ComputerScienceExpert
$18/per page/
Hardware/Software Setup Required
Problem Description
J2ME is a Java-based runtime platform created by Sun Microsystems. It is targeted for devices that are small, standalone, network connectable, or embedded, such as cellular phones or personal digital assistants (PDAs). J2ME allows users to use the Java language and related tools to create programs for small mobile wireless devices.
In this Lab, you will need to read more about J2ME and then write a simple J2ME application that prints “Hello, World!”.
Outcome
Report the steps to perform the tasks
Validation/Evaluation
Assignment help
Code for a simple J2ME application that prints “Hello, World!”.
package hello;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class HelloMIDlet extends MIDlet implements CommandListener {
private boolean midletPaused = false;
private Command exitCommand;
private Form form;
private StringItem stringItem;
/**
* The HelloMIDlet constructor.
*/
public HelloMIDlet() {
}
/**
* Initilizes the application.
* It is called only once when the MIDlet is started. The method is called before the <code>startMIDlet</code> method.
*/
private void initialize() {
}
/**
* Performs an action assigned to the Mobile Device - MIDlet Started point.
*/
public void startMIDlet() {
switchDisplayable(null, getForm());
}
/**
* Performs an action assigned to the Mobile Device - MIDlet Resumed point.
*/
public void resumeMIDlet() {
}
/**
* Switches a current displayable in a display. The <code>display</code> instance is taken from <code>getDisplay</code> method. This method is used by all actions in the design for switching displayable.
* @param alert the Alert which is temporarily set to the display; if <code>null</code>, then <code>nextDisplayable</code> is set immediately
* @param nextDisplayable the Displayable to be set
*/
public void switchDisplayable(Alert alert, Displayable nextDisplayable) {
Display display = getDisplay();
if (alert == null) {
display.setCurrent(nextDisplayable);
} else {
display.setCurrent(alert, nextDisplayable);
}
}
/**
* Called by a system to indicated that a command has been invoked on a particular displayable.
* @param command the Command that was invoked
* @param displayable the Displayable where the command was invoked
*/
public void commandAction(Command command, Displayable displayable) {
if (displayable == form) {
if (command == exitCommand) {
exitMIDlet();
}
}
}
/**
* Returns an initiliazed instance of exitCommand component.
* @return the initialized component instance
*/
public Command getExitCommand() {
if (exitCommand == null) {
exitCommand = new Command("Exit", Command.EXIT, 0);
}
return exitCommand;
}
/**
* Returns an initiliazed instance of form component.
* @return the initialized component instance
*/
public Form getForm() {
if (form == null) {
form = new Form("Welcome", new Item[] { getStringItem() });
form.addCommand(getExitCommand());
form.setCommandListener(this);
}
return form;
}
/**
* Returns an initiliazed instance of stringItem component.
* @return the initialized component instance
*/
public StringItem getStringItem() {
if (stringItem == null) {
stringItem = new StringItem("Hello", "Hello, World!");
}
return stringItem;
}
/**
* Returns a display instance.
* @return the display instance.
*/
public Display getDisplay () {
return Display.getDisplay(this);
}
/**
* Exits MIDlet.
*/
public void exitMIDlet() {
switchDisplayable (null, null);
destroyApp(true);
notifyDestroyed();
}
/**
* Called when MIDlet is started.
* Checks whether the MIDlet have been already started and initialize/starts or resumes the MIDlet.
*/
public void startApp() {
if (midletPaused) {
resumeMIDlet ();
} else {
initialize ();
startMIDlet ();
}
midletPaused = false;
}
/**
* Called when MIDlet is paused.
*/
public void pauseApp() {
midletPaused = true;
}
/**
* Called to signal the MIDlet to terminate.
* @param unconditional if true, then the MIDlet has to be unconditionally terminated and all resources has to be released.
*/
public void destroyApp(boolean unconditional) {
}
}