources.zip result from the build server

3. Launch Android Studio and create a new project

4. Make  sure  to  use  the  same  package  and  app  name  as  you  did  in  the  Codename  One  project,

select to not create an activity

5. Unzip  the  sources.zip  file  and  copy  the  main  directory  from  its  src  directory  to  the  Android

Studio projects src directory make sure to overwrite files/directories.

6. Copy its libs directory on top of the existing libs

7. Copy the source gradle dependencies content to the destination gradle file

8. Connect your device and press the Debug button for the IDE

 You might need to copy additional gradle file meta-data such as multi-dexing etc.

You  might  not  need  to  repeat  the  whole  thing  with  every  build.  E.g.  it  might  be  practical  to  only

584

copy the userSources.jar from the libs directory to get the latest version of your code. You can copy
the src/main directory to get the latest up to date Android port.

16.5. Native Interfaces

Sometimes you may wish to use an API that is unsupported by Codename One or integrate with a

3rd party library/framework that isn’t supported. These are achievable tasks when writing native

code and Codename One lets you encapsulate such native code using native interfaces.

16.5.1. Introduction

Notice  that  when  we  say  "native"  we  do  not  mean  C/C++  always  but  rather  the  platforms  "native"

environment. So in the case of Android the Java code will be invoked with full access to the Android

API, in case of iOS an Objective-C message would be sent and so forth.



You  can  still  access  C  code  under  Android  either  by  using  JNI  from  the  Android

native code or by using a library

Native  interfaces  are  designed  to  only  allow  primitive  types,  Strings,  arrays  of  primitive  types

(single  dimension  only)  &  PeerComponent  [https://www.codenameone.com/javadoc/com/codename1/ui/

PeerComponent.html] values. Any other type of parameter/return type is prohibited. However, once in

the native layer the native code can act freely and query the Java layer for additional information.



The  reason  for  the  limits  is  the  disparity  between  the  platforms.  Mapping  a  Java
Object  to  an  Objective-C  NSObject  is  possible  but  leads  to  odd  edge  cases  and
complexity e.g. GC vs. ARC in a disparate object graph

Furthermore,  native  methods  should  avoid  features  such  as  overloading,  varargs  (or  any  Java  5+

feature for that matter) to allow portability for languages that do not support such features.

 Do  not  rely  on  pass  by  reference/value  behavior  since  they  vary  between

platforms

Implementing a native layer effectively means:

1. Creating  an  interface  that  extends  NativeInterface  [https://www.codenameone.com/javadoc/com/

codename1/system/NativeInterface.html] and only defines methods with the arguments/return values

declared in the previous paragraph.

2. Creating  the  proper  native  implementation  hierarchy  based  on  the  call  conventions  for  every

platform within the native directory

E.g. to create a simple hello world interface do something like:

585

package com.mycompany.myapp;
import com.codename1.system.NativeInterface;
public interface MyNative extends NativeInterface {
    String helloWorld(String hi);
}

We now need to right click the class in the IDE and select the Generate Native Access menu item:

Figure 473. Generating the native code

Figure 474. Once generated we are prompted that the native code is in the "native" directory

We can now look int the  native directory in the project root (in NetBeans you can see that in the

Files tab) and you can see something that looks like this:

Figure 475. Native directory structure containing stubs for the various platforms

These are effectively stubs you can edit to implement the methods in native code.

586



If you re-run the Generate Native Access tool you will get this dialog, if you answer

yes  all  the  files  will  be  overwritten,  if  you  answer  no  only  files  you

deleted/renamed will be recreated

Figure 476. Running "Generate Native Access" when some/all of the native files exist already

For now lets leave the stubs and come back to them soon. From the Codename One Java code we

can call the implementation of this native interface using:

MyNative my = NativeLookup.create(MyNative.class);
if(my != null && my.isSupported()) {
    Log.p(my.helloWorld("Hi"));
}

Notice that for this to work you must implement the native code on all supported platforms.

We’ll start with Android which should be familiar and intuitive to many developers, this is how the
generated file under the native/android directory looks:

package com.mycompany.myapp;

public class MyNativeImpl {
    public String helloWorld(String param) {
        return null;
    }

    public boolean isSupported() {
        return false;
    }

}

The stub implementation always returns false, null or 0 by default. The isSupported also defaults to
false  thus  allowing  us  to  implement  a  NativeInterface  on  some  platforms  and  leave  the  rest  out
without really knowing anything about these platforms.

We can implement the Android version using code similar to this:

587

package com.mycompany.myapp;

import android.util.Log; ①

public class MyNativeImpl { ②
    ③
    public String helloWorld(String param) {
        Log.d("MyApp", param);
        return "Tada";
    }

    public boolean isSupported() { ④
        return true;
    }
}

① Notice  that  we  are  using  the  Android  native  android.util.Log  class  which  isn’t  accessible  from

standard Codename One code

② The impl class doesn’t physically implement the MyNative interface!

This is intentional and due to the PeerComponent functionality mentioned below. You don’t need
to add an implements clause.

③ Notice that there is no constructor and the class is public. It is crucial that the system will be able
to  allocate  the  class  without  obstruction.  You  can  use  a  constructor  but  it  can’t  have  any

arguments and you shouldn’t rely on semantics of construction.

④ We implemented the native method and that we set isSupported to true.

The IDE won’t provide completion suggestions and will claim that there are errors

in the code!

Codename  One  doesn’t  include  the  native  platforms  in  its  bundle  e.g.  the  full

Android SDK or the full xcode Objective-C runtime. However, since the native code

is compiled on the servers (where these runteims are present) this shouldn’t be a

problem

When  implementing  a  non-trivial  native  interface,  send  a  server  build  with  the

"Include Source" option checked. Implement the native interface in the native IDE

then copy and paste the native code back into Codename One





The implementation of this interface is nearly identical for Android, J2ME & Java SE.

Use the Android Main Thread (Native EDT)

iOS,  Android  &  pretty  much  any  modern  OS  has  an  EDT  like  thread  that  handles  events  etc.  The

problem is that they differ in their nuanced behavior. E.g. Android will usually respect calls off of

the EDT and iOS will often crash. Some OS’s enforce EDT access rigidly and will throw an exception

when you violate that…

Normally  you  don’t  need  to  know  about  these  things,  hidden  functionality  within  our

588

implementation bridges between our EDT and the native EDT to provide consistent cross platform

behavior. But when you write native code you need awareness.

Why not Implicitly call Native Interfaces on the Native EDT?

Calling into the native EDT includes overhead and it might not be necessary for some features

(e.g. IO, polling etc.). Furthermore, some calls might work well with asynchronous calls while

others might need synchronous results and we can’t know in advance which ones you would

need.

How do we Access the Native EDT?

Within your native code in Android do something like:

com.codename1.impl.android.AndroidNativeUtil.getActivity().runOnUiThread(new Runnable() {
    public void run() {
       // your native code here...
    }
});

This  will  execute  the  block  within  run()  asynchronously  on  the  native  Android  UI  thread.  If  you
need synchronous execution we have a special method for Codename One:

com.codename1.impl.android.AndroidImplementation.runOnUiThreadAndBlock(new Runnable() {
    public void run() {
       // your native code here...
    }
});

This blocks in a way that’s OK with the Codename One EDT which is unique to our Android port.

Gradle Dependencies

Integrating a native OS library isn’t hard but it sometimes requires some juggling. Most instructions

target  developers  working  with  xcode  or  Android  Studio  &  you  need  to  twist  your  head  around

them. In Android the steps for integration in most modern libraries include a gradle dependency.

E.g.  we  published  a  library  that  added  support  for  Intercom  [https://www.codenameone.com/blog/

intercom-support.html]. The native Android integration instructions for the library looked like this:

Add the following dependency to your app’s build.gradle file:

dependencies {
    compile 'io.intercom.android:intercom-sdk:3.+'
}

589

Which instantly raises the question: "How in the world do I do that in Codename One"?

Well, it’s actually pretty simple. You can add the build hint:

android.gradleDep=compile 'io.intercom.android:intercom-sdk:3.+'

This would "work" but there is a catch…

You  might  need  to  define  the  specific  version  of  the  Android  SDK  used  and  specific  version  of

Google play services version used. Intercom is pretty sensitive about those and demanded that we

also add:

android.playServices=9.8.0
android.sdkVersion=25

Once  those  were  defined  the  native  code  for  the  Android  implementation  became  trivial  to  write

and the library was easy as there were no jars to include.

16.5.2. Objective-C (iOS)

When  generating  the  Objective-C  code  the  "Generate  Native  Sources"  tool  produces  two  files:
com_mycompany_myapp_MyNativeImpl.h & com_mycompany_myapp_MyNativeImpl.m.

The  .m  files  are  the  Objective-C  equivalent  of  .c  files  and  .h  files  contain  the  header/include
information. In this case the com_mycompany_myapp_MyNativeImpl.h contains:

#import <Foundation/Foundation.h>

@interface com_mycompany_myapp_MyNativeImpl : NSObject {
}

-(NSString*)helloWorld:(NSString*)param;
-(BOOL)isSupported;
@end

And com_mycompany_myapp_MyNativeImpl.m contains:

590

#import "com_mycompany_myapp_MyNativeImpl.h"

@implementation com_mycompany_myapp_MyNativeImpl

-(NSString*)helloWorld:(NSString*)param{
    return nil;
}

-(BOOL)isSupported{
    return NO;
}

@end



Objective-C relies on argument names as part of the message (method) signature.

-(NSString*)helloWorld:(NSString*)param 

So 
-(NSString*)helloWorld:(NSString*)iChangedThisName!
Don’t change argument names in the Objective-C native interface!

isn’t 

the 

same 

as

Here is a simple implementation similar to above:

#import "com_mycompany_myapp_MyNativeImpl.h"

@implementation com_mycompany_myapp_MyNativeImpl

-(NSString*)helloWorld:(NSString*)param{
    NSLog(@"MyApp: %@", param);
    return @"Tada";
}

-(BOOL)isSupported{
    return YES;
}

@end

Using the iOS Main Thread (Native EDT)

iOS has a native thread you should use for all calls just like Android. Check out the Native EDT on

Android section above for reference.

On iOS this is pretty similar to Android (if you consider objective-c to be similar). This is used for

asynchronous invocation:

591

dispatch_async(dispatch_get_main_queue(), ^{
    // your native code here...
});

You can use this for synchronous invocation, notice the lack of the a in the dispatch call:

dispatch_sync(dispatch_get_main_queue(), ^{
    // your native code here...
});

The problem with the synchronous call is that it will block the caller thread, if the caller thread is

the EDT this can cause performance issues and even a deadlock. It’s important to be very cautious

with this call!

Use Cocoapods For Dependencies

Cocoapods are the iOS equivalent of gradle dependencies.

CocoaPods  allow  us  to  add  a  native  library  dependency  to  iOS  far  more  easily  than  Gradle.  By

default  we  target  iOS  7.0  or  newer  which  is  supported  by  Intercom  only  for  older  versions  of  the

library. Annoyingly CocoaPods might seem to work but some specific API’s won’t work since it fell

back  to  an  older  version…  To  solve  this  you  have  to  explicitly  define  the  build  hint
ios.pods.platform=8.0 to force iOS 8 or newer. You might need to force it to even newer versions as
some libraries force an iOS 9 minimum etc.

Including  intercom  itself  required  a  single  build  hint:  ios.pods=Intercom  which  you  can  obviously
extend  by  using  commas  to  include  multiple  libraries.  You  can  search  the  cocoapods  website

[https://cocoapods.org/] for supported 3rd party libraries which includes everything you would expect.

One  important  advantage  when  working  with  CocoaPods  is  the  faster  build  time  as  the  upload  to

the Codename One website is smaller and the bandwidth we have to CocoaPods is faster. Another

advantage is the ability to keep up with the latest developments from the library providers.

16.5.3. Javascript

Native  interfaces  in  Javascript  look  a  little  different  than  the  other  platforms  since  Javascript

doesn’t  natively  support  threads  or  classes.  The  native  implementation  should  be  placed  in  a  file

with name matching the name of the package and the class name combined where the "." elements

are replaced by underscores.

The default generated stubs for the JavaScript build look like this com_mycompany_myapp_MyNative:

592

(function(exports){

var o = {};

    o.helloWorld__java_lang_String = function(param1, callback) {
        callback.error(new Error("Not implemented yet"));
    };

    o.isSupported_ = function(callback) {
        callback.complete(false);
    };

exports.com_mycompany_myapp_MyNative= o;

})(cn1_get_native_interfaces());

A simple implementation looks like this.

(function(exports){

var o = {};

    o.helloWorld__java_lang_String = function(param1, callback) {
        callback.complete("Hello World!!!");
    }

    o.isSupported_ = function(callback) {
        callback.complete(true);
    };

exports.com_my_code_MyNative = o;

})(cn1_get_native_interfaces());

Notice that we use the complete() method of the provided callback to pass the return value rather
than  using  the  return  statement.  This  is  to  work  around  the  fact  that  Javascript  doesn’t  natively
support threads. The Java thread that is calling your native interface will block until your method
calls  callback.complete().  This  allows  you  to  use  asynchronous  APIs  inside  your  native  method
while still allowing Codename One to work use your native interface via a synchronous API.



Make sure you call either callback.complete() or callback.error() in your method
at some point, or you will cause a deadlock in your app (code calling your native

method will just sit and "wait" forever for your method to return a value).

The  naming  conventions  for  the  methods  themselves  are  modeled  after  the  naming  conventions

shown in the previous examples:

<method-name>__<param-1-type>_<param-2-type>_…<param-n-type>

593

Where  <method-name>  is  the  name  of  the  method  in  Java,  and  the  `<param-X-type>`s  are  a  string
representing the parameter type. The general rule for these strings are:

1. Primitive types are mapped to their type name. (E.g. int to "int", double to "double", etc…).

2. Reference  types  are  mapped  to  their  fully-qualified  class  name  with  '.'  replaced  with

underscores. E.g. java.lang.String would be "java_lang_String".

3. Array  parameters  are  marked  by  their  scalar  type  name  followed  by  an  underscore  and
"1ARRAY". E.g. int[] would be "int_1ARRAY" and String[] would be "java_lang_String_1ARRAY".

JavaScript Examples

Java API:

public void print(String str);

becomes

o.print__java_lang_String = function(param1, callback) {
    console.log(param1);
    callback.complete();
}

Java API:

public int add(int a, int b);

becomes

o.add__int_int = function(param1, param2, callback) {
    callback.complete(param1 + param2);
}

public int add(int[] a);

becomes

594

o.add__int_1ARRAY = function(param1, callback) {
    var c = 0, len = param1.length;
    for (var i =0; i<len; i++) {
        c += param1[i];
    }
    callback.complete(c);
}

16.5.4. Native GUI Components

PeerComponent 

[https://www.codenameone.com/javadoc/com/codename1/ui/PeerComponent.html] 

return

values are automatically translated to the platform native peer as an expected return value. E.g. for
a NativeInterface method such as this:

public PeerComponent` createPeer();

Android native implementation would use:

public View createPeer() {
    return null;
}

The iphone would need to return a pointer to a view e.g.:

- (UIView*)createPeer;



Not  all  platforms  support  native  peers.  Specifically  JavaSE  doesn’t  support  them

due to the way the JavaSE native interfaces are mapped to their implementation.

Note that this won’t limit the code from running on an unsupported platform. Only

that specific method won’t work.

Javascript would expect a DOM Element (e.g. a <div> tag to be returned.). E.g.

o.createHelloComponent_ = function(callback) {
    var c = jQuery('<div>Hello World</div>')
            .css({'background-color' : 'yellow', 'border' : '1px solid blue'});
    callback.complete(c.get(0));
};

Notice that if you want to use a native library (jar, .a file etc.) just places it within the appropriate

native  directory  and  it  will  be  packaged  into  the  final  executable.  You  would  only  be  able  to

reference it from the native code and not from the Codename One code, which means you will need

to build native interfaces to access it.

595

This is discussed further below.

16.5.5. Type Mapping & Rules

Several rules govern the creation of NativeInterfaces and we only briefly covered some of them.

• The implementation class must have a default public constructor or no constructor at all

• Native methods can’t throw exceptions, checked or otherwise

• A native method can’t have the name init as this is a reserved method in Objective-C

• Only the supported types listed below can be used

• Native implementations can’t rely on pass by reference/value semantics as those might change

between platforms

• hashCode, equals & toString are reserved and won’t be mapped to native code

Table 11. NativeInterface Supported Types

Android

JavaSE

Obj-C

C#

byte

boolean

boolean

Java

byte

boolean

int

short

long

float

sbyte[]

char[]

short[]

int[]

byte

BOOL

char

int

long

float

char

bool

short

int

long

float

double

byte[]

sbyte

char

short

int

long long

float

String

byte[]

double

double

NSString*

String

char[]

short[]

char[]

NSData

NSData*

short[]

NSData*

int[]

NSData*

long[]

float[]

long[]

float[]

char

short

int

long

double

String

byte[]

char[]

int[]

long[]

float[]

char

short

int

float

double

String

NSSData*

bool[]

short[]

int[]

long[]

NSData*

boolean[]

boolean[]

boolean[]

NSData*

float[]

double[]

double[]

double[]

NSData*

double[]



JavaScript is excluded from the table above as it isn’t a type safe language and thus

has no such type mapping

 PeerComponent on iOS is void* but UIView is expected as a result

The examples below demonstrate the signatures for this method on all platforms:

596

Listing 22. NativeInterface definition

public void test(byte b, boolean boo, char c, short s,
    int i, long l, float f, double d, String ss,
    byte[] ba, boolean[] booa, char[] ca, short[] sa, int[] ia,
    long[] la, float[] fa, double[] da,
    PeerComponent cmp);

Listing 23. Android Version

public void test(byte param, boolean param1, char param2,
    short param3, int param4, long param5, float param6,
    double param7, String param8, byte[] param9,
    boolean[] param10, char[] param11, short[] param12,
    int[] param13, long[] param14, float[] param15,
    double[] param16, android.view.View param17) {
}

Listing 24. iOS Version

-(void)test:(char)param param1:(BOOL)param1
    param2:(int)param2 param3:(short)param3 param4:(int)param4
    param5:(long long)param5 param6:(float)param6
    param7:(double)param7 param8:(NSString*)param8
    param9:(NSData*)param9 param10:(NSData*)param10
    param11:(NSData*)param11 param12:(NSData*)param12
    param13:(NSData*)param13 param14:(NSData*)param14
    param15:(NSData*)param15 param16:(NSData*)param16
    param17:(void*)param17;
}

 We had to break lines for the print version, the JavaScript version is a really long

method name that literally broke the book!

Listing 25. JavaScript Version

o.test__byte_boolean_char_short_int_long_float_double
_java_lang_String_byte_1ARRAY_boolean_1ARRAY_char_1ARRAY
_short_1ARRAY_int_1ARRAY_long_1ARRAY_float_1ARRAY_double
_1ARRAY_com_codename1_ui_PeerComponent = function(param1, param2, param3, param4, param5, param6, param7, param8, param9,
param10, param11, param12, param13, param14, param15, param16, param17, param18, callback) {
    callback.error(new Error("Not implemented yet"));
};

Listing 26. Java SE Version

public void test(byte param, boolean param1, char param2, short param3, int param4, long param5, float param6, double
param7, String param8, byte[] param9, boolean[] param10, char[] param11, short[] param12, int[] param13, long[] param14,
float[] param15, double[] param16, com.codename1.ui.PeerComponent param17) {
}

597

Listing 27. C# Version

public void test(byte param, bool param1, char param2, short param3, int param4, long param5, float param6, double
param7, String param8, byte[] param9, boolean[] param10, char[] param11, short[] param12, int[] param13, long[] param14,
float[] param15, double[] param16, FrameworkElement param17) {
}

16.5.6. Android Native Permissions

Normally  permissions  in  Codename  One  are  seamless.  Codename  One  traverses  the  bytecode  and

automatically  assigns  permissions  to  Android  applications  based  on  the  API’s  used  by  the

developer.

However, when accessing native functionality this just won’t work since native code might require

specialized  permissions  and  we  don’t/can’t  run  any  serious  analysis  on  it  (it  can  be  just  about

anything).

So  if  you  require  additional  permissions  in  your  Android  native  code  you  need  to  define  them  in
the  build  arguments  using  android.permission.<PERMISSION_NAME>=true  for  each  permission  you
want  to  include.  A  full  list  of  permissions  are  listed  in  Android’s  Manifest.permission

documentation [https://developer.android.com/reference/android/Manifest.permission.html].

E.g.

android.permission.ADD_VOICEMAIL=true
android.permission.BATTERY_STATS=true
...

You  can  specify  the  maximum  SDK  version  in  which  the  permission  is  needed  using  the
android.permission.<PERMISSION_NAME>.maxSdkVersion  build  hint.  You  can  also  specify  whether  the
permission is required for the app to run using the android.permission.<PERMISSION_NAME>.required
build hint.

E.g.

android.permission.ADD_VOICEMAIL=true
android.permission.BATTERY_STATS=true
android.permission.ADD_VOICEMAIL.required=false
android.permission.ADD_VOICEMAIL.maxSdkVersion=18
...

You  can  alternatively  use  the  android.xpermissions  build  hint  to  inject  <uses-permission>  tags  into
the manifest file. E.g.:

android.xpermissions=<uses-permission android:name="android.permission.READ_CALENDAR" />

598

 You need to include the full XML snippet. You can unify multiple lines into a single

line in the GUI as XML allows that.

16.5.7. Native AndroidNativeUtil

If  you  do  any  native  interfaces  programming  in  Android  you  should  be  familiar  with  the
AndroidNativeUtil class which allows you to access native device functionality more easily from the
native  code.  E.g.  many  Android  API’s  need  access  to  the  Activity  which  you  can  get  by  calling
AndroidNativeUtil.getActivity().

The native util class includes quite a few other features such as:

• runOnUiThreadAndBlock(Runnable) - this is such a common pattern that it was generalized into a
public  static  method.  Its  identical  to  Activity.runOnUiThread  but  blocks  until  the  runnable
finishes execution.

• addLifecycleListener/removeLifecycleListener - These essentially provide you with a callback to

lifecycle events: onCreate etc. which can be pretty useful for some cases.

• registerViewRenderer 

-  PeerComponent 

[https://www.codenameone.com/javadoc/com/codename1/ui/

PeerComponent.html]'s  are  usually  shown  on  top  of  the  UI  since  they  are  rendered  within  their

own 

thread  outside  of 

the  EDT  cycle.  So  when  we  need 

to  show  a  Dialog

[https://www.codenameone.com/javadoc/com/codename1/ui/Dialog.html]  on  top  of  the  peer  we  grab  a

screenshot of the peer, hide it and then show the dialog with the image as the background (the

same applies for transitions). Unfortunately some components (specifically the MapView) might

not  render  properly  and  require  custom  code  to  implement  the  transferal  to  a  native  Bitmap,

this API allows you to do just that.

You can work with AndroidNativeUtil using native code such as this:

import com.codename1.impl.android.AndroidNativeUtil;

class NativeCallsImpl {
     public void nativeMethod() {
        AndroidNativeUtil.getActivity().runOnUiThread(new Runnable() {
            public void run() {
               ...
            }
        });
     }
    ....
}

16.5.8. Broadcast Receiver

A  common  way  to  implement  features  in  Android  is  the  BroadcastReceiver  API.  This  allows
intercepting operating system events for common use cases.

A  good  example  is  intercepting  incoming  SMS  which  is  specific  to  Android  so  we’d  need  a

599

broardcast receiver to implement that. This is often confusing to developers who sometimes derive

the impl class from broadcast receiver. That’s a mistake…

The  solution  is  to  place  any  native  Android  class  into  the  native/android  directory.  It  will  get
compiled  with  the  rest  of  the  native  code  and  "just  works".  So  you  can  place  this  class  under
native/android/com/codename1/sms/intercept:

package com.codename1.sms.intercept;

import android.content.*;
import android.os.Bundle;
import android.telephony.*;
import com.codename1.io.Log;

public class SMSListener extends BroadcastReceiver {

    @Override
    public void onReceive(Context cntxt, Intent intent) {
        // based on code from https://stackoverflow.com/questions/39526138/broadcast-receiver-for-receive-sms-is-not-
working-when-declared-in-manifeststat
        if(intent.getAction().equals("android.provider.Telephony.SMS_RECEIVED")) {
            Bundle bundle = intent.getExtras();
            SmsMessage[] msgs = null;
            if (bundle != null){
                try{
                    Object[] pdus = (Object[]) bundle.get("pdus");
                    msgs = new SmsMessage[pdus.length];
                    for(int i=0; i<msgs.length; i++){
                        msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);
                        String msgBody = msgs[i].getMessageBody();
                        SMSCallback.smsReceived(msgBody);
                    }
                } catch(Exception e) {
                    Log.e(e);
                    SMSCallback.smsReceiveError(e);
                }
            }
        }
    }
}

The code above is pretty standard native Android code, it’s just a callback in which most of the logic

is 

similar 

to 

the  native  Android  code  mentioned 

in 

this 

stackoverflow  question

[https://stackoverflow.com/questions/39526138/broadcast-receiver-for-receive-sms-is-not-working-when-declared-in-

manifeststat].

But there is still more you need to do. In order to implement this natively we need to register the
permission and the receiver in the manifest.xml file as explained in that question. This is how their
native manifest looked:

600

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.bulsy.smstalk1">
    <uses-permission android:name="android.permission.RECEIVE_SMS" />
    <uses-permission android:name="android.permission.READ_SMS" />
    <uses-permission android:name="android.permission.SEND_SMS"/>
    <uses-permission android:name="android.permission.READ_CONTACTS" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <receiver android:name="com.bulsy.smstalk1.SmsListener"
               android:enabled="true"
               android:permission="android.permission.BROADCAST_SMS"
               android:exported="true">
            <intent-filter android:priority="2147483647">//this doesnt work
                <category android:name="android.intent.category.DEFAULT" />
                <action android:name="android.provider.Telephony.SMS_RECEIVED" />
            </intent-filter>
        </receiver>
    </application>
</manifest>

We only need the broadcast permission XML and the permission XML. Both are doable via the build

hints. The former is pretty easy:

android.xpermissions=<uses-permission android:name="android.permission.RECEIVE_SMS" />

The  latter  isn’t  much  harder,  notice  I  took  multiple  lines  and  made  them  into  a  single  line  for

convenience:

android.xapplication=<receiver android:name="com.codename1.sms.intercept.SMSListener"  android:enabled="true"
android:permission="android.permission.BROADCAST_SMS"  android:exported="true">                    <intent-filter
android:priority="2147483647"><category android:name="android.intent.category.DEFAULT" />        <action
android:name="android.provider.Telephony.SMS_RECEIVED" />                 </intent-filter>             </receiver>

Here it is formatted nicely:

601

<receiver android:name="com.codename1.sms.intercept.SMSListener"
              android:enabled="true"
              android:permission="android.permission.BROADCAST_SMS"
              android:exported="true">
                   <intent-filter android:priority="2147483647">
                          <category android:name="android.intent.category.DEFAULT" />
                          <action android:name="android.provider.Telephony.SMS_RECEIVED" />
                   </intent-filter>
</receiver>

Listening & Permissions

You will notice that these don’t include the actual binding or permission prompts you would expect

for something like this. To do this we need a native interface.

The  native  sample  in  stack  overflow  bound  the  listener  in  the  activity  but  here  we  want  the  app

code to decide when we should bind the listening:

public interface NativeSMSInterceptor extends NativeInterface {
    public void bindSMSListener();
    public void unbindSMSListener();
}

That’s easy!

Notice  that  isSupported()  returns  false  for  all  other  OS’s  so  we  won’t  need  to  ask  whether  this  is
"Android" we can just use isSupported().

The implementation is pretty easy too:

602

package com.codename1.sms.intercept;

import android.Manifest;
import android.content.IntentFilter;
import com.codename1.impl.android.AndroidNativeUtil;

public class NativeSMSInterceptorImpl {
    private SMSListener smsListener;
    public void bindSMSListener() {
        if(AndroidNativeUtil.checkForPermission(Manifest.permission.RECEIVE_SMS, "We can automatically enter the SMS code
for you")) { ①
            smsListener = new SMSListener();
            IntentFilter filter = new IntentFilter();
            filter.addAction("android.provider.Telephony.SMS_RECEIVED");
            AndroidNativeUtil.getActivity().registerReceiver(smsListener, filter); ②
        }
    }

    public void unbindSMSListener() {
        AndroidNativeUtil.getActivity().unregisterReceiver(smsListener);
    }

    public boolean isSupported() {
        return true;
    }
}

① This will trigger the permission prompt on Android 6 and newer. Even though the permission is
declared in XML this isn’t enough for 6+. Notice that even when you run on Android 6 you still

need to declare permissions in XML!

② Here we actually bind the listener, this allows us to grab one SMS and not listen in on every SMS

coming thru

16.5.9. Native Code Callbacks

Native  interfaces  standardize  the  invocation  of  native  code  from  Codename  One,  but  it  doesn’t

standardize  the  reverse  of  callbacks  into  Codename  One  Java  code.  The  reverse  is  naturally  more

complicated since its platform specific and more error prone.

A common "trick" for calling back is to just define a static method and then trigger it from native

code. This works nicely for Android, Java SE, Blackberry & Java ME since those platforms use Java

for their "native code". Mapping this to iOS requires some basic understanding of how the iOS VM

works.

For  the  purpose  of  this  explanation  lets  pretend  we  have  a  class  called  NativeCallback  in  the  src
hierarchy under the package com.mycompany that has the method: public static void callback().

package com.mycompany;
public class NativeCallback {
    public static void callback() {
        // do stuff
    }
}

603

So  if  I  want  to  call  it  from  Android  or  all  of  the  Java  based  platforms  I  can  just  write  this  in  the

"native" code:

com.mycompany.NativeCallback.callback();

I can also pass a argument as we do later on:

com.mycompany.NativeCallback.callback("My Arg");

Accessing Callbacks from Objective-C

If we want to invoke that method from Objective-C we need to do the following.

Add an include statement as such:

#include "com_mycompany_NativeCallback.h"
#include "CodenameOne_GLViewController.h"

that 

Notice 
CN1_THREAD_STATE_PASS_SINGLE_ARG.

the  CodenameOne_GLViewController.h 

include  defines  various  macros  such  as

Then when we want to trigger the method just do:

com_mycompany_NativeCallback_callback__(CN1_THREAD_STATE_PASS_SINGLE_ARG);



most 

For 
macro
CN1_THREAD_GET_STATE_PASS_SINGLE_ARG  instead  of  CN1_THREAD_STATE_PASS_SINGLE_ARG
also make sure to add `#include "cn1_globals.h" in the file

callbacks 

should 

you 

use 

the 

The VM passes the thread context along method calls to save on API calls (thread context is heavily

used in Java for synchronization, gc and more).

We can easily pass arguments like:

public static void callback(int arg)

Which maps to native as (notice the extra _ before the int):

com_mycompany_NativeCallback_callback___int(CN1_THREAD_GET_STATE_PASS_ARG intValue);

Notice that there is no comma between the CN1_THREAD_GET_STATE_PASS_ARG and the value!

604

Why No Comma?

The comma is included as part of the macro which makes for code that isn’t as readable.

The  reason  for  this  dates  to  the  migration  from  XMLVM  [10]  to  the  current  ParparVM
implementation. CN1_THREAD_GET_STATE_PASS_ARG is defined as nothing in XMLVM since

it didn’t use that concept. Yet under ParparVM it will include the necessary comma.

A  common  use  case  is  passing  string  values  to  the  Java  side,  or  really  NSString*  which  is  iOS

equivalent. Assuming a method like this:

public static void callback(String arg)

You  would  need  to  convert  the  NSString*  value  you  already  have  to  a  java.lang.String  which  the
callback expects.

The fromNSString function also needs this special argument so you will need to modify the method
as such:

com_mycompany_NativeCallback_callback___java_lang_String(CN1_THREAD_GET_STATE_PASS_ARG
fromNSString(CN1_THREAD_GET_STATE_PASS_ARG nsStringValue));

And finally you might want to return a value from callback as such:

public static int callback(int arg)

This  is  tricky  since  the  method  name  changes  to  support  covariant  return  types  and  so  the

signature would be:

com_mycompany_NativeCallback_callback___int_R_int(intValue);

The upper case R allows us to differentiate between void callback(int,int) and int callback(int).



Covariant  return  types  are  a  little  known  Java  5  feature.  E.g.  the  method  Object
getX()  can  be  overriden  by  MyObject  getX().  However,  in  the  VM  level  they  can
both exist side by side.

Accessing Callbacks from Javascript

The mechanism for invoking static callback methods from Javascript (for the Javascript port only) is
similar to Objective-C’s. The this object in your native interface method contains a property named
$GLOBAL$  that  provides  access  to  static  java  methods.  This  object  will  contain  Javascript  mirror
objects  for  each  Java  class  (though  the  property  name  is  mangled  by  replacing  "."  with

underscores).  Each  mirror  object  contains  a  wrapper  method  for  its  underlying  class’s  static

605

methods where the method name follows the same naming convention as is used for the Javascript

native methods themselves (and very similar to the naming conventions used in Objective-C).

For example, the Google Maps project includes the static callback method:

static void fireMapChangeEvent(int mapId, final int zoom, final double lat, final double lon) { ... }

defined in the com.codename1.googlemaps.MapContainer class.

This method is called from Javascript inside a native interface using the following code:

var fireMapChangeEvent = this.$GLOBAL$.com_codename1_googlemaps_MapContainer.fireMapChangeEvent__int_int_double_double;
google.maps.event.addListener(this.map, 'bounds_changed', function() {
    fireMapChangeEvent(self.mapId, self.map.getZoom(), self.map.getCenter().lat(), self.map.getCenter().lng());
});

In this example we first obtain a reference to the fireMapChangeEvent method, and then call it later.
However, we could have called it directly also.

code 

MUST 

Your 
path
this.$GLOBAL$.your_class_name.your_method_name  or  the  build  server  will  not  be
able  to  recognize  that  your  code  requires  this  method.  The  $GLOBAL$  object  is
populated  by  the  build  server  only  with  those  classes  and  methods  that  are  used

contain 

string 

full 

the 



inside your native methods. If the build server doesn’t recognize that the methods

are being used (via this pattern) it won’t generate the necessary wrappers for your

Javascript code to access the Java methods.

Callbacks of the SMS Receiver

The SMS Broadcast Receiver code from before also used callbacks such as this:

606

package com.codename1.sms.intercept; ①

import com.codename1.util.FailureCallback;
import com.codename1.util.SuccessCallback;
import static com.codename1.ui.CN.*;

/**
 * This is an internal class, it's package protect to hide that
 */
class SMSCallback {
    static SuccessCallback<String> onSuccess;
    static FailureCallback onFail;

    public static void smsReceived(String sms) {
        if(onSuccess != null) {
            SuccessCallback<String> s = onSuccess;
            onSuccess = null;
            onFail = null;
            SMSInterceptor.unbindListener();
            callSerially(() -> s.onSucess(sms)); ②
        }
    }

    public static void smsReceiveError(Exception err) {
        if(onFail != null) {
            FailureCallback f = onFail;
            onFail = null;
            SMSInterceptor.unbindListener();
            onSuccess = null;
            callSerially(() -> f.onError(null, err, 1, err.toString()));
        } else {
            if(onSuccess != null) {
                SMSInterceptor.unbindListener();
                onSuccess = null;
            }
        }
    }
}

① Notice  that  the  package  is  the  same  as  the  native  code  and  the  other  classes.  This  allows  the
callback class to be package protected so it isn’t exposed via the API (the class doesn’t have the

public modifier)

② We wrap the callback in call serially to match the Codename One convention of using the EDT by
default.  The  call  will  probably  arrive  on  the  Android  native  thread  so  it  makes  sense  to

normalize it and not expose the Android native thread to the user code

Asynchronous Callbacks & Threading

One  of  the  problematic  aspects  of  calling  back  into  Java  from  Javascript  is  that  Javascript  has  no

607

notion of multi-threading. Therefore, if the method you are calling uses Java’s threads at all (e.g. It
includes a wait(), notify(), sleep(), callSerially(), etc…) you need to call it asynchronously from
Javascript.  You  can  call  a  method  asynchronously  by  appending  $async  to  the  method  name.  E.g.
With the Google Maps example above, you would change :

this.$GLOBAL$.com_codename1_googlemaps_MapContainer.fireMapChangeEvent__int_int_double_double;

to

this.$GLOBAL$.com_codename1_googlemaps_MapContainer.fireMapChangeEvent__int_int_double_double$async;

This  will  cause  the  call  to  be  wrapped  in  the  appropriate  bootstrap  code  to  work  properly  with

threads - and it is absolutely necessary in cases where the method may use threads of any kind. The
side-effect  of  calling  a  method  with  the  $async  suffix  is  that  you  can’t  use  return  values  from  the
method.



In most cases you should use the async version of a method when calling it from

your  native  method.  Only  use  the  synchronous  (default)  version  if  you  are

absolutely sure that the method doesn’t use any threading primitives.

16.6. Libraries - cn1lib

Support for JAR files in Codename One has been a source of confusion so its probably a good idea to

revisit this subject again and clarify all the details.

The first source of confusion is changing the classpath. You should NEVER change the classpath or

add an external JAR via the IDE classpath UI. The reasoning here is very simple, these IDE’s don’t

package  the  JAR’s  into  the  final  executable  and  even  if  they  did  these  JAR’s  would  probably  use
features unavailable or inappropriate for the device (e.g. java.io.File etc.).

Figure 477. Don’t change the classpath, this is how it should look for a typical Java 8 Codename One

application

Cn1libs  are  Codename  One’s  file  format  for  3rd  party  extensions.  It’s  physicially  a  zip  file

containing other zip files and some meta-data.

608

16.6.1. Why Not Use JAR?

A jar can be compiled with usage of any Java API that might not be supported, it can be compiled

with a Java target version that isn’t tested.

Jars  don’t  include  support  for  writing  native  code,  you  could  use  JNI  in  jars  (awkwardly)  but  that

doesn’t match Codename One’s needs for native support (see section above).

Jars don’t support "proper" code completion, a common developer trick is to stick source code into

the  jar  but  that  prevents  usage  with  proprietary  code.  Cn1libs  provide  full  IDE  code  completion

(with JavaDoc hints) without exposing the sources.

There are two use cases for wanting JAR’s and they both have very different solutions:

1. Modularity

2. Working with an existing JARs

Cn1lib’s  address  the  modularity  aspect  allowing  you  to  break  that  down.  Existing  jars  can

sometimes be used native code settings but for the most part you would want to adapt the code to

abide by Codename One restrictions.

16.6.2. How To Use cn1libs?

Codename One has a large repository of 3rd party cn1libs [https://www.codenameone.com/cn1libs.html],

you  can  install  a  cn1lib  by  placing  it  in  the  lib  directory  of  your  project  then  right  clicking  the

project and selecting Codename One → Refresh cn1lib files.

Figure 478. Refresh cn1lib files menu option

Once refreshed the content of the cn1lib will be available to code completion and you could just use

it.



Notice that some cn1libs require additional configurations such as build hints etc.

so  make  sure  to  read  the  developers  instructions  when  integrating  a  3rd  party

library.

609

Under the Hood of cn1lib Install

Refresh cn1lib files  invokes  the  ant  task  refresh-libs.  You  could  automatically  trigger  a
refresh as part of your build process by invoking that ant task manually.

Technically that task invokes a custom task that unzips the content of the cn1lib into a set of

directories  accessible  to  the  build  process.  Classes  and  stub  sources  are  installed  in
lib/impl/cls & lib/impl/stubs respectively.

The native files are extracted to lib/impl/native. The classpath for the main project and the
ant build process know about these directories and include them within their path.

16.6.3. Creating a Simple cn1lib

Creating a cn1lib is trivial, we will get into more elaborate uses soon enough but for a hello world

cn1lib we can just use this 2 step process:

Figure 479. Select the CodenameOne Library Option

Figure 480. Select the file name/destination. Notice that a Java 8 cn1lib requires Java 8 support in the parent

project!

Once  we  go  thru  these  steps  we  can  define  any  source  file  within  the  library  and  it  will  be

accessible to the users of the library.

16.6.4. Build Hints in cn1libs

Some  cn1libs  are  pretty  simple  to  install,  just  place  them  under  the  lib  directory  and  refresh.

However, many of the more elaborate cn1libs need some pretty complex configurations. This is the

case when native code is involved where we need to add permissions or plist entries for the various

native platforms to get everything to work. This makes the cn1lib’s helpful but less than seamless

which is where we want to go.

Codename  One 

cn1libs 

include 

two 

files 

that 

can  be  placed 

into 

the 

root:

610

codenameone_library_required.properties & codenameone_library_appended.properties.

In  these  files  you  can  just  write  a  build  hint  as  codename1.arg.ios.plistInject=…  for  the  various
hints.



Notice the usage of the properties syntax for the build hint with the codename1.arg
prefix you would also need to escape reserved characters for properties files.

The best way to discover the right syntax for such build hints is to set them via the

build  hints  GUI 
in  a 
codenameone_settings.properties into the cn1lib file.

regular  project  and 

copy/paste 

them 

from

The obvious question is why do we need two files?

There are two types of build hints: required and appended.

Required build hints can be something like ios.objC=true which we want to always work. E.g. if a
cn1lib defines ios.objC=true and another cn1lib defines ios.objC=false things won’t work since one
cn1lib won’t get what it needs…

In this case we’d want the build to fail so we can remove the faulty cn1lib.

 If two cn1libs define ios.objC=true there will be no collision as the value would be

identical

An 
ios.plistInject=<key>UIBackgroundModes</key><array><string>audio</string> </array>

appended 

property 

something 

would 

be 

like

Notice that this can still collide e.g. if a different cn1lib defines its own background mode. However,
there  are  many  valid  cases  where  ios.plistInject  can  be  used  for  other  things.  In  this  case  we’ll
append the content of the ios.plistInject into the build hint if it’s not already there.

There are a couple of things you need to keep in mind:

• Properties are merged with every "refresh libs" call not dynamically on the server. This means

it should be pretty simple for the developer to investigate issues in this process.

• Changing flags is problematic - there is no "uninstall" process. Since the data is copied into the
codenameone_settings.properties  file.  If  you  need  to  change  a  flag  later  on  you  might  need  to
alert users to make changes to their properties essentially negating the value of this feature…

So be very careful when adding properties here.

It’s your responsibility as a library developer to decide which build hint goes into which file!

Codename One can’t automate this process as the whole process of build hints is by definition an ad

hoc process.

The  rule  of  thumb  is  that  a  build  hint  with  a  numeric  or  boolean  value  is  always  a  required

property.  If  an  entry  has  a  string  that  you  can  append  with  another  string  then  its  probably  an

appended entry.

These build hints are probably of the "required" type:

611

android.debug
android.release
android.installLocation
android.licenseKey
android.stack_size
android.statusbar_hidden
android.googleAdUnitId
android.includeGPlayServices
android.headphoneCallback
android.gpsPermission
android.asyncPaint
android.supportV4
android.theme
android.cusom_layout1
android.versionCode
android.captureRecord
android.removeBasePermissions
android.blockExternalStoragePermission
android.min_sdk_version
android.smallScreens
android.streamMode
android.enableProguard
android.targetSDKVersion
android.web_loading_hidden
facebook.appId
ios.keyboardOpen
ios.project_type
ios.newStorageLocation
ios.prerendered_icon
ios.application_exits
ios.themeMode
ios.xcode_version
javascript.inject_proxy
javascript.minifying
javascript.proxy.url
javascript.sourceFilesCopied
javascript.teavm.version
rim.askPermissions
google.adUnitId
ios.includePush
ios.headphoneCallback
ios.enableAutoplayVideo
ios.googleAdUnitId
ios.googleAdUnitIdPadding
ios.enableBadgeClear
ios.locationUsageDescription
ios.bundleVersion
ios.objC
ios.testFlight
desktop.width
desktop.height

612

desktop.adaptToRetina
desktop.resizable
desktop.fontSizes
desktop.theme
desktop.themeMac
desktop.themeWin
desktop.windowsOutput
noExtraResources
j2me.iconSize
android.permission.<PERMISSION_NAME>

These build hints should probably be appended:

android.xapplication
android.xpermissions
android.xintent_filter
android.facebook_permissions
android.stringsXml
android.style
android.nonconsumable
android.xapplication_attr
android.xactivity
android.pushVibratePattern
android.proguardKeep
android.sharedUserId
android.sharedUserLabel
ios.urlScheme
ios.interface_orientation
ios.plistInject
ios.facebook_permissions
ios.applicationDidEnterBackground
ios.viewDidLoad
ios.glAppDelegateHeader
ios.glAppDelegateBody
ios.beforeFinishLaunching
ios.afterFinishLaunching
ios.add_libs

613

cn1lib Structure/File Format

The  cb1lib  file  format  is  quite  simple,  it’s  a  zip  file  containing  zip  files  within  it  with  fixed

names to support the various features.

The table below covers the files that can/should be a part of a cn1lib file:

Table 12. cn1lib structure

File Name

main.zip

stubs.zip

manifest.properties

codenameone_ library_

appended.properties

codenameone_ library_

required.properties

nativeios.zip

nativeand.zip

nativejavascript.zip

nativerim.zip

nativese.zip

nativewin.zip

nativeme.zip

Required

Purpose

✓

✓

×

×

×

×

×

×

×

×

×

×

Contains the bytecode and the library binary

data. This is effectively the portable portion

of the jar

Stub source files (auto-generated) containing

javadocs to provide code completion

General properties of the library, this isn’t

used for much at the moment

Discussed above

Discussed above

Native iOS sources if applicable

Native Android sources if applicable

Native JavaScript sources if applicable

Native RIM sources if applicable

Native JavaSE sources if applicable

Native Windows sources if applicable

Native Java ME sources if applicable

16.7. Integrating Android 3rd Party Libraries & JNI

While  its  pretty  easy  to  use  native  interfaces  to  write  Android  native  code  some  things  aren’t

necessarily as obvious. E.g. if you want to integrate a 3rd party library, specifically one that includes

native C JNI code this process isn’t as straightforward.

If you need to integrate such a library into your native calls you have the following options:

1. The  first  option  (and  the  easiest  one)  is  to  just  place  a  Jar  file  in  the  native/android  directory.

This will link your binary with the jar file. Just place the jar under the native/android and the

build server will pick it up and will add it to the classpath.

Notice that Android release apps are obfuscated by default which might cause issues with such

libraries  if  they  reference  API’s  that  are  unavailable  on  Android.  You  can  workaround  this  by

adding  a  build  hint  to  the  proguard  obfuscation  code  that  blocs  the  obfuscation  of  the

614

problematic classes using the build hint:
android.proguardKeep=-keep class com.mypackage.ProblemClass { *; }`

2. Another  option  is  the  aar  file  is  a  binary  format  Google  introduced  to  represent  an  Android
Library  project  (similarly  to  the  cn1lib  format).  One  of  the  problem  with  the  Android  Library

projects  was  the  fact  that  it  required  the  project  sources  which  made  it  difficult  for  3rd  party

vendors to publish libraries.
As a result so android introduced the aar file which is a binary format that represents a Library
project.  To  learn  more  about  arr  you  can  read  this  [https://developer.android.com/studio/projects/

android-library.html#aar-contents].

You can link an aar file by placing it under the native/android and the build server will link it to
the project.

3. There  is  another  obsolete  approach  that  we  are  mentioning  for  legacy  purposes  (e.g.  if  you
need to port code written with this legacy option). This predated the aar option from Google…
Not  all  3rd  party  tools  can  be  packaged  as  a  simple  jar,  some  3rd  party  tools  need  to  declare
activities add permissions, resources, assets, and/or even add native code (.so files).
To link a Library project to your Codename One project open the Library project in Eclipse or

Android Studio and make sure the project builds, after the project was built successfully remove

the bin directory from the project and zip the whole project.

Rename  the  extension  from  .zip  to  .andlib  and  place  the  andlib  file  under  the  native/android
directory. The build server will pick it up and will link it to the project.

16.8. Drag & Drop

Unlike  other  platforms  that  tried  to  create  overly  generic  catch  all  API’s  Codename  One  tried  to

make things as simple as possible.

In Codename One only components can be dragged and drop targets are always components. The

logic of actually performing the operation indicated by the drop is the responsibility of the person

implementing the drop.



Some  platforms  e.g.  AWT  allow  dragging  abstract  concepts  such  as  mime  type

elements. This allows dragging things like a text file into the app, but that use case

isn’t realistic in mobile

The code below allows you to rearrange the items based on a sensible order. Notice it relies on the
default Container drop behavior.

615

Form hi = new Form("Rearrangeable Items", new BorderLayout());
String[] buttons = {"A Game of Thrones", "A Clash Of Kings",  "A Storm Of Swords",
    "A Feast For Crows", "A Dance With Dragons", "The Winds of Winter", "A Dream of Spring" };

Container box = new Container(BoxLayout.y());
box.setScrollableY(true);
box.setDropTarget(true);
java.util.List<String> got = Arrays.asList(buttons);
Collections.shuffle(got);
for(String current : got) {
    MultiButton mb = new MultiButton(current);
    box.add(mb);
    mb.setDraggable(true);
}

hi.add(BorderLayout.NORTH, "Arrange The Titles").add(BorderLayout.CENTER, box);
hi.show();

Figure 481. Drag and drop demo

To enable dragging a component it must be flagged as draggable using setDraggable(true), to allow
dropping  the  component  onto  another  component  you  must  first  enable  the  drop  target  with
setDropTarget(true) and override some methods (more on that later).

When  dragging  on  top  of  a  child  component  of  a  drop  target  the  code  recursively  searches  for  a

drop target parent. Dropping a component on the child will automatically find the right drop target,

hence there is no need to make "everything" into a drop target.

You can override these methods in the draggable components:

• getDragImage  -  this  generates  an  image  preview  of  the  component  that  will  be  dragged.  This

automatically generates a sensible default so you don’t need to override it.

• drawDraggedImage - this method will be invoked to draw the dragged image at a given location, it
might  be  useful  to  override  it  if  you  want  to  display  some  drag  related  information  such  an

additional icon based on location etc. (e.g. a move/copy icon).

In the drop target you can override the following methods:

• draggingOver - returns true if a drop operation at this point is permitted. Otherwise releasing the

component will have no effect.

616

• dragEnter/Exit - useful to track and cleanup state related to dragging over a specific component.

• drop - the logic for dropping/moving the component must be implemented here!

16.9. Continuous Integration & Release Engineering

Codename  One  was  essentially  built  for  continuous  integration  since  the  build  servers  are

effectively  a  building  block  for  such  an  architecture.  However,  there  are  several  problems  with

that: the first of which is limited server capacity.

If  all  users  would  start  sending  builds  with  every  commit  the  servers  would  instantly  become

unusable  due  to  the  heavy  load.  To  circumvent  this  CI  support  is  limited  only  on  the  Enterprise

level which allows Codename One to stock more servers and cope with the rise in demand related

to the feature.

To integrate with any CI solution just use the standard Ant targets such as build-for-android-device,
build-for-iphone-device etc.

Normally, this would be a problem since the build is sent but since it isn’t blocking you wouldn’t get

the build result and wouldn’t be able to determine if the build passed or failed. To enable this just
edit  the  build  XML  and  add  the  attribute  automated="true"  to  the  codeNameOne  tag  in  the
appropriate targets.

This will deliver a result.zip file under the dist folder containing the binaries of a successful build.
It  will  also  block  until  the  build  is  completed.  This  should  be  pretty  easy  to  integrate  with  any  CI

system together with our automated testing solutions .

E.g. we can do a synchronous build like this:

<target name="build-for-javascript-sync" depends="clean,copy-javascript-override,copy-libs,jar,clean-override">
    <codeNameOne
        jarFile="${dist.jar}"
        displayName="${codename1.displayName}"
        packageName = "${codename1.packageName}"
        mainClassName = "${codename1.mainName}"
        version="${codename1.version}"
        icon="${codename1.icon}"
        vendor="${codename1.vendor}"
        subtitle="${codename1.secondaryTitle}"
        automated="true"
        targetType="javascript"
        />
</target>

This allows us to build a JavaScript version of the app automatically as part of a release build script.

16.10. Android Lollipop ActionBar Customization

When running on Android Lollipop (5.0 or newer) the native action bar will use the Lollipop design.

This  isn’t  applicable  if  you  use  the  Toolbar  [https://www.codenameone.com/javadoc/com/codename1/ui/

Toolbar.html]  or  SideMenuBar  [https://www.codenameone.com/javadoc/com/codename1/ui/SideMenuBar.html]

617

this will be used only in the task switcher.

To  customize  the  colors  of  the  native  ActionBar  on  Lollipop  define  a  colors.xml  file  in  the
native/android directory of your project. It should look like this:

<resources>
   <color name="colorPrimary">#ff00ff00</color>
   <color name="colorPrimaryDark">#80ff0000</color>
   <color name="colorAccent">#800000ff</color>
</resources>

16.11. Intercepting URL’s On iOS & Android

A  common  trick  in  mobile  application  development,  is  communication  between  two  unrelated

applications.

In  Android  we  can  use  intents  which  are  pretty  elaborate  and  can  be  used  via  Display.execute,
however  what  if  you  would  like  to  expose  the  functionality  of  your  application  to  a  different

application running on the device. This would allow that application to launch your application.

This isn’t something we builtin to Codename One, however it does expose enough of the platform

capabilities to enable that functionality rather easily on Android.

On  Android  we  need  to  define  an  intent  filter  which  we  can  do  using  the  android.xintent_filter
build hint, this accepts the XML to filter whether a request is relevant to our application:

android.xintent_filter=<intent-filter>   <action android:name="android.intent.action.VIEW" />    <category
android:name="android.intent.category.DEFAULT" />    <category android:name="android.intent.category.BROWSABLE" />
<data android:scheme="myapp" />  </intent-filter>

You can read more about it in this stack overflow question [http://stackoverflow.com/questions/11421048/

android-ios-custom-uri-protocol-handling].

To bind the myapp:// URL to your application. As a result typing myapp://x into the Android browser
will launch the application.

16.11.1. Passing Launch Arguments To The App

You can access the value of the URL that launched the app using:

String arg = Display.getInstance().getProperty("AppArg");

This value would be null if the app was launched via the icon.

iOS is practically identical to Android with some small caveats, iOS’s equivalent of the manifest is

the plist.

618

You can inject more data into the plist by using the ios.plistInject build hint.

So the equivalent in the iOS side would be

ios.plistInject=<key>CFBundleURLTypes</key>     <array>         <dict>             <key>CFBundleURLName</key>
<string>com.yourcompany.myapp</string>         </dict>         <dict>             <key>CFBundleURLSchemes</key>
<array>                 <string>myapp</string>             </array>         </dict>     </array>

However,  that  can  conflict  with  the  Facebook  integration  if  you  use  FacebookConnect  which  needs
access to the schemes. To workaround it you can use the build hint ios.urlScheme e.g.:

ios.urlScheme=<string>myapp</string>

16.12. Native Peer Components

Many  Codename  One  developers  don’t  truly  grasp  the  reason  for  the  separation  between  peer

(native)  components  and  Codename  One  components.  This  is  a  crucial  thing  you  need  to

understand especially if you plan on working with native widgets e.g. Web Browser, native maps,
text input, media and native interfaces (which can return a PeerComponent).

Codename One draws all of its widgets on its own, this is a concept which was modeled in part after

Swing. This allows functionality that can’t be achieved in native widget platforms:

1. The Codename One GUI builder & simulator are almost identical to the device - notice that this

also enables the build cloud, otherwise device specific bugs would overwhelm development and

make the build cloud redundant.

2. Ability  to  override  everything  -  paint,  pointer,  key  events  are  all  overridable  and  replaceable.

Developers can also paint over everything e.g. glasspane and layered pane.

3. Consistency - provides identical functionality on all platforms for the most part.

This  all  contributes  to  our  ease  of  working  with  Codename  One  and  maintaining  Codename  One.

More  than  95%  of  Codename  One’s  code  is  in  Java  hence  its  really  portable  and  pretty  easy  to

maintain!

16.12.1. Why does Codename One Need Native Widgets at all?

We need the native device to do input, html rendering etc. these are just too big and too complex

tasks for Codename One to do from scratch.

They  are  sometimes  impossible  to  perform  without  the  native  platform.  E.g.  the  virtual  keyboard

input on the devices is tied directly to the native text input. It’s impractical to implement everything

from scratch for all languages, dictionaries etc. The result would be sub-par.

A web browser can’t be implemented in this day and age without a JavaScript JIT and including a

JIT within an iOS app is prohibited by Apple.

619

16.12.2. So what’s the problems with native widgets?

Codename One does pretty much everything on the EDT (Event Dispatch Thread), this provides a lot

of cool features e.g. modal dialogs, invokeAndBlock etc.

However native widgets have to be drawn on the devices native UI thread.

This means that drawing looks something like this:

1. Loop over all Codename One components and paint them.

2. Loop over all native peer components and paint them.

This  effectively  means  that  all  peer  components  are  drawn  on  top  of  the  Codename  One

components.

 This was also the case in AWT/Swing to one degree or another…

16.12.3. So how do we show dialogs on top of Peer Components?

Codename  One  grabs  a  screenshot  of  the  peer,  hide  it  and  then  we  can  just  show  the  screenshot.

Since  the  screenshot  is  static  it  can  be  rendered  via  the  standard  UI.  Naturally  we  can’t  do  that

always since grabbing a screenshot is an expensive process on all platforms and must be performed

on the native device thread.

16.12.4. Why can’t we combine peer component scrolling and Codename
One scrolling?

Since the form title/footer etc. are drawn by Codename One the peer component might paint itself

on top of them. Clipping a peer component is often pretty difficult. Furthermore, if the user drags

his  finger  within  the  peer  component  he  might  trigger  the  native  scroll  within  the  might  collide

with our scrolling?

16.12.5. Native Components In The First Form

There  is  also  another  problem  that  might  be  counter  intuitive.  iOS  has  screenshot  images

representing the first form. If your first page is an HTML or a native map (or other peer widget) the

screenshot  process  on  the  build  server  will  show  fallback  code  instead  of  the  real  thing  thus

providing sub-par behavior.

Its impractical to support something like HTML for the screenshot process since it would also look

completely different from the web component running on the device.



You can read more about the screenshot process here [https://www.codenameone.com/

manual/appendix-ios.html#section-ios-screenshots].

16.13. Integrating 3rd Party Native SDKs

The  following  is  a  description  of  the  procedure  that  was  used  to  create  the  Codename  One

FreshDesk  library  [http://shannah.github.io/cn1-freshdesk/].  This  process  can  be  easily  adapted  to  wrap

620

any native SDK on Android and iOS.

16.13.1. Step 1 : Review the FreshDesk SDKs

Before we begin, we’ll need to review the Android and iOS SDKs.

1. FreshDesk  Android  SDK: 

Integration  Guide 

[http://developer.freshdesk.com/mobihelp/android/

integration_guide/] | API Docs [http://developer.freshdesk.com/mobihelp/android/api/reference/com/freshdesk/

mobihelp/package-summary.html]

2. FreshDesk  iOS  SDK:  Integration  Guide  [http://developer.freshdesk.com/mobihelp/ios/integration_guide/]

| API Docs [http://developer.freshdesk.com/mobihelp/ios/api/]

In reviewing the SDKs, we are looking for answers to two questions:

1. What should my Codename One FreshDesk API look like?

2. What will be involved in integrating the native SDK in my app or lib?

16.13.2. Step 2: Designing the Codename One Public API

When  designing  the  Codename  One  API,  we  should  begin  by  looking  at  the  Javadocs

[http://developer.freshdesk.com/mobihelp/android/api/reference/com/freshdesk/mobihelp/package-summary.html]

for  the  native  Android  SDK.  If  the  class  hierarchy  doesn’t  look  too  elaborate,  we  may  decide  to

model  our  Codename  One  public  API  fairly  closely  on  the  Android  API.  On  the  other  hand,  if  we

only need a small part of the SDK’s functionality, we may choose to create my abstractions around

just the functionality that we need.

In  the  case  of  the  FreshDesk  SDK,  it  looks  like  most  of  the  functionality  is  handled  by  one  central
class Mobihelp, with a few other POJO classes for passing data to and from the service. This is a good
candidate for a comprehensive Codename One API.

Before  proceeding,  we  also  need  to  look  at  the  iOS  API  to  see  if  there  are  any  features  that  aren’t

included. While naming conventions in the iOS API are a little different than those in the Android

API, it looks like they are functionally the same.

Therefore, I choose to create a class hierarchy and API that closely mirrors the Android SDK.

16.13.3. Step 3: The Architecture and Internal APIs

A Codename One library that wraps a native SDK, will generally consist of the following:

1. Public  Java  API,  consisting  of  pure  Java  classes  that  are  intended  to  be  used  by  the  outside

world.

2. Native  Interface(s).  The  Native  Interface(s)  act  as  a  conduit  for  the  public  Java  API  to

communicate to the native SDK. Parameters in native interface methods are limited to primitive

types, arrays of primitive types, and Strings, as are return values.

3. Native  code.  Each  platform  must  include  an  implementation  of  the  Native  Interface(s).  These

implementations are written in the native language of the platform (e.g. Java for Android, and

Objective-C for iOS).

621

4. Native dependencies. Any 3rd party libraries required for the native code to work, need to be

included for each platform. On android, this may mean bundling .jar files, .aar files, or .andlib

files. On iOS, this may mean bundling .h files, .a files, .framework, and .bundle files.

5. Build hints. Some libraries will require you to add some extra build hints to your project. E.g.

On  Android  you  may  need  to  add  permissions  to  the  manifest,  or  define  services  in  the
<Application>  section  of  the  manifest.  On  iOS,  this  may  mean  specifying  additional  core
frameworks for inclusion, or adding build flags for compilation.

The following diagram shows the dependencies in a native library:

Figure 482. Relationship between native & Codename One API UML Diagram

In the specific case of our FreshDesk API, the public API and classes will look like:

Figure 483. Freshdesk API Integration

622

Things to Notice

1. The  public  API  consists  of  the  main  class  (Mobihelp  [https://github.com/shannah/cn1-freshdesk/blob/
master/cn1-freshdesk-demo/src/com/codename1/freshdesk/Mobihelp.java]),  and  a  few  supporting  classes
(FeedbackRequest 
[https://github.com/shannah/cn1-freshdesk/blob/master/cn1-freshdesk-demo/src/com/
codename1/freshdesk/FeedbackRequest.java],  FeedbackType  [https://github.com/shannah/cn1-freshdesk/blob/
MobihelpConfig
master/cn1-freshdesk-demo/src/com/codename1/freshdesk/FeedbackType.java], 

[https://github.com/shannah/cn1-freshdesk/blob/master/cn1-freshdesk-demo/src/com/codename1/freshdesk/
MobihelpConfig.java],  MobihelpCallbackStatus  [https://github.com/shannah/cn1-freshdesk/blob/master/cn1-
freshdesk-demo/src/com/codename1/freshdesk/MobihelpCallbackStatus.java]),  which  were  copied  almost

directly from the Android SDK.

2. The only way for the public API to communicate with the native SDK is via the MobihelpNative
[https://github.com/shannah/cn1-freshdesk/blob/master/cn1-freshdesk-demo/src/com/codename1/freshdesk/

MobihelpNative.java] interface.

3. We  introduced  the  MobihelpNativeCallback  [https://github.com/shannah/cn1-freshdesk/blob/master/cn1-
freshdesk-demo/src/com/codename1/freshdesk/MobihelpNativeCallback.java]  class  to  facilitate  native  code

calling back into the public API. This was necessary for a few methods that used asynchronous

callbacks.

16.13.4. Step 4: Implement the Public API and Native Interface

We have already looked at the final product of the public API in the previous step, but let’s back up

and walk through the process step-by-step.

I wanted to model my API closely around the Android API, and the central class that includes all of

the 

functionality 

of 

the 

SDK 

is 

the 

com.freshdesk.mobihelp.Mobihelp 

class

[http://developer.freshdesk.com/mobihelp/android/api/reference/com/freshdesk/mobihelp/Mobihelp.html],  so  we

begin there.

We’ll  start  by  creating  our  own  package  (com.codename1.freshdesk)  and  our  own  Mobihelp  class
inside it.

Adapting Method Signatures

The Context parameter

In  a  first  glance  at  the  com.freshdesk.mobihelp.Mobihelp  API  [http://developer.freshdesk.com/mobihelp/

android/api/reference/com/freshdesk/mobihelp/Mobihelp.html]  we  see  that  many  of  the  methods  take  a

parameter  of 

type  android.content.Context 

[http://developer.android.com/reference/android/content/

Context.html].  This  class  is  part  of  the  core  Android  SDK,  and  will  not  be  accessible  to  any  pure

Codename One APIs. Therefore, our public API cannot include any such references. Luckily, we’ll be

able  to  access  a  suitable  context  in  the  native  layer,  so  we’ll  just  omit  this  parameter  from  our

public API, and inject them in our native implementation.

Hence, the method signature public static final void setUserFullName (Context context, String
name)  will  simply  become  public  static  final  void  setUserFullName  (String  name)  in  our  public
API.

623

Non-Primitive Parameters

Although our public API isn’t constrained by the same rules as our Native Interfaces with respect to

parameter  and  return  types,  we  need  to  be  cognizant  of  the  fact  that  parameters  we  pass  to  our

public  API  will  ultimately  be  funnelled  through  our  native  interface.  Therefore,  we  should  pay

attention to any parameters or return types that can’t be passed directly to a native interface, and

start  forming  a  strategy  for  them.  E.g.  consider  the  following  method  signature  from  the  Android
Mobihelp class:

public static final void showSolutions (Context activityContext, ArrayList<String> tags)

We’ve already decided to just omit the Context parameter in our API, so that’s a non-issue. But what
about the ArrayList<String> tags parameter? Passing this to our public API is no problem, but when
we implement the public API, how will we pass this ArrayList to our native interface, since native
interfaces don’t allow us to arrays of strings as parameters?

I generally use one of three strategies in such cases:

1. Encode the parameter as either a single String (e.g. using JSON or some other easily parseable

format) or a byte[] array (in some known format that can easily be parsed in native code).

2. Store the parameter on the Codename One side and pass some ID or token that can be used on

the native side to retrieve the value.

3. If the data structure can be expressed as a finite number of primitive values, then simply design

the  native  interface  method  to  take  the  individual  values  as  parameters  instead  of  a  single

object. E.g. If there is a User [https://www.codenameone.com/javadoc/com/codename1/facebook/User.html]
class  with  properties  name  and  phoneNumber,  the  native  interface  can  just  have  name  and
phoneNumber parameters rather than a single `user parameter.

In this case, because an array of strings is such a simple data structure, I decided to use a variation

on strategy number 1: Merge the array into a single string with a delimiter.

In any case, we don’t have to come up with the specifics right now, as we are still on the public API,

but it will pay dividends later if we think this through ahead of time.

Callbacks

It is quite often the case that native code needs to call back into Codename One code when an event

occurs. This may be connected directly to an API method call (e.g. as the result of an asynchronous

method invocation), or due to something initiated by the operating system or the native SDK on its

own (e.g. a push notification, a location event, etc..).

Native code will have access to both the Codename One API and any native APIs in your app, but on

some platforms, accessing the Codename One API may be a little tricky. E.g. on iOS you’ll be calling

from  Objective-C  back  into  Java  which  requires  knowledge  of  Codename  One’s  java-to-objective  C

conversion process. In general, I have found that the easiest way to facilitate callbacks is to provide

abstractions  that  involve  static  java  methods  (in  Codename  One  space)  that  accept  and  return

primitive types.

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In the case of our Mobihelp class, the following method hints at the need to have a "callback plan":

public static final void getUnreadCountAsync (Context context, UnreadUpdatesCallback callback)

The interface definition for UnreadUpdatesCallback is:

public interface UnreadUpdatesCallback {
    //This method is called once the unread updates count is available.
    void onResult(MobihelpCallbackStatus status, Integer count);

}

I.e. If we were to implement this method (which I plan to do), we need to have a way for the native
code to call the callback.onResult() method of the passed parameter.

So we have two issues that will need to be solved here:

1. How to pass the callback object through the native interface.

2. How to call the callback.onResult() method from native code at the right time.

For the first issue, we’ll use strategy #2 that we mentioned previously: (Store the parameter on the

Codename One side and pass some ID or token that can be used on the native side to retrieve the

value).

For the second issue, we’ll create a static method that can take the token generated to solve the first
issue, and call the stored callback object’s onResult() method. We abstract both sides of this process
using  the  MobihelpNativeCallback  class  [https://github.com/shannah/cn1-freshdesk/blob/master/cn1-freshdesk-
demo/src/com/codename1/freshdesk/MobihelpNativeCallback.java].

625

public class MobihelpNativeCallback {
    private static int nextId = 0;
    private static Map<Integer,UnreadUpdatesCallback> callbacks = new HashMap<Integer,UnreadUpdatesCallback>();

    static int registerUnreadUpdatesCallback(UnreadUpdatesCallback callback) {
        callbacks.put(nextId, callback);
        return nextId++;
    }

    public static void fireUnreadUpdatesCallback(int callbackId, final int status, final int count) {
        final UnreadUpdatesCallback cb = callbacks.get(callbackId);
        if (cb != null) {
            callbacks.remove(callbackId);
            Display.getInstance().callSerially(new Runnable() {

                public void run() {
                    MobihelpCallbackStatus status2 = MobihelpCallbackStatus.values()[status];
                    cb.onResult(status2, count);
                }

            });
        }
    }

}

Things to notice here:

1. This  class  uses  a  static  Map<Integer,UnreadUpdatesCallback>  member  to  keep  track  of  all

callbacks, mapping a unique integer ID to each callback.

2. The registerUnreadUpdatesCallback() method takes an UnreadUpdatesCallback object, places it in
the callbacks map, and returns the integer token that can be used to fire the callback later. This
method  would  be  called  by  the  public  API  inside  the  getUnreadCountAsync()  method
implementation to convert the callback into an integer, which can then be passed to the native
API.

3. The  fireUnreadUpdatesCallback()  method  would  be  called  later  from  native  code.  Its  first

parameter is the token for the callback to call.

4. We  wrap  the  onResult()  call  inside  a  Display.callSerially()  invocation  to  ensure  that  the
callback  is  called  on  the  EDT.  This  is  a  general  convention  that  is  used  throughout  Codename

One,  and  you’d  be  well-advised  to  follow  it.  Event  handlers  should  be  run  on  the  EDT  unless

there  is  a  good  reason  not  to  -  and  in  that  case  your  documentation  and  naming  conventions

should make this clear to avoid accidentally stepping into multithreading hell!

Initialization

Most  Native  SDKs  include  some  sort  of  initialization  method  where  you  pass  your  developer  and

application  credentials  to  the  API.  When  I  filled  in  FreshDesk’s  web-based  form  to  create  a  new

application, it generated an application ID, an app "secret", and a "domain". The SDK requires me to
pass all three of these values to its init() method via the MobihelpConfig class.

Note, however, that FreshDesk (and most other service provides that have native SDKs) requires me

to  create  different  Apps  for  each  platform.  This  means  that  my  App  ID  and  App  secret  will  be

626

different on iOS than they will be on Android.

Therefore our public API needs to enable us to provide multiple credentials in the same app, and

our  API  needs  to  know  to  use  the  correct  credentials  depending  on  the  device  that  the  app  is

running on.

There are many solutions to this problem, but the one I chose was to provide two different init()
methods:

public final static void initIOS(MobihelpConfig config)

and

public final static void initAndroid(MobihelpConfig config)

Then I can set up the API with code like:

MobihelpConfig config = new MobihelpConfig();
config.setAppSecret("xxxxxxx");
config.setAppId("freshdeskdemo-2-xxxxxx");
config.setDomain("codenameonetest1.freshdesk.com");
Mobihelp.initIOS(config);

config = new MobihelpConfig();
config.setAppSecret("yyyyyyyy");
config.setAppId("freshdeskdemo-1-yyyyyyyy");
config.setDomain("https://codenameonetest1.freshdesk.com");
Mobihelp.initAndroid(config);

The Resulting Public API

public class Mobihelp {

    private static char[] separators = new char[]{',','|','/','@','#','%','!','^','&','*','=','+','*','<'};
    private static MobihelpNative peer;

    public static boolean isSupported() {
        ....
    }

    public static void setPeer(MobihelpNative peer) {
        ....
    }

    //Attach the given custom data (key-value pair) to the conversations/tickets.
    public final static void    addCustomData(String key, String value) {
        ...
    }
    //Attach the given custom data (key-value pair) to the conversations/tickets with the ability to flag sensitive data.
    public final static void    addCustomData(String key, String value, boolean isSensitive) {
        ...
    }

627

    //Clear all breadcrumb data.
    public final static void    clearBreadCrumbs() {
        ...
    }
    //Clear all custom data.
    public final static void    clearCustomData() {
        ...
    }
    //Clears User information.
    public final static void    clearUserData() {
        ...
    }
    //Retrieve the number of unread items across all the conversations for the user synchronously i.e.
    public final static int getUnreadCount() {
        ...
    }

    //Retrieve the number of unread items across all the conversations for the user asynchronously, count is delivered to
the supplied UnreadUpdatesCallback instance Note : This may return 0 or stale value when there is no network connectivity
etc
    public final static void    getUnreadCountAsync(UnreadUpdatesCallback callback) {
        ...
    }
    //Initialize the Mobihelp support section with necessary app configuration.
    public final static void    initAndroid(MobihelpConfig config) {
        ...
    }

    public final static void initIOS(MobihelpConfig config) {
        ...
    }

    //Attaches the given text as a breadcrumb to the conversations/tickets.
    public final static void    leaveBreadCrumb(String crumbText) {
        ...
    }
    //Set the email of the user to be reported on the Freshdesk Portal
    public final static void    setUserEmail(String email) {
        ...
    }

    //Set the name of the user to be reported on the Freshdesk Portal.
    public final static void    setUserFullName(String name) {
        ...
    }

    //Display the App Rating dialog with option to Rate, Leave feedback etc
    public static void  showAppRateDialog() {
        ...
    }
    //Directly launch Conversation list screen from anywhere within the application
    public final static void    showConversations() {
        ...
    }
    //Directly launch Feedback Screen from anywhere within the application.
    public final static void    showFeedback(FeedbackRequest feedbackRequest) {
        ...
    }
    //Directly launch Feedback Screen from anywhere within the application.
    public final static void    showFeedback() {
        ...
    }
    //Displays the Support landing page (Solution Article List Activity) where only solutions tagged with the given tags
are displayed.
    public final static void    showSolutions(ArrayList<String> tags) {
        ...

628

    }

    private static String findUnusedSeparator(ArrayList<String> tags) {
        ...

    }

    //Displays the Support landing page (Solution Article List Activity) from where users can do the following
    //View solutions,
    //Search solutions,
    public final static void    showSolutions() {
        ...
    }
    //Displays the Integrated Support landing page where only solutions tagged with the given tags are displayed.
    public final static void    showSupport(ArrayList<String> tags) {
        ...
    }

    //Displays the Integrated Support landing page (Solution Article List Activity) from where users can do the following
    //View solutions,
    //Search solutions,
    //  Start a new conversation,
    //View existing conversations update/ unread count etc
    public final static void    showSupport() {
        ...
    }

}

The Native Interface

The final native interface is nearly identical to our public API, except in cases where the public API

included non-primitive parameters.

public interface MobihelpNative extends NativeInterface {

    /**
     * @return the appId
     */
    public String config_getAppId();

    /**
     * @param appId the appId to set
     */
    public void config_setAppId(String appId);

    /**
     * @return the appSecret
     */
    public String config_getAppSecret();

    /**
     * @param appSecret the appSecret to set
     */
    public void config_setAppSecret(String appSecret);
    /**
     * @return the domain
     */
    public String config_getDomain();
    /**
     * @param domain the domain to set
     */
    public void config_setDomain(String domain) ;

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    /**
     * @return the feedbackType
     */
    public int config_getFeedbackType() ;

    /**
     * @param feedbackType the feedbackType to set
     */
    public void config_setFeedbackType(int feedbackType);

    /**
     * @return the launchCountForReviewPrompt
     */
    public int config_getLaunchCountForReviewPrompt() ;
    /**
     * @param launchCountForReviewPrompt the launchCountForReviewPrompt to set
     */
    public void config_setLaunchCountForReviewPrompt(int launchCountForReviewPrompt);
    /**
     * @return the prefetchSolutions
     */
    public boolean config_isPrefetchSolutions();
    /**
     * @param prefetchSolutions the prefetchOptions to set
     */
    public void config_setPrefetchSolutions(boolean prefetchSolutions);
    /**
     * @return the autoReplyEnabled
     */
    public boolean config_isAutoReplyEnabled();

    /**
     * @param autoReplyEnabled the autoReplyEnabled to set
     */
    public void config_setAutoReplyEnabled(boolean autoReplyEnabled) ;

    /**
     * @return the enhancedPrivacyModeEnabled
     */
    public boolean config_isEnhancedPrivacyModeEnabled() ;

    /**
     * @param enhancedPrivacyModeEnabled the enhancedPrivacyModeEnabled to set
     */
    public void config_setEnhancedPrivacyModeEnabled(boolean enhancedPrivacyModeEnabled) ;

    //Attach the given custom data (key-value pair) to the conversations/tickets.
    public void addCustomData(String key, String value);
    //Attach the given custom data (key-value pair) to the conversations/tickets with the ability to flag sensitive data.
    public void addCustomDataWithSensitivity(String key, String value, boolean isSensitive);
    //Clear all breadcrumb data.
    public void clearBreadCrumbs() ;
    //Clear all custom data.
    public void clearCustomData();
    //Clears User information.
    public void clearUserData();
    //Retrieve the number of unread items across all the conversations for the user synchronously i.e.
    public int getUnreadCount();

    //Retrieve the number of unread items across all the conversations for the user asynchronously, count is delivered to
the supplied UnreadUpdatesCallback instance Note : This may return 0 or stale value when there is no network connectivity
etc
    public void getUnreadCountAsync(int callbackId);

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    public void initNative();

    //Attaches the given text as a breadcrumb to the conversations/tickets.
    public  void leaveBreadCrumb(String crumbText);
    //Set the email of the user to be reported on the Freshdesk Portal

    public void setUserEmail(String email);

    //Set the name of the user to be reported on the Freshdesk Portal.
    public void setUserFullName(String name);

    //Display the App Rating dialog with option to Rate, Leave feedback etc
    public void showAppRateDialog();
    //Directly launch Conversation list screen from anywhere within the application
    public void showConversations();

    //Directly launch Feedback Screen from anywhere within the application.
    public void showFeedbackWithArgs(String subject, String description);
    //Directly launch Feedback Screen from anywhere within the application.
    public void showFeedback();

    //Displays the Support landing page (Solution Article List Activity) where only solutions tagged with the given tags
are displayed.
    public void showSolutionsWithTags(String tags, String separator);

    //Displays the Support landing page (Solution Article List Activity) from where users can do the following
    //View solutions,
    //Search solutions,
    public void showSolutions();
    //Displays the Integrated Support landing page where only solutions tagged with the given tags are displayed.
    public void showSupportWithTags(String tags, String separator);

    //Displays the Integrated Support landing page (Solution Article List Activity) from where users can do the following
    //View solutions,
    //Search solutions,
    //  Start a new conversation,
    //View existing conversations update/ unread count etc
    public void showSupport();
}

Notice also, that the native interface includes a set of methods with names prefixed with config__.
This is just a naming conventions I used to identify methods that map to the MobihelpConfig class. I
could have used a separate native interface for these, but decided to keep all the native stuff in one

class for simplicity and maintainability.

Connecting the Public API to the Native Interface

So we have a public API, and we have a native interface. The idea is that the public API should be a

thin wrapper around the native interface to smooth out rough edges that are likely to exist due to

the  strict  set  of  rules  involved  in  native  interfaces.  We’ll,  therefore,  use  delegation  inside  the
Mobihelp class to provide it a reference to an instance of MobihelpNative:

public class Mobihelp {
    private static MobihelpNative peer;
    //...
}

We’ll initialize this peer inside the init() method of the Mobihelp class. Notice, though that init() is

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private since we have provided abstractions for the Android and iOS apps separately:

    //Initialize the Mobihelp support section with necessary app configuration.
    public final static void initAndroid(MobihelpConfig config) {
        if ("and".equals(Display.getInstance().getPlatformName())) {
            init(config);
        }
    }

    public final static void initIOS(MobihelpConfig config) {
        if ("ios".equals(Display.getInstance().getPlatformName())) {
            init(config);
        }
    }

    private static void init(MobihelpConfig config) {
        peer = (MobihelpNative)NativeLookup.create(MobihelpNative.class);
        peer.config_setAppId(config.getAppId());
        peer.config_setAppSecret(config.getAppSecret());
        peer.config_setAutoReplyEnabled(config.isAutoReplyEnabled());
        peer.config_setDomain(config.getDomain());
        peer.config_setEnhancedPrivacyModeEnabled(config.isEnhancedPrivacyModeEnabled());
        if (config.getFeedbackType() != null) {
            peer.config_setFeedbackType(config.getFeedbackType().ordinal());
        }
        peer.config_setLaunchCountForReviewPrompt(config.getLaunchCountForReviewPrompt());
        peer.config_setPrefetchSolutions(config.isPrefetchSolutions());
        peer.initNative();

    }

Things to Notice:

1. The  initAndroid()  and  initIOS()  methods  include  a  check  to  see  if  they  are  running  on  the

correct platform. Ultimately they both call init().

2. The  init()  method,  uses  the  NativeLookup  [https://www.codenameone.com/javadoc/com/codename1/

system/NativeLookup.html] class to instantiate our native interface.

Implementing the Glue Between Public API and Native Interface

For  most  of  the  methods  in  the  Mobihelp  class,  we  can  see  that  the  public  API  will  just  be  a  thin
wrapper around the native interface. E.g. the public API implementation of setUserFullName(String)
is:

public final static void setUserFullName(String name) {
    peer.setUserFullName(name);
}

For some other methods, the public API needs to break apart the parameters into a form that the

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native interface can accept. E.g. the init() method, shown above, takes a MobihelpConfig object as a
parameter, but it passed the properties of the config object individually into the native interface.

Another  example,  is  the  showSupport(ArrayList<String>  tags)  method.  The  corresponding  native
interface  method  that  is  wraps  is  showSupport(String  tags,  `String  separator)`  -  i.e  it  needs  to
merge  all  tags  into  a  single  delimited  string,  and  pass  then  to  the  native  interface  along  with  the

delimiter used. The implementation is:

public final static void showSupport(ArrayList<String> tags) {
    String separator = findUnusedSeparator(tags);
    StringBuilder sb = new StringBuilder();
    for (String tag : tags) {
        sb.append(tag).append(separator);
    }
    peer.showSupportWithTags(sb.toString().substring(0, sb.length()-separator.length()), separator);
}

The only other non-trivial wrapper is the getUnreadCountAsync() method that we discussed before:

   public final static void getUnreadCountAsync(UnreadUpdatesCallback callback) {
        int callbackId = MobihelpNativeCallback.registerUnreadUpdatesCallback(callback);
        peer.getUnreadCountAsync(callbackId);
    }

16.13.5. Step 5: Implementing the Native Interface in Android

Now that we have set up our public API and our native interface, it is time to work on the native

side of things. You can generate stubs for all platforms in your IDE (Netbeans in my case), by right
clicking on the MobihelpNative class in the project explorer and selecting "Generate Native Access".

Figure 484. Generate Native Access Menu Item

This will generate a separate directory for each platform inside your project’s native directory:

Figure 485. Native generated sources directory view

Inside the android directory, this generates a com/codename1/freshdesk/MobihelpNativeImpl class with
stubs for each method.

633

Our  implementation  will  be  a  thin  wrapper  around  the  native  Android  SDK.  See  the  source  here

[https://github.com/shannah/cn1-freshdesk/blob/master/cn1-freshdesk-demo/native/android/com/codename1/

freshdesk/MobihelpNativeImpl.java].

Some highlights:

1. Context : The native API requires us to pass a context object as a parameter on many methods.
This  should  be  the  context  for  the  current  activity.  It  will  allow  the  FreshDesk  API  to  know

where  to  return  to  after  it  has  done  its  thing.  Codename  One  provides  a  class  called
AndroidNativeUtil that allows us to retrieve the app’s Activity (which includes the Context). We’ll
wrap this with a convenience method in our class as follows:

private static Context context() {
    return com.codename1.impl.android.AndroidNativeUtil.getActivity().getApplicationContext();
}

This will enable us to easily wrap the freshdesk native API. E.g.:

public void clearUserData() {
    com.freshdesk.mobihelp.Mobihelp.clearUserData(context());
}

2. runOnUiThread()  -  Many  of  the  calls  to  the  FreshDesk  API  may  have  been  made  from  the
Codename One EDT. However, Android has its own event dispatch thread that should be used

for interacting with native Android UI. Therefore, any API calls that look like they initiate some
sort of native Android UI process should be wrapped inside Android’s runOnUiThread() method
which is similar to Codename One’s Display.callSerially() method. E.g. see the showSolutions()
method:

    public void showSolutions() {
        activity().runOnUiThread(new Runnable() {
            public void run() {
                com.freshdesk.mobihelp.Mobihelp.showSolutions(context());
            }
        });

    }

(Note  here  that  the  activity()  method  is  another  convenience  method  to  retrieve  the  app’s
current Activity from the AndroidNativeUtil class).

3. Callbacks. We discussed, in detail, the mechanisms we put in place to enable our native code to

perform  callbacks  into  Codename  One.  You  can  see  the  native  side  of  this  by  viewing  the
getUnreadCountAsync() method implementation:

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    public void getUnreadCountAsync(final int callbackId) {
        activity().runOnUiThread(new Runnable() {
            public void run() {
                com.freshdesk.mobihelp.Mobihelp.getUnreadCountAsync(context(), new
com.freshdesk.mobihelp.UnreadUpdatesCallback() {
                    public void onResult(com.freshdesk.mobihelp.MobihelpCallbackStatus status, Integer count) {
                        MobihelpNativeCallback.fireUnreadUpdatesCallback(callbackId, status.ordinal(), count);
                    }
                });
            }
        });

    }

16.13.6. Step 6: Bundling the Native SDKs

The last step (at least on the Android side) is to bundle the FreshDesk SDK. For Android, there are a

few different scenarios you’ll run into for embedding SDKs:

1. The SDK includes only Java classes - NO XML UI files, assets, or resources that aren’t included

inside  a  simple  .jar  file.  In  this  case,  you  can  just  place  the  .jar  file  inside  your  project’s
native/android directory.

2. The SDK includes some XML UI files, resources, and assets. In this case, the SDK is generally

distributed as an Android project folder that can be imported into an Eclipse or Android studio

workspace. In general, in this case, you would need to zip the entire directory and change the
extension  of  the  resulting  .zip  file  to  ".andlib",  and  place  this  in  your  project’s  native/android
directory.

3. The  SDK  is  distributed  as  an  .aar  file  -  In  this  case  you  can  just  copy  the  .aar  file  into  your

native/android directory.

The FreshDesk SDK

The FreshDesk (aka Mobihelp) SDK is distributed as a project folder (i.e. scenario 2 from the above

list).  Therefore,  our  procedure  is  to  download  the  SDK  (download  link  [https://s3.amazonaws.com/
assets.mobihelp.freshpo.com/sdk/mobihelp_sdk_android.zip]), and rename it from mobihelp_sdk_android.zip
to mobihelp_sdk_android.andlib, and copy it into our native/android directory.

Dependencies

Unfortunately, in this case there’s a catch. The Mobihelp SDK includes a dependency:

Mobihelp SDK depends on AppCompat-v7 (Revision 19.0+) Library. You will

need to update project.properties to point to the Appcompat library.

If we look inside the project.properties file (inside the Mobihelp SDK directory--- i.e. you’d need to
extract it from the zip to view its contents), you’ll see the dependency listed:

android.library.reference.1=../appcompat_v7

635

I.e.  it  is  expecting  to  find  the  appcompat_v7  library  located  in  the  same  parent  directory  as  the
Mobihelp  SDK  project.  After  a  little  bit  of  research  (if  you’re  not  yet  familiar  with  the  Android
AppCompat  support  library),  we  find  that  the  AppCompat_v7  library  is  part  of  the  Android  Support
library,  which  can  can  installed  into  your  local  Android  SDK  using  Android  SDK  Manager.

Installation processed specified here [https://developer.android.com/tools/support-library/setup.html].

After  installing  the  support  library,  you  need  to  retrieve  it  from  your  Android  SDK.  You  can  find

that 
the
file 
ANDROID_HOME/sdk/extras/android/m2repository/com/android/support/appcompat-v7/19.1.0/  directory
(for version 19.1.0). The contents of that directory on my system are:

inside 

.aar 

appcompat-v7-19.1.0.aar     appcompat-v7-19.1.0.pom
appcompat-v7-19.1.0.aar.md5 appcompat-v7-19.1.0.pom.md5
appcompat-v7-19.1.0.aar.sha1    appcompat-v7-19.1.0.pom.sha1

There are two files of interest here:

1. appcompat-v7-19.1.0.aar  -  This  is  the  actual  library  that  we  need  to  include  in  our  project  to

satisfy the Mobisdk dependency.

2. appcompat-v7-19.1.0.pom  -  This  is  the  Maven  XML  file  for  the  library.  It  will  show  us  any

dependencies that the appcompat library has. We will also need to include these dependencies:

  <dependencies>
    <dependency>
      <groupId>com.android.support</groupId>
      <artifactId>support-v4</artifactId>
      <version>19.1.0</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

i.e. We  need  to  include  the  support-v4  library  version  19.1.0  in  our  project.  This  is  also  part  of
the  Android 
to:
couple  of  directories 
ANDROID_HOME/sdk/extras/android/m2repository/com/android/support, we’ll see it listed there:

If  we  back  up  a 

Support 

library. 

appcompat-v7            palette-v7
cardview-v7         recyclerview-v7
gridlayout-v7           support-annotations
leanback-v17            support-v13
mediarouter-v7          support-v4
multidex            test
multidex-instrumentation

+  And 
(in
ANDROID_HOME/sdk/extras/android/m2repository/com/android/support/support-v4/19.1.0), we see:

the  appropriate  version  directory  of  support-v4 

if  we 

inside 

look 

636

support-v4-19.1.0-javadoc.jar       support-v4-19.1.0.jar
support-v4-19.1.0-javadoc.jar.md5   support-v4-19.1.0.jar.md5
support-v4-19.1.0-javadoc.jar.sha1  support-v4-19.1.0.jar.sha1
support-v4-19.1.0-sources.jar       support-v4-19.1.0.pom
support-v4-19.1.0-sources.jar.md5   support-v4-19.1.0.pom.md5
support-v4-19.1.0-sources.jar.sha1  support-v4-19.1.0.pom.sha1

Looks like this library is pure Java classes, so we only need to include the support-v4-19.1.0.jar
file into our project. Checking the .pom file we see that there are no additional dependencies we
need to add.

So,  to  summarize  our  findings,  we  need  to  include  the  following  files  in  our  native/android
directory:

1. appcompat-v7-19.1.0.aar

2. support-v4-19.1.0.jar

And  since  our  Mobihelp  SDK  lists  the  appcompat_v7  dependency  path  as  "../appcompat_v7"  in  its
project.properties file, we are going to rename appcompat-v7-19.1.0.aar to appcompat_v7.aar.

When all is said and done, our native/android directory should contain the following:

appcompat_v7.aar    mobihelp.andlib
com         support-v4-19.1.0.jar

16.13.7. Step 7 : Injecting Android Manifest and Proguard Config

The final step on the Android side is to inject necessary permissions and services into the project’s

AndroidManifest.xml file.

We can find the manifest file injections required by opening the AndroidManifest.xml file from the
MobiHelp SDK project. Its contents are as follows:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.freshdesk.mobihelp"
    android:versionCode="1"
    android:versionName="1.0" >

     <uses-sdk
        android:minSdkVersion="10" />

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_LOGS" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application>
        <activity

637

            android:name="com.freshdesk.mobihelp.activity.SolutionArticleListActivity"
            android:configChanges="orientation|screenSize"
            android:theme="@style/Theme.Mobihelp"
            android:windowSoftInputMode="adjustPan" >
        </activity>
        <activity
            android:name="com.freshdesk.mobihelp.activity.FeedbackActivity"
            android:configChanges="keyboardHidden|orientation|screenSize"
            android:theme="@style/Theme.Mobihelp"
            android:windowSoftInputMode="adjustResize|stateVisible" >
        </activity>
        <activity
            android:name="com.freshdesk.mobihelp.activity.InterstitialActivity"
            android:configChanges="orientation|screenSize"
            android:theme="@style/Theme.AppCompat">
        </activity>
        <activity
            android:name="com.freshdesk.mobihelp.activity.TicketListActivity"
            android:parentActivityName="com.freshdesk.mobihelp.activity.SolutionArticleListActivity"
            android:theme="@style/Theme.Mobihelp" >

            <!-- Parent activity meta-data to support 4.0 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.freshdesk.mobihelp.activity.SolutionArticleListActivity" />
        </activity>
        <activity
            android:name="com.freshdesk.mobihelp.activity.SolutionArticleActivity"
            android:parentActivityName="com.freshdesk.mobihelp.activity.SolutionArticleListActivity"
            android:theme="@style/Theme.Mobihelp"
            android:configChanges="orientation|screenSize|keyboard|keyboardHidden" >

            <!-- Parent activity meta-data to support 4.0 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.freshdesk.mobihelp.activity.SolutionArticleListActivity" />
        </activity>
        <activity
            android:name="com.freshdesk.mobihelp.activity.ConversationActivity"
            android:parentActivityName="com.freshdesk.mobihelp.activity.SolutionArticleListActivity"
            android:theme="@style/Theme.Mobihelp"
            android:windowSoftInputMode="adjustResize|stateHidden" >

            <!-- Parent activity meta-data to support 4.0 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.freshdesk.mobihelp.activity.SolutionArticleListActivity" />
        </activity>
        <activity
            android:name="com.freshdesk.mobihelp.activity.AttachmentHandlerActivity"
            android:configChanges="keyboardHidden|orientation|screenSize"
            android:parentActivityName="com.freshdesk.mobihelp.activity.SolutionArticleListActivity"
            android:theme="@style/Theme.Mobihelp" >

            <!-- Parent activity meta-data to support 4.0 and lower -->
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"

638

                android:value="com.freshdesk.mobihelp.activity.SolutionArticleListActivity" />
        </activity>

        <service android:name="com.freshdesk.mobihelp.service.MobihelpService" />

        <receiver android:name="com.freshdesk.mobihelp.receiver.ConnectivityReceiver" >
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
            </intent-filter>
        </receiver>
    </application>

</manifest>

We’ll need to add the <uses-permission> tags and all of the contents of the <application> tag to our
manifest file. Codename One provides the following build hints for these:

1. android.xpermissions  -  For  your  <uses-permission>  directives.  Add  a  build  hint  with  name

android.xpermissions, and for the value, paste the actual <uses-permission> XML tag.

2. android.xapplication - For the contents of your <application> tag.

Proguard Config

For  the  release  build,  we’ll  also  need  to  inject  some  proguard  configuration  so  that  important

classes don’t get stripped out at build time. The FreshDesk SDK instructions state:

If  you  use  Proguard,  please  make  sure  you  have  the  following  included  in

your project’s proguard-project.txt

-keep class android.support.v4.** { *; }
-keep class android.support.v7.** { *; }

In addition, if you look at the proguard-project.txt file inside the Mobihelp SDK, you’ll see the rules:

-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.app.Activity
-keep public class * extends android.preference.Preference
-keep public class com.freshdesk.mobihelp.exception.MobihelpComponentNotFoundException

-keepclassmembers class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator *;
}

We’ll  want  to  merge  this  and  then  paste  them  into  the  build  hint  android.proguardKeep  of  our
project.

639

Troubleshooting Android Stuff

If, after doing all this, your project fails to build, you can enable the "Include Source" option of the

build  server,  then  download  the  source  project,  open  it  in  Eclipse  or  Android  Studio,  and  debug

from there.

16.14. Part 2: Implementing the iOS Native Code

Part 1 of this tutorial focused on the Android native integration. Now we’ll shift our focus to the iOS

implementation.

After selecting "Generate Native Interfaces" for our "MobihelpNative" class, you’ll find a native/ios
directory in your project with the following files:

1. com_codename1_freshdesk_MobihelpNativeImpl.h 

[https://github.com/shannah/cn1-freshdesk/blob/master/

cn1-freshdesk-demo/native/ios/com_codename1_freshdesk_MobihelpNativeImpl.h]

2. com_codename1_freshdesk_MobihelpNativeImpl.m 

[https://github.com/shannah/cn1-freshdesk/blob/master/

cn1-freshdesk-demo/native/ios/com_codename1_freshdesk_MobihelpNativeImpl.m]

These files contain stub implementations corresponding to our MobihelpNative class.

We make use of the API docs [http://developer.freshdesk.com/mobihelp/ios/api/] to see how the native SDK
needs to be wrapped. The method names aren’t the same. E.g. instead of a method showFeedback(), it
has a message -presentFeedback:

We  more-or-less  just  follow  the  iOS  integration  guide  [http://developer.freshdesk.com/mobihelp/ios/

integration_guide/#getting-started] for wrapping the API. Some key points include:

1. Remember to import the Mobihelp.h file in your header file:

#import "Mobihelp.h"

2. Similar  to  our  use  of  runOnUiThread()  in  Android,  we  will  wrap  all  of  our  API  calls  in  either
dispatch_async()  or  dispatch_sync()  calls  to  ensure  that  we  are  interacting  with  the  Mobihelp
API on the app’s main thread rather than the Codename One EDT.

3. Some  methods/messages  in  the  Mobihelp  SDK  require  us  to  pass  a  UIViewController  as  a
parameter.  In  Codename  One,  the  entire  application  uses  a  single  UIViewController:
CodenameOne_GLViewController.  You 
can 
[CodenameOne_GLViewController instance] message. We need to import its header file:

this  using 

reference 

obtain 

the

to 

a 

#import "CodenameOne_GLViewController.h"

As an example, let’s look at the showFeedback() method:

640

-(void)showFeedback{

    dispatch_async(dispatch_get_main_queue(), ^{
        [[Mobihelp sharedInstance] presentFeedback:[CodenameOne_GLViewController instance]];
    });
}

16.14.1. Using the MobihelpNativeCallback

We  described  earlier  how  we  created  a  static  method  on  the  MobihelpNativeCallback  class  so  that
native code could easily fire a callback method. Now let’s take a look at how this looks from the iOS
side of the fence. Here is the implementation of getUnreadCountAsync():

-(void)getUnreadCountAsync:(int)param{
  dispatch_async(dispatch_get_main_queue(), ^{
    [[Mobihelp sharedInstance]
      unreadCountWithCompletion:^(NSInteger count){
        com_codename1_freshdesk_MobihelpNativeCallback_fireUnreadUpdatesCallback___int_int_int(
                CN1_THREAD_GET_STATE_PASS_ARG param, 3 /*SUCCESS*/, count);
      }];
  });
}

In our case the iOS SDK version of this method is +unreadCountWithCompletion: which takes a block
(which is like an anonymous function) as a parameter.

The callback to our Codename One function occurs on this line:

com_codename1_freshdesk_MobihelpNativeCallback_fireUnreadUpdatesCallback___int_int_int(
    CN1_THREAD_GET_STATE_PASS_ARG param, 3 /*SUCCESS*/, count);

Some things worth mentioning here:

1. The 

is 

name 

method 

taking 
(MobihelpNativeCallback.fireUpdateUnreadUpdatesCallback(int,  int,  int) 
the  package
com.codename1.freshdesk)  and  replacing  all  .  characters  with  underscores,  suffixing  two
underscores  after  the  end  of  the  method  name,  then  appending  _int  once  for  each  of  the  int
arguments.

result 

FQN

the 

the 

in 

of 

2. We also need to import the header file for this class:

#import "com_codename1_freshdesk_MobihelpNativeCallback.h"

16.14.2. Bundling Native iOS SDK

Now that we have implemented our iOS native interface, we need to bundle the Mobihelp iOS SDK

641

into our project. There are a few different scenarios you may face when looking to include a native

SDK:

1. The  SDK  includes  .bundle  resource  files.  In  this  case,  just  copy  the  .bundle  file(s)  into  your

native/ios directory.

2. The  SDK  includes  .h  header  files.  In  this  case,  just  copy  the  .h  file(s)  into  your  native/ios

directory.

3. The SDK includes .a files. In this case, just copy the .a file(s) into your native/ios directory.

4. The SDK includes .framework files. In this case, you’ll need to zip up the framework, and copy it
into your native/ios directory. E.g. If the framework is named, MyFramework.framework, then
the  zip  file  should  be  named  MyFramework.framework.zip,  and  should  be  located  at
native/ios/MyFramework.framework.zip.

The FreshDesk SDK doesn’t include any .framework files, so we don’t need to worry about that last
scenario.  We  simply  download  the  iOS  SDK  [https://s3.amazonaws.com/assets.mobihelp.freshpo.com/sdk/
mobihelp_sdk_ios.zip],  copy  the  libFDMobihelpSDK.a,  Mobihelp.h.  MHModel.bundle,  MHResources.bundle,
and MHLocalization/en.proj/MHLocalizable.strings into native/ios.

16.14.3. Troubleshooting iOS

If  you  run  into  problems  with  the  build,  you  can  select  "Include  Sources"  in  the  build  server  to

download the resulting Xcode Project. You can then debug the Xcode project locally, make changes

to  your  iOS  native  implementation  files,  and  copy  them  back  into  your  project  once  it  is  building

properly.

16.14.4. Adding Required Core Libraries and Frameworks

The  iOS  integration  guide  for  the  FreshDesk  SDK  lists  the  following  core  frameworks  as

dependencies:

Figure 486. IOS link options

We can add these dependencies to our project using the ios.add_libs build hint. E.g.

Figure 487. iOS’s "add libs" build hint

I.e.  we  just  list  the  framework  names  separated  by  semicolons.  Notice  that  my  list  in  the  above

image  doesn’t  include  all  of  the  frameworks  that  they  list  because  many  of  the  frameworks  are

already included by default (I obtained the default list by simply building the project with "include

sources" checked, then looked at the frameworks that were included).

642

16.15. Part 3 : Packaging as a cn1lib

During the initial development, I generally find it easier to use a regular Codename One project so

that I can run and test as I go. But once it is stabilized, and I want to distribute the library to other

developers, I will transfer it over to a Codename One library project. This general process involves:

1. Create a Codename One Library project.

2. Copy the .java files from my original project into the library project.

3. Copy the native directory from the original project into the library project.

4. Copy  the  relevant  build  hints  from  the  original  project’s  codenameone_settings.properties  file

into the library project’s codenameone_library_appended.properties file.

In  the  case  of  the  FreshDesk  .cn1lib,  I  modified  the  original  project’s  build  script  to  generate  and

build a library project automatically. But that is beyond the scope of this tutorial.

16.16. Building Your Own Layout Manager

A  Layout  [https://www.codenameone.com/javadoc/com/codename1/ui/layouts/Layout.html]  contains  all  the

logic  for  positioning  Codename  One  components.  It  essentially  traverses  a  Codename  One

Container 

[https://www.codenameone.com/javadoc/com/codename1/ui/Container.html] 

and 

positions

components absolutely based on internal logic.

When we build the layout we need to take margin into consideration and make sure to add it into

the  position/size  calculations.  Building  a 
layoutContainer & getPreferredSize.

layout  manager  involves  two  simple  methods:

layoutContainer  is  invoked  whenever  Codename  One  decides  the  container  needs  rearranging,
Codename  One  tries  to  avoid  calling  this  method  and  only  invokes  it  at  the  last  possible  moment.

Since  this  method  is  generally  very  expensive  (imagine  the  recursion  with  nested  layouts).

Codename  One  just  marks  a  flag  indicating  layout  is  "dirty"  when  something  important  changes

and tries to avoid "reflows".

getPreferredSize allows the layout to determine the size desired for the container. This might be a
difficult call to make for some layout managers that try to provide both flexibility and simplicity.

Most  of  FlowLayout  bugs  stem  from  the  fact  that  this  method  is  just  impossible  to  implement
correctly & efficiently for all the use cases of a deeply nested FlowLayout. The size of the final layout
won’t necessarily match the requested size (it probably won’t) but the requested size is taken into

consideration, especially when scrolling and also when sizing parent containers.

This is a layout manager that just arranges components in a center column aligned to the middle.

We then show the proper usage of margin to create a stair like effect with this layout manager:

643

class CenterLayout extends Layout {
    public void layoutContainer(Container parent) {
        int components = parent.getComponentCount();
        Style parentStyle = parent.getStyle();
        int centerPos = parent.getLayoutWidth() / 2 + parentStyle.getMargin(Component.LEFT);
        int y = parentStyle.getMargin(Component.TOP);
        boolean rtl = parent.isRTL();
        for (int iter = 0; iter < components; iter++) {
            Component current = parent.getComponentAt(iter);
            Dimension d = current.getPreferredSize();
            Style currentStyle = current.getStyle();
            int marginRight = currentStyle.getMarginRight(rtl);
            int marginLeft = currentStyle.getMarginLeft(rtl);
            int marginTop = currentStyle.getMarginTop();
            int marginBottom = currentStyle.getMarginBottom();
            current.setSize(d);
            int actualWidth = d.getWidth() + marginLeft + marginRight;
            current.setX(centerPos - actualWidth / 2 + marginLeft);
            y += marginTop;
            current.setY(y);
            y += d.getHeight() + marginBottom;
        }
    }

    public Dimension getPreferredSize(Container parent) {
        int components = parent.getComponentCount();
        Style parentStyle = parent.getStyle();
        int height = parentStyle.getMargin(Component.TOP) + parentStyle.getMargin(Component.BOTTOM);
        int marginX = parentStyle.getMargin(Component.RIGHT) + parentStyle.getMargin(Component.LEFT);
        int width = marginX;
        for (int iter = 0; iter < components; iter++) {
            Component current = parent.getComponentAt(iter);
            Dimension d = current.getPreferredSize();
            Style currentStyle = current.getStyle();
            width = Math.max(d.getWidth() + marginX + currentStyle.getMargin(Component.RIGHT)
                    + currentStyle.getMargin(Component.LEFT), width);
            height += currentStyle.getMargin(Component.TOP) + d.getHeight()
                    + currentStyle.getMargin(Component.BOTTOM);
        }
        Dimension size = new Dimension(width, height);
        return size;
    }
}

Form hi = new Form("Center Layout", new CenterLayout());
for(int iter = 1 ; iter < 10 ; iter++) {
    Label l = new Label("Label: " + iter);
    l.getUnselectedStyle().setMarginLeft(iter * 3);
    l.getUnselectedStyle().setMarginRight(0);
    hi.add(l);
}
hi.add(new Label("Really Wide Label Text!!!"));
hi.show();

644

Figure 488. Center layout staircase effect with margin

16.16.1. Porting a Swing/AWT Layout Manager

The  GridBagLayout 

[https://www.codenameone.com/javadoc/com/codename1/ui/layouts/GridBagLayout.html]

was  ported  to  Codename  One  relatively  easily  considering  the  complexity  of  that  specific  layout

manager.  Here  are  some  tips  you  should  take  into  account  when  porting  a  Swing/AWT  layout

manager:

1. Codename One doesn’t have Insets, we added some support for them in order to port GridBag
but  components  in  Codename  One  have  a  margin  they  need  to  consider  instead  of  the  Insets
(the padding is in the preferred size and is thus hidden from the layout manager).

2. AWT  layout  managers  also  synchronize  a  lot  on  the  AWT  thread.  This  is  no  longer  necessary

since Codename One is single threaded, like Swing.

3. AWT considers the top left position of the Container to be 0,0 whereas Codename One considers
the  position  based  on  its  parent  Container.  The  top  left  position  in  Codename  One  is  getX(),
getY().

Other  than  those  things  it’s  mostly  just  fixing  method  and  import  statements,  which  are  slightly

different. Pretty trivial stuff.

16.17. Port a Language to Codename One

As  you  may  have  already  read,  we  have  just  added  support  for  Kotlin  in  Codename  One.  This  is

something  that  you  can  achieve  without  the  help  of  Codename  One.  You  could  port  a  3rd  party

language like Scala, Ruby, Python etc. to Codename One.

16.17.1. What is a JVM Language?

A JVM Language is any programming language that can be compiled to byte-codes that will run on

the JVM (Java Virtual Machine). Java was the original JVM language, but many others have sprung

up  over  the  years.  Kotlin  [https://kotlinlang.org/],  Scala  [https://www.scala-lang.org/],  Groovy  [http://groovy-

lang.org/],  and  JRuby  [http://jruby.org/]  come  to  mind  as  well-established  and  mature  languages,  but

there are many others [https://en.wikipedia.org/wiki/List_of_JVM_languages].

645

16.17.2. How Hard is it to Port a JVM Language to Codename One?

The  difficulty  of  porting  a  particular  language  to  Codename  One  will  vary  depending  on  such

factors as:

1. Does it require a runtime library?

a. How  complex  is  the  runtime  library?  (E.g.  Does  it  require  classes  that  aren’t  currently

offered in Codename One’s subset of the java standard libraries?)

2. Does it need reflection?

a. Codename One doesn’t support reflection because it would result in a very large application

size.  If  a  JVM  language  requires  reflection  just  to  get  off  the  ground  then  adding  it  to

Codename one would be tricky.

3. Does it perform any runtime byte-code manipulation?

a. Some  dynamic  languages  may  perform  byte-code  manipulation  at  runtime.  This  is

problematic on iOS (and possibly other platforms) which prohibits such runtime behavior.

Step 1: Assess the Language

The  more  similar  a  language,  and  its  build  outputs  are  to  Java,  the  easier  it  will  be  to  port

(probably). Most JVM languages have two parts:

1. A compiler, which compiles source files to JVM byte-code (usually as .class files).

2. A runtime library.

Currently I’m only aware of one language (other than Java) that doesn’t require a runtime library,

and that is Mirah [http://www.mirah.org/].

 Codename  One  also  supports  Mirah  [https://www.codenameone.com/blog/mirah-for-

codename-one.html]

Assessing the Byte-Code

The first thing I do is take a look at the byte-code that is produced by the compiler. I use javap to
print out a nice version.

Consider this sample Kotlin class:

646

package com.codename1.hellokotlin2

import com.codename1.ui.Button
import com.codename1.ui.Form
import com.codename1.ui.Label
import com.codename1.ui.layouts.BoxLayout

/**
 * Created by shannah on 2017-07-10.
 */
class KotlinForm : Form {

    constructor() : super("Hello Kotlin", BoxLayout.y()) {
        val label = Label("Hello Kotlin")
        val clickMe = Button("Click Me")
        clickMe.addActionListener {
            label.setText("You Clicked Me");
            revalidate();
        }

        add(label).add(clickMe);

    }

}

Let’s take a look at the bytecode that Kotlin produced for this class:

$ javap -v com/codename1/hellokotlin2/KotlinForm.class

  Last modified 10-Jul-2017; size 1456 bytes
  MD5 checksum 1cb00f6e63b918bb5a9f146ca8b0b78e
  Compiled from "KotlinForm.kt"
public final class com.codename1.hellokotlin2.KotlinForm extends com.codename1.ui.Form
  SourceFile: "KotlinForm.kt"
  InnerClasses:
       static final #31; //class com/codename1/hellokotlin2/KotlinForm$1
  RuntimeVisibleAnnotations:
    0: #56(#57=[I#58,I#58,I#59],#60=[I#58,I#61,I#58],#62=I#58,#63=[s#64],#65=[s#55,s#66,s#6,s#67])
  minor version: 0
  major version: 50
  flags: ACC_PUBLIC, ACC_FINAL, ACC_SUPER
Constant pool:
   #1 = Utf8               com/codename1/hellokotlin2/KotlinForm
   #2 = Class              #1             //  com/codename1/hellokotlin2/KotlinForm
   #3 = Utf8               com/codename1/ui/Form
   #4 = Class              #3             //  com/codename1/ui/Form
   #5 = Utf8               <init>
   #6 = Utf8               ()V
   #7 = Utf8               Hello Kotlin
   #8 = String             #7             //  Hello Kotlin
   #9 = Utf8               com/codename1/ui/layouts/BoxLayout

647

  #10 = Class              #9             //  com/codename1/ui/layouts/BoxLayout
  #11 = Utf8               y
  #12 = Utf8               ()Lcom/codename1/ui/layouts/BoxLayout;
  #13 = NameAndType        #11:#12        //  y:()Lcom/codename1/ui/layouts/BoxLayout;
  #14 = Methodref          #10.#13        //  com/codename1/ui/layouts/BoxLayout.y:()Lcom/codename1/ui/layouts/BoxLayout;
  #15 = Utf8               com/codename1/ui/layouts/Layout
  #16 = Class              #15            //  com/codename1/ui/layouts/Layout
  #17 = Utf8               (Ljava/lang/String;Lcom/codename1/ui/layouts/Layout;)V
  #18 = NameAndType        #5:#17         //  "<init>":(Ljava/lang/String;Lcom/codename1/ui/layouts/Layout;)V
  #19 = Methodref          #4.#18         //
com/codename1/ui/Form."<init>":(Ljava/lang/String;Lcom/codename1/ui/layouts/Layout;)V
  #20 = Utf8               com/codename1/ui/Label
  #21 = Class              #20            //  com/codename1/ui/Label
  #22 = Utf8               (Ljava/lang/String;)V
  #23 = NameAndType        #5:#22         //  "<init>":(Ljava/lang/String;)V
  #24 = Methodref          #21.#23        //  com/codename1/ui/Label."<init>":(Ljava/lang/String;)V
  #25 = Utf8               com/codename1/ui/Button
  #26 = Class              #25            //  com/codename1/ui/Button
  #27 = Utf8               Click Me
  #28 = String             #27            //  Click Me
  #29 = Methodref          #26.#23        //  com/codename1/ui/Button."<init>":(Ljava/lang/String;)V
  #30 = Utf8               com/codename1/hellokotlin2/KotlinForm$1
  #31 = Class              #30            //  com/codename1/hellokotlin2/KotlinForm$1
  #32 = Utf8               (Lcom/codename1/hellokotlin2/KotlinForm;Lcom/codename1/ui/Label;)V
  #33 = NameAndType        #5:#32         //  "<init>":(Lcom/codename1/hellokotlin2/KotlinForm;Lcom/codename1/ui/Label;)V
  #34 = Methodref          #31.#33        //
com/codename1/hellokotlin2/KotlinForm$1."<init>":(Lcom/codename1/hellokotlin2/KotlinForm;Lcom/codename1/ui/Label;)V
  #35 = Utf8               com/codename1/ui/events/ActionListener
  #36 = Class              #35            //  com/codename1/ui/events/ActionListener
  #37 = Utf8               addActionListener
  #38 = Utf8               (Lcom/codename1/ui/events/ActionListener;)V
  #39 = NameAndType        #37:#38        //  addActionListener:(Lcom/codename1/ui/events/ActionListener;)V
  #40 = Methodref          #26.#39        //
com/codename1/ui/Button.addActionListener:(Lcom/codename1/ui/events/ActionListener;)V
  #41 = Utf8               com/codename1/ui/Component
  #42 = Class              #41            //  com/codename1/ui/Component
  #43 = Utf8               add
  #44 = Utf8               (Lcom/codename1/ui/Component;)Lcom/codename1/ui/Container;
  #45 = NameAndType        #43:#44        //  add:(Lcom/codename1/ui/Component;)Lcom/codename1/ui/Container;
  #46 = Methodref          #2.#45         //
com/codename1/hellokotlin2/KotlinForm.add:(Lcom/codename1/ui/Component;)Lcom/codename1/ui/Container;
  #47 = Utf8               com/codename1/ui/Container
  #48 = Class              #47            //  com/codename1/ui/Container
  #49 = Methodref          #48.#45        //
com/codename1/ui/Container.add:(Lcom/codename1/ui/Component;)Lcom/codename1/ui/Container;
  #50 = Utf8               clickMe
  #51 = Utf8               Lcom/codename1/ui/Button;
  #52 = Utf8               label
  #53 = Utf8               Lcom/codename1/ui/Label;
  #54 = Utf8               this
  #55 = Utf8               Lcom/codename1/hellokotlin2/KotlinForm;
  #56 = Utf8               Lkotlin/Metadata;
  #57 = Utf8               mv
  #58 = Integer            1
  #59 = Integer            6
  #60 = Utf8               bv
  #61 = Integer            0
  #62 = Utf8               k
  #63 = Utf8               d1
  #64 = Utf8
                           \n\n\20¢¨
  #65 = Utf8               d2
  #66 = Utf8               Lcom/codename1/ui/Form;
  #67 = Utf8               HelloKotlin2
  #68 = Utf8               KotlinForm.kt
  #69 = Utf8               Code
  #70 = Utf8               LocalVariableTable

648

  #71 = Utf8               LineNumberTable
  #72 = Utf8               SourceFile
  #73 = Utf8               InnerClasses
  #74 = Utf8               RuntimeVisibleAnnotations
{
  public com.codename1.hellokotlin2.KotlinForm();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=5, locals=3, args_size=1
         0: aload_0
         1: ldc           #8                  // String Hello Kotlin
         3: invokestatic  #14                 // Method
com/codename1/ui/layouts/BoxLayout.y:()Lcom/codename1/ui/layouts/BoxLayout;
         6: checkcast     #16                 // class com/codename1/ui/layouts/Layout
         9: invokespecial #19                 // Method
com/codename1/ui/Form."<init>":(Ljava/lang/String;Lcom/codename1/ui/layouts/Layout;)V
        12: new           #21                 // class com/codename1/ui/Label
        15: dup
        16: ldc           #8                  // String Hello Kotlin
        18: invokespecial #24                 // Method com/codename1/ui/Label."<init>":(Ljava/lang/String;)V
        21: astore_1
        22: new           #26                 // class com/codename1/ui/Button
        25: dup
        26: ldc           #28                 // String Click Me
        28: invokespecial #29                 // Method com/codename1/ui/Button."<init>":(Ljava/lang/String;)V
        31: astore_2
        32: aload_2
        33: new           #31                 // class com/codename1/hellokotlin2/KotlinForm$1
        36: dup
        37: aload_0
        38: aload_1
        39: invokespecial #34                 // Method
com/codename1/hellokotlin2/KotlinForm$1."<init>":(Lcom/codename1/hellokotlin2/KotlinForm;Lcom/codename1/ui/Label;)V
        42: checkcast     #36                 // class com/codename1/ui/events/ActionListener
        45: invokevirtual #40                 // Method
com/codename1/ui/Button.addActionListener:(Lcom/codename1/ui/events/ActionListener;)V
        48: aload_0
        49: aload_1
        50: checkcast     #42                 // class com/codename1/ui/Component
        53: invokevirtual #46                 // Method add:(Lcom/codename1/ui/Component;)Lcom/codename1/ui/Container;
        56: aload_2
        57: checkcast     #42                 // class com/codename1/ui/Component
        60: invokevirtual #49                 // Method
com/codename1/ui/Container.add:(Lcom/codename1/ui/Component;)Lcom/codename1/ui/Container;
        63: pop
        64: return
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
           32      32     2 clickMe   Lcom/codename1/ui/Button;
           22      42     1 label   Lcom/codename1/ui/Label;
            0      65     0  this   Lcom/codename1/hellokotlin2/KotlinForm;
      LineNumberTable:
        line 13: 0
        line 14: 12
        line 15: 22
        line 16: 32
        line 21: 48
}

That’s a big mess of stuff, but it’s pretty easy to pick through it when you know what you’re looking

for.  The  layout  of  this  output  is  pretty  straight  forward.  The  beginning  shows  that  this  is  a  class

definition:

649

public final class com.codename1.hellokotlin2.KotlinForm extends com.codename1.ui.Form {
    //...
}

Even  just  comparing  this  line  with  the  class  definition  from  the  source  file  we  have  learned
something  about  the  Kotlin  compiler.  It  has  made  the  class  final  by  default.  That  observation
shouldn’t affect our assessment here, but it is kind of interesting.

After the class definition, it shows the internal classes:

InnerClasses:
     static final #31; //class com/codename1/hellokotlin2/KotlinForm$1

The Constant Pool

And the constants that are used in the class:

Constant pool:
   #1 = Utf8               com/codename1/hellokotlin2/KotlinForm
   #2 = Class              #1             //  com/codename1/hellokotlin2/KotlinForm
   #3 = Utf8               com/codename1/ui/Form
   #4 = Class              #3             //  com/codename1/ui/Form
   #5 = Utf8               <init>
   #6 = Utf8               ()V
   #7 = Utf8               Hello Kotlin
   #8 = String             #7             //  Hello Kotlin
   #9 = Utf8               com/codename1/ui/layouts/BoxLayout
   ... etc...

The  constant  pool  will  consist  of  class  names,  and  strings  mostly.  You’ll  want  to  peruse  this  list  to

see  if  the  compiler  has  added  any  classes  that  aren’t  in  the  source  code.  In  the  example  above,  it

looks like Kotlin is pretty faithful to the original source’s dependencies. It didn’t inject any classes

that aren’t in the original source.

Even if the compiler does inject other dependencies into the bytecode, it might not be a problem. It

is  only  a  problem  if  those  classes  aren’t  supported  by  Codename  One.  Keep  your  eyes  peeled  for
anything  in  the  java.lang.reflect  package  or  unsolicited  use  of  java.net,  java.nio,  or  any  other
package  that  aren’t  part  of  the  Codename  One  standard  library.  If  you’re  not  sure  if  a  class  or

package 

is  available 

in 

the  Codename  One 

standard 

library,  check 

the 

javadocs

[https://www.codenameone.com/javadoc/].

The ByteCode Instructions:

After  the  constant  pool,  we  see  each  of  the  methods  of  the  class  written  out  as  a  list  of  bytecode

instructions. E.g.

650

public com.codename1.hellokotlin2.KotlinForm();
  descriptor: ()V
  flags: ACC_PUBLIC
  Code:
    stack=5, locals=3, args_size=1
       0: aload_0
       1: ldc           #8                  // String Hello Kotlin
       3: invokestatic  #14                 // Method
com/codename1/ui/layouts/BoxLayout.y:()Lcom/codename1/ui/layouts/BoxLayout;
       6: checkcast     #16                 // class com/codename1/ui/layouts/Layout
       9: invokespecial #19                 // Method
com/codename1/ui/Form."<init>":(Ljava/lang/String;Lcom/codename1/ui/layouts/Layout;)V
      12: new           #21                 // class com/codename1/ui/Label
      15: dup
      16: ldc           #8                  // String Hello Kotlin
      etc...

In  the  above  snippet,  the  first  instruction  is  aload_0  (which  adds  this  to  the  stack).  The  2nd
instruction  is  ldc,  (which  loads  constant  #8 — the  string  "Hello  Kotlin"  to  the  stack).  The  3rd
instruction is invokestatic which calls the static method define by Constant #14 from the constant
pool, with the two parameters that had just been added to the stack.

 You  don’t  need  to  understand  what  all  of  these  instructions  do.  You  just  need  to

look for instructions that may be problematic.

The  only  instruction  that  I  think  might  be  problematic  is  "invokedynamic".  All  other  instructions

should work find in Codename One. (I don’t know for a fact that invokedynmic won’t work - I just

suspect it might not work on some platforms).

Summary of Byte-code Assessment

So to summarize, the byte-code assessment phase, we’re basically just looking to make sure that the

compiler doesn’t tend to add dependencies to parts of the JDK that Codename One doesn’t currently

support. And we want to make sure that it doesn’t use invokedynamic.

If you find that the compiler does use invokedynamic or add references to classes that Codename

One doesn’t support, don’t give up just yet. You might be able to create your own "porting" runtime

library that will provide these dependencies at runtime.

Assessing the Runtime Library

The  process  for  assessing  the  runtime  library  is  pretty  similar  to  the  process  for  the  bytecodes.
You’ll want to get your hands on the language’s runtime library, and use javap to inspect the .class
files.  You’re  looking  for  the  same  things  as  you  were  looking  for  in  the  compiler’s  output:

"invokedynamic" and classes that aren’t supported in Codename One.

Step 2: Convert the Runtime Library into a CN1Lib

Once you have assessed the language and are optimistic that it is a good candidate for porting, you

can  proceed  to  port  the  runtime  library  into  Codename  One.  Usually  that  language’s  runtime

library will be distributed in .jar format. You need to convert this into a cn1lib so that it can be used

in a Codename One project. If you can get your hands on the source code for the runtime library

651

then the best approach is to paste the source files into a Codename One Library project, and try to

build  it.  This  has  the  advantage  that  it  will  validate  the  source  during  compile  to  ensure  that  it

doesn’t depend on any classes that Codename One doesn’t support.

If you can’t find the sources of the runtime library or they don’t seem to be easily "buildable", then

the next best thing is to just get the binary distribution’s jar file and convert it to a cn1lib. This is

what we did for the Kotlin runtime library [https://github.com/shannah/codenameone-kotlin].

This procedure exploits the fact that a cn1lib file is just a zip file with a specific file structure inside

it. The cross-platform Java .class files are all contained inside a file named "main.zip", inside the zip

file. This is the only mandatory file that must be inside a cn1lib.

To  make  the  library  easier  to  use  the  cn1lib  file  can  also  contain  a  file  named  "stubs.zip"  which

includes stubs of the Java sources. When you build a cn1lib using a Codename One Library project,

it will automatically generate stubs of the source so that the IDE will have access to nice things like

Javadoc when using the library. The kotlin distribution includes a separate jar file with the runtime

sources, named "kotlin-runtime-sources.jar", so we used this as the "stubs". It contains full sources,

which isn’t necessary, but it also doesn’t hurt.

So now that we had my two jar files: kotlin-runtime.jar and kotlin-runtime-sources.jar, I created a

new  empty  directory,  and  copied  them  inside.  I  renamed  the  jars  "main.zip"  and  "stubs.zip"

respectively. Then I zipped up the directory and renamed the zip file "kotlin-runtime.cn1lib".



Building  cn1libs  manually  in  this  way  is  a  very  bad  habit,  as  it  bypasses  the  API

verification  step  that  normally  occurs  when  building  a  library  project.  It  is

possible,  even  likely,  that  the  jar  files  that  you  convert  depend  on  classes  that

aren’t  in  the  Codename  One  library,  so  your  library  will  fail  at  runtime  in

unexpected  ways.  The  only  reason  we  could  do  this  with  kotlin’s  runtime  (with

some confidence) is because I already analyzed the bytecodes to ensure that they

didn’t include anything problematic.

Step 3: Hello World

For  our  "Hello  World"  test  we  will  need  to  create  a  separate  project  in  our  JVM  language  and

produce  class  files  that  we  will  manually  copy  into  an  appropriate  location  of  our  project.  We’ll

want  to  use  the  normal  tools  for  the  language  and  not  worry  about  how  it  integrates  with

Codename One. For Kotlin, I just followed the getting started tutorial on the Kotlin site to create a

new Kotlin project in IntelliJ. When Steve ported Mirah, he just used a text editor and the mirahc

command-line  compiler  to  create  my  Hello World  class.  The  tools  and  process  will  depend  on  the

language.

Here is the "hello world" we created in Kotlin:

652

package com.mycompany.myapp

class HelloKotlin {

    fun hello() {
        System.out.println("Hello from Kotlin");
    }
}

After building this, I have a directory that contains "com/mycompany/myapp/HelloKotlin.class".

It also produced a .jar file that contains this class.

The easiest way to integrate external code into a Codename One project, is just to wrap it as a cn1lib

file  and  place  it  into  my  Codename  One  project’s  lib  directory.  That  way  you  don’t  have  to  mess

with  any  of  the  build  files.  So,  using  roughly  the  same  procedure  as  we  used  to  create  the  kotlin-

runtime.cn1lib, I wrap my hellokotlin.jar as a cn1lib to produce "hellokotlin.cn1lib" and copy it to

the "lib" directory of a Codename One project.

 Remember to select "Codename One" → "Refresh CN1Libs" after placing the cn1lib

in your lib directory or it won’t get picked up.

Finally, I call my library from the start() method of my app:

HelloKotlin hello = new HelloKotlin();
hello.hello();

If we run this in the Simulator, it should print "Hello from Kotlin" in the output console. If we get an

error,  then  we  can  dig  in  and  try  to  figure  out  what  went  wrong  using  my  standard  debugging

techniques.  EXPECT  an  error  on  the  first  run.  Hopefully  it  will  just  be  a  missing  import  or

something simple.

Step 4: A More Complex Hello World

In the case of Kotlin, the hello world example app would actually run without the runtime library

because it was so simple. So it was necessary to add a more complex example to prove the need for

the runtime library. It doesn’t matter what you do with your more complex example, as long as it

doesn’t require classes that aren’t in Codename One.

If  you  want  to  use  the  Codename  One  inside  your  project,  you  should  add  the  CodenameOne.jar

(found inside any Codename One project) to your classpath so that it will compile.

Step 5: Automation and Integration

At  this  point  we  already  have  a  manual  process  for  incorporating  files  built  with  our  alternate

language into a Codename One project. The process looks like:

1. Use standard tools for your JVM language to write your code.

653

2. Use the JVM language’s standard build tools (e.g. command-line compiler, etc..) to compile your

code so that you have .class files (and optionally a .jar file).

3. Wrap your .class files in a cn1lib.

4. Add the cn1lib to the lib directory of a Codename One project.

5. Use your library from the Codename One project.

When  Steve  first  developed  Mirah  support  he  automated  this  process  using  an  ANT  script

[https://github.com/shannah/CN1MirahNBM/blob/master/src/ca/weblite/codename1/mirah/build.xml].  He 

also

automatically generated some bootstrap code so that he could develop the whole app in Mirah and

he woudn’t have to write any Java. However, this level of integration has limitations.

For  example,  with  this  approach  alone,  you  couldn’t  have  two-way  dependencies  between  Java

source  and  Mirah  source.  Yes,  Mirah  code  could  use  Java  libraries  (and  it  did  depend  on

CodenameOne.jar), and my Java code could use my Mirah code. However, Mirah source code could

not depend on the Java source code in my project. This has to do with the order in which code is

compiled. It’s a bit of a chicken and egg issue. If we are building a project that has Java source code

and  Mirah  source  code,  we  are  using  two  different  compilers:  mirahc  to  compile  the  Mirah  files,

and javac to compile the Java files. If we are starting from a clean build, and we run mirahc first,

then the .java files haven’t yet been compiled to .class files - and thus mirahc can’t reference them -

and any mirah code that depends on those uncompiled Java classes will fail. If we compile the .java

files first, then we have the opposite problem.

Steve worked around this problem in Mirah by writing my own pseudo-compiler [https://github.com/

shannah/mirah-ant/blob/master/src/ca/weblite/asm/JavaExtendedStubCompiler.java]  that  produced  stub  class

files for the java source that would be referenced by mirahc when compiling the Mirah files. In this

way he was able to have two-way dependencies between Java and Mirah in the same project.

Kotlin also supports two-way dependencies, probably using a similar mechanism.

How Seamless Can You Make It?

For both the Kotlin and Mirah support, we wanted integration to be seamless. We didn’t want users

to  have  to  create  a  separate  project  for  their  Kotlin/Mirah  code. We  wanted  them  to  simply  add  a

Kotlin/Mirah  file  into  their  project  and  have  it  just  work.  Achieving  this  level  of  integration  in

Kotlin  was  quite  easy,  since  they  provide  an  ANT  plugin  [https://kotlinlang.org/docs/reference/using-
ant.html] that essentially allowed me to just add one tag inside my <javac/> tags:

<withKotlin/>

And it would automatically handle Kotlin and Java files together: Seamlessly. There are a few places

in a Codename One’s build.xml file where we call "javac" so we just needed to inject these tags in

those places. This injection is performed automatically by the Codename One IntelliJ plugin.

For  Mirah,  Steve  developed  his  own  ANT  plugins  [https://github.com/shannah/mirah-ant]  and  Netbeans

module [https://github.com/shannah/mirah-nbm] that do something similar in Netbeans.

654

16.18. Update Framework

When we launched Codename One in 2012 we needed a way to ship updates and fixes faster than

the plugin update system. So we built the client lib update system. Then we needed a way to update

the designer tool (resource editor), the GUI builder & the skins… We also needed a system to update
the builtin builder code (CodeNameOneBuildClient.jar so we built a tool for that too).

The Update Framework [https://github.com/codenameone/UpdateCodenameOne] solves several problems in

the old systems:

• Download  once  -  if  you  have  multiple  projects  the  library  will  only  download  once  to  the

.codenameone directory. All the projects will update from local storage

• Skins  update  automatically  -  this  is  hugely  important.  When  we  change  a  theme  we  need  to

update it in the skins and if you don’t update the skin you might see a difference between the

simulator and the device

• Update of settings/designer without IDE plugin update - The IDE plugin update process is slow

and tedious. This way we can push out a bug fix for the GUI builder without going through the

process of releasing a new plugin version

For the most part this framework should be seamless. You should no longer see the "downloading"

message  whenever  we  push  an  update  after  your  build  client  is  updated.  Your  system  would  just

poll for a new version daily and update when new updates are available.

You can also use the usual method of  Codename One Settings →  Basic →  Update Client Libs which

will force an update check. Notice that the UI will look a bit different after this update.

16.18.1. How does it Work?

You can see the full code here [https://github.com/codenameone/UpdateCodenameOne] the gist of it is very
simple.  We  create  a  jar  called  UpdateCodenameOne.jar  under  ~/.codenameone  (~  represents  the  users
home directory).

An update happens by running this tool with a path to a Codename One project e.g.:

java -jar ~/.codenameone/UpdateCodenameOne.jar path_to_my_codenameone_project

E.g.:

655

java -jar ~/.codenameone/UpdateCodenameOne.jar ~/dev/AccordionDemo
Checking: JavaSE.jar
Checking: CodeNameOneBuildClient.jar
Checking: CLDC11.jar
Checking: CodenameOne.jar
Checking: CodenameOne_SRC.jar
Checking: designer_1.jar
Checking: guibuilder_1.jar
Updating the file: /Users/shai/dev/AccordionDemo/JavaSE.jar
Updating the file: /Users/shai/dev/AccordionDemo/CodeNameOneBuildClient.jar
Updating the file: /Users/shai/dev/AccordionDemo/lib/CLDC11.jar
Updating the file: /Users/shai/dev/AccordionDemo/lib/CodenameOne.jar
Updated project files

Notice  that  no  download  happened  since  the  files  were  up  to  date.  You  can  also  force  a  check

against the server by adding the force argument as such:

java -jar ~/.codenameone/UpdateCodenameOne.jar path_to_my_codenameone_project

The way this works under the hood is thought a Versions.properties within your directory that lists
the versions of local files. That way we know what should be updated.



Exclude Versions.properties from Git

Under  the  ~/.codenameone  directory  we  have  a  more  detailed  UpdateStatus.properties  file  that
includes  versions  of  the  locally  downloaded  files.  Notice  you  can  delete  this  file  and  it  will  be

recreated as all the jars get downloaded over again.

16.18.2. What isn’t Covered

You will notice 3 big things that aren’t covered in this unified framework:

• We don’t update cn1libs - I’m not sure if this is something we would like to update automatically

• Versioned  builds  -  there  is  a  lot  of  complexity  in  the  versioned  build  system.  This  might  be

something we address in the future but for now I wanted to keep the framework simple.

• Offline  builds  -  Offline  builds  work  through  manual  download  and  aren’t  subjected  to  this

framework

[10] The old Codename One VM

656

17. Signing, Certificates & Provisioning

In this section we attempt to explain how to acquire certificates for the various platforms and how

to set them up.

The good news is that this is usually a "one time issue" and once it’s done the work becomes easier

(except for the case of iOS where a provisioning profile should be maintained).

17.1. Common Terms In Signing & Distribution

This section uses some terms that you might not be familiar with if you haven’t used cryptography

or  built  mobile  apps  before.  Here  is  a  quick  "FAQ"  covering  some  common  terms/concepts  in  this

section.

17.1.1. What Is A Certificate?

Certificates  use  cryptographic  principals  to  "sign"  data  (e.g.  an  application).  Think  of  them  as  you

would think of a company stamp, you use them to sign an app so users know who it’s from.

17.1.2. What Is Provisioning?

Provisioning  provides  the  hints/guidelines  for  the  application  install.  E.g.  if  an  application  needs

some service from the OS such as push it can usually request that with provisioning.

In iOS provisioning is separate from the app and you need to also define the devices supported by

the app during development.

17.1.3. What’s a Signing Authority?

Normally  certificates  are  issued  by  a  signing  authority  which  is  a  body  that  certifies  that  you  are

who you say you are. Apple issues certificates for iOS and is in effect a signing authority.

Android  uses  self  signed  certificates  which  don’t  use  a  signing  authority  so  anyone  can  ship  an

Android app.

The logic with the Android approach is that a signature indicates that you are the same person who

previously shipped the app. Hence an app will be updated only with the exact same certificate.

17.1.4. What is UDID?

The UDID is the Universal Device Identifier. It identifies mobile devices uniquely, notice that some

operating systems e.g. iOS block access to this value due to privacy concerns.

You need the iOS device UDID value during development to add the device into the list of allowed

devices.

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

Don’t use an app to get the UDID!

Most  return  the  wrong  value,  the  official  way  to  get  the  UDID  is  thru  itunes.  We

can also recommend trying http://get.udid.io/ which seems to work rather well

17.1.5. Should I Reuse the Same Certificate for All Apps?

For iOS yes. It’s designed to work in that way.

We  would  recommend  it  for  all  platforms  for  simplicity  but  some  developers  prefer  creating  per-

application certificates for Android. The advantage here is that you can transfer ownership of the

application later on without giving away what is effectively "you house keys".

17.2. iOS Signing Wizard

Codename One features a wizard to generate certificates/provisioning for iOS without requiring a

Mac  or  deep  understanding  of  the  signing  process  for  iOS.  There  is  still  support  for  manually

generating the P12/provisioning files when necessary but for most intents and purposes using the

wizard will simplify this error prone process significantly.

To  generate  your  certificates  and  profiles,  open  project’s  properties  and  click  on  "iOS"  in  the  left

menu.  This  will  show  the  "iOS  Signing"  panel  that  includes  fields  to  select  your  certificates  and

mobile provisioning profiles.

Figure 489. Netbeans iOS Signing properties panel

If  you  already  have  valid  certificates  and  profiles,  you  can  just  enter  their  locations  here.  If  you

don’t, then you can use the wizard by clicking the Generate button in the lower part of the form.

17.2.1. Logging into the Wizard

After clicking Generate you’ll be shown a login form. Log into this form using your iTunes Connect

user ID and password. NOT YOUR CODENAME ONE LOGIN.

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Figure 490. Wizard login form

17.2.2. Selecting Devices

Once  you  are  logged  in  you  will  be  shown  a  list  of  all  of  the  devices  that  you  currently  have

registered on your Apple developer account.

Figure 491. Devices form

Select the ones that you want to include in your provisioning profile and click next.

 Apple supports up to 100 devices for testing purposes so if you want to install the

built app on your device you need to add it here

Figure 492. After selecting devices

If you don’t have any devices registered yet, you can click the "Add New Device" button, which will

prompt you to enter the UDID for your device.

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17.2.3. Decisions & Edge Cases

 If you already have iOS P12 development/distribution certificates you should reuse

them for all your apps from that account and you shouldn’t regenerate them

After  you  click  Next  on  the  device  form,  the  wizard  checks  to  see  if  you  already  have  a  valid

certificate.  If  your  project  already  has  a  valid  certificate  and  it  matches  the  one  that  is  currently

active  in  your  apple  developer  account,  then  it  will  just  use  the  same  certificate.  If  the  certificate

doesn’t match the currently-active one, or you haven’t provided a certificate, you will be prompted

to overwrite the old certificate with a new one.

Figure 493. Prompt to overwrite existing certificate

Figure 494. Prompt to overwrite other certificate

The same decision need to be made twice: Once for the development certificate, and once for the

Apptore certificate.



You  can  revoke  a  certificate  when  you  have  an  application  in  the  store  shipping

with said certificate!

This won’t affect the shipping app see this [http://stackoverflow.com/questions/6320255/if-

i-revoke-an-existing-distribution-certificate-will-it-mess-up-anything-with].

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Why Two Certificates?

A typical iOS app has at least two certificates:

• Development  -  this  is  used  during  development  and  can’t  be  shipped  to  3rd  parties.  An

application  signed  with  this  certificate  can  only  be  installed  on  one  of  the  up  to  100

devices listed above.

• Distribution  -  this  is  used  when  you  are  ready  to  upload  your  app  to  itunes  whether  for

final  shipping  or  beta  testing.  Notice  that  you  can’t  install  a  distribution  build  on  your

own device. You need to upload it to itunes.

• There  are  two  push  certificates,  they  are  separate  from  the  signing  certificates.  Don’t

confuse them!

They are used to authenticate with Apple when sending push messages.

17.2.4. App IDs and Provisioning Profiles

The  next  form  in  the  wizard  asks  for  your  app’s  bundle  ID.  This  should  have  been  pre-filled,  but

you can change the app ID to a wildcard ID if you prefer.

Figure 495. Enter the app bundle ID

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Wildcard Card Provisioning

Wildcard ids such as com.mycompany.\* or even \* allow you to create one generic certificate

to use with all applications. This is remarkably useful for the global settings dialog and allows

you  to  create  an  app  without  launching  the  wizard.  Notice  that  wildcards  apps  can’t  use

features such as push etc.

You  can  set  the  global  defaults  for  the  IDE  by  going  to  IDE  settings/preferences  and  setting

default values e.g.:

Figure 496. Setting the development certificate and a global \* provisioning profile allows you to

create a new app and built it to device without running the certificate wizard. Notice that you will

need to run it when going into production

17.2.5. Installing Files Locally

Once the wizard is finished generating your provisioning profiles, you should click "Install Locally",

which will open a file dialog for you to navigate to a folder in which to store the generated files.

Figure 497. Install files locally

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Figure 498. Select directory to save files in

Figure 499. Final Done Message



You can see the password for the P12 files in the codenameone_settings.properties
file. You can use the values defined there when creating a new application

17.2.6. Building Your App

After  selecting  your  local  install  location,  and  closing  the  wizard,  you  should  see  the  fields  of  the

"iOS  Signing"  properties  panel  filled  in  correctly.  You  should  now  be  able  to  send  iOS  debug  or

Appstore builds without the usual hassles.

Figure 500. Filled in signing panel after wizard complete

17.3. Advanced iOS Signing



You  should  use  the  certificate  wizard,  especially  if  you  don’t  have  a  Mac.  This

section  is  here  mostly  for  reference  and  edge  cases  that  don’t  work  with  the

certificate wizard

iOS signing has two distinct modes: App Store signing which is only valid for distribution via iTunes

(you won’t be able to run the resulting application without submitting it to Apple) and development

mode signing.

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You have two major files to keep track of:

1. Certificate - your signature

2. Provisioning Profile - details about the application and who is allowed to execute it

You need two versions of each file (4 total files) one pair is for development and the other pair is for

uploading to the itunes App Store.

 You need to use a Mac in order to create a certificate file for iOS

The  first  step  you  need  to  accomplish  is  signing  up  as  a  developer  to  Apple’s  iOS  development

program [http://developer.apple.com/], even for testing on a device this is required!

This step requires that you pay Apple on an annual basis.

The Apple website will guide you through the process of applying for a certificate at the end of this

process you should have a distribution and development certificate pair. After that point you can

login  to  the  iOS  provisioning  portal  [https://developer.apple.com/ios/manage/overview/index.action]  where

there  are  plenty  of  videos  and  tutorials  to  guide  you  through  the  process.  Within  the  iOS

provisioning portal you need to create an application ID and register your development devices.

You can then create a provisioning profile which comes in two flavors:

• Distribution - for building the release version of your application

• Development - the development provisioning profile needs to contain the devices on which you

want to test.

You can then configure the 4 files in the IDE and start sending builds to the Codename One cloud.

17.4. Provisioning Profile & Certificates Visual Guide

One of the hardest parts in developing for iOS is the certificate & provisioning process. In this step

by  step  guide  we  walk  over  the  manual  certificate  generation  process.  Notice  that  the  UI  for  the

Apple website changes occasionally but the basic process remains the same…

Start by logging in to the iOS-provisioning portal

Figure 501. Login for the iOS provisioning portal

In the certificates section you can download your development and distribution certificates.

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Figure 502. Download development provisioning profile

Figure 503. Download distribution provisioning profile

In  the  devices  section  add  device  ids  for  the  development  devices  you  want  to  support.  Notice  no

more than 100 devices are supported!

Figure 504. Add devices

Create an application id; it should match the package identifier of your application perfectly!

Figure 505. Create application id

Create a provisioning profile for development, make sure to select the right app and make sure to

add the devices you want to use during debug.

Figure 506. Create provisioning profile step 1

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Figure 507. Create provisioning profile step 2

Refresh the screen to see the profile you just created and press the download button to download

your development provisioning profile.

Figure 508. Create provisioning profile step 3

Create a distribution provisioning profile; it will be used when uploading to the app store. There is

no need to specify devices here.

Figure 509. Create distribution provisioning profile

Download the distribution provisioning profile.

Figure 510. Download distribution provisioning profile

We  can  now  import  the  cer  files  into  the  key  chain  tool  on  a  Mac  by  double  clicking  the  file,  on

Windows the process is slightly more elaborate

Figure 511. Import cer files

We can export the p12 files for the distribution and development profiles through the keychain tool

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Figure 512. Export p12 files

In the IDE we enter the project settings, configure our provisioning profile, the password we typed

when exporting and the p12 certificates. It is now possible to send the build to the server.

Figure 513. IOS Project Settings

17.4.1. iOS Code Signing Failure Checklist

Below is a list of common issues when singing and a set of suggestions for things to check. Notice

that some of these signing failures will sometimes manifest themselves during build and sometimes

will manifest during the install of the application.



Most  of  these  issues  aren’t  applicable  when  using  the  wizard  e.g.  a  Mac  isn’t

required for the certificate wizard as it uses the Codename One cloud

• You must use a Mac to generate P12 certificates manually. The only workaround we found is

the certificate wizard!

Notice that this is something you need to do once a year (generate P12), you will also need a Mac

to upload your final app to the store at this time.

• When  exporting  the  P12  certificate  make  sure  that  you  selected  BOTH  the  public  and  the

private keys as illustrated here. If you only see one entry (no private key) then you created the

CSR  (singing  request)  on  a  different  machine  than  the  one  where  you  imported  the  resulting

CER file.

Figure 514. p12 export

• Make  sure  the  package  matches  between  the  main  preferences  screen  in  the  IDE  and  the  iOS

settings screen.

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Figure 515. Package ID matching App ID

• Make sure the prefix for the app id in the iOS section of the preferences matches the one you

have from Apple

Figure 516. App prefix

• Make sure your provisioning profile’s app id matches your package name or is a * provisioning

profile. Both are sampled in the pictures below, notice that you would need an actual package

name for push/in-app-purchase support as well as for app store distribution.

Figure 517. The star (*) Provisioning Profile

Figure 518. Provisioning Profile with app id

• Make sure the certificate and provisioning profile are from the same source (if you work with

multiple accounts), notice that provisioning profiles and certificates expire so you will need to

regenerate provisioning when your certificate expires or is revoked.

• If  you  declare  push  in  the  provisioning  profile  then  ios.includePush  (in  the  build  arguments)
MUST  be  set  to  true,  otherwise  it  MUST  be  set  to  false  (see  pictures  below).  Notice  that  this

should be configured via the UI in the iOS section.

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Figure 519. Include push build hint

17.5. Android

Signing Android applications is trivial when compared to the pain of iOS signing.

The  NetBeans  and  Eclipse  plugins  have  a  simple  wizard  to  generate  the  certificate  that  you  can

launch by pressing this button:

Figure 520. Android keystore generation wizard

Then fill out your details and password in the form:

Figure 521. UI for Android certificate details

This  will  seamlessly  generate  a  certificate  for  your  project,  you  can  reuse  it  for  other  projects  as

well.

17.5.1. Generating an Android Certificate Manually

You need the JDK’s keytool executable (it should be under the JDK’s bin directory) and execute the

following command:

keytool -genkey -keystore Keystore.ks -alias [alias_name] -keyalg RSA -keysize 2048 -validity 15000 -dname "CN=[full
name], OU=[ou], O=[comp], L=[City], S=[State], C=[Country Code]" -storepass [password] -keypass [password]

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The elements in the brackets should be filled up based on this:

Alias: [alias_name] (just use your name/company name without spaces)
Full name: [full name]
Organizational Unit: [ou]
Company: [comp]
City: [City]
State: [State]
CountryCode: [Country Code]
Password: [password] (we expect both passwords to be identical)

Executing  the  command  will  produce  a  Keystore.ks  file  in  that  directory  which  you  need  to  keep

since if you lose it you will no longer be able to upgrade your applications! Fill in the appropriate

details in the project properties or in the CodenameOne section in the Netbeans preferences dialog.

For more details see http://developer.android.com/guide/publishing/app-signing.html

17.6. RIM/BlackBerry

You  can  now  get  signing  keys  for  free  from  Blackberry  by  going  here  [https://www.blackberry.com/

SignedKeys/].  Once  you  obtain  the  certificates  you  need  to  install  them  on  your  machine  (you  will
need  the  Blackberry  development  environment  for  this).  You  will  have  two  files:  sigtool.db  and
sigtool.csk  on  your  machine  (within  the  JDE  directory  hierarchy).  We  need  them  and  their
associated password to perform the signed build for Blackberry application.

17.7. J2ME

Currently  signing  J2ME  applications  isn’t  supported.  You  can  use  tools  such  as  the  Sprint  WTK  to
sign the resulting jad/jar produced by Codename One.  

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18. Working with iOS

18.1. Troubleshooting iOS Debug Build installs

In 9 cases out of 10 if you have a problem installing an app make sure your device is a 64 bit device.
If  not  you  will  need  to  add  the  build  hint  ios.debug.archs=armv7.  Notice  that  a  32  bit  app  will  still
work on a 64 bit device it will just display a performance warning.

If you have access to a Mac you can connect a cable and open xcode where you can use the device

explorer console to look at messages which sometimes give a clue about what went wrong. If not

here is a laundry list of a few things that might fail:

• Make sure you built the debug version and not the appstore version. The appstore version won’t

install on the device and can only be distributed via Apple’s store or testflight

• Verify  that  you  are  sending  a  32  bit  build  in  the  build  hints  using  the  build  hint
ios.debug.archs=armv7.  It’s  only  necessary  if  you  have  an  older  32  bit  device,  see  this
[https://www.codenameone.com/blog/moving-to-64bit-by-default.html].  Notice  that  this  only  applies  for

debug builds, release builds include both 32 and 64 bit versions



Devices prior to iPad Air & iPhone 5s were 32 bit devices so iPhone 5s won’t need

that flag but iPhone 5 or iPhone 5c will need it

• Check the the UDID is correct - if you got the UDID from an app then it’s probably wrong as apps

don’t  have  access  to  the  device  UDID  anymore.  The  way  to  get  the  UDID  is  either  thru  iOS

Settings app or itunes

• Make  sure  the  device  isn’t  locked  for  installing  3rd  party  apps.  I’ve  had  this  when  trying  to

install on my kids tablet which I configured to be child safe. This is configured in the settings as

parental controls

• Check that you "own" the package name. E.g. if you previously installed an app with the same

package name but a different certificate a new install will fail (this is true for Android too). So if

you installed the kitchen sink from the store then built one of your own and installed it there

will be a collision.

Notice that this might be problematic if you use overly generic package names as someone else

might have used them which is why you must always use your own domain

• Make  sure  the  device  has  a  modern  enough  version  of  iOS  for  the  dependencies.  I  think  the

current  minimum  for  hello  world  is  6.0.1  but  some  apps  might  require  a  newer  version  e.g.

Intercom requires OS 8 or newer

• Verify that you are using Safari when installing on the device (if you tried via cable that’s not a

problem), some developers had issues with firefox not launching the install process

• Check that the build hint ios.includePush is set in a way that matches your iOS provisioning. So

it must be false if you don’t have push within the provisioning profile

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18.2. The iOS Screenshot/Splash Screen Process



As of version 5.0 (September 2018), screenshot generation is no longer enabled by

default.  Instead,  the  launch  storyboard  is  used.  Therefore  much  of  the  following

section is no longer relevant.

iOS apps seem to start almost instantly in comparison to Android apps.
There is a trick to that, iOS applications have a file traditionally called Default.png that includes a
320x480 pixel image of the first screen of the application. This creates an "illusion" of the application
instantly coming to life and filling up with data, this is rather clever but is a source trouble as the
platform grows [11].



You can disable the screenshot process entirely with the ios.fastBuild=true build
hint.  This  will  only  apply  for  debug  builds  so  you  don’t  need  to  worry  about

accidentally forgetting it in production.

The screenshot process was a pretty clever workaround but as Apple introduced the retina display
640x960 it required a higher resolution Default@2x.png file, then it added the iPad, iPad Retina and
iPhone 5 [12] iPhone 6 & 6+ all of which required images of their own.

To  make  matters  worse  iPad  apps  (and  iPhone  6+  apps)  can  be  launched  in  landscape  mode  so

that’s two more resolutions for the horizontal orientation iPad. Overall as of this writing (or until

Apple adds more resolutions) we need 16 screenshots for a typical iOS app:

Table 13. iOS Device Screenshot Resolutions

Resolution

320x480

640x960

640x1136

1024x768

768x1024

2048x1536

1536x2048

750x1334

1242x2208

2208x1242

2048×2732

2732x2048

1668×2224

672

File Name

Default.png

Default@2x.png

Default-568h@2x.png

Default-Portrait.png

Devices

iPhone 3gs

iPhone 4x

iPhone 5x

Non-retina ipads in portrait

mode

Default-Landscape.png

Non-retina ipads in landscape

Default-Portrait@2x.png

Default-Landscape@2x.png

Default-667h@2x.png

Default-736h@3x.png

mode

Retina ipads in portrait mode

Retina ipads in landscape mode

iPhone 6

iPhone 6 Plus Portrait

Default-736h-Landscape@3x.png

iPhone 6 Plus Landscape

Default-iPadPro@2.png

Default-iPadPro-
Landscape@2.png

iPad Pro Portrait

iPad Pro Landscape

Default-iPadProSmall@2.png

10.5" iPad Pro Portrait

Resolution

2224x1668

1125×2436

2436x1125

File Name

Devices

Default-iPadProSmall-
Landscape@2.png

Default-iPhoneX@3.png

Default-iPhoneX-
Landscape@3.png

10.5" iPad Pro Landscape

iPhone X Portrait

iPhone X Landscape



You can predefine any of these files within the native/ios directory in your project.
If  the  build  server  sees  a  file  matching  that  exact  name  it  will  not  generate  a

screenshot for that resolution

Native iOS developers can run their applications 16 times with blank data to grab these screenshots

every time they change something in the first view of their application!

With  Codename  One  this  will  not  be  feasible  since  the  fonts  and  behavior  might  not  match  the

device. Thus Codename One runs the application 16 times in the build servers, grabs the right sized

screenshots in the simulator and then builds the app!

This  means  the  process  of  the  iPhone  splash  screen  is  almost  seamless  to  the  developer,  however

like every abstraction this too leaks.

The  biggest  problem  developers  have  with  this  approach  is  for  apps  that  use  a  web  browser  or

native maps in the first screen of their app. This won’t work well as those are native widgets. They

will look different during the screenshot process.

Another  problem  is  with  applications  that  require  a  connection  immediately  on  startup,  this  can

fail for the build process.

A solution to both problems is to create a special case for the first launch of the app where no data

exists. This will setup the screenshot process correctly and let you proceed with the app as usual.

18.2.1. Size

One of the first things we ran into when building one of our demos was a case where an app that

wasn’t very big in terms of functionality took up 30mb!

After inspecting the app we discovered that the iPad retina PNG files were close to 5mb in size…

Since we had 2 of them (landscape and portrait) this was the main problem.

The  iPad  retina  is  a  2048x1536  device  and  with  the  leather  theme  the  PNG  images  are  almost

impossible  to  compress  because  of  the  richness  of  details  within  that  theme.  This  produced  the

huge screenshots that ballooned the application.

18.2.2. Mutable first screen

A  very  common  use  case  is  to  have  an  application  that  pops  up  a  login  dialog  on  first  run.  This

doesn’t  work  well  since  the  server  takes  a  picture  of  the  login  screen  and  the  login  screen  will

appear briefly for future loads and will never appear again.

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18.2.3. Unsupported component

One of the biggest obstacles is with heavyweight components, e.g. if you use a browser or maps on

the  first  screen  of  the  app  you  will  see  a  partially 

loaded/distorted  MapComponent

[https://www.codenameone.com/javadoc/com/codename1/maps/MapComponent.html]  and  the  native  webkit

browser obviously can’t be rendered properly by our servers.

The workaround for such issues is to have a splash screen that doesn’t include any of the above. Its

OK to show it for a very brief amount of time since the screenshot process is pretty fast.

18.3. Launch Screen Storyboards

With  the  shift  to  Xcode  9,  which  is  the  default  version  on  the  Codename  One  build  servers  as  of

February  2018  [https://www.codenameone.com/blog/xcode-9-on-by-default.html],  it  is  now  possible  to  use  a

launch-screen storyboard as the splash screen instead of launch images. This will potentially solve

the issue of the proliferation of screenshots, as you can supply a single storyboard which will work

on  all  devices.  Launch  screen  storyboards  are  enabled  by  default  (as  of  version  5.0/September
2018). You can disable them by adding the ios.generateSplashScreens=true build hint.

18.3.1. Launch Storyboard vs Launch Images

The key benefit of using a launch storyboard right now is that it allows your app to be used in split-

screen  mode.  Storyboards,  however,  work  a  little  bit  differently  than  launch  images.  They  don’t

show  a  screenshot  of  the  first  page  of  your  app.  The  default  Codename  One  launch  storyboard

simply shows your app’s icon in the middle of the screen. You can customize the launch screen by

providing one or more of the following files in your project’s native/ios directory

1. Launch.Foreground.png - Will be shown instead of your app’s icon in the center of the screen.

2. Launch.Background.png - Will fill the background of the screen.

3. LaunchScreen.storyboard - A custom storyboard developed in Xcode, that will be used instead of

the default storyboard.

 Make sure to add the ios.multitasking=true build hint, or your launch storyboard

will not be used.



Changes  to  the  launch  screen  will  not  take  effect  until  the  device  has  been

restarted.  I.e.  If  you  install  your  app  on  a  device,  then  you  make  changes  to  the

launch screen and update the app, the launch screen won’t change until the device

is restarted.

18.4. Local Notifications on iOS and Android

Local notifications are similar to push notifications, except that they are initiated locally by the app,

rather than remotely. They are useful for communicating information to the user while the app is

running  in  the  background,  since  they  manifest  themselves  as  pop-up  notifications  on  supported

devices.

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

the  notification 

To  set 
icon  named
ic_stat_notify.png  under  the  native/android  folder  of  the  app.  The  icon  can  be
white with transparency areas

icon  on  Android  place  a  24x24 

18.4.1. Sending Notifications

The process for sending a notification is:

1. Create 

a 

LocalNotification 

[https://www.codenameone.com/javadoc/com/codename1/notifications/

LocalNotification.html] object with the information you want to send in the notification.

2. Pass the object to Display.scheduleLocalNotification().

Notifications can either be set up as one-time only or as repeating.

Example Sending Notification

LocalNotification n = new LocalNotification();
n.setId("demo-notification");
n.setAlertBody("It's time to take a break and look at me");
n.setAlertTitle("Break Time!");
n.setAlertSound("beep-01a.mp3");

Display.getInstance().scheduleLocalNotification(
        n,
        System.currentTimeMillis() + 10 * 1000, // fire date/time
        LocalNotification.REPEAT_MINUTE  // Whether to repeat and what frequency
);

The resulting notification will look like

Figure 522. Resulting notification in iOS

18.4.2. Receiving Notifications

The  API  for  receiving/handling  local  notifications  is  also  similar  to  push.  Your  application’s  main
lifecycle  class  needs  to  implement  the  com.codename1.notifications.LocalNotificationCallback

675

interface which includes a single method:

public void localNotificationReceived(String notificationId)

The  notificationId  parameter  will  match  the  id  value  of  the  notification  as  set  using
LocalNotification.setId().

Example Receiving Notification

public class BackgroundLocationDemo implements LocalNotificationCallback {
    //...

    public void init(Object context) {
        //...
    }

    public void start() {
        //...

    }

    public void stop() {
        //...
    }

    public void destroy() {
        //...
    }

    public void localNotificationReceived(String notificationId) {
        System.out.println("Received local notification "+notificationId);
    }
}



localNotificationReceived()  is  only  called  when  the  user  responds  to  the
notification  by  tapping  on  the  alert.  If  the  user  doesn’t  click  on  the  notification,

then this event handler will never be fired.

18.4.3. Canceling Notifications

Repeating  notifications  will  continue  until  they  are  canceled  by  the  app.  You  can  cancel  a  single

notification by calling:

Display.getInstance().cancelLocalNotification(notificationId);

Where 

notificationId 

is 

the 

string 

id 

that  was 

set 

for 

the  notification  using

676

LocalNotification.setId().

18.5. iOS Beta Testing (Testflight)

Apple  provides  the  ability  to  distribute  beta  versions  of  your  application  to  beta  testers  using

testflight. This allows you to recruit up to 1000 beta testers without the typical UDID limits a typical

Apple account has.

 This is supported for pro users as part of the crash protection feature.

To take advantage of that capability use the build hint ios.testFlight=true and then submit the app
to the store for beta testing. Make sure to use a release build target.

18.6. Accessing Insecure URL’s

Due  to  security  exploits  Apple  blocked  some  access  to  insecure  URL’s  which  means  that  http  code

that worked before could stop working for you on iOS 9+. This is generally a good move, you should

use  https  and  avoid  http  as  much  as  possible  but  that’s  sometimes  impractical  especially  when

working with an internal or debug environment.

You can disable the strict URL checks from Apple by using the venerable ios.plistInject build hint
and setting it to:

<key>NSAppTransportSecurity</key><dict><key>NSAllowsArbitraryLoads</key><true/></dict>

However,  it  seems  that  Apple  will  reject  your  app  if  you  just  include  that  and  don’t  have  a  good

reason.

18.7. Using Cocoapods

CocoaPods [https://cocoapods.org/] is a dependency manager for Swift and Objective-C Cocoa projects.

It  has  over  eighteen  thousand  libraries  and  can  help  you  scale  your  projects  elegantly.  Cocoapods

can  be  used  in  your  Codename  One  project  to  include  native  iOS  libraries  without  having  to  go

through the hassle of bundling the actual library into your project. Rather than bundling .h and .a
files in your ios/native directory, you can specify which "pods" your app uses via the ios.pods build
hint. (There are other build hints also if you need more advanced features).

Examples

Include the AFNetworking [https://github.com/AFNetworking/AFNetworking] library in your app:

ios.pods=AFNetworking

Include the AFNetworking [https://github.com/AFNetworking/AFNetworking] version 3.0.x library in your

app:

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ios.pods=AFNetworking ~> 3.0

For  full  versioning  syntax  specifying  pods  see  the  Podfile  spec  for  the  "pod"  directive

[https://guides.cocoapods.org/syntax/podfile.html#pod].

18.7.1. Including Multiple Pods

Multiple pods can be separated by either commas or semi-colons in the value of the ios.pods build
hint. E.g. To include GoogleMaps and AFNetworking, you could:

ios.pods=GoogleMaps,AFNetworking

Or specifying versions:

ios.pods=AFNetworking ~> 3.0,GoogleMaps

18.7.2. Other Pod Related Build Hints

ios.pods.platform  :  The  minimum  platform  to  target.  In  some  cases,  Cocoapods  require
functionality that is not in older version of iOS. For example, the GoogleMaps pod requires iOS 7.0
or higher, so you would need to add the ios.pods.platform=7.0 build hint.

ios.pods.sources  :  Some  pods  require  that  you  specify  a  URL  for  the  source  of  the  pod  spec.  This
may  be  optional  if  the  spec  is  hosted  in  the  central  CocoaPods  source  (https://github.com/
CocoaPods/Specs.git).

18.7.3. Converting PodFile To Build Hints

Most  documentation  for  Cocoapods  "pods"  provide  instructions  on  what  you  need  to  add  to  your

Xcode  project’s  PodFile.  Here  is  an  example  from  the  GoogleMaps  cocoapod  to  show  you  how  a

PodFile can be converted into equivalent build hints in a Codename One project.

The GoogleMaps cocoapod directs you to add the following to your PodFile:

source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '7.0'
pod 'GoogleMaps'

This would translate to the following build hints in your Codename One project:

ios.pods.sources=https://github.com/CocoaPods/Specs.git
ios.pods.platform=7.0
ios.pods=GoogleMaps

678

(Note that the ios.pods.sources directive is optional).

18.8. Including Dynamic Frameworks

If  you  need  to  use  a  dynamic  framework  (e.g.  SomeThirdPartySDK.framework),  and  it  isn’t

available  via  cocoapods,  then  you  can  add  it  to  your  project  by  simply  zipping  up  the  framework

and copying it to your native/ios directory.

e.g. native/ios/SomeThirdPartySDK.framework.zip

There are no build hints necessary for this approach. The build server will automatically detect the

framework and link it into your app.

[11] Apple provided another trick with XIB files starting with iOS 8 but that doesn’t apply to games or Codename One. It has its own

set of problems

[12] slightly larger screen and different aspect ratio

679

680

19. Working with JavaScript

This  section  covers  the  Codename  One  Javascript  port,  which  allows  you  to  compile  your  app  as

native  javascript  and  run  it  inside  a  browser.  This  is  different  from  the  BrowserComponent

[https://www.codenameone.com/javadoc/com/codename1/ui/BrowserComponent.html]  and  other  methods  of

displaying HTML/Javascript inside a Codename One app.

19.1. Limitations of the Javascript Port

19.1.1. No Multithreaded Code inside Static Initializers

 This section pertains to Codename One 3.6 and older. Newer versions of Codename

One support multithreaded code inside static initializers now.

Codename One’s Javascript port uses TeaVM [http://teavm.org/] to compile your application directly to

Javascript so that it can run inside modern web browsers without the need for any plugins (i.e. NOT

as  an  applet).  One  of  the  revolutionary  features  that  TeaVM  provides  is  the  ability  to  run  multi-

threaded  code  (i.e.  it  has  full  support  for  Object.wait(),  Object.notify(),  Object.notifyAll(),  and  the
synchronized  keyword).  The  one  caveat  to  be  aware  of  is  that  you  cannot  use  any  threading
primitives  inside  static  initializers.  This  is  due  to  technical  limitations  in  the  browser

environment  and  the  way  that  TeaVM  compiles  class  definitions  into  Javascript.  The  workaround

for this issue is to do lazy initialization in cases where you need to use multithreaded code.

Example

The following code will result in a build error when deploying a Javascript build:

Class1.java

import com.codename1.io.Log;
class Class1 {
    public static int getValue() {
        Log.p("Hello world");
        return 1;
    }
}

Class2.java

class Class2 {
    public static int value = Class1.getValue();

}

This fails because Class2 calls Class1.getValue() in its static initializer, and getValue() calls Log.p(),
which, underneath the covers, writes to Storage - which involves some synchronous network access

681

in the Javascript port (i.e. it uses wait() and notify() under the hood.

If we simply remove the call to Log.p() from getValue(), as follows:

    public static int getValue() {
        return 1;
    }

Then everything would be fine.

But How do we Know if A method includes wait()/notify somewhere along the line?

When you try to build your app as a Javascript app, it will fail (if code in your static initializers uses
wait()/notify() somewhere along the line).

How to Work Around this Issue

Use  lazy  initialization  wherever  you  can.  You  don’t  need  to  worry  about  this  for  setting  static
variables to literal values. E.g.: static int someVal = 20; will always be fine. But static int someVal
=  OtherClass.calculateSomeVal();  may  or  may  not  be  fine,  because  you  don’t  know  whether
calculateSomeVal()  uses  a  wait/notify.  So  instead  of  initializing  someVal  in  the  static  initializer,
create a static accessor that lazily initializes it. Or initialize it inside your app’s init() method. Or
initialize it inside the class constructor.

19.2. Troubleshooting Build Errors

If your Javascript build fails, you should download the error log and see what the problem is. The

most common errors are:

1. "[ERROR]  Method  XXX.<clinit>()V  is  claimed  to  be  synchronous,  but  it  is  has  invocations  of

asynchronous methods"

This  error  will  occur  if  you  have  static  initializers  that  use  multithreaded  code  (e.g.

wait/notify/sleep, etc…). See Static Initializers for information about troubleshooting this error.

In  some  cases  TeaVM  may  give  a  false-positive  here  (i.e.  it  thinks  you  are  doing  some

multithreaded stuff, but you’re really not), then you can force the build to "succeed" by adding
the javascript.stopOnErrors=false build hint.

2. "Method XXX was not found"

TeaVM  uses  its  own  Java  runtime  library.  It  is  mostly  complete,  but  you  may  occasionally  run

into methods that haven’t been implemented. If you run into errors saying that certain classes

or  methods  were  not  found,  please  post  them  to  the  Codename  One  issue  tracker

[https://github.com/codenameone/CodenameOne/issues].  You  can  also  work  around  these  by  changing

your own code to not use such functions. If this missing method doesn’t fall on a critical path on

your  app,  you  can  also  force  the  app  to  still  build  despite  this  error  by  adding  the
javascript.stopOnErrors=false build hint.

682

19.3. ZIP, WAR, or Preview.  What’s the difference?

The Javascript build target will result in up to three different bundles being generated:

1. YourApp-1.0.war

2. YourApp-1.0.zip

3. YourApp-1.0-Preview.html

YourApp-1.0.war is a self contained application bundle that can be installed in any JavaEE servlet

container. If you haven’t customized any proxy settings, then the application will be configured to

use a proxy servlet that is embedded into the .war file.

As an example, the PropertyCross .war file contains the following files:

$ jar tvf PropertyCross-1.0.war
     0 Thu Apr 30 15:57:38 PDT 2015 META-INF/
   132 Thu Apr 30 15:57:36 PDT 2015 META-INF/MANIFEST.MF
     0 Thu Apr 30 15:57:36 PDT 2015 assets/
     0 Thu Apr 30 15:57:36 PDT 2015 assets/META-INF/
     0 Thu Apr 30 15:57:36 PDT 2015 js/
     0 Thu Apr 30 15:57:36 PDT 2015 teavm/
     0 Thu Apr 30 15:57:36 PDT 2015 WEB-INF/
     0 Thu Apr 30 15:57:36 PDT 2015 WEB-INF/classes/
     0 Thu Apr 30 15:57:36 PDT 2015 WEB-INF/classes/com/
     0 Thu Apr 30 15:57:36 PDT 2015 WEB-INF/classes/com/codename1/
     0 Thu Apr 30 15:57:36 PDT 2015 WEB-INF/classes/com/codename1/corsproxy/
     0 Thu Apr 30 15:57:36 PDT 2015 WEB-INF/lib/
 27568 Thu Apr 30 15:57:12 PDT 2015 assets/CN1Resource.res
306312 Thu Apr 30 15:57:12 PDT 2015 assets/iOS7Theme.res
427737 Thu Apr 30 15:57:12 PDT 2015 assets/iPhoneTheme.res
   350 Thu Apr 30 15:57:12 PDT 2015 assets/META-INF/MANIFEST.MF
 92671 Thu Apr 30 15:57:12 PDT 2015 assets/theme.res
 23549 Thu Apr 30 15:57:14 PDT 2015 icon.png
  2976 Thu Apr 30 15:57:14 PDT 2015 index.html
 30695 Thu Apr 30 15:57:12 PDT 2015 js/fontmetrics.js
 84319 Thu Apr 30 15:57:12 PDT 2015 js/jquery.min.js
 13261 Thu Apr 30 15:57:12 PDT 2015 progress.gif
  2816 Thu Apr 30 15:57:12 PDT 2015 style.css
1886163 Thu Apr 30 15:57:36 PDT 2015 teavm/classes.js
359150 Thu Apr 30 15:57:36 PDT 2015 teavm/classes.js.map
1147502 Thu Apr 30 15:57:36 PDT 2015 teavm/classes.js.teavmdbg
 30325 Thu Apr 30 15:57:36 PDT 2015 teavm/runtime.js
  1011 Thu Apr 30 15:57:18 PDT 2015 WEB-INF/classes/com/codename1/corsproxy/CORSProxy.class
232771 Wed Nov 05 17:35:12 PST 2014 WEB-INF/lib/commons-codec-1.6.jar
 62050 Wed Apr 15 14:35:56 PDT 2015 WEB-INF/lib/commons-logging-1.1.3.jar
590004 Wed Apr 15 14:35:58 PDT 2015 WEB-INF/lib/httpclient-4.3.4.jar
282269 Wed Apr 15 14:35:56 PDT 2015 WEB-INF/lib/httpcore-4.3.2.jar
 14527 Wed Apr 15 14:35:56 PDT 2015 WEB-INF/lib/smiley-http-proxy-servlet-1.6.jar
   903 Thu Apr 30 15:57:12 PDT 2015 WEB-INF/web.xml
  9458 Thu Apr 30 15:57:14 PDT 2015 META-INF/maven/com.propertycross/PropertyCross/pom.xml
   113 Thu Apr 30 15:57:36 PDT 2015 META-INF/maven/com.propertycross/PropertyCross/pom.properties

683

Some things to note in this file listing:

1. The index.html file is the entry point to the application.

2. CORSProxy.class is the proxy servlet for making network requests to other domains.

3. The  assets  directory  contains  all  of  your  application’s  jar  resources.  All  resource  files  in  your

app will end up in this directory.

4. The  teavm  directory  contains  all  of  the  generated  javascript  for  your  application.  Notice  that
there are some debugging files generated (classes.js.map and classes.js.teavmdbg). These are

not  normally  loaded  by  the  browser  when  your  app  is  run,  but  they  can  be  used  by  Chrome

when you are doing debugging.

5. The jar files in the WEB-INF/lib directory are dependencies of the proxy servlet. They are not

required for your app to run - unless you are using the proxy.

YourApp-1.0.zip is appropriate for deploying the application on any web server. It contains all of

the same files as the .war file, excluding the WEB-INF directory (i.e. it doesn’t include any servlets,

class files, or Java libraries - it contains purely client-side javascript files and HTML).

As an example, this is a listing of the files in the zip distribution of the PropertyCross demo:

$ unzip -vl PropertyCross-1.0.zip
Archive:  /path/to/PropertyCross-1.0.zip
 Length   Method    Size  Ratio   Date   Time   CRC-32    Name
--------  ------  ------- -----   ----   ----   ------    ----
   27568  Defl:N    26583   4%  04-30-15 15:57  9dc91739  assets/CN1Resource.res
  306312  Defl:N   125797  59%  04-30-15 15:57  0b5c1c3a  assets/iOS7Theme.res
  427737  Defl:N   218975  49%  04-30-15 15:57  3de499c8  assets/iPhoneTheme.res
     350  Defl:N      241  31%  04-30-15 15:57  7e7e3714  assets/META-INF/MANIFEST.MF
   92671  Defl:N    91829   1%  04-30-15 15:57  004ad9d7  assets/theme.res
   23549  Defl:N    23452   0%  04-30-15 15:57  acd79066  icon.png
    2903  Defl:N     1149  60%  04-30-15 15:57  e5341de1  index.html
   30695  Defl:N     7937  74%  04-30-15 15:57  2e008f6c  js/fontmetrics.js
   84319  Defl:N    29541  65%  04-30-15 15:57  15b91689  js/jquery.min.js
   13261  Defl:N    11944  10%  04-30-15 15:57  51b895c7  progress.gif
    2816  Defl:N      653  77%  04-30-15 15:57  a12159c7  style.css
 1886163  Defl:N   315437  83%  04-30-15 15:57  2b34c50f  teavm/classes.js
  359150  Defl:N    92874  74%  04-30-15 15:57  30abdf13  teavm/classes.js.map
 1147502  Defl:N   470472  59%  04-30-15 15:57  e5c456f7  teavm/classes.js.teavmdbg
   30325  Defl:N     5859  81%  04-30-15 15:57  46651f06  teavm/runtime.js
--------          -------  ---                            -------
 4435321          1422743  68%                            15 files

You’ll  notice  that  it  has  many  of  the  same  files  as  the  .war  distribution.  It  is  just  missing  the  the

proxy servlet and dependencies.

YourApp-1.0-Preview.html  is  a  single-page  HTML  file  with  all  of  the  application’s  resources

embedded  into  a  single  page.  This  is  generated  for  convenience  so  that  you  can  preview  your

application  on  the  build  server  directly.  While  you  could  use  this  file  in  production,  you  are

probably  better  to  use  the  ZIP  or  WAR  distribution  instead  as  some  mobile  devices  have  file  size

684

limitations that may cause problems for the "one large single file" approach. If you do decide to use

this file for your production app (i.e. copy the file to your own web server), you will need to change

the proxy settings, as it is configured to use the proxy on the Codename One build server - which

won’t be available when the app is hosted on a different server.

19.4. Setting up a Proxy for Network Requests

The 

Codename 

One 

API 

includes 

a 

network 

layer 

(the  NetworkManager

[https://www.codenameone.com/javadoc/com/codename1/io/NetworkManager.html]  and  ConnectionRequest

[https://www.codenameone.com/javadoc/com/codename1/io/ConnectionRequest.html] classes) that allows you to

make HTTP requests to arbitrary destinations. When an application is running inside a browser as

a Javascript app, it is constrained by the same origin policy. You can only make network requests to

the same host that served the app originally.

E.g.  If  your  application  is  hosted  at  http://example.com/myapp/index.html,  then  your  app  will  be

able to perform network requests to retrieve other resources under the example.com domain, but

it won’t be able to retrieve resources from example2.com, foo.net, etc..



The  HTTP  standard  does  support  cross-origin  requests  in  the  browser  via  the
Access-Control-Allow-Origin  HTTP  header.  Some  web  services  supply  this  header
when serving resources, but not all. The only way to be make network requests to

arbitrary resources is to do it through a proxy.

Luckily  there  is  a  solution.  The  .war  javascript  distribution  includes  an  embedded  proxy  servlet,

and  your  application  is  configured,  by  default,  to  use  this  servlet.  If  you  intend  to  use  the  .war

distribution, then it should just work. You shouldn’t need to do anything to configure the proxy.

If, however, you are using the .zip distribution or the single-file preview, you will need to set up a

Proxy servlet and configure your application to use it for its network requests.

19.4.1. Step 1: Setting up a Proxy



This section is only relevant if you are using the .zip or single-file distributions of

your  app.  You  shouldn’t  need  to  set  up  a  proxy  for  the  .war  distribution  since  it

includes a proxy built-in.

The easiest way to set up a proxy is to use the Codename One cors-proxy [https://github.com/shannah/

cors-proxy] project. This is the open-source project from which the proxy in the .war distribution is

derived.  Simply  download  and  install  the  cors-proxy  .war  file  in  your  JavaEE  compatible  servlet

container.

If  you  don’t  want  to  install  the  .war  file,  but  would  rather  just  copy  the  proxy  servlet  into  an

existing web project, you can do that also. See the cors-proxy wiki for more information about this

[https://github.com/shannah/cors-proxy/wiki/Embedding-Servlet-into-Existing-Project].

19.4.2. Step 2: Configuring your Application to use the Proxy

There are three ways to configure your application to use your proxy.

685

1. Using the javascript.proxy.url build hint.

E.g.:

javascript.proxy.url=http://example.com/myapp/cn1-cors-proxy?_target=

2. By modifying your app’s index.html file after the build.

E.g.:

<script type="text/javascript">
    window.cn1CORSProxyURL='http://example.com/myapp/cn1-cors-proxy?_target=';
</script>

3. By setting the javascript.proxy.url property in your Java source. Generally you would do this
inside  your  init()  method,  but  it  just  has  to  be  executed  before  you  make  a  network  request
that requires the proxy.

Display.getInstance().setProperty(
        "javascript.proxy.url",
        "http://example.com/myapp/cn1-cors-proxy?_target="
);

The method you choose will depend on the workflow that you prefer. Options #1 and #3 will almost

always result in fewer changes than #2 because you only have to set them up once, and the builds

will retain the settings each time you build your project.

19.5. Using the CORS Proxy for Same Origin Requests

By default, the CORS proxy is only used for HTTP requests to URLS at a different domain than the

one that the app is running in. There are some circumstances where you may want to even use the
proxy  for  same  domain  requests.  You  can  do  this  by  setting  the  javascript.useProxyForSameDomain
display property to true. E.g.

Display.getInstance().setProperty("javascript.useProxyForSameDomain", "true");

Why would you want to do this?

The browser shields some HTTP headers (e.g. "Set-Cookie") from Javascript so that your app cannot

access them. Going through the proxy works around this limitation by copying and encoding such

headers in a format that the browser will allow, and then decoding them client-side to make them

available to your app seamlessly.

686

Using Apache as a Proxy

If you are hosting your application on an Apache 2 web server with mod_proxy installed, and you

only  need  to  make  CORS  requests  to  a  single  domain  (or  a  limited  set  of  domains),  you  can  use

Apache  to  serve  as  your  proxy.  One  sample  configuration  (which  you  would  place  either  in  your

VirtualHost definition or your .htaccess file is as follows:

SSLProxyEngine on
ProxyPass /app https://www.myexternaldomain.com
ProxyPassReverse /app https://www.myexternaldomain.com

This tells Apache to proxy all requests for '/app' to the domain https://www.myexternaldomain.com.

You would then need to set your CORS proxy URL in your CN1 app to "/app/".

The syntax is the same if you have multiple domains, but keep attention to the order of the lines to

make the proxy working correctly. For example:

SSLProxyEngine on
ProxyPass /app https://www.myexternaldomain1.com
ProxyPassReverse /app https://www.myexternaldomain1.com
ProxyPass /storage https://www.myexternaldomain2.com
ProxyPassReverse /storage https://www.myexternaldomain2.com

This 

tells 

Apache 

to 

proxy 

all 

requests 

for 

'/app' 

to 

the 

domain

https://www.myexternaldomain1.com  and  all 

requests 

for 

'/storage' 

to 

the  domain

https://www.myexternaldomain2.com

19.6. Customizing the Splash Screen

Since  your  application  may  include  many  resource  files,  videos,  etc..,  the  the  build-server  will

generate a splash screen for your app to display while it is loading. This basically shows a progress

indicator with your app’s icon.

You can customize this splash screen by simply modifying the HTML source inside the cn1-splash
div tag of your app’s index.html file:

<div id="cn1-splash">
    <img class="icon" src="icon.png"/>

    <img class="progress" src="progress.gif"/>
    <p>...Loading...</p>
</div>

19.7. Debugging

If you run into problems with your app that only occur in the Javascript version, you may need to

687

do a little bit of debugging. There are many debugging tools for Javascript, but the preferred tool for

debugging Codename One apps is Chrome’s debugger.

If your application crashes and you don’t have a clue where to begin, follow these steps:

1. Load your application in Chrome.

2. Open the Chrome debugger.

3. Enable the "Pause on Exceptions" feature, then click the "Refresh" button to reload your app.

4. Step  through  each  exception  until  you  reach  the  one  you  are  interested  in.  Chrome  will  then

show you a stack trace that includes the name of the Java source file and line numbers.

Figure 523. Debugging using Chrome tools

19.8. Including Third-Party Javascript Libraries

Codename  One  allows  you  to  interact  directly  with  Javascript  using  native  interfaces.  Native
interfaces  are  placed  inside  your  project’s  native/javascript  directory  using  a  prescribed  naming
convention. If you want to, additionally, include third-party Javascript libraries in your application
you  should  also  place  these  libraries  inside  the  native/javascript  directory  but  you  must  specify
which  files  should  be  treated  as  "libraries"  and  which  files  are  treated  as  "resources".  You  can  do
this  by  adding  a  file  with  extension  .cn1mf.json  file  either  the  root  of  your  native/javascript
directory or the root level of the project’s src directory.

19.8.1. Libraries vs Resources

A  resource  is  a  file  whose  contents  can  be  loaded  by  your  application  at  runtime  using
Display.getInstance().getResourceAsStream().  In  a  typical  Java  environment,  resources  would  be
stored  on  the  application’s  classpath  (usually  inside  a  Jar  file).  On  iOS,  resources  are  packaged
inside the application bundle. In the Javascript port, resources are stored inside the APP_ROOT/assets
directory. Historically, javascript files have always been treated as resources in Codename One, and

688

many  apps 

include  HTML  and  Javascript  files  for  use 

inside  the  BrowserComponent

[https://www.codenameone.com/javadoc/com/codename1/ui/BrowserComponent.html].

With the Javascript port, it isn’t quite so clear whether a Javascript file is meant to be a resource or

a library that the application itself uses. Most of the time you probably want Javascript files to be

used as libraries, but you might also have Javascript files in your app that are meant to be loaded at

runtime and displayed inside a Web View - these would be considered resources.

19.8.2. The Javascript Manifest File

In order to differentiate libraries from resources, you should provide a cn1mf.json file inside your
native/javascript directory that specifies any files or directories that should be treated as libraries.
This  file  can  be  named  anything  you  like,  as  long  as  its  name  ends  with  cn1mf.json.  Any  files  or
directories that you list in this manifest file will be packaged inside your app’s includes directory
instead  of  the  assets  directory.  Additionally  it  add  appropriate  <script>  tags  to  include  your
libraries as part of the index.html page of your app.



If you include the cn1mf.json file in your project’s src directory it could potentially
be  used  to  add  configuration  parameters  to  platform’s  other  than  Javascript

(although currently no other platforms use this feature). If you place it inside your
native/javascript  directory, 
configuration contained therein.

Javascript  port  will  use 

then  only 

the 

the

A simple manifest file might contain the following JSON:

{
    "javascript" : {
        "libs" : [
            "mylib1.js"
        ]
    }
}

I.e. It contains a object with key libs whose value is a list of files that should be treated as libraries.
In the above example, we are declaring that the file native/javascript/mylib1.js should be treated
as a library. This will result in the following <script> tag being added to the index.html file:

<script src="includes/mylib1.js"></script>

 This  also  caused  the  mylib1.js  file  to  be  packaged  inside  the  includes  directory

instead of the assets directory.



A  project  may  contain  more  than  one  manifest  file.  This  allows  you  to  include

manifest files with your cn1libs also. You just need to make sure that each manifest

file has a different name.

689

How to NOT generate the <script> tag

In some cases you may want a Javascript file to be treated as a library (i.e. packaged in the includes
directory) but not automatically included in the index.html page. Rather than simply specifying the
name of the file in the libs list, you can provide a structure with multiple options about the file. E.g.

{
    "javascript" : {
        "libs" : [
            "mylib1.js",
            {
                "file" : "mylib2.js",
                "include" : false
            }
        ]
    }
}

In the above example, the mylib2.js file will be packaged inside the includes directory, but the build
server won’t insert its <script> tag in the index.html page.

Library Directories

You  can  also  specify  directories  in  the  manifest  file.  In  this  case,  the  entire  directory  will  be
packaged inside the includes directory of your app.

If  you  are  including  Javascript  files  in  your  app  that  are  contained  inside  a

directory hierarchy, you should specify the root directory of the hierarchy in your

manifest file and use the sub "includes" property of the directory entry to specify
which files should be included with <script> tags. Specifying the file directly inside
the "libs" list will result in the file being packed directly in the your app’s includes
directory. This may or may not be what you want.



E.g.

690

{
    "javascript" : {
        "libs" : [
            "mylib1.js",
            {
                "file" : "mylib2.js",
                "include" : false
            },
            {
                "file" : "mydir1",
                "includes" : ["subfile1.js", "subfile2.js"]
            }
        ]
    }
}

In this example the entire mydir1 directory would be packed inside the app’s includes directory, and
the following script tags would be inserted into the index.html file:

<script src="includes/mydir1/subfile1.js"></script>
<script src="includes/mydir1/subfile2.js"></script>



Libraries  included  from  a  directory  hierarchy  may  not  work  correctly  with  the

single file preview that the build server generates. For that version, it will embed
the contents of each included Javascript file inside the index.html file, but the rest
of  the  directory  contents  will  be  omitted.  If  your  the  library  depends  on  the

directory hierarchy and supporting files and you require the single-file preview to

work,  then  you  may  consider  hosting  the  library  on  a  separate  server,  and

including  the  library  directly  from  there,  rather  than  embedding  it  inside  your

project’s "native/javascript" directory.

Including Remote Libraries

The  examples  so  far  have  only  demonstrated  the  inclusion  of  libraries  that  are  part  of  the  app

bundle.  However,  you  can  also  include  libraries  over  the  network  by  specifying  the  URL  to  the

library directly. This is handy for including common libraries that are hosted by a CDN.

E.g.  The  Google  Maps  library  requires  the  Google  maps  API  to  be  included.  This  is  accomplished

with the following manifest file contents:

691

{
    "javascript" : {
        "libs" : [
            "//maps.googleapis.com/maps/api/js?v=3.exp"
        ]
    }
}

This  example  uses  the  "//"  prefix  for  the  URL  instead  of  specifying  the  protocol

directly. This allow the library to work for both http and https hosting. You could

however specify the protocol as well:



+

{
    "javascript" : {
        "libs" : [
            "https://maps.googleapis.com/maps/api/js?v=3.exp"
        ]
    }
}

Including CSS Files

CSS files can be included using the same mechanism as is used for Javascript files. If the file name
ends  with  ".css",  then  it  will  be  treated  as  a  CSS  file  (and  included  with  a  <link>  tag  instead  of  a
<script> tag. E.g.

{
    "javascript" : {
        "libs" : [
            "mystyles.css"
        ]
    }
}

or

{
    "javascript" : {
        "libs" : [
            "https://example.com/mystyles.css"
        ]
    }
}

692

Embedding Variables in URLs

In some cases the URL for a library may depend on the values of some build hints in the project. For

example, in the Google Maps cn1lib, the API key must be appended to the URL for the API as a GET

parameter.  E.g. 

https://maps.googleapis.com/maps/api/js?v=3.exp&key=SOME_API_KEY,  but 

the

developer of the library doesn’t want to put his own API key in the manifest file for the library. It

would  be  better  for  the  API  key  to  be  supplied  by  the  developer  of  the  actual  app  that  uses  the

library and not the library itself.

The solution for this is to add a variable into the URL as follows:

{
    "javascript" : {
        "libs" : [
            "//maps.googleapis.com/maps/api/js?v=3.exp&key={{javascript.googlemaps.key}}"
        ]
    }
}

The  {{javascript.googlemaps.key}}  variable  will  be  replaced  with 
the
javascript.googlemaps.key  build  hint  by  the  build  server,  so  the  resulting  include  you  see  in  the
index.html page will be something like:

the  value  of 

<script src="//maps.googleapis.com/maps/api/js?v=3.exp&key=XYZ"></script>

19.9. Browser Environment Variables

Native  interfaces  allow  you  to  interact  with  the  Javascript  environment  in  unlimited  ways,  but

Codename  One  provide’s  a  simpler  method  of  obtaining  some  common  environment  information
from the browser via the Display.getInstance().getProperty() method. The following environment
variables are currently available:

Table 14. Property hints for the JavaScript port

Name

Description

browser.window.location.href

browser.window.location.search

browser.window.location.host

browser.window.location.hash

A String, representing the entire URL of the

page, including the protocol (like http://)

A String, representing the querystring part of a

URL, including the question mark (?)

A String, representing the domain name and

port number, or the IP address of a URL

A String, representing the anchor part of the

URL, including the hash sign (#)

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Name

Description

browser.window.location.origin

browser.window.location.pathname

browser.window.location.protocol

browser.window.location.port

A String, representing the protocol (including

://), the domain name (or IP address) and port

number (including the colon sign (:) of the URL.

For URL’s using the "file:" protocol, the return

value differs between browsers

A String, representing the pathname

A String, representing the protocol of the

current URL, including the colon (:)

A String, representing the port number of a URL.

+ Note: If the port number is not specified or if it

is the scheme’s default port (like 80 or 443), an

empty string is returned

browser.window.location.hostname

A String, representing the domain name, or the

User-Agent

browser.language

browser.name

Platform

browser.codeName

browser.version

javascript.deployment.type

IP address of a URL

The User-agent string identifying the browser,

version etc..

The language code that the browser is currently

set to. (e.g. en-US)

the name of the browser as a string.

a string that must be an empty string or a string

representing the platform on which the browser

is executing. + For example: "MacIntel", "Win32",

"FreeBSD i386", "WebTV OS"

the internal name of the browser

the version number of the browser

Specifies the deployment type of the app. This

will be "file" for the single-file preview,

"directory" for the zip distribution, and "war" for

the war distribution.

19.10. Changing the Native Theme

Since  a  web  application  could  potentially  be  run  on  any  platform,  it  isn’t  feasible  to  bundle  all

possible themes into the application (at least it wouldn’t be efficient for most use cases). By default

we have bundled the iOS7 theme for javascript applications. This means that the app will look like

iOS7 on all devices: desktop, iOS, Android, WinPhone, etc…

You  can  override  this  behavior  dynamically  by  setting  the  javascript.native.theme  Display
[https://www.codenameone.com/javadoc/com/codename1/ui/Display.html]  property  to  a  theme  that  you  have

included in your app. All of the native themes are available on GitHub, so you can easily copy these
into  your  application.  The  best  place  to  add  the  theme  is  in  your  native/javascript  directory  -  so
that they won’t be included for other platforms.

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19.10.1. Example:  Using Android Theme on Android



As of Codename One 6.0, apps will automatically use the Android theme when run

on an Android device, so this example is not necessary. However the technique of

changing the native theme at runtime is still applicable.

First,  download 

androidTheme.res 

[https://github.com/codenameone/CodenameOne/raw/master/Ports/

Android/src/androidTheme.res]  from  the  Android  port  on  GitHub,  and  copy  it  into  your  app’s
native/javascript directory.

Then in your app’s init() method, add the following:

Display d = Display.getInstance();
if (d.getProperty("User-Agent", "Unknown").indexOf("Android") != -1) {
    d.setProperty("javascript.native.theme", "/androidTheme.res");
}

19.11. Disabling the 'OnBeforeUnload' Handler

By default, apps will display warning/confirm dialog when the user attempts to leave the page.

can 

explicitly 

You 
the
disable 
"platformHint.javascript.beforeUnloadMessage"  display  property.  Setting  the  property  to  null  will
disable this behaviour, so that users will not be harassed by this dialog when they navigate away

behaviour 

enable 

setting 

this 

by 

or 

from the app. Setting it to a string value, like "leaving so soon?", will re-enable this behaviour.



Some  browsers  don’t  allow  you  to  specify  the  message  that  is  displayed  in  this

dialog. In those browsers, this property can be viewed as boolean: A null value will

result  in  no  prompt  being  shown,  and  a  non-null  value  will  result  in  a  prompt

being shown.

19.11.1. Example: Toggling the BeforeUnload Prompt On/Off

Form f = new Form("Test Before Unload", BoxLayout.y());
CheckBox enableBeforeUnload = new CheckBox("Enable Before Unload");
enableBeforeUnload.setSelected(true);
enableBeforeUnload.addActionListener(e->{
    if (enableBeforeUnload.isSelected()) {
        CN.setProperty("platformHint.javascript.beforeUnloadMessage", "Are you sure you want to leave this page?  It
might be bad");
    } else {
        CN.setProperty("platformHint.javascript.beforeUnloadMessage", null);
    }
});
f.add(enableBeforeUnload);
f.show();

695

19.12. Deploying as a Progressive Web App

Out of the box, your app is ready to be deployed as a progressive web app (PWA). That means that

users can access the app directly in their browser, but once the browser determines that the user is

frequenting the app, it will "politely" prompt the user to install the app on their home screen. Once

installed  on  the  home  screen,  the  app  will  behave  just  like  a  native  app.  It  will  continue  to  work

while offline, and if the user launches the app, it will open without the browser’s navigation bar. If

you  were  to  install  the  native  and  PWA  versions  of  your  app  side  by  side,  you  would  be  hard

pressed to find the difference - especially on newer devices.

Below  is  a  screenshot  from  Chrome  for  Android  where  the  browser  is  prompting  the  user  to  add

the app to their home screen.

Figure 524. Add app to homescreen banner

If  the  app  is  available  as  a  native  app,  in  the  Play  store,  you  can  indicate  this  using  the
javascript.manifest.related_applications  and  javascript.manifest.prefer_related_applications
build hints. Then, instead of prompting the user to add the web app to their home screen, they’ll be

prompted to install the native app from the Play store, as shown below.

Figure 525. Add native app banner

696



The  PWA  standard  requires  that  you  host  your  app  on  over  HTTPS.  For  testing
purposes, it will also work when accessed at a localhost address. You can use the
Lighthoust  PWA  analysis  tool  [https://developers.google.com/web/ilt/pwa/lighthouse-pwa-

analysis-tool] to ensure compliance.

For  more  information  about  Progressive  Web  Apps  see  Google’s  introduction  to  the  subject

[https://developers.google.com/web/progressive-web-apps/].

19.12.1. Customizing the App Manifest File

At the heart of a progressive web app is the web app manifest [https://developer.mozilla.org/en-US/docs/

Web/Manifest].  It  specifies  things  like  the  app’s  name,  icons,  description,  preferred  orientation,

display  mode  (e.g.  whether  to  display  browser  navigation  or  to  open  with  the  full  screen  like  a

native  app),  associated  native  apps,  etc..  The  Codename  One  build  server  will  automatically

generate a manifest file for your app but you can (and should) customize this file via build hints.

Build hints of the form javascript.manifest.XXX will be injected into the app manifest. E.g. To set the
app’s description, you could add the build hint:

javascript.manifest.description=An app for doing cool stuff

You  can  find  a  full  list  of  available  manifest  keys  here  [https://developer.mozilla.org/en-US/docs/Web/

Manifest].  The  build  server  will  automatically  generate  all  of  the  icons  so  you  don’t  need  to  worry

about  those.  The  "name"  and  "short_name"  properties  will  default  to  the  app’s  display  name,  but
they can be overridden via the javascript.manifest.name and javascript.manifest.short_name build
hints respectively.

 The javascript.manifest.related_applications build hint expects a JSON formatted

list, just like in the raw manifest file.

19.12.2. Related Applications

One  nice  feature  (discussed  above)  of  progressive  web  apps,  is  the  ability  to  specify  related

applications  in  the  app  manifest.  Browsers  that  support  the  PWA  standard  use  some  heuristics  to

"offer" the user to install the associated native app when it is clear that the user is using the app on
a regular basis. Use the javascript.manifest.related_applications build hint to specify the location
of the native version of your app. E.g.

javascript.manifest.related_applications=[{"platform":"play", "id":"my.app.id"}]

You  can  declare  that  the  native  app  is  the  preferred  way  to  use  the  app  by  setting  the
javascript.manifest.prefer_related_applications build hint to "true".



According  to  the  app  manifest  documentation  [https://developer.mozilla.org/en-US/docs/

Web/Manifest],  this  should  only  be  used  if  the  related  native  apps  really  do  offer

something that the web application can’t do.

697

19.12.3. Device/Browser Support for PWAs

Chrome and Firefox both support PWAs on desktop and on Android. iOS doesn’t support the PWA

standard, however, many aspects of it are supported. E.g. On iOS you can add the app to your home

screen, after which time it will appear and behave like a native app - and it will continue to work

while  offline.  However,  many  other  nice  features  of  PWA  like  "Install  this  app  on  your  home

screen" banners, push notifications, and invitations to install the native version of the app, are not

supported. It is unclear when, or even, whether Apple will ever add full support; but most experts

predict that they will join the rest of the civilized world and add PWA support in the near future.

On the desktop, Chrome provides an analogous feature to "add to your homescreen": "Add to shelf".

If it looks like the user is using the app on a regular basis, and it isn’t yet installed, it will show a

banner at the top of the page asking the user if they want to add to their shelf.

Figure 526. Add to shelf banner

Clicking the "Add button" prompts the user for the name they wish the app to appear as:

Figure 527. Add to shelf prompt

Upon submission, Chrome will generate a real application (on Mac, it will be a ".app", on Windows,

an  "exe",  etc..)  which  the  user  can  double  click  to  open  the  app  directly  in  the  Chrome.  And,

importantly, the app will still work when the user is offline.

The  app  will  also  appear  in  their  "Shelf"  which  you  can  always  access  at  chrome://apps,  or  by
opening  the  "Chrome  App  Launcher"  app  (on  OS  X  this  is  located  in  "~/Applications/Chrome

Apps/Application Launcher").

Figure 528. Chrome App Launcher

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The Chrome App Launcher lists apps installed both via the Chrome Web Store and



via the "Add to Shelf" feature that we discuss here. The features we describe in this

article  are  orthogonal  to  the  Chrome  Web  Store  and  will  not  be  affected  by  its

closure.

19.13. Playing Media and Opening Links

People don’t like it when the browser automatically starts playing sounds, or opening links without

their  permission.  For  this  reason,  modern  browsers  generally  restrict  your  ability  to

programmatically do these things, unless they are in response to a user action, like a mouse click.

If  your  app  needs  to  play  media  (e.g.  Media.play()),  or  open  a  link  (e.g.  Display.execute("…"))
without the user actually interacting physically (e.g. key press or pointer press), then it will display

a popup dialog confirming that the user actually wants to perform this action.

In some cases this dialog may affect the utility of the app. For example, suppose you want to play a

video in response to a voice command. Having to press an "OK" button after the command, may be
annoying. For such cases, you can use the platformHint.javascript.backsideHooksInterval property
to poll for media play requests on an authorized event.

For example:

CN.setProperty("platformHint.javascript.backsideHooksInterval", "1000");

// Now your app will process media.play() and Display.execute(...) calls
// once per second (1000ms).  If play() or execute() has been called anytime
// in that second (since the last poll), it will seamlessly process the
// request.

// To disable polling, just set it to an interval 0 or lower.
// e.g.
CN.setProperty("platformHint.javascript.backsideHooksInterval", "0");



Do not abuse this feature. You should enable this polling only when necessary. E.g.

If your app enables the user to listen for voice commands, only enable polling for

the  period  of  time  that  it  is  listening.  When  the  user  wants  to  stop  listening,  you

should also stop the polling by setting the interval to "0".

699

700

20. Working with UWP

UWP Apps may distributed in 2 different ways:

1. In the Windows App Store. (This should be used for deployment of any production app).

2. Outside of the Windows App Store via sideloading directly onto a device. This should only be

used for development.

20.1. Deploying Outside of the Windows App Store
(Sideloading)

UWP apps may be deployed directly to Windows 10 desktop and mobile devices without any need

to involve the Windows Store. This process is only realistic, though, for testing and debugging your

app during development because it requires you to enable "Development" mode on the device. In

addition,  installation  is  a  little  bit  more  complicated  than  simply  downloading  an  app  over  the

internet. The process for deploying to Windows 10 desktop devices is different than the process for

mobile devices. These are described in the following sections.

20.1.1. Side-loading to Windows 10 Mobile Devices

Enabling Developer Mode on Device

Before you can side-load apps onto your phone, you’ll need to set up your phone for development.

1. In "Settings", select "Update & Security" > "For developers"

701

2. Select "Developer mode"

3. Under "Device Discovery", make sure that the "Make your device visible to USB connections and

your local network" is set to "On".

4. Make sure that "Device Portal" is set to "On"

5. When you switch "Device Portal" to "On" it should show you an address that you can access the

Phone at via wifi. (E.g. https://10.0.1.11). Remember this address, you’re going to use it to install

all of your apps onto the device.

 This will be a local address within your local network. It won’t be available to

the outside world.

702

At this point, your phone should be ready to receive "Side-loaded" apps. This was a one-time setup,

so you shouldn’t have to do it again, until you set up another device.

Building App for UWP

Now that your device is set up for development, you can proceed to build your app.

1. Select the "Mobile Debug Build" option in the UWP Codename One Settings.

2. Select the "Send Windows UWP Build" option in the Codename One menu of your IDE. This will

initiate the build on the Codename One build server.

3. Log into the Codename One dashboard to watch the build progress. When it is complete, you’ll

be able to download the ".appxbundle" file to your desktop.



You  cannot  simply  download  the  .appxbundle  file  directly  to  your  Windows

Phone 10 mobile device and install it. It will indeed allow you to download it,

and will give you an option to install it, but the install will silently fail.

Installing App On Device

1. Point your computer’s web browser to the address for your mobile device. (This is the address

listed  when  you  turned  on  the  "Device  Portal"  in  the  "Enabling  Developer  Mode  on  Device"

section above. This will open the App Manager page.

2. Click on the "Apps" item in the left menu.

703

3. If this is the first time installing a UWP (debug) app on your device, you will need to install the

dependencies.  You  can  find  the  dependencies  for  mobile/ARM  apps  here  [https://github.com/

codenameone/cn1-binaries/tree/master/uwp/Dependencies/ARM]. 
both
Microsoft.NET.CoreRuntime.1.0.appx  and  Microsoft.VCLibs.ARM.Debug.14.00.appx.  If  this  is  not
the first time installing a UWP app, you can skip to the next step.

install 

You’ll 

need 

to 

a. Under the "Install App" section, click the "Choose File" button and navigate through the file

chooser to select the "Microsoft.NET.CoreRuntime.1.0.appx" file. Then click "Go".

b. Do the same for the "Microsoft.VCLibs.ARM.Debug.14.00.appx" file.

4. Under  the  "Install  App"  section,  click  the  "Choose  File"  button  and  navigate  through  the  file

chooser to select the .appxbundle file for your app.

5. Once you have the appxbundle selected, you should press "Go" under the "Deploy" subheading.

This  will  install  the  app  and,  if  all  went  well,  your  app  will  appear  in  the  "Recently  Added"

section in the apps list of the phone.

20.1.2. Side-loading to Windows 10 Desktop Devices

Enabling Developer Mode on PC

The  easiest  way  to  be  able  to  run  your  development  apps  on  a  Windows  10  PC  is  to  enable

developer mode. This will allow you to install any app even if it is just "self-signed".

To  enable  developer  mode,  open  "Settings",  then  select  "Updates  an  Security".  Under  the  "For

Developers" menu item, select "Developer Mode" as shown below:

704

Building the App

Before building the app, you’ll need to ensure that the build target is set to "Debug Desktop" in the

Codename One Settings panel for Windows apps.

Steps:

1. Open  Codename  One  Settings  (steps  vary  by  IDE).  On  Netbeans  you  will  find  "Codename  One

Settings"  by  right  clicking  your  project’s  node  in  the  project  explorer,  and  look  in  the

"Codename One" submenu:

2. Click on "Windows Settings":

3. Under "Build Type", make sure that "Desktop Debug Build" is selected, as shown below:

4. Save the changes by clicking the "Disk" icon in the upper right:

Now you can proceed to send the build to the build server.

1. Select the "Send Windows UWP Build" option in the Codename One menu of your IDE. This will

initiate the build on the Codename One build server.

705

2. Log into the Codename One dashboard to watch the build progress. When it is complete, you’ll

be able to download the ".zip" file to the Windows 10 PC on which you wish to install the app.

Installing the App

Start by extracting the .zip file. (Navigate to the folder where the zip was downloaded, right click it,

and select "Extract all" as shown below:

Figure 529. Extract UWP zip file

After extraction, open the resulting directory. You should see contents similar to the following:

Figure 530. UWP Zip file contents

Downloading Dependencies

If  this  is  your  first  time  installing  a  UWP  app  on  this  PC,  you  may  need  to  add  the  dependencies

before  you  can  install.  You  can  download  the  dependencies  here  [https://github.com/codenameone/cn1-

binaries/raw/master/uwp/Dependencies.zip].  Extract 

"Dependencies.zip"  and  copy 

the  resulting

"Dependencies" directory into the app install directory. Your app install directory should now look

like:

Figure 531. UWP Zip file contents with dependencies

706

Running the Powershell Script

We are finally at the point where we can run the installer.

Right-click on the "Add-AppDevPackage" icon, and select "Run in Powershell", as shown:

Figure 532. UWP Install by run in powershell

You may be prompted that you need to change the execution policy, in Powershell:

Figure 533. UWP Powershell change execution policy

Enter "Y" at the prompt to allow this.

If all goes well, you should see a message saying that the app as successfully installed.

Figure 534. UWP Powershell app successfully installed

And if you look in your "Windows Menu" under "All Apps", you should see your app listed there:

Figure 535. Windows 10 App listed in All Apps

20.1.3. Building for the Windows Store

If you want to be able to distribute your app to the public, the Windows Store is your best channel.

707

Building for the Windows store involves roughly 3 steps:

1. Reserve a name for your app in the Windows Store

2. Build your app using the "Windows Store Upload" build type.

3. Upload the resulting .appxupload file to the Windows store.

Let’s  go  through  these  steps  in  more  detail.  Start  here  [https://developer.microsoft.com/en-us/windows/

publish].

Figure 536. Publish windows apps webpage

If you don’t already have an account, sign up for one. Then log in. Once logged in, you can click the

"Dashboard" link on the toolbar.

Figure 537. Windows Store dashboard

Under  the  "Your  apps"  section  (on  the  left  in  the  above  screenshot),  click  the  "Create  new  app"

button.

Figure 538. Reserve name form

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Enter a name for your app, and click "Reserve app name".

If the name was available, it should take you to the app overview page for your new app. There’s

quite a few options there to play with, but we’re not going to worry about any of them for now. All

we need to know is:

1. Your App’s ID

2. Your App’s Publisher ID

You  can  get  this  information  by  scrolling  down  to  the  bottom  of  the  "App  overview"  page  and

clicking the "View app identity details" under the "App Management" > "App identity" section:

Figure 539. App Identity section

You’ll see a page with the information we need shown below:

Figure 540. App identity details

The next step is to copy this information into your Codename One project.

Open up the Codename One Settings for your project and go to the "Windows Settings" section.

Copy  and  paste  the  "Package/Identity/Name"  and  "Package/Properties/PublisherDisplayName"

values from the windows store into the "App ID" and "Publisher Display Name" fields respectively.



It is important that your App ID and Publisher Display Name match exactly what

you have in the store, or your app will fail at the validation stage when you try to

upload your app to the store.

Next, click on the "Generate" button next to the Certificate field.

This  will  open  a  dialog 

titled 

"Certificate  Generator".  Paste 

the  value 

from 

the

"Package/Identity/Publisher"  listed  in  the  Windows  Store  into  the  Publisher  ID  field  as  shown

below:

709

Figure 541. Certificate Generator

Then click OK. This will generate a .pfx file inside your project folder.

The "Display Name" must also match that app name in the store.

Finally,  make  sure  that  "Windows  Store  Upload"  is  selected  in  the  "Build  Type"  field.  For  the

example above, my settings form looks like the following screenshot when I am done.

Figure 542. Settings for Windows Store uploads

When  you  are  done,  hit  the  "Save"  icon  in  the  upper  right  corner  of  the  window  to  save  your

changes.

Finally, select "Codename One" > "Send Windows UWP Build" in your IDE’s project explorer.

This will produce an .appxupload file that you can upload to the Windows Store.

See  the  Microsoft’s  documentation  on  uploading  app  packages  [https://msdn.microsoft.com/en-us/

windows/uwp/publish/upload-app-packages] for more information on the remaining steps.

20.2. Debugging UWP Apps

On  most  platforms,  there  is  a  device  log  that  records  errors,  exceptions,  and  messages  written  to

STDOUT. UWP, unfortunately, doesn’t seem to provide this. If you are running on Windows Phone

10, there doesn’t seem to be any device log at all. There is a separate program called "Field Medic"

that you can use to do some logging, but it doesn’t capture application errors or STDOUT messages.

The best way to debug apps on device is to enable crash protection in your app. This can be enabled
by adding the following to your app’s init() method:

Log.bindCrashProtection(true);

With crash protection enabled, you’ll receive an email whenever an exception is thrown that isn’t

caught in your application code. The email will include the stack trace of the error along with any
output you had previously provided using the com.codename1.io.Log class (e.g. Log.p() and Log.e()).

 A Pro account (or higher) is required to receive crash protection emails.

20.2.1. No Line Numbers in Stack Traces

One  major  annoyance  of  UWP  is  that  it  doesn’t  provide  line  numbers  in  its  stack  traces.  Here  is

what you can expect to see in a stack trace:

710

[EDT] 0:0:7,683 - Results null
[EDT] 0:0:7,799 - Exception: java.lang.NullPointerException - null
   at com.codename1.ui.Display.invokeAndBlock(Runnable r, Boolean dropEvents)[EDT] 0:0:7,815 - Exception in AppName
version 1.1
[EDT] 0:0:7,830 - OS win
[EDT] 0:0:7,836 - Error java.lang.NullPointerException
[EDT] 0:0:7,836 - Current Form null
[EDT] 0:0:7,836 - Exception: java.lang.NullPointerException - null
at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)
   at System.Environment.get_StackTrace()
   at UWPApp.IKVMReflectionHelper.getCurrentStackTrace()
   at java.lang.ThrowableHelper.getCurrentStackTrace()
   at java.lang.Throwable..ctor()
   at java.lang.Exception..ctor()
   at java.lang.RuntimeException..ctor()
   at java.lang.NullPointerException..ctor()
   at java.lang.Throwable.__mapImpl(Exception )
   at IKVM.Internal.ExceptionHelper.MapException[T](Exception x, Boolean remap, Boolean unused)
   at IKVM.Runtime.ByteCodeHelper.MapException[T](Exception x, MapFlags mode)
   at com.codename1.ui.Display.invokeAndBlock(Runnable r, Boolean dropEvents)
   at com.codename1.ui.Display.invokeAndBlock(Runnable r)
   at com.codename1.impl.SilverlightImplementation.editString(Component n1, Int32 n2, Int32 n3, String n4, Int32 n5)
   at com.codename1.impl.CodenameOneImplementation.editStringImpl(Component cmp, Int32 maxSize, Int32 constraint, String
text, Int32 initiatingKeycode)
   at com.codename1.ui.Display.editString(Component cmp, Int32 maxSize, Int32 constraint, String text, Int32
initiatingKeycode)
   at com.codename1.ui.Display.editString(Component cmp, Int32 maxSize, Int32 constraint, String text)
   at com.codename1.ui.TextArea.editString()
   at com.codename1.ui.TextArea.pointerReleased(Int32 x, Int32 y)
   at com.codename1.ui.TextField.pointerReleased(Int32 x, Int32 y)
   at com.codename1.ui.Form.pointerReleased(Int32 x, Int32 y)
   at com.codename1.ui.Component.pointerReleased(Int32[] x, Int32[] y)
   at com.codename1.ui.Display.handleEvent(Int32 offset)
   at com.codename1.ui.Display.edtLoopImpl()
   at com.codename1.ui.Display.mainEDTLoop()
   at com.codename1.ui.RunnableWrapper.run()
   at com.codename1.impl.CodenameOneThread.run()
   at java.lang.Thread.threadProc2()
   at java.lang.Thread.threadProc()
   at java.lang.Thread.1.Invoke()
   at com.codename1.impl.NativeThreadImpl.<>c__DisplayClass6_0.<init>b__0()
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
   at System.Threading.Tasks.Task.ExecutionContextCallback(Object obj)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot)
   at System.Threading.Tasks.Task.ExecuteEntry(Boolean bPreventDoubleExecution)
   at System.Threading.Tasks.ThreadPoolTaskScheduler.LongRunningThreadWork(Object obj)
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart(Object obj)
Originating from:
Message=Object reference not set to an instance of an object.
   at com.propertycross.codename1.PropertyCross.1.run()
   at com.codename1.ui.Display.processSerialCalls()
   at com.codename1.ui.Display.edtLoopImpl()
   at com.codename1.ui.Display.invokeAndBlock(Runnable r, Boolean dropEvents)

It  will  show  you  the  call  stack  with  the  names  of  the  methods.  But  it  won’t  show  you  the  line
numbers.  If  the  stack  trace  isn’t  specific  enough,  you  can  add  Log.p()  statements  in  various
positions in my code to help narrow down the source of the exception.

711

20.3. Customizing the Status Bar

On mobile, the status bar (the bar across the top of the screen with the time, battery level etc…) is

updated  each  time  a  form  is  shown.  The  foreground  color,  background  color,  and  background

opacity are set using the unselected style of the form being shown.

You can override these colors application-wide using the following display properties:

1. windows.StatusBar.ForegroundColor - A string representation of an integer RGB color.

2. windows.StatusBar.BackgroundColor - A string representation of an integer RGB color.

3. windows.StatusBar.BackgroundTransparency - A string representation of 0-255 integer.

e.g.

Display d = Display.getInstance();
d.setProperty("windows.StatusBar.ForegroundColor", String.valueOf(0xff0000));  // red
d.setProperty("windows.StatusBar.BackgroundColor", String.valueOf(0xffffff));  // white
d.setProperty("windows.StatusBar.BackgroundOpacity", String.valueOf(255));  // fully opaque

20.4. Associating App with File Types

It is possible to associate your application with file types on UWP using the standard Codename One
"AppArg"  method  in  conjunction  with  the  windows.extensions  build  hint.  Any  content  you  place  in
the  windows.extensions  build  hint  will  be  embedded  inside  the  <Extensions/>  section  of  the
Package.appxmanifest  file.  Then  if  the  app  is  opened  as  a  result  of  the  user  opening  a  file  of  the

specified 
Display.getProperty("AppArg").

type, 

then 

the  path 

to 

that 

file  will  be  made  available 

to 

the  app  via

Example windows.extensions Value:

The following value would associate the app with the file extension ".alsdk". This example is taken

from 

this  MSDN  document 

[https://msdn.microsoft.com/vi-vn/windows/uwp/launch-resume/handle-file-

activation?f=255&MSPPError=-2147217396].

<uap:Extension Category="windows.fileTypeAssociation">
  <uap:FileTypeAssociation Name="alsdk">
    <uap:Logo>images\icon.png</uap:Logo>
    <uap:SupportedFileTypes>
      <uap:FileType>.alsdk</uap:FileType>
    </uap:SupportedFileTypes>
  </uap:FileTypeAssociation>
</uap:Extension>

To register your app to be able to handle PDFs, you would add:

712

<uap:Extension Category="windows.fileTypeAssociation">
    <uap:FileTypeAssociation Name="pdf">
        <uap:Logo>images\icon.png</uap:Logo>
        <uap:SupportedFileTypes>
            <uap:FileType ContentType="application/pdf">.pdf</uap:FileType>
        </uap:SupportedFileTypes>
    </uap:FileTypeAssociation>
</uap:Extension>

For  more 

information  about  using 

the 

"AppArg"  property, 

see 

this  blog  post

[https://www.codenameone.com/blog/intercepting-urls-on-ios-android.html]  which  describes  its  usage  on  iOS

and Android for intercepting URL types.

713

714

21. Working with Mac OS X

21.1. Mac OS Desktop Build Options

You can configure Desktop Mac OS build settings, by opening Codename One Settings, and clicking

the "Mac Desktop Settings" button:

Figure 543. Mac Desktop settings

This will bring you to the following form:

Figure 544. Mac Desktop settings form

Here you can provide your certificate(s) as a .p12 file, and select a bundle type.

21.1.1. Bundle Types

There are three bundle types which dictate what the build server produces for you when you build

your project as a Desktop Mac OS App.

1. DMG - Produces a .DMG disk image with your app. This is the preferred format for distributing

your app outside of the Mac Appstore. If you provide a Developer ID Application certificate (see

"Understanding  Certificates"  below),  this  the  app  will  be  signed  so  that  users  won’t  receive

warnings about "Unidentified developer" when they install your app.

2. Sandboxed  DMG  -  Same  as  DMG  bundle  type  except  that  your  app  is  set  up  to  use  the  app

sandbox. Generally this would be used to test an app that is being distributed via the Appstore,

since Appstore apps must use the sandbox. If you select this bundle type, you are required to

provide  a  Mac  App  Distribution  Certificate,  and  you  should  additionally  specify  entitlements

required  for  your  app  to  function  properly.  For  more  information  about  the  app  sandbox,  see

Apple’s documentation on the subject [https://developer.apple.com/app-sandboxing/].

3. Mac  Appstore  Upload  (PKG)  -  Produces  a  .PKG  file  that  you  can  upload  to  the  Mac  appstore.

This requires that you provide both a Mac App Distribution certificate, and a Mac App Installer

certificate  (see  "Understanding  Certificates"  below).  Both  of  these  certificates  should  be

embedded into a single .p12 file (See "Exporting Certificates as p12" below).

21.1.2. Understanding Mac Certificates

For  the  purposes  of  Mac  application  distribution,  there  are  3  types  of  certificates  that  we  will  be

interested  in.  The  type(s)  of  certificate  required  will  depend  on  the  type  of  bundle  you  generate.

The certificate types are:

1. Developer ID Application Certificate (Mac applications)

715

This type of certificate is used to sign an app to be distributed outside of the Mac Appstore as a

DMG  image.  This  corresponds  to  the  "DMG"  bundle  type  in  Codename  one  settings.  You  can

easily  identity  this  kind  of  certificate  because  its  identity  will  be  of  the  form  "Developer  ID

Application:  YOUR  COMPANY  NAME  (SOMECODE)".  E.g.  Developer  ID  Application:  Acme

Widgets Corp. (XYSD5YF).

2. Mac App Distribution Certificate (Mac Appstore)

This type of certificate is used to sign the .app bundle for an app that is to be distributed in the

Mac  Appstore.  This  certificate  is  required  for  both  the  "Sandboxed  DMG",  and  "Mac  Appstore

Upload (PKG)" bundle types. You can easily identify this kind of certificate because its identity

will  be  of  the  form  "3rd  Party  Mac  Developer  Application:  YOUR  COMPANY  NAME

(SOMECODE)". E.g. 3rd Party Mac Developer Application: Acme Widgets Corp. (XYSD5YF).

3. Mac App Installer Certificate (Mac Appstore)

This type of certificate is used to sign the .pkg installer for an app that is being submitted to the

Mac Appstore. This certificate is required for the "Mac Appstore Upload (PKG)" bundle type only.

You can easily identify this kind of certificate because its identity will be of the form "3rd Party

Mac  Developer  Installer:  YOUR  COMPANY  NAME  (SOMECODE)".  E.g.  3rd  Party  Mac  Developer

Installer: Acme Widgets Corp. (XYXD5YF).

21.1.3. Obtaining Certificates



Apple  provides  documentation  on  obtaining  certificates  on 

its  website

[https://developer.apple.com/library/content/documentation/IDEs/Conceptual/
AppDistributionGuide/MaintainingCertificates/MaintainingCertificates.html#//apple_ref/doc/uid/

TP40012582-CH31-SW6]  but  the  process  described  there  involves  Xcode.  This  section

describes an alternate process that doesn’t require Xcode.

If  you  have  an  Apple  developer  account,  you  can  manage  your  certificates  here

[https://developer.apple.com/account/mac/certificate].

Figure 545. Mac Developer portal certificates

The  screenshot  above  shows  an  account  that  already  has  the  three  kinds  of  certificates  we  will

require:

1. Developer ID Application - Used for the DMG bundle type.

2. Mac App Distribution - Used for the Sandboxed DMG and Mac Appstore Upload (PKG) bundle

types.

3. Mac App Installer - Used for the Mac Appstore Upload (PKG) bundle type.

If your account doesn’t yet have a certificate of the required type, you should begin by pressing the

716

"+" button in the upper right. This will bring you to a page asking "What type of Certificate do you

need?". There are only two options on this page that we’ll be interested in:

Figure 546. Creating a new certificate

1. Production  >  Mac  App  Store  -  For  both  the  Mac  App  Distribution  and  Mac  App  Installer

certificates.

2. Production > Developer ID - For the Developer ID Application certificate.

Select  the  option  corresponding  to  the  certificate  you  wish  to  generate.  In  either  case,  you’ll  be

taken to a form to select whether you want an "Installer" certificate or an "Application" certificate.

Select the appropriate type.

You  will  then  be  prompted  to  upload  a  Certificate  Signing  Request  (CSR)  file,  and  it  will  provide

instructions on how to do this via the Keychain app.



You can reuse the same CSR file for generating all 3 certificates.

After  generating  the  certificates,  you  should  download  them  to  your  Mac,  and  import  them  into

your  keychain.  You  should  be  able  to  accomplish  this  by  simply  double-clicking  the  downloaded

".cer" file, and following the prompts.

21.1.4. Exporting Certificates as P12

 The following section requires access to a Mac, and assumes that you have already

generated your 3 certificates

Notice  that  Mac  apps  may  require  three  different  kinds  of  certificates,  yet  the  settings  page  only

provides  space  for  a  single  certificate  (P12)  file.  This  is  not  a  mistake.  P12  files  may  contain  more

than one certificate, and you are expected to include all of the certificates that the build server may

require  inside  a  single  P12.  The  build  server  will  automatically  extract  the  certificates  it  needs

according to the bundle type.

When  building  the  "DMG"  bundle  type,  the  build  server  will  look  for  a  "Developer  ID  Application

717

Certificate" inside the P12. If one is found, it will be used to sign the app bundle.

The "Sandboxed DMG" target will look for a "Mac App Distribution Certificate" certificate in the P12.

The "Mac Appstore Upload (PKG)" target will require both a "Mac App Distribution Certificate" and

a "Mac App Installer Certificate" to be included in the P12.

The easiest way to produce a P12 that includes all 3 kinds of certificates is to export them from the

Keychain Access app (Requires a Mac). Select all 3 certificates at once (using CMD-click), then right

click and select "Export 3 Items…"

You will then be prompted to select a location to save the .p12 file, as well as selecting a password

for the file.

21.1.5. Entitlements

When  distributing  apps  in  the  Mac  Appstore,  or  when  using  the  "Sandboxed  DMG"  bundle  type,

your app is run inside a sandboxed environment, meaning that it doesn’t have access to the outside

world.  It  is  provided  its  own  "sandboxed"  container  for  file  system  access,  and  it  doesn’t  get  any

network access. If your app requires access to the "outside world", you need to request entitlements

for that access. If you select a bundle type that uses the sandbox, you you will be shown a list of all

of the available entitlements from which you can "check" the ones that you wish to include.

Figure 547. App sandbox entitlements

For  more  information  about  the  app  sandbox,  and  a  full  list  of  entitlements,  see  Apple’s

documentation  on  the  subject  [https://developer.apple.com/library/content/documentation/Miscellaneous/

Reference/EntitlementKeyReference/Chapters/EnablingAppSandbox.html].

718

22. Security

Security is a "big word". It implies many things and that is also true for the mobile app development

so before we get started lets try to define the scope of security.

We  will  deal  only  with  application  security  and  its  communication  mechanisms  while  ignoring

everything beyond that scope. Let’s start with a simple fact:

Codename One applications are secure on the devices by the nature of the

mobile OS security.

For  most  intents  and  purposes  this  will  be  enough,  unless  you  are  specifically  concerned  about

security this section isn’t for you. Mobile OS’s isolate applications from one another so it’s hard for

an application to damage the OS or even damage/spy on a different app.

The restrictions laid on apps are here to make them extra secure and on top of that Codename One

lays a few big advantages in terms of security:

• Codename One code is compiled (unlike e.g. PhoneGap/Cordova)

• We obfuscate by default which makes the binaries harder to reverse engineer

• We compile the UI to native code too which means typical reverse engineering code will have a

harder time following

• We disable debug flags so a hacker won’t be able to debug your production app on the device

Despite that you still need to keep in mind that the binary could still be reverse engineered and so it

is  important  to  avoid  storing  keys  in  the  client  side  code.  E.g.  if  you  have  an  API  key  to  access  a

service  (e.g.  Google  Cloud  key)  it  needs  to  be  stored  in  your  server  and  not  as  a  constant  in  your

app!

Each  section  below  discusses  some  attack  vectors  against  applications  and  how  they  can  be

stopped. Pretty much all of these attacks require a very sophisticated attacker which will only exist

for high value targets (e.g. bank apps, government etc.).

22.1. Constant Obfuscation

One  of  the  first  things  a  hacker  will  do  when  compromising  an  app  is  look  at  it.  E.g.  if  I  want  to

exploit  a  bank’s  login  UI  I  would  look  at  the  label  next  to  the  login  and  then  search  for  it  in  the

decompiled code. So if the UI has the String "enter user name and password" I can search for that.

It  won’t  lead  directly  to  a  hack  or  exploit  but  it  will  show  you  the  approximate  area  of  the  code

where we should look and it makes the first step that much easier. Obfuscation helps as it removes

descriptive method names but it can’t hide the Strings we use in constants. If an app has a secret

key within obfuscating it can make a difference (albeit a slight difference).

Notice that this is a temporary roadblock as any savvy hacker would compile the app and connect a

debugger eventually (although this is blocked in release builds) and would be able to inspect values

of variables/flow. But the road to reverse engineering the app would be harder even with a simple

719

xor obfuscation.

 We’re  not  calling  this  encoding  or  encryption  since  it’s  neither.  It’s  a  simple

obfuscation of the data

There are two simple methods in the Util class:

public static String xorDecode(String s);
public static String xorEncode(String s);

They use a simple xor based obfuscation to make a String less readable. E.g. if you have code like

this:

private static final String SECRET = "Don't let anyone see this....";

You might be concerned about the secret, then this would make it slightly harder to find out:

// Don't let anyone see this....
private static final String SECRET = Util.xorDecode("RW1tI3Ema219KmpidGFhdTFhdnE1Yn9xajQ1MjM=");

Notice that this is not secure, if you have a crucial value that must not be found you need to store it

in the server. There is no alternative as everything that is sent to the client can be compromised by

a determined hacker



Use the comment to help you find the string in the code

Our builtin user specific constants are obfuscated with this method, e.g. normally an app built with

Codename One carries some internal data such as the user who built the app etc. This is obfuscated

now. We built this small app to encode strings easily so we can copy and paste them into our app

easily:

Form hi = new Form("Encoder", BoxLayout.y());
TextField bla = new TextField("", "Type Text Here", 20, TextArea.ANY);
TextArea encoded = new TextArea();
SpanLabel decoded = new SpanLabel();
hi.addAll(bla, encoded, decoded);
bla.addDataChangedListener((a, b) -> {
    String s = bla.getText();
    String e = Util.xorEncode(s);
    encoded.setText(e);
    decoded.setText(Util.xorDecode(e));
    hi.getContentPane().animateLayout(100);
});

hi.show();

720

This allows you to type in the first text field and the second text area shows the encoded result. We

used a text area so copy/paste would be easy.

For  your  convenience  this  app  can  be  accessed  here:  https://www.codenameone.com/demos/

StringEncoder/index.html

22.2. Storage Encryption

Codename One had support for bouncy castle encryption for quite a while but it’s not as intuitive as

we’d like it to be. This makes securing/encrypting your app more painful than it should.

Codename  One  supports  full  encryption  of  the  Storage  (notice  the  distinction,  Storage  is  not
FileSystemStorage).  This  is  available  by  installing  the  bouncy  castle  cn1lib  from  the  extensions
menu then using one line of code

EncryptedStorage.install("your-pass-encryption-key");



Normally you would want that code within your init(Object) method

Notice  that  you  can’t  use  storage  or  preferences  to  store  this  data  as  it  would  be  encrypted
(Preferences uses Storage internally). You can use a password for this key and it would make it way
more secure but if a user changes his password you might have a problem. In that case you might

need the old password to migrate to a new password.

This  works  thru  a  new  mechanism  in  storage  where  you  can  replace  the  storage  instance  with

another instance using:

Storage.setStorageInstance(new MyCustomStorageSubclass());

We  can  leverage  that  knowledge  to  change  the  encryption  password  on  the  encryption  storage

using pseudo code like this:

EncryptedStorage.install(oldKey);
InputStream is = Storage.getInstance().createInputStream(storageFileName);
byte[] data = Util.readInputStream(is);
EncryptedStorage.install(newKey);
OutputStream o = Storage.getInstance().createOutputStream("TestEncryption");
o.write(data);
o.close();

 It’s  not  a  good  idea  to  replace  storage  objects  when  an  app  is  running  so  this  is

purely for this special case…

If you use preferences it might be a good idea to set their builtin location to a different path using
something like Preferences.setPreferencesLocation("EncryptedPreferences");.

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This is useful as it prevents the encrypted preferences from colliding with the regular preferences.

22.3. Disabling Screenshots

One of the common security features some apps expect is the ability to block a screenshot. In the

past  apps  like  snapchat  required  that  you  touch  the  screen  to  view  a  photo  to  block  the  ability  to

grab a screenshot (on iOS). This no longer works…

Blocking  screenshots  is  an  Android  specific  feature  that  can’t  be  implemented  on  iOS.  This  is

implemented  by  classifying  the  app  window  as  secure  and  you  can  do  that  via  the  build  hint
android.disableScreenshots=true. Once that is added screenshots should no longer work for the app,
this  might  impact  other  things  as  well  such  as  the  task  view  which  will  no  longer  show  the

screenshot either.

22.4. Blocking Copy & Paste

Blocking copy & paste is useful for cases where a device might have spyware installed that monitors

the clipboard. This also prevents a user from using a password manager (which usually rely on the

clipboard), those managers could be compromised and thus if you are building a very secure app

this might be necessary.

You can block copy & paste on Android & iOS. Blocking of copy & paste can be implemented globally

or on a specific field.

To block copy & paste globally use:

Display.getInstance().setProperty("blockCopyPaste", "true");

To block copy & paste on a specific field do:

textCmp.putClientProperty("blockCopyPaste", Boolean.TRUE);

 Notice that the inverse of using false might not work as expected

22.5. Blocking Jailbreak

iOS & Android are walled gardens which is both a blessing and a curse. Looking at the bright side

the walled garden aspect of locked down devices means the devices are more secure by nature. E.g.

on a PC that was compromised we can detect the banking details of a user logging into a bank. But

on a phone it would be much harder due to the deep process isolation.

This  isn’t  true  for  jailbroken  or  rooted  devices.  In  these  devices  security  has  been  compromised

often with good intentions (opening up the ecosystem) but it can also be used as a step in a serious

attack on an application!

For  obvious  reasons  it’s  really  hard  to  accurately  detect  a  jailbroken  or  rooted  device  but  when

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possible if you have a high security app you might want to block the functionality or even raise a
"silent alarm" in such a case. To detect this you can use the isJailbrokenDevice method as such:

if(Display.getInstance().isJailbrokenDevice()) {
    // probably jailbroken or rooted
} else {
   // probably not
}

Notice  that  this  isn’t  accurate,  we  can’t  be  100%  sure  as  there  are  no  official  ways  to  detect

jailbreak. That is why it’s crucial to encrypt everything and assume the device was compromised to

begin with when dealing with very sensitive data. Still it’s worthwhile to use these API’s to make the

life of an attacker just a little bit harder.

22.6. Strong Android Certificates

When  Android  launched  RSA1024  with  SHA1  was  considered  strong  enough  for  the  foreseeable

future, this hasn’t changed completely but the recommendation today is to use stronger cyphers for

signing & encrypting as those can be compromised.

APK’s are signed as part of the build process when we upload an app to the Google Play Store. This

process  seems  redundant  as  we  generate  the  signature/certificate  ourselves  (unlike  Apple  which

generates  it  for  us).  However,  this  is  a  crucial  step  as  it  allows  the  device  to  verify  upgrades  and

make sure a new update is from the same original author!

This  means  that  if  a  hacker  takes  over  your  account  on  Google  Play,  he  still  won’t  be  able  to  ship

fake updates to your apps without your certificate. That’s important since if a hacker would have

access  to  your  certificate  he  could  create  an  app  update  that  would  just  send  him  all  the  users

private information e.g. if you are a bank this could be a disaster.

Android launched with RSA1024/SHA1 as the signing certificates. This was good enough at the time

and  is  still  pretty  secure.  However,  these  algorithms  are  slowly  eroding  and  it  is  conceivable  that

within the 10-15 year lifetime of an app they might be compromised using powerful hardware. That

is  why  Google  introduced  support  for  stronger  cryptographic  signing  into  newer  versions  of

Android and you can use that.

22.6.1. The Bad News

There is a downside…

Google  only  introduced  that  capability  in  Android  4.3  so  using  these  new  keys  will  break

compatibility with older devices. If you are building a highly secure app this is probably a tradeoff

you should accept. If not this might not be worth it for some theoretical benefit.

Furthermore,  if  your  app  is  already  shipping  you  are  out  of  luck.  Due  to  the  obvious  security

implications  once  you  shipped  an  app  the  certificate  is  final.  Google  doesn’t  provide  a  way  to

update the certificate of a shipping app. Thus this feature only applies to apps that aren’t yet in the

play store.

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22.6.2. The Good

If you are building a new app this is pretty easy to integrate and requires no changes on your part.

Just  a  new  certificate.  You  can  generate  the  new  secure  key  using  instructions  in  articles  like  this

one [https://guardianproject.info/2015/12/29/how-to-migrate-your-android-apps-signing-key/].

If you are using Codename One Setting  you can check the box to generate an SHA512 key which will

harden the security for the APK.

22.7. Certificate Pinning

When we connect to HTTPS servers our networking code checks the certificate on the server. If the

certificate was issued by a trusted certificate authority then the connection goes thru otherwise it

fails.  Let’s  imagine  a  case  where  I’m  sitting  in  a  coffee  shop  connected  to  the  local  wifi,  I  try  to

connect to gmail to check my email. Since I use HTTPS to Google I trust my connection is secure.



What if the coffee shop was hacked and the router is listening in on everything?

So HTTPS is encrypted and the way encryption works is thru the certificate. The server sends me a

certificate and we can use that to send encrypted data to it.



What if the router grabs the servers certificate and communicates with Google in

my name?

This  won’t  work  since  the  data  we  send  to  the  server  is  encrypted  with  the  certificate  from  the

server.



So what if the router sends its own "fake certificate"?

That  won’t  work  either.  All  certificates  are  signed  by  a  "certificate  authority"  indicating  that  a

google.com certificate is valid.



What  if  I  was  able  to  get  my  fake  certificate  authorized  by  a  real  certificate

authority?

That’s a problem!

It’s obviously hard to do but if someone was able to do this he could execute a "man in the middle"

attack as described above. People were able to fool certificate authorities in the past and gain fake

certificates using various methods so this is possible and probably doable for any government level

attacker.

22.7.1. Certificate Pinning

This  is  the  attack  certificate  pinning  (or  SSL  pinning)  aims  to  prevent.  We  code  into  our  app  the

"fingerprint"  of  the  certificate  that  is  "good"  and  thus  prevent  the  app  from  working  when  the

certificate is changed. This might break the app if we replace the certificate at some point but that

might be reasonable in such a case.

724

To  do  this  we  have  a  cn1lib  [https://github.com/codenameone/SSLCertificateFingerprint/].  that  fetches  the

certificate  fingerprint  from  the  server,  we  can  just  check  this  fingerprint  against  a  list  of
"authorized" keys to decide whether it is valid. You can install the SSLCertificateFingerprint from
the extensions section in Codename One Settings and use something like this to verify your server:

if(CheckCert.isCertCheckingSupported()) {
    String f = CheckCert.getFingerprint(myHttpsURL);
    if(validKeysList.contains(f)) {
        // OK it's a good certificate proceed
    } else {
       if(Dialog.show("Security Warning", "WARNING: it is possible your commmunications are being tampered! We suggest
quitting the app at once!", "Quit", "Continue")) {
          Display.getInstance().exitApplication();
       }
    }
} else {
    // certificate fingerprint checking isn't supported on this platform... It's your decision whether to proceed or not
}

Notice that once connection is established you don’t need to verify again for the current application

run.

725

726

23. Travis CI Integration

This  page  includes  instructions  on  setting  up  continuous  integration  for  Codename  One

applications using GitHub and Travis-CI.

Travis  CI  is  a  hosted,  distributed  continuous  integration  service  used  to

build and test software projects hosted at GitHub.

Open  source  projects  may  be  tested  at  no  charge  via  travis-ci.org.  Private

projects  may  be  tested  at  travis-ci.com  on  a  fee  basis.  TravisPro  provides

custom  deployments  of  a  proprietary  version  on  the  customer’s  own

hardware.

Although the source is technically free software and available piecemeal on

GitHub under permissive licenses, the company notes that it is unlikely that

casual users could successfully integrate it on their own platforms.

— Wikipedia

Codename One provides single-click integration with Travis-CI via the Codename One Settings tool.

Once integration is set up, Travis will automatically build your project and run unit tests following

each commit of your project to GitHub.

23.1. Quick Start

Assuming  you  already  have  a  Codename  One  project,  you  only  need  to  do  three  things  to  enable

Travis:

1. Enable Travis in Codename One Settings

2. Push the project to GitHub.

3. Turn on your repository on travis-ci.org [https://travis-ci.org] if your repository is public or travis-

ci.com [https://travis-ci.com] if your repository is private.



Travis  CI  is  free  for  public  Github  repositories.  If  your  repository  is  private,  then

you’ll need a travis-ci.com [https://travis-ci.com/] account. See their plans and pricing

here [https://travis-ci.com/plans].

23.1.1. Enabling Travis

Open  Codename  One  settings  by  right  clicking  the  project,  and  selecting  "Codename  One"  >

Codename One Settings"

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Then click on the "Travis CI Integration" button

If your project isn’t already configured for travis, you’ll see a form as follows:

728

Click the "Enable Travis CI" button.

This  will  install  some  travis  scripts  from  the  cn1-travis-template  [https://github.com/shannah/cn1-travis-

template] project. In particular, it will add the following files to your project:

1. .travis.yml - A travis script that is set up to build your project and run its unit tests.

2. .travis/ - A directory containing some utility shell scripts that are used the .travis.yml script.

Activating/Deactivating Jobs

The .travis.yml script that was installed in the previous step includes jobs for testing your app on
many  different  platforms.  Currently  JavaSE  (the  Codename  One  simulator),  and  a  selection  of  iOS

and Android versions are included, but we will be adding more platforms as time goes on. The goal

is to provide jobs for every platform that Codename One supports.

You can select the platforms you want Travis to test against by selecting or deselecting the platform,

as shown below.

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



Only  the  JavaSE  job  is  available  for  non-enterprise  subscribers.  If  you  don’t  have

an  enterprise  subscription,  the  Android  and  iOS  options  will  be  disabled  in  your

settings. If you have an enterprise subscription, and your Android and iOS options

are disabled, then you may not be logged in correctly. Check on the main menu of

settings to ensure that you’re logged into the correct account.

On-device  jobs  such  as  Android  and  iOS  require  that  you  have  the  CN1USER  and
CN1PASS environment variables set in your Travis settings. These are used to build
your project on the build server.

23.1.2. Pushing to GitHub

The process of setting up a Github repository is beyond the scope of this document. Please refer to

github’s documentation [https://guides.github.com/activities/hello-world/] for details on this process.

Add a .gitignore file to your project to prevent you from committing all of your .jar



files  along  with  your  project.  Take  a  look  at  the  .gitignore  file  from  the  Kitchen

Sink  demo  app  [https://github.com/codenameone/KitchenSink/blob/master/.gitignore]  for  a

sample .gitignore file that is suitable for a typical Codename One project.

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23.1.3. Activate Repository On Travis

Now  that  your  project  is  in  a  Github  repository,  you  just  need  to  activate  the  repository  within

Travis. For this part, you’ll need an account on travis-ci.org (for public repositories) or travis-ci.com

(for private repositories).

Steps to activate your repository in Travis.

1. Go to travis-ci [https://travis-ci.org], and login.

2. Click on your name in the upper right corner, to go to your profile page.

3. Click the "Sync account" button in the upper right to load your Github repositories.

4. Flip the switch next to the repository you want to activate in the list.

23.1.4. Setting Environment Variables

If you have any Android or iOS jobs activated in your travis script, you’ll need to set the CN1PASS and
CN1USER  environment  variables  in  Travis.  Do  this  by  first  clicking  on  the  repository,  then  select

731

"More Options" in the upper right, and "Settings".

The settings form will allow you to enter environment variables.

23.1.5. Testing Travis Script

To test the travis script, all you need to do is commit a change to your project in it, then push it to

github.

$ git add .
$ git commit -m "Some changes"
$ git push origin master

Then go to https://travis-ci.org, and you should see your repository listed in the left menu. Click on it

to follow your build status

732

23.1.6. Writing Unit Tests

In order to make the most out of continuous integration, you’ll want to write unit tests for your app.

See this video/post [https://www.codenameone.com/blog/test-it.html] for a light introduction to Codename

One  unit  testing,  and  also  check  out  the  javadocs  for  the  com.codename1.testing  package

[https://www.codenameone.com/javadoc/com/codename1/testing/package-summary.html].

Disabling Travis

If  you  want  to  disable  travis,  or  start  fresh  with  a  new  travis  script,  you  can  simply  delete  the
.travis directory and .travis.yml file from your project. If you want to reactivate travis later, you
can do so through the Codename One settings using the same procedure as described above. That

will re-download the latest travis script from the online template [https://github.com/shannah/cn1-travis-

733

template].

734

24. Working with Codename One Sources

24.1. Checking out the Sources

$ mkdir workspace
$ cd workspace
$ git clone https://github.com/codenameone/CodenameOne

Creating  a  clean  "workspace"  directory  is  optional,  and  there  is  nothing  special



about  the  name  "workspace".  It  is  just  recommended  to  create  a  clean  directory

into  which  you  check  out  Codename  One,  because  building  Codename  One  will

check  out  a  few  dependent  projects  and  place  then  at  the  same  level  as  the

CodenameOne folder, so having a clean workspace will make it easier to manage.

24.2. Building Sources

$ cd CodenameOne
$ ant



The cd CodenameOne command should take you to the root project directory which
contains  subfolders  "CodenameOne",  "Ports",  etc..  -  not  the  subfolder  named

"CodenameOne".

24.3. Running Unit Tests

You  can  run  the  unit  test  suite  locally  in  the  Codename  One  simulator  using  the  "test-javase"  ant

target.

$ ant test-javase

24.4. Running iOS Unit Tests

 Running iOS Unit tests is currently limited to interal use only by Codename One.

TLDR: You can run Codename One’s unit tests on a local iOS simulator by running the "test-ios" ant

target in the main CodenameOne directory. E.g.

ant test-ios

This assumes the following requirements

735

1. You are running Mac OS X with Xcode 7.3 or higher installed.

2. You have npm installed and in your environment PATH.

3. You have appium installed and running.

24.4.1. Installing npm

Either download the installer from https://nodejs.org/en/ OR run brew install node from terminal.

24.4.2. Installing and Running Appium

Open a new terminal window, then

$ mkdir appium
$ cd appium
$ npm install appium
$ ./node_modules/.bin/appium

 You may want to run the last command ./node_modules/.bin/appium as a daemon so

terminal  window.  E.g.

to  use 

same 

the 

that  you 
continue 
can 
./node_modules/.bin/appium &

24.4.3. Running the Unit tests

$ cd CodenameOne
$ ant test-ios

24.4.4. Overriding the Codename One Build Server Target

$ ant test-ios -Dcn1.iphone.target=iphone_new

This will send to the "iphone_new" build server instead of the default "iphone" server.

736