我的代码给全了啊！ 我把我的程序代码和运行时抛出的异常标示如下，麻烦大家看一下，我实在是被这一类问题烦死了，谢谢大家帮忙一下吧！！！ （本程序中用到的为一张28*40像素png格式的图片） import javax.microedition.lcdui.*; import java.util.*; import java.io.*; import javax.microedition.midlet.*;

public class yuchun extends MIDlet implements CommandListener{ private Command cmd_exit; public Display display; mycanvas canvas; public yuchun(){ canvas=new mycanvas(display.getDisplay(this)); } public void startApp(){ Command cmd_exit=new Command("exit",Command.EXIT,1); canvas.addCommand(cmd_exit); canvas.setCommandListener(this); canvas.start(); } public void pauseApp(){} public void destroyApp(boolean a){} public void commandAction(Command c,Displayable d){ if(c==cmd_exit){ canvas.stop(); destroyApp(false); notifyDestroyed(); } } }//class yuchun

import javax.microedition.lcdui.*; import javax.microedition.lcdui.game.*; import java.util.*; import java.io.*;

public class mycanvas extends GameCanvas implements Runnable{ //定义的GameCanvas一个类mycanvas private Sprite yuchu; private long frameDelay; public boolean sleeping; public int x=0,y=0; private Display display; private Random rand;

public mycanvas(Display d){ super(true); display=d; frameDelay=33; }

public void start(){ display.setCurrent(this); rand=new Random(); sleeping=false; try{ yuchu=new Sprite(Image.createImage("1.png")); }catch(IOException e){System.err.println("failure");} yuchu.setPosition(0,0); Thread t=new Thread(this); t.start(); }

public void run(){ Graphics g=getGraphics(); while(!sleeping){ update(); draw(g); try{Thread.sleep(frameDelay); }catch(InterruptedException e){} } }

public void stop(){ sleeping=true; }

public void update(){ if(rand.nextInt()%5==0){ int a=Math.max(-8,rand.nextInt()%2); x=Math.min(a,8); int b=Math.max(-8,rand.nextInt()%2); y=Math.min(b,8); yuchu.move(x,y); }

if(yuchu.getX()<=-yuchu.getWidth()) // 此段代码为如果精灵超出了显示范围，就折回屏幕的另一端 yuchu.setPosition(getWidth(),yuchu.getY()); else if(yuchu.getX()>=getWidth()) yuchu.setPosition(-yuchu.getWidth(),yuchu.getY()); if(yuchu.getY()<=-yuchu.getHeight()) yuchu.setPosition(yuchu.getX(),getHeight()); else if(yuchu.getY()>=getHeight()) yuchu.setPosition(yuchu.getX(),-yuchu.getHeight()); }

public void draw(Graphics g){ g.setColor(0,0,0); g.fillRect(0,0,getWidth(),getHeight()); yuchu.paint(g); flushGraphics(); } }//class mycanvas 以下为程序在运行过程中抛出的异常：

项目设置已保存 正在生成 "pro1" 生成完成 正在通过存储根 DefaultColorPhone 来运行 failure startApp threw an Exception java.lang.NullPointerException java.lang.NullPointerException at mycanvas.start(+58) at yuchun.startApp(+36) at javax.microedition.midlet.MIDletProxy.startApp(+7) at com.sun.midp.midlet.Scheduler.schedule(+270) at com.sun.midp.main.Main.runLocalClass(+28) at com.sun.midp.main.Main.main(+116)

[此贴子已经被作者于2005-10-26 22:35:29编辑过]