package com.j2medev.chapter2;

import java.io.IOException;
import java.util.TimerTask;
import java.util.Timer;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class HelloMIDlet extends MIDlet implements CommandListener {
    
    private Display display = null;
    private Command exitCommand = new Command("Exit",Command.EXIT,1);
    
    public void startApp() {
        //初始化display和MyCanvas對象
        display = Display.getDisplay(this);
        MyCanvas canvas = new MyCanvas();
        canvas.addCommand(exitCommand);
        canvas.setCommandListener(this);
        display.setCurrent(canvas);
    }
    
    public void pauseApp() {
    }
    
    public void destroyApp(boolean unconditional) {
    }
    
    public void commandAction(Command cmd,Displayable displayable){
        if(cmd == exitCommand){
            //退出應(yīng)用程序
            destroyApp(false);
            notifyDestroyed();
        }
    }
    
    class MyCanvas extends Canvas{
        
        private Timer timer = new Timer();//定時器
        private int x = 10;
        private int y = 10;
        private int width = 0;//畫布的寬度
        private int height = 0;//畫布的高度
        private Image img = null;
        
        public MyCanvas(){
            width = getWidth();
            height = getHeight();
            try{
                img = Image.createImage("/helloworld.png");
            }catch(IOException ex){
                ex.printStackTrace();
            }
        }
        
        public void paint(Graphics g){
            int color = g.getColor();
            g.setColor(0xFFFFFF);
            g.fillRect(0,0,width,height);
            g.setColor(color);
            g.drawImage(img,x,y,Graphics.LEFT|Graphics.TOP);
        }
        //當(dāng)Canvas顯示到當(dāng)前屏幕的時候此方法自動被調(diào)用
        public void showNotify(){
            //啟動定時器，每100毫秒執(zhí)行一次
            timer.schedule(new TimerTask(){
                
                private int dx = 2;
                private int dy = 2;
                public static final int SIGN = -1;
                
                public void run(){
                    x = x + dx;
                    y = y + dy;
                    //判斷圖片是否到達屏幕邊界
                    if(x+2+img.getWidth() > width || x-2 < 0)
                        dx = SIGN*dx;
                    if(y + 2 +img.getHeight()> height || y-4 < 0)
                        dy = SIGN*dy;
                    repaint();
                    serviceRepaints();
                }
            },0,100);
        }
        //當(dāng)Canvas從當(dāng)前屏幕刪除的時候此方法被調(diào)用
        public void hideNotify(){
            timer.cancel();
            img = null;
        }
    }
}