手机上可移动的图片

main programm:ScrollScreen.java

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

public class ScrollScreen extends MIDlet
{
    private Display dispaly=null;
    public void startApp()
    {
        try
        {
            dispaly=Display.getDisplay(this);
            MainCanvas gameCanvas=new MainCanvas(this);
            gameCanvas.start();
            dispaly.setCurrent(gameCanvas);
        }
        catch(Exception ex)
        {
            ex.printStackTrace();
            
        }
    }
    
    public void pauseApp()
    {
    }
    
    public void destroyApp(boolean unconditional)
    {
    }
    public void exit()
    {
        System.gc();
        destroyApp(false);
        notifyDestroyed();
    }
}

Next Programm:MainCanvas.java

import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;


//注意这extends的是GameCanvas而不是Canvas
public class MainCanvas extends GameCanvas implements Runnable, CommandListener  
{
    private ScrollScreen midlet = null;
    private boolean isPlay;
    private long delay; //线程休眠的时间间隔
    private int width; // 屏幕宽度
    private int height; //屏幕高度
    private int scnX, scnY; //可视窗口的左上角坐标
    
    Image backgroundImage;
    private Sprite backgroundSprite;
    private LayerManager layerManager;
    
    public static final Command exitCommand = new Command("退出",Command.EXIT, 1);
    public MainCanvas(ScrollScreen midlet)throws Exception
    {
        
        super(true);
        this.midlet = midlet;
        width = getWidth();
        height = getHeight();
        scnX = 55;
        scnY = 20;
        delay = 20;
        backgroundImage = Image.createImage("/background.png");
        backgroundSprite = new Sprite(backgroundImage);
        layerManager = new LayerManager();
        layerManager.append(backgroundSprite);
        this.addCommand(exitCommand);
        this.setCommandListener(this);
      
    }
    public void start()
    {
        isPlay=true;
        Thread t =new Thread(this);
        t.start();
    }
    public void stop()
    {
        isPlay=false;
    }
    public void run()
    {
        Graphics g=getGraphics();
        while(isPlay==true)
        {
            input();
            drawScreen(g);
            try 
            {
                Thread.sleep(delay);
            }
            catch(InterruptedException ie)
            {
                
            }
        }
    }
    private void input()
    {
        int keyStates = getKeyStates();
        if((keyStates&LEFT_PRESSED)!=0)
        {
            if(scnX-1>0)
            {
                scnX--;
            }
        }
            else if ((keyStates&RIGHT_PRESSED)!=0)
            {
                if(scnX+1+140<backgroundImage.getWidth())
                {
                    scnX++;
                }
            }
            else if((keyStates&UP_PRESSED)!=0)
            {
                if(scnY-1>0)
                {
                    scnY--;
                }
            }
            else if((keyStates&DOWN_PRESSED)!=0)
            {
                if(scnY+1+140<backgroundImage.getHeight())
                {
                    scnY++;
                }
            }
      }
    private void drawScreen(Graphics g)
    {
        g.setColor(0xffffff);
        g.fillRect(0,0,getWidth(),getHeight());
        g.setColor(0x0000ff);
        layerManager.setViewWindow(scnX,scnY,140,140);
        layerManager.paint(g,20,20);
        flushGraphics();
    }
    public void commandAction(Command command, Displayable displayable)
    {
        if(command==exitCommand)
        {
            stop();
            midlet.exit();
        }
    }
    
}