[german]MIDlet-States für Anfänger[/german][english]MIDlet-States for beginners[/english]

[german]Bei der recherche nach den MIDlet-States erstellte ich folgendes Programm. Vielleicht ist es für Andere ((Kommentare willkommen)) hilfreich. Außerdem fand ich folgende Dinge heraus:

  • Nokia 6300 (Symbian Series 40) kennt keinen pausierten Status für MIDlets
  • SonyEricsson K800i kann MIDlets pausieren (aus dem MIDlet und auch aus dem Telefon)
  • Wenn das K800i das MIDlet in den Hintergrund packt, werden weder pauseApp() noch startApp() aufgerufen – das Midlet läuft also vollständig im Hintergrund.
  • K800i kann nur dann wirklich pausieren, wenn man in der pauseApp() das currentDisplay auf null setzt (display.setCurrent(null);). Ein einfaches Aufrufen von notifyPaused() funktioniert nicht.
  • Suns Wireless Toolkit reagiert auf pauseApp() und notifyPaused() gleichermaßen.

[english]While exploring the MIDlet-States i created the following program. Maybe it is useful ((Comments welcome *hint*)) for others. In writing the program the following peculiarities were found:

  • Nokia 6300 (Symbian Series 40) apparently does not know a paused-state
  • SonyEricsson K800i can pause MIDlets (either from the MIDlet itself or by the phone’s request)
  • If the telephone sets the midlet to paused state neither pauseApp() nor startApp() are called. Therefore the MIDlet runs the same way as if it was not paused.
  • K800i can only pause the MIDlet if you set the current display to null inside pauseApp() (display.setCurrent(null);). Simply calling notifyPaused won’t do the trick.
  • Suns Wireless Toolkit reacts to pauseApp() and notifyPaused().



Source-Files and compiled MIDlet as a zip-file (4KB)


import java.util.Timer;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

 * DEMO-Midlet to try State-Changes initiated by AMS and User-interaction
 * Feel free to use and modify this.
 * @author http://amenthes.de
 * @link http://amenthes.de/
 * This is free code. Use, Change and redistribute it to your liking. 
public class StateChanges extends MIDlet implements CommandListener {
	// all my commands
	public static final Command PAUSEAPP = new Command("pauseApp",Command.SCREEN,40);
	public static final Command NOTIFYPAUSE = new Command("notifyPause",Command.SCREEN,40);
	public static final Command DESTROYAPP = new Command("destroyApp",Command.EXIT,40);
	public static final Command NOTIFYDESTROYED = new Command("notifyDestroyed",Command.EXIT,40);
	public static final Command STARTAPP = new Command("startApp",Command.ITEM,40);
	public static final Command RESUMEREQUEST = new Command("resumeRequest",Command.ITEM,40);
	// other stuff
	private Display display;
	private TextBox tb = new TextBox("State-Changes","",2000,TextField.ANY);
	private Timer timer = new Timer();
	protected static StateChanges sc = null;
	public StateChanges() {
		sc = this;
		display = Display.getDisplay(this);

	 * destroyApp, pauseApp and startApp are the abstract methods of MIDlet.
	 * They are called by your device (cellphone, for example). You can also
	 * call them in your application (as we do here with the commands)
	 * These functions should _prepare_ the state-change.
	protected void destroyApp(boolean unconditional) throws MIDletStateChangeException {
		addLine("destroyApp(" + unconditional + ") was called");
	protected void pauseApp() {
		addLine("pauseApp was called");
		timer.schedule(new ResumeTask(this), 5000);
	protected void startApp() throws MIDletStateChangeException {
		addLine("startApp was called");

	 * As you can see we prepare the state-change before actually notifying the AMS.
	 * you will see a difference in behaviour when calling the different
	public void commandAction(Command c, Displayable d) {
		if (c == PAUSEAPP) {
		} else if (c == NOTIFYPAUSE) {
		} else if (c == DESTROYAPP) {
			try{destroyApp(false);} catch (MIDletStateChangeException unhandled) {}
		} else if (c == NOTIFYDESTROYED) {
		} else if (c == STARTAPP) {
			try { startApp(); } catch (MIDletStateChangeException unhandled) {}
		} else if (c == RESUMEREQUEST) {

	 * This function will give you output in two forms: on your Console (if you are running an emulator) and on the device's screen.
	 * @param line What text should be displayed?
	private void addLine(String line) {
		String current = tb.getString();
		tb.setString(current + "\n" + line);


import java.util.TimerTask;
import javax.microedition.midlet.MIDlet;

public class ResumeTask extends TimerTask {
	private MIDlet midlet;
	public ResumeTask(MIDlet parentMidlet) {
		midlet = parentMidlet;
	public void run() {

2 Gedanken zu „[german]MIDlet-States für Anfänger[/german][english]MIDlet-States for beginners[/english]“

  1. Laut Wikipedia gibts kein „Symbian Series 40“, sondern nur „Nokia Series 40“, welches nur von Nokia ohne Symbian entwickelt wird

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