挡板接小球（Java小程序）

package ball;
import javax.swing.JFrame;
public class BallFrame {
    public static void main(String[] args) {
        JFrame f=new JFrame();
        BallPanel p=new BallPanel();
        f.add(p);
        f.setTitle("挡板接小球");
        f.setSize(800, 600);
        f.setLocationRelativeTo(null);//居中
        f.setDefaultCloseOperation(3);
        f.setVisible(true); 
        f.addMouseMotionListener(p);
        f.addMouseListener(p);
        p.move();
        
    }

}

package ball;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
/*
 * 状态：1.就绪 2.运行 3.暂停 4.结束 5.重新开始
 * 就绪--->运行    点击鼠标
 * 运行--->暂停     移出鼠标
 * 运行--->结束   
 * 暂停---.>运行   移入鼠标
 * 结束----> 重新开始 点击鼠标
 * 重新开始---. >运行
 */

import javax.swing.JOptionPane;
import javax.swing.JPanel;
@SuppressWarnings("serial")
public class BallPanel extends JPanel implements MouseMotionListener,MouseListener {
    int state=1;
    public static final int START=1;
    public static final int RUNNING=2;
    public static final int PAUSE=3;
    public static final int OVER=4;
    public static final int RESTART=5;
    
    int px = 200;
    int bx = 300, by = 100;
    int score=0,pw=200;
    boolean flag=true;//游戏没结束
    // 定义变量表示小球的路径
    int dir = (int) (Math.random() * 4) + 1;
    int sleep=30;
    Color c=Color.RED;
    @Override
    public void paint(Graphics g) {
        // TODO 自动生成的方法存根
        super.paint(g);
//        int c=getRandColorCode();
        g.setColor(c);
        g.fillOval(bx, by, 50, 50);
        g.setColor(Color.BLACK);
        g.fillRect(px, 500, pw, 10);
        g.setColor(Color.BLUE);
        g.setFont(new Font("宋体",Font.BOLD,24));
        g.drawString("游戏得分："+score, 20,50);
        if(state==PAUSE){
            g.drawString("游戏暂停", 300, 200);
            
        }
    }
       
    
    public void move() {
        new Thread() {
            public void run() {
                while (true) {
                    if(state==RUNNING){
                    if (dir == 1) {
                        bx += 10;
                        by += 10;
                    }
                    if (dir == 2) {
                        bx -= 10;
                        by += 10;
                    }
                    if (dir == 3) {
                        bx -= 10;
                        by -= 10;
                    }
                    if (dir == 4) {
                        bx += 10;
                        by -= 10;
                    }
                    if (bx > 700) {
                        if (dir == 1) {
                            dir = 2;
                        }
                        if (dir == 4) {
                            dir = 3;
                        }
                    }
                    if (bx < 0) {
                        if (dir == 2) {
                            dir = 1;
                        }
                        if (dir == 3) {
                            dir = 4;
                        }
                    }
                    if (by > 450) {
                        if (px-50<bx&&bx < (px + 200)) {
                            if (dir == 1) {
                                dir = 4;
                            }
                            if (dir == 2) {
                                dir = 3;}
                               score+=5;
                               //长度
                             if(score%20==0){
                                 if(pw>200){
                                     pw-=20; } }
                             
                  c=new Color ((int)(Math.random()*256),    
                               (int)(Math.random()*256),
                               (int)(Math.random()*256));}
                        else
                        {
                         by = 450;    
                         state=OVER;
    //JOptionPane.showMessageDialog(null,"游戏结束,你得了"+score+"分","GAMEOVER",JOptionPane.INFORMATION_MESSAGE);
                      
                        }
                    }
                    if (by < 0) {
                        if (dir == 4) {
                            dir = 1;
                        }
                        if (dir == 3) {
                            dir = 2;
                        }
                    }

                    repaint();
                    try {
                        Thread.sleep(sleep-score/20);
                    } catch (InterruptedException e) {
                        // TODO 自动生成的 catch 块
                        e.printStackTrace();
                    }
                }
            }}
        }.start();
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        // TODO 自动生成的方法存根

    }

    @Override
    public void mouseMoved(MouseEvent e) {
        // TODO 自动生成的方法存根
        px = e.getX() - 200;
        // 把鼠标的坐标给挡板
        repaint();

    }

    @Override
    public void mouseClicked(MouseEvent e) {
        // TODO 自动生成的方法存根
        if(state==START){
            state=RUNNING;}
        else if (state==PAUSE){
            state=RUNNING;}
        else if(state==OVER){
            score=0;
            bx=400;
            by=100;
            state=RUNNING;    
            }
         repaint();
    }

    @Override
    public void mousePressed(MouseEvent e) {
        // TODO 自动生成的方法存根
        
    }

    @Override
    public void mouseReleased(MouseEvent e) {
        // TODO 自动生成的方法存根
        
    }

    @Override
    public void mouseEntered(MouseEvent e) {
        // TODO 自动生成的方法存根
        if(state==PAUSE){
            state=RUNNING;
        }
    }

    @Override
    public void mouseExited(MouseEvent e) {
        // TODO 自动生成的方法存根
        if(state==RUNNING){
            state=PAUSE;}
        
    }

    

}