The J2ME Development Environment

1
The J2ME Development Environment

• Shwetak Patel
• shwetak_at_cc.gatech.edu

2
Intro to J2ME

• J2ME Java 2 Micro Edition
• Introduced by sun in 1999 for mobile devices
• Scaled down version of J2SE
• Smaller footprint
• No heavyweight classes (swing, awt, etc)
• Highly optimized runtime environment

3
J2ME Architecture
OEM Specific API

• KVM - Kilobyte Virtual Machine
• 40 80 KB in size
• For devices with 160 KB of memory and 16 or
  32-bit RISC/CISC microprocessors

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J2ME Architecture (cont.)
OEM Specific API

• CLDC - Connected Limited Device Configuration
• Provides core lower level functionality
• Bare minimum IO and utilities
• Currently consists of java.io, java.lang,
  java.util, java.microedition.io

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J2ME Architecture (cont.)
OEM Specific API

• MIDP Mobile Information Device Profile
• MIDP provides the core application functionality
  for mobile devices
• Network connectivity, data storage, and user
  interfaces

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J2ME Architecture (cont.)
OEM Specific API

• OEM Specific API
• Access to proprietary features and functionality
• Audio system, camera, lighting system, etc

7
J2ME Programming Environment

• Sun provides IDE for the generic java-enable
  mobile phone
• Most mobile phone companies like Motorola or
  Nokia have their own IDEs

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J2ME Applications

• A J2ME app is called a Midlet

Midlet life cycle
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J2ME UI

• MIDP provides some limited UI elements
• Form
• Alert
• Choice and ChoiceGroup
• List
• StringItem
• TextBox
• TextField
• DateField
• Guage
• Ticker

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J2ME UI vs J2SE UI

• MIDP UI elements ARE NOT subsets of AWT/Swing
• Interaction with the user is based around a
  succession of screens
• MIDP only has a single command listener

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J2ME Canvas

• J2ME does allows lower level access to the Canvas
• Can create custom graphics and user interfaces by
  extending Canvas

12
Lightweight Window Toolkit

• Motorola introduced the LWT to address the
  limitation of MIDP
• Works on all java-enable mobile phone
• Similar to J2SE Swing
• Layout management with absolute or relative
  widget placement
• Notion of containers
• Component Listeners

13
LWT Hierarchy
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Sample J2ME Applications
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Questions?

• For more info
• http//java.sun.com/j2me/
• http//idenphones.motorola.com/iden/developer/deve
  loper_home.jsp
• shwetak_at_cc.gatech.edu