updatemidlet.java

来自「JAVAME Core technology and best practice」· Java 代码 · 共 53 行

package com.j2medev.chapter3;

import java.util.Random;
import javax.microedition.io.ConnectionNotFoundException;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class UpdateMIDlet extends MIDlet implements CommandListener {
    
    private Display display = null;
    private Form main = new Form("application");
    private Command exitCommand = new Command("Exit",Command.EXIT,1);
    
    public void startApp() {
        if (display == null) {
            display = Display.getDisplay(this);
            main.append("when quit application,check update");
            main.addCommand(exitCommand);
            main.setCommandListener(this);
        }
        display.setCurrent(main);
    }
    
    public void pauseApp() {
    }
    
    public void destroyApp(boolean unconditional) {
    }

    private boolean checkUpdate(){
        //返回值为1需要更新，0不需要更新
        int i = (new Random().nextInt()>>>1)%2;
        return (i>0)?true:false;
    }
    public void commandAction(Command command, Displayable displayable) {
        if(command == exitCommand){
            //退出前检查是否需要更新MIDlet套件
            if(checkUpdate()){
                try{
                    //从jad文件中读取更新中心的地址并更新
                    String url = this.getAppProperty("update");
                    if(url != null)
                        platformRequest(url);
                }catch(ConnectionNotFoundException ex){
                    ex.printStackTrace();
                }
            }
            destroyApp(true);
            notifyDestroyed();
        }
    }
}