j2me 线程与Command的有关问题

j2me 线程与Command的问题
今天我用j2me实现一个很简单的程序,程序的实现功能是通过每点击一次软键Start,就会在Canvase画板上画一个小球,并且小球会在频幕上走动,碰到墙壁就会反弹.我本来的意思是,点一次软键Start,就创建一个线程处理一个小球行走路线,但在测试的过程,发现当点击一次软键Start第一个线程启动(线程是在commandAction内开始的)以后,软键Start就无效了,再怎么点也没效果,用Println()测试,发现原来commandAction没有被持行.
哪位大虾能给我讲下为什么吗,并且给出解决办法?谢谢.
下面给出未完成的代码,帮我看看.

import   javax.microedition.lcdui.Canvas;
import   javax.microedition.lcdui.Command;
import   javax.microedition.lcdui.CommandListener;
import   javax.microedition.lcdui.Displayable;
import   javax.microedition.lcdui.Graphics;

public   class   LuckyBollCanvas   extends   Canvas   {

private   int   x;//球的x坐标
private   int   y;//球的y坐标
private   int   offx,offy;//球跳跃的步长
public   boolean   pause;//控制是否结束

public   LuckyBollCanvas()   {
//   TODO   Auto-generated   constructor   stub

offx=offy=20;
x=(this.getWidth()+offx)/2;
y=(this.getHeight()+offy)/2;
pause=false;

this.addCommand(new   Command( "Start ",Command.OK,1));
this.addCommand(new   Command( "Stop ",Command.BACK,1));
this.setCommandListener(new   CanvasCommand());
}

protected   void   paint(Graphics   arg0)   {
//   TODO   Auto-generated   method   stub
//刷新画板
arg0.setColor(255,   255,   255);
arg0.fillRect(0,   0,   this.getWidth(),   this.getHeight());
//画球
arg0.setColor(0,   0,   0);
arg0.fillArc(x,   y,   20,   20,   0,   360);
}
//线程内部类
class   LuckyBollThread   implements   Runnable{
public   LuckyBollThread()   {
super();
//   TODO   Auto-generated   constructor   stub
this.run();
}

public   void   run()   {
while   (pause)   {
//   TODO   Auto-generated   method   stub
x+=offx;
y+=offy;
if(x <0)
{
offx=20;
x=0;
}else   if(x> getWidth()-offx)
{
x=getWidth()-offx;
offx=-20;
}
if(y <0)
{
offy=20;
y=0;
}else   if(y> getHeight()-offy)
{
y=getHeight()-offy;
offy=-20;
}
repaint();
serviceRepaints();
try   {
Thread.sleep(1000);
}   catch   (InterruptedException   e)   {
//   TODO   Auto-generated   catch   block
e.printStackTrace();
}
}
}

}
//Command内部类
class   CanvasCommand   implements   CommandListener{

public   void   commandAction(Command   arg0,   Displayable   arg1)   {
//   TODO   Auto-generated   method   stub
switch(arg0.getCommandType())
{
case   Command.OK:
System.out.println( "aaaaaaaaaaaa ");//测试
pause=true;
LuckyBollThread   t=new   LuckyBollThread();
break;
case   Command.BACK:
pause=false;
System.out.println( "bbbbbbbbbb ");//测试
break;
}
}

}
}

------解决方案--------------------------------------------------------
这样写可能简单些：

import java.awt.*;
import java.awt.event.*;

class Ball extends Thread
{
private Canvas c;