Canvas类画布范围问题....

import javax.microedition.lcdui.Canvas;

import javax.microedition.lcdui.Display;

import javax.microedition.lcdui.Graphics;

import javax.microedition.midlet.MIDlet;

import javax.microedition.midlet.MIDletStateChangeException;



import com.sun.perseus.parser.ColorParser;



public class bool extends MIDlet {

     Display dis;

     Can ca;

	public bool() {

		dis=Display.getDisplay(this);

		ca=new Can();

		ca.setTitle("会滚动的小球");

		dis.setCurrent(ca);

		new Thread(ca).start();

	}

	protected void startApp() throws MIDletStateChangeException {

         

	}



	protected void destroyApp(boolean arg0) throws MIDletStateChangeException {

		// TODO 自动生成方法存根



	}



	protected void pauseApp() {

		// TODO 自动生成方法存根



	}



	class Can extends Canvas implements Runnable

	{

         int x=0,y=0;

         int Width=this.getWidth();

         int Heigth=this.getHeight();

         int dx=8,dy=8;

         final int r=7;

         Can()

         {

        	//setFullScreenMode(true);

         }

         void move()

         {

            x=x+dx;

            y=y+dy;

            if(x+r>=Width)

            {

            	x=Width-r;

            	dx=-dx;

            }

            if(x-r<0)

            {

            	x=0;

            	dx=-dx;

            }

        	if(y+r>=Heigth)

        	{

    

        		y=Heigth-r;

        		dy=-dy;

        	}

        	if(y-r<0)

        	{

        		y=0;

        		dy=-dy;

        	}

         }

         

		protected void paint(Graphics g) {

			g.setColor(250,250,250);

			g.fillRect(0, 0, Width, Heigth);

			move();

			g.setColor(100,255,20);

			g.fillRoundRect(x, y, r,r,90,90);

		}



		public void run() {

			while(true)

			{

				repaint();

				try {

					Thread.sleep(200);

				} catch (InterruptedException e) {

					// TODO 自动生成 catch 块

					e.printStackTrace();

				}

			}

		}

		

	}



}