bounceexpress.java

此示例效果用Java多线程来实现,通过设置线程的优先级,来控制小球的运行速度. 程序运行后,单击"Start"按钮,弹出一个黑色小球 单击"Express"按钮,弹出一个红色小球.如果你的内存足够

//BounceExpress.java

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;

public class BounceExpress{
  public static void main(String[] args)
  {
    JFrame frame =new BounceFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.show();
  }
}

class BounceFrame extends JFrame{

  public static final int WIDTH=450;
  public static final int HEIGHT=350;
  private BallCanvas canvas;

  public BounceFrame()
  {
    setSize(WIDTH, HEIGHT);
    setTitle("BounceExpress");

    Container contentPane=getContentPane();
    canvas=new BallCanvas();
    contentPane.add(canvas, BorderLayout.CENTER);

    JPanel buttonPanel=new JPanel();
    addButton(buttonPanel, "Start",
              new ActionListener()
              {
                public void actionPerformed(ActionEvent evt)
                {
                  addBall(Thread.NORM_PRIORITY, Color.black);
                }
              });
    addButton(buttonPanel, "Express",
              new ActionListener()
              {
                public void actionPerformed(ActionEvent evt)
                {
                  addBall(Thread.NORM_PRIORITY+2, Color.red);
                }
              });
     addButton(buttonPanel, "Close",
               new ActionListener()
               {
                 public void actionPerformed(ActionEvent evt)
                 {
                   System.exit(0);
                 }
               });
      contentPane.add(buttonPanel, BorderLayout.SOUTH);
  }

  public void addButton(Container c, String title, ActionListener listener)
  {
        JButton button=new JButton(title);
        c.add(button);
        button.addActionListener(listener);
  }

  public void addBall(int priority, Color color)
  {
    Ball b=new Ball(canvas, color);
    canvas.add(b);
    BallThread thread=new BallThread(b);
    thread.setPriority(priority);
    thread.start();
  }
}

class BallCanvas extends JPanel{

  private ArrayList balls=new ArrayList();

  public void add(Ball b)
  {
    balls.add(b);
  }
  public void paintComponent(Graphics g)
  {
    super.paintComponent(g);
    Graphics2D g2=(Graphics2D)g;
    for(int i=0; i<balls.size();i++)
    {
      Ball b=(Ball)balls.get(i);
      b.draw(g2);
    }
  }
}

class BallThread extends Thread{

  private Ball b;

  public BallThread(Ball aBall)
  {
    b=aBall;
  }
  public void run()
  {
    try{
      for(int i=1; i<=1000; i++)
      {
        b.move();
        sleep(3);
      }
    }
    catch(InterruptedException exception){}
  }
}

class Ball{
  private static final int XSIZE=15;
  private static final int YSIZE=15;
  private Component canvas;
  private Color color;
  private int x=0;
  private int y=0;
  private int dx=2;
  private int dy=2;

  public Ball(Component c, Color aColor)
  {
    canvas=c;
    color=aColor;
  }

  public void draw(Graphics2D g2)
  {
    g2.setColor(color);
    g2.fill(new Ellipse2D.Double(x,y, XSIZE, YSIZE));
  }

  public void move()
  {
    x+=dx;
    y+=dy;
    if(x<0)
    {
      x=0;
      dx=-dx;
    }
    if(x+XSIZE>=canvas.getWidth())
    {
      x=canvas.getWidth()-XSIZE;
      dx=-dx;
    }
    if(y<0)
    {
      y=0;
      dy=-dy;
    }
    if(y+YSIZE>=canvas.getHeight())
    {
      y=canvas.getHeight()-YSIZE;
      dy=-dy;
    }
    canvas.repaint();
  }
}