bounceball.java

来自「java课件 java课件 java课件 java课件」· Java 代码 · 共 45 行

//<applet code="BounceBall.class" width="300" height="200">
//</applet>
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class BounceBall extends JApplet {
  Timer timer;
  BallPanel p=null;
  
  public void init(){
    p=new BallPanel();
    p.setBackground(Color.LIGHT_GRAY);
    getContentPane().add(p);
  }
  public void start(){
    timer=new Timer(20,p);
    timer.start();
  }
 }
class BallPanel extends JPanel implements ActionListener{
    private int x=-1;
    private int y=-1;
    private int dx=2;
    private int dy=2;
    private int w=0;
    private int h=0;
   public void paintComponent(Graphics g){
   	 super.paintComponent(g);
   	 w=getSize().width;
     h=getSize().height;  	
     g.setColor(Color.BLUE);
     x=x+dx;
     y=y+dy;
     if(x>w-50|x<-1) 
       dx=-dx;
     if(y>h-50|y<-1) 
       dy=-dy;
     g.fillOval(x,y,50,50);  	 
   }	 
   public void actionPerformed(ActionEvent e){
     repaint();
   }	 
}