Repaint轨迹保留？（待处理，待编辑）

 1 import java.awt.Color;
 2 import java.awt.Graphics;
 3 
 4 import javax.swing.JFrame;
 5 import javax.swing.JPanel;
 6 
 7 
 8 public class SimpleAnimation {
 9 
10     /**
11      * @param args
12      */
13     int x=0,y=0;
14     public static void main(String[] args) {
15         // TODO Auto-generated method stub
16         SimpleAnimation gui=new SimpleAnimation();
17         gui.test();
18     }
19     public void test() {
20         JFrame frame=new JFrame();
21         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
22         
23         MyDrawPanel drawPanel=new MyDrawPanel();
24         
25         frame.getContentPane().add(drawPanel);
26         frame.setSize(500, 500);
27         frame.setVisible(true);
28         
29         for (int i = 0; i < frame.getHeight()-60; i++) {
30             x++;
31             y++;
32             drawPanel.repaint();
33             try {
34                 Thread.sleep((int)(Math.random()*140));
35             } catch (Exception ex) {
36                 // TODO: handle exception
37                 ex.printStackTrace();
38             }
39         }
40     }
41     class MyDrawPanel extends JPanel{
42         public void paintComponent(Graphics g) {
43             int red=(int)(Math.random()*255);
44             int green=(int)(Math.random()*255);
45             int blue=(int)(Math.random()*255);
46             g.setColor(Color.red);
47             g.fillRect(0, 0, this.getWidth(), this.getHeight());
48             g.setColor(new Color(red,green,blue));
49             g.fillOval(x, y, 40, 40);
50         }
51     }
52 
53 }