Java开发网 - Re:java.lang.NullPointerException

Java开发网

您没有登录

» Java开发网 » Java SE 综合讨论区 » Java与OOP初步

打印话题 寄给朋友 订阅主题

作者

Re:java.lang.NullPointerException [Re:linqiuppp]

linqiuppp

发贴: 8
积分: 0

于 2005-10-25 00:48

哪位大吓愿意指点小弟一下！下面是源程序。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.geom.*;

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

class BoundFrame extends JFrame
{
public BoundFrame()
{
setTitle("BoundThread");
setSize(500,400);
panel=new BoundPanel();
Container contentPane=getContentPane();
contentPane.add(panel,BorderLayout.CENTER);
JButton start=new JButton("Start");
JButton close=new JButton("Close");
start.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
Ball ball=new Ball(panel);
panel.add(ball);
BallThread thread=new BallThread(ball);
thread.start();

}
});

close.addActionListener(new ActionListener()
{
  public void actionPerformed(ActionEvent event)
   {
     System.exit(0);
   }

});
  JPanel buttonPanel=new JPanel();
  buttonPanel.add(start);
  buttonPanel.add(close);
  contentPane.add(buttonPanel,BorderLayout.SOUTH);
}

private BoundPanel panel;
}

class BallThread extends Thread
{
public BallThread(Ball aball)
{
  ball=aball;

}
public void run()
{
try{

  for(int i=0;i<10000;i++)
   {
      ball.move();
      sleep(5);
   }
   }
  catch( InterruptedException e){}
}

private Ball ball;
}

class BoundPanel extends JPanel
{
public void add(Ball aball)
{
balls.add(aball);
}

public void paintComponent(Graphics g)
{
super.paintComponent Present

;

Graphics2D g2=(Graphics2D)g;

for(int i=0;i<balls.size();i++)
{
Ball ball=(Ball)balls.get Light Bulb

;
g2.fill(new Ellipse2D.Double(ball.x,ball.y,ball.Scale,ball.Scale));
}
}
private ArrayList balls;
}

class Ball
{
public Ball(Component apanel)
{
panel=(BoundPanel)apanel;

}
public void move()
{
x=x+dx;
y=y+dy;
if(x<0){x=0;dx=-dx;}
if(y<0){y=0;dy=-dy;}
if(x+Scale>panel.getWidth()) {x=panel.getWidth()-Scale;dx=-dx;}
if(y+Scale>panel.getHeight()) {y=panel.getHeight()-Scale;dy=-dy;}
panel.repaint();
}
private BoundPanel panel;
private int dx=2;
private int dy=2;
public int x=0;
public int y=0;
public int Scale=10;

}

• 有了Swing为什么还要SWT?

话题树型展开

人气	标题	作者	字数	发贴时间
21287	java.lang.NullPointerException	linqiuppp	49	2005-10-25 00:46
19176	Re:java.lang.NullPointerException	linqiuppp	2539	2005-10-25 00:48
19028	Re:java.lang.NullPointerException	linqiuppp	29	2005-10-25 15:11
19558	Re:java.lang.NullPointerException	andony756	156	2005-11-27 14:33
18784	Re:java.lang.NullPointerException	why	233	2005-11-27 19:15
18848	Re:java.lang.NullPointerException	youyigong	146	2005-11-28 13:56
18939	Re:java.lang.NullPointerException	andony756	1368	2005-11-28 21:21
19121	Re:java.lang.NullPointerException	ntshenwh	128	2005-11-28 22:09
18820	Re:java.lang.NullPointerException	andony756	156	2005-11-28 22:32
18765	Re:java.lang.NullPointerException	why	561	2005-11-29 18:22
18825	Re:java.lang.NullPointerException	andony756	113	2005-11-29 20:37
18660	Re:java.lang.NullPointerException	why	340	2005-11-30 17:50
18789	Re:java.lang.NullPointerException	wangyabing	49	2005-12-29 16:22
18807	Re:java.lang.NullPointerException	why	131	2005-12-29 20:46

已读帖子

新的帖子

被删除的帖子