直接上代码了。

package cn.hncu.threadDemo.thread2;import java.awt.Canvas;import java.awt.Color;import java.awt.Graphics;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.FocusEvent;import java.awt.event.FocusListener;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;import javax.swing.JSpinner;import javax.swing.Timer;import javax.swing.event.ChangeEvent;import javax.swing.event.ChangeListener;public class BallsJFrame extends JFrame implements ChangeListener{
         private BallsCanvas ball;    private JSpinner spinner;    public BallsJFrame(){        super("弹弹球");        this.setBounds(300, 200, 400, 300);        this.setDefaultCloseOperation(EXIT_ON_CLOSE);        Color colors[] = {Color.red,Color.green,Color.blue,Color.magenta,Color.cyan};        ball = new BallsCanvas(colors,100);        this.getContentPane().add(ball);//默认是CENTER位置        JPanel panel = new JPanel();        this.getContentPane().add(panel,"South");        panel.add(new JLabel("Delay"));        spinner = new JSpinner();        spinner.setValue(100);        panel.add(spinner);        spinner.addChangeListener(this);        this.setVisible(true);    }    @Override    public void stateChanged(ChangeEvent e) {        int value = Integer.parseInt(""+spinner.getValue());        ball.setDelay(value);    }    public static void main(String[] args) {        new BallsJFrame();    }}class BallsCanvas extends Canvas implements ActionListener, FocusListener{    private Ball balls[];//存放所有的球    private Timer timer;//javax.swing.Timer    public BallsCanvas(Color colors[] ,int delay){        this.balls = new Ball[colors.length];        for(int i=0,x=40;i
     
      =this.getWidth()-24){                balls[i].left = !balls[i].left;//切换方向            }            //让每个球的坐标变化一下---（y坐标）            balls[i].y = balls[i].up ? balls[i].y-10:balls[i].y+10;            //当球碰壁时，更改球的方向            if(balls[i].y<=0||balls[i].y>=this.getHeight()-22){                balls[i].up = !balls[i].up;//切换方向            }            g.fillOval(balls[i].x, balls[i].y, 20, 20);        }    }    @Override    public void actionPerformed(ActionEvent e) {        //System.out.println("aaa");        repaint();//刷新画布.调用paint(Graphics g)    }    @Override    public void focusGained(FocusEvent e) {        timer.stop();    }    @Override    public void focusLost(FocusEvent e) {        timer.restart();    }    private static class Ball{
             int x,y;        boolean up,left;        Color color;        public Ball(int x, int y, Color color) {            this.x = x;            this.y = y;            this.color = color;            up = left = false;        }    }}