traffic.java

编写一个Swing应用程序

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

public class traffic extends SimpleFrame{
		   public traffic(int width,int height) {
        super(width,height);
        setTitle("红绿灯");
        
        ColorPanel panel=new ColorPanel();
        Container contentPane=getContentPane();
        contentPane.add(panel);
    }
    
    public static void main(String[] args){
        traffic frame=new traffic(400,300);
        frame.setVisible(true);
    }    
}

class ColorPanel extends JPanel{
    public ColorPanel(){
        redButton= new  JButton("红灯");
        greenButton=new  JButton("绿灯");
        yellowButton=new  JButton("黄灯");
        add(redButton);
        add(greenButton);
        add(yellowButton);
        redButton.addActionListener(new ColorActionListener());
        yellowButton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent event){
                setyellow();
            }
        });
        greenButton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent event){
                setgreen();
            }
        });
    }
    
    private void setyellow(){
    	w=3;
    	repaint();
	}
    
    private void setgreen(){
        w=2;
        repaint();
     }
    
    private class ColorActionListener implements ActionListener{
        public void actionPerformed(ActionEvent event){
             setred();
      }
    }
    
   public void paintComponent(Graphics g)  {
        super.paintComponent(g);
       switch(w){
       	case 1:g.setColor(Color.RED);
        	   g.fillOval(90,100,50,50);
        break;
        case 2:g.setColor(Color.GREEN);
           	   g.fillOval(160,100, 50, 50);
        break;
     	case 3:g.setColor(Color.yellow);
        	   g.fillOval(230,100, 50, 50);
 }
     }
    

	private void setred(){
      w=1;
      repaint();
    }
    
    private Color backgroundColor;
    private Color g;
    private JButton redButton;
    private JButton greenButton;
    private JButton yellowButton;
    public int w;
}