Introduction to J2ME, Albeski

8/8/2019 Introduction to J2ME, Albeski

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Developing Java 2 ME Applications

AbelskieLearning

www.abelski.com
http://www.abelski.com/http://www.abelski.com/


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Introduction


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04/02/08 Abelski eLearning

J2SE, J2EE & J2ME

Sun Microsystems groups its Java technologies into groups.

The three most important groups are the following platforms:

Java 2 SE (J2SE) Java 2 Standard Edition Platform

Java 2 EE (J2EE) Java 2 Enterprise Edition Platform

Java 2 ME (J2ME) Java 2 Micro Edition Platform

The various platforms aren't fully separated from each other.

Each platform includes a JVM, libraries of classes &

development tools.


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J2SE, J2EE & J2ME

J2EE J2SE J2ME


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J2ME Configurations

J2SE CDC CLDC


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J2ME Profiles

On top of the configuration we can expect a profile (one or

more) to be deployed.

A J2ME profile addresses a specific need, and it typically

includes class libraries that are more specific than the

classes libraries the configuration includes.

Currently, MIDP (Mobile Information Device Profile) is the

most popular profile.


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J2ME Profiles

J2ME

CLDC CDC

Foundation Profile

RMI ProfilePersonalProfile

PDAPProfile

MIDPProfile


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J2ME (CLDC/MIDP)

This course focuses on developing J2ME application for

mobile telephones with J2ME running environment CLDC

configuration and MIDP profile.

The mobile telephones mass market includes mobile

telephones that support the J2ME(CLDC/MIDP) running

environment.


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04/02/08 Abelski eLearning 1

The KVM

The KVM is a compact portable small JVM designed for

resource constrained devices.

The J2ME (CLDC/MIDP) devices use the KVM.


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J2ME (CLDC/MIDP) & J2SE

J2ME(CLDC\MIDP) java.lang package is a subset of the

J2SE java.lang package.

J2ME(CLDC\MIDP) doesnt allow controlling the class loader.

J2ME(CLDC\MIDP) doesnt support object finalization.

J2ME(CLDC\MIDP) doesnt support reflection.


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J2ME(CLDC\MIDP) doesnt support a mechanism (like the

JNI) that enables writing native methods.

J2ME(CLDC\MIDP) multi threading mechanism is very

similar to the one that the J2SE has.

J2ME(CLDC\MIDP) Math class is a subset.

J2ME(CLDC\MIDP) has smaller version of the String and

the StringBuffer classes.


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J2ME(CLDC\MIDP) has smaller version of the System and

the Runtime classes.

J2ME(CLDC\MIDP) java.util package includes only few of

the classes and interface that exist in the J2SE version.

J2ME(CLDC\MIDP) java.io package include only few of the

classes and the interfaces that exist in the J2SE version.


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Developing The First Midlet

The J2ME application model is very similar to the one used

by Java applets and Java servlets.

You need to declare a class that extends the Midlet class.

That class must be public and it must include a constructor

without parameters.


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import javax.microedition.midlet.*;

import javax.microedition.lcdui.*;

public class Hello extends MIDlet{

private Display display;

private Form form;

public Hello()

{

form = new Form("Hello");

display = Display.getDisplay(this);

}

public void startApp(){

display.setCurrent(form);

}

public void pauseApp() { }

public void destroyApp(boolean cond) { }

}


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Run the Wireless Toolkit.


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Create new project.

File -> New Project

Fill in the details of the new project.

Project Name

The project name is the name of the project you choose for your new work.

MIDlet Class Name

The MIDlet class name is the name of the class you declared as one that

extends Midlet. When developing a J2ME application composed of several

classes, among those classes there must be a class that extends Midlet. That

would be the main class (similar to the Applet model).


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Press the Create Project button to create your project.

The wizard pop up dialog window allows you to configure

the project you are about to develop.


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One of the outcomes for creating the new project is the

creation of folders hierarchy specifically for the new project.

Each project has its own specific folder.

All projects folders are kept within the apps folder.

Each project folder includes the following sub folders:

bin ...this folder will include the JAR/JAD created files.

src ...this folder should include all project source code.

lib ...this folder should include all additional third party classes we add.

res ...this folder should include all additional resource files (images, sound etc.).


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Write your source code and save it within the src folder.

Choose Build to compile & preverify your code.


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Choose Project -> Package -> Create Package in order

to create the JAR/JAD files.


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You can now find the JAR/JAD files within the bin folder of

your project.

You can install the JAR and the JAD files on your mobile

telephone.

Alternatively, you can choose Run and run your code via

the wireless toolkit on one of its emulators.


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The Java Application Manager (JAM

The MIDlet life cycle is controlled by the Java Application

Manager (JAM).The JAM is a MIDlet management software that controls the process of

installing, running and removing the MIDlets.

When the user chooses to run a MIDlet, it is the JAM that

creates an instance of the MIDlet class and runs methods

on it.The sequence of method that will be invoked on the MIDlet subclass instance is

defined by the MIDlet life cycle. Like the servlets and the applets, the midlets

also have a well-defined set of states.


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The Java Application Manager (JAM

The JAM calls various methods on the midlet to signify

changes from one state to another.These methods include the following: startApp(), pauseApp(), destroyApp() and

the MIDlet subclass constructors as well.


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indell Technologies, Ltd. 04

belski eLearning


Developing Java 2 ME Applications

AbelskieLearning

www.abelski.com


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belski eLearning


Introduction


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belski eLearning


J2SE, J2EE & J2ME

Sun Microsystems groups its Java technologies into groups.

The three most important groups are the following platforms:

Java 2 SE (J2SE) Java 2 Standard Edition Platform

Java 2 EE (J2EE) Java 2 Enterprise Edition Platform

Java 2 ME (J2ME) Java 2 Micro Edition Platform

The various platforms aren't fully separated from each other.

Each platform includes a JVM, libraries of classes &

development tools.

Browsing at http://java.sun.com/ you can find on the right a listof all available Java technologies.


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belski eLearning


J2SE, J2EE & J2ME

J2EE J2SE J2ME


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belski eLearning


J2ME Configurations

The Java 2 Micro Edition platform has two possibleconfigurations:

CLDC Connected Limited Device Configuration

CDC Connected Device Configuration

These two configurations target two different categories of

products:

Low End Devices

High End Devices

These two configurations target two categories of products:High-end devices (TV set-top boxes, Internet TVs, automobilenavigation systems etc) which have large range of userinterface capabilities, high-bandwidth network connections(usually TCP/IP) and more memory and CPU power.

andLow-end devices (Cell phones, pagers, PDAs etc) whichhave very simple user interface and small screen size, lessmemory, less CPU power, lower bandwidth and most of themare usually operated using batteries.


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belski eLearning


J2ME Configurations

J2SE CDC CLDC


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belski eLearning


J2ME Profiles

On top of the configuration we can expect a profile (one ormore) to be deployed.

A J2ME profile addresses a specific need, and it typically

includes class libraries that are more specific than the

classes libraries the configuration includes.

Currently, MIDP (Mobile Information Device Profile) is the

most popular profile.

A J2ME configuration defines the Java language, the virtualmachine features and the minimum class libraries for acategory\group of devices (horizontal market).A J2ME profile is layered on top of configuration and addressthe specific demands of a specific vertical market (or device

category). The profile typically includes class libraries that arefar more specific than the class libraries provided in aconfiguration.


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belski eLearning


J2ME Profiles

J2ME

CLDC CDC

Foundation Profile

RMI ProfilePersonalProfile

PDAPProfile

MIDPProfile


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belski eLearning


J2ME (CLDC/MIDP)

This course focuses on developing J2ME application formobile telephones with J2ME running environment CLDC

configuration and MIDP profile.

The mobile telephones mass market includes mobile

telephones that support the J2ME(CLDC/MIDP) running

environment.

According to the specification, the MID profile has the followingcharacteristics:At least 128KB of non-volatile memory (non-volatile memory ismemory that is capable of keeping its contents intact as thedevice is turned on and off. The ROM is one example for non-

volatile memory) for the MIDP implementation.At least 32KB of volatile memory for the heap.At least 8KB of non-volatile memory for persistent data.A screen of at least 96x54 pixels.Pixel ratio approximately 1:1.An Input mechanism one of the following: keypad, keyboardor touch screen.Two-way network connection.The classes a MIDP application can use come from packages

in both the CLDC and the MIDP. The packages the CLDC hasare: java.lang, java.io, java.util, javax.microedition.io. Thepackages the MID profile adds are: javax.microedition.lcdui,

javax.microedition.midlet and javax.microedition.rms.


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belski eLearning


The KVM

The KVM is a compact portable small JVM designed forresource constrained devices.

The J2ME (CLDC/MIDP) devices use the KVM.

According to the specification, the MID profile has the followingcharacteristics:At least 128KB of non-volatile memory (non-volatile memory ismemory that is capable of keeping its contents intact as thedevice is turned on and off. The ROM is one example for non-

volatile memory) for the MIDP implementation.At least 32KB of volatile memory for the heap.At least 8KB of non-volatile memory for persistent data.A screen of at least 96x54 pixels.Pixel ratio approximately 1:1.An Input mechanism one of the following: keypad, keyboardor touch screen.Two-way network connection.The classes a MIDP application can use come from packages

in both the CLDC and the MIDP. The packages the CLDC hasare: java.lang, java.io, java.util, javax.microedition.io. Thepackages the MID profile adds are: javax.microedition.lcdui,

javax.microedition.midlet and javax.microedition.rms.


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belski eLearning



J2ME(CLDC\MIDP) java.lang package is a subset of the

J2SE java.lang package.

J2ME(CLDC\MIDP) doesnt allow controlling the class loader.

J2ME(CLDC\MIDP) doesnt support object finalization.

J2ME(CLDC\MIDP) doesnt support reflection.


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belski eLearning



J2ME(CLDC\MIDP) doesnt support a mechanism (like the

JNI) that enables writing native methods.

J2ME(CLDC\MIDP) multi threading mechanism is very

similar to the one that the J2SE has.

J2ME(CLDC\MIDP) Math class is a subset.

J2ME(CLDC\MIDP) has smaller version of the String and

the StringBuffer classes.


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belski eLearning



J2ME(CLDC\MIDP) has smaller version of the System and

the Runtime classes.

J2ME(CLDC\MIDP) java.util package includes only few of

the classes and interface that exist in the J2SE version.

J2ME(CLDC\MIDP) java.io package include only few of the

classes and the interfaces that exist in the J2SE version.


49/70


belski eLearning



The J2ME application model is very similar to the one used

by Java applets and Java servlets.

You need to declare a class that extends the Midlet class.

That class must be public and it must include a constructor

without parameters.


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belski eLearning



import javax.microedition.midlet.*;

import javax.microedition.lcdui.*;

public class Hello extends MIDlet

{

private Display display;

private Form form;

public Hello()

{

form = new Form("Hello");

display = Display.getDisplay(this);

}

public void startApp()

{

display.setCurrent(form);

}

public void pauseApp() { }

public void destroyApp(boolean cond) { }}


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belski eLearning



Run the Wireless Toolkit.


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belski eLearning



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belski eLearning



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belski eLearning



Create new project.

File -> New Project

Fill in the details of the new project.

Project Name

The project name is the name of the project you choose for your new work.

MIDlet Class Name

The MIDlet class name is the name of the class you declared as one that

extends Midlet. When developing a J2ME application composed of several

classes, among those classes there must be a class that extends Midlet. That

would be the main class (similar to the Applet model).


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belski eLearning



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belski eLearning



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belski eLearning



Press the Create Project button to create your project.

The wizard pop up dialog window allows you to configure

the project you are about to develop.

Press OK when the project configuration pop up window dialogis shown. For now we will accept all default setting.


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belski eLearning



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belski eLearning



One of the outcomes for creating the new project is the

creation of folders hierarchy specifically for the new project.

Each project has its own specific folder.

All projects folders are kept within the apps folder.

Each project folder includes the following sub folders:

bin ...this folder will include the JAR/JAD created files.

src ...this folder should include all project source code.

lib ...this folder should include all additional third party classes we add.

res ...this folder should include all additional resource files (images, sound etc.).


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belski eLearning



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belski eLearning



Write your source code and save it within the src folder.

Choose Build to compile & preverify your code.

When developing a J2ME application there is a need topreverify the source code (in addition to the compilation). TheKVM unlike the JVM is not capable of doing all code checksbefore it runs it. Therefore, these checks are carried out via thepreverification stage.


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belski eLearning



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belski eLearning



Choose Project -> Package -> Create Package in order

to create the JAR/JAD files.


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belski eLearning



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belski eLearning



You can now find the JAR/JAD files within the bin folder of

your project.

You can install the JAR and the JAD files on your mobile

telephone.

Alternatively, you can choose Run and run your code via

the wireless toolkit on one of its emulators.


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belski eLearning


Click to add title

Click to add an outline


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belski eLearning


Click to add title



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belski eLearning


Click to add title



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belski eLearning


The Java Application Manager (JAM)

The MIDlet life cycle is controlled by the Java Application

Manager (JAM).

The JAM is a MIDlet management software that controls the process of

installing, running and removing the MIDlets.

When the user chooses to run a MIDlet, it is the JAM that

creates an instance of the MIDlet class and runs methods

on it.

The sequence of method that will be invoked on the MIDlet subclass instance is

defined by the MIDlet life cycle. Like the servlets and the applets, the midlets

also have a well-defined set of states.


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The Java Application Manager (JAM)

The JAM calls various methods on the midlet to signify

changes from one state to another.

These methods include the following: startApp(), pauseApp(), destroyApp() and

the MIDlet subclass constructors as well.

Introduction to J2ME, Albeski

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