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Pass J2ME (1) - MIDP State

摘要: Pass J2ME (1) - MIDP State

对于Midlet状态，有一个叫application management software的会专门负责管理。你所有要关心的，就是怎样和这个AM打交道。

pauseApp()
destroyApp()
startApp()

重写这三个方法。AM将会在相应的时间调用。

而
notifyDestroyed()
notifyPaused()
resumeRequest()
则是让你有机会去通知AM需要做什么。

下面是一个简单的例子，可以根据自己扩充测试一下。有一点比较奇怪的就是，理论上说，在Midlet处于Active状态的时候，如果有电话进入，AM会调用pauseApp()。但是实际测试时，没有发现AM调用这个方法。

package net.csdn.blog.vincint;

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

/**
* This is a simple test to help me understanding the Midlet state
*
*

Title: Midlet Test

*

Description:

*

Copyright: Copyright (c) 2005

*

Company: http://blog.csdn.net/Vincint

* @author Vincint
* @version 1.0
*/
public class MidletState
extends MIDlet
implements
CommandListener {
protected Form form;
protected Command exitCmd;
protected Command debugCmd;
protected Display display;
protected String debug;
public MidletState() {
addDebugInfo("In MidletState()");
display = Display.getDisplay(this);
form = new Form("Hello world.");
form.append("What a new world!");
exitCmd = new Command("Exit", Command.EXIT, 1);
debugCmd = new Command("Debug", Command.SCREEN, 2);
form.addCommand(exitCmd);
form.addCommand(debugCmd);
form.setCommandListener(this);
}

/**
* startApp
*/
protected void startApp() {
addDebugInfo("In startApp()");
display.setCurrent(form);
}

/**
* pauseApp
*/
protected void pauseApp() {
addDebugInfo("In pauseApp()");
}

/**
* destroyApp
*
* @param boolean0 boolean
*/
protected void destroyApp(boolean boolean0) {
addDebugInfo("In destroyApp(" + boolean0 + ")");
}

/**
* commandAction
*
* @param command Command
* @param displayable Displayable
*/
public void commandAction(Command command, Displayable displayable) {
addDebugInfo("In commandAction(...)");
if (command == exitCmd) {
destroyApp(true);
notifyDestroyed();
}
else if (command == debugCmd) {
notifyUser(debug, form);
}
}

protected String addDebugInfo(String debugMsg) {
if (debug == null) {
debug = new String();
}
debug = debug.concat(debugMsg + "\n");
return debugMsg;
}

protected void notifyUser(String message, Displayable screen) {
Alert alert = new Alert("Info", message, null, AlertType.INFO);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert, screen);
}
}