Java 2 Platform, Micro Edition (J2ME) By Xiaorong Wang

Agenda Introduction CLDC and MIDP Programming with CLDC/MIDP Summary and Resources

Java TM 2 Platform Java 2 Enterprise Edition (J2EE) Java 2 Standard Edition (J2SE) Java 2 Micro Edition (J2ME)

What is J2ME? Java 2 Micro Edition (J2ME) is Sun’s version of Java aimed at machines with limited hardware resources Limited screen size, memory, and processing power PDAs, cell phones, other consumer electronic and embedded devices

Configuration The foundation of J2ME is configurations A configuration defines Java APIs and a specification of a java virtual machine A configuration defines a minimum Java platform for a family of devices

Two Types of Configuration Connected device configuration (CDC) Connected limited device configuration (CLDC)

The Architecture of J2ME

Profiles On top of the configurations are the profiles Mobile Information Device Profile (MIDP)  The foundation configuration is CLDC  MIDP is a profile for mobile information devices, such as: cellular phones, two-way pagers, and PDAs

Agenda Introduction CLDC and MIDP Programming with CLDC/MIDP Summary and Resources

Overview Native OS & Apps Native Interface KVM OS Interface CLDC (Java) KVM (C) Native Call CLDC Interface J2ME MIDP MIDP Interface Memory Java Application Manager MIDlet 1MIDlet 2

Connected, Limited Device Configuration (CLDC) Targets at devices with  160KB to 512KB total memory available for Java technology  Limited power (often battery)  Limited connectivity to a network (often wireless)  Extremely constrained UI, small screens

CLDC Language and VM Compatibility Full Java Language and Java Virtual Machine Specification compatibility Language-level different: Floating point not supported in CLDC 1.0 CLDC libraries are limited

CLDC Libraries Classes inherited from Java 2 Platform, Standard Edition (J2SE version 1.3) are in packages:  java.lang.*  java.util.*  java.io.* New classes introduced by CLDC:  javax.microedition.*

MIDP: Overview Mobile Information Device Profile (MIDP) covers  Timers  Application lifecycle  Persistent storage  Networking  User interface

MIDP: Libraries Classes inherited from J2SE:  java.lang.*: IllegalStateException  java.util.*: Timer, TimerTask New classes introduced by MIDP:  javax.microedition.rms.*  javax.microedition.midlet.*  javax.microedition.io.*  javax.microedition.lcdui.*

Agenda Introduction CLDC and MIDP Programming with CLDC/MIDP Summary and Resources

Steps Flowchart Edit Source Code Compile and Preverify Emulator *.java *.class Archive MIDlet Download To Device *.jar *.class Resources:text, image,… Manifest File

import javax.microedition.midlet.*; import javax.microedition.lcdui.*; public class HelloMidlet extends MIDlet implements CommandListener { // Initialize the Midlet Display variable private Display midletDisplay; // Initialize a variable for the doneCommand private Command doneCommand; public HelloMidlet() { // Retrieve the display from the static display object midletDisplay = Display.getDisplay(this); // Initialize the doneCommand doneCommand = new Command("DONE", Command.SCREEN, 1); }

public void startApp() { // Create the TextBox containing the "Hello Midlet World!!" message TextBox textBox = new TextBox("Hello Midlet", "Hello Midlet World!!", 256, 0); // Add the done Command to the TextBox textBox.addCommand(doneCommand); // Set the command listener for the textBox to the current midlet textBox.setCommandListener( (CommandListener) this); // Set the current display of the midlet to the textBox screen midletDisplay.setCurrent(textBox); } public void pauseApp() { } public void destroyApp(boolean unconditional) { }

/* The commandAction method is implemented by this * midlet to satisfy the CommandListener interface and * handle the done action. */ public void commandAction(Command command, Displayable screen) { // If the command is the doneCommand if (command == doneCommand) { // Call the destroyApp method destroyApp(false); // Notify the midlet platform that the midlet has completed notifyDestroyed(); }

Life Cycle Of Midlet Paused Active Destroyed pauseApp() startApp() destroyApp() New()

Developing Tools Java 2 Standard Edition, version or higher ( J2ME Wireless Toolkit (

Using the KToolBar

KToolBar

Building the MIDlet Compile the Java source files Preverify the class files Package:  Jar up the verified class files  Jar up the resource files

Running the Midlet

Agenda Introduction CLDC and MIDP Programming with CLDC/MIDP Summary and Resources

Summary Some of the companies that making J2ME products:  Research in Motion (RIM): Blackberry two- way handhelds  Nokia: Mobile phones  NEXTEL: Mobile phones – i85s and i50sx  American Express: Java Card for its Blue credit cards

Resources