JAVA----repaint后不执行update

blue601 2010-05-13 09:46:55

都说在repaint()后，系统会自动运行update(),但为什么我这个不执行呢，我想做个类似时钟的，但指针走后会留下痕迹，请指教



import java.awt.*;

import java.util.Date;

import javax.swing.*;



public class DrawClock extends JApplet implements Runnable{



    int xCenter,yCenter,width,height,radius;

    int xSec,ySec,xMin,yMin,xHour,yHour;

    long hour,min,sec;

    Date date;

    Thread clockThread = null;

    public void init(){

        width = 100;

        height = 100;

        xCenter = (int)(width*0.5)+80;

        yCenter = (int)(width*0.5)+80;

        radius = (int)(Math.min(width, height));

    }



    public void start(){

        if(clockThread==null){

            clockThread=new Thread(this);

        }

        clockThread.start();

    }



    public void stop(){

       clockThread = null;

    }

    public void run(){

        while(null!=clockThread){

            

           repaint();

            try{

                Thread.sleep(1000);

            }

            catch(InterruptedException p){

            }

        }

    }



    //public synchronized void update(Graphics g){

public void update(Graphics g){

        g.setColor(Color.BLUE);

        g.fillRect(0, 0,width+1000,height+1000);

        //paint(g);

    }

    

    public void paint(Graphics g){

       

        int x,y;

        g.setColor(Color.red);

        g.drawOval(30,30, width+100, height+100);

        for(int i=0;i<60;i+=5){

            x = (int) (xCenter + radius * Math.sin(i*2*Math.PI/60));

            y = (int) (yCenter - radius * Math.cos(i*2*Math.PI/60));

            g.fillRect(x-1,y-1,3,3);

        }



        date = new Date();

        hour = date.getHours()%12;

        min = date.getMinutes();

        sec = date.getSeconds();



        xSec = (int)(xCenter + radius*0.9*Math.sin(sec*2*Math.PI/60));

        ySec = (int)(yCenter - radius*0.9*Math.cos(sec*2*Math.PI/60));

        g.drawLine(xCenter, yCenter, xSec, ySec);

        repaint();

    }

}