和luster一起学习java编程(4)

import java.awt.Color;
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;
class SwingUI extends JFrame
implements ActionListener {
   JLabel text, clicked;
   JLabel warn;
   JButton button, clickButton;
   JPanel panel;
   private boolean _clickMeMode = true;
   SwingUI(){ //Begin Constructor
     text = new JLabel("I'm a Simple Program");
     warn = new JLabel("Heheh");
     button = new JButton("Click Me");
     button.addActionListener(this);
     panel = new JPanel();
     panel.setLayout(new BorderLayout());
     panel.setBackground(Color.white);
     getContentPane().add(panel);
     panel.add(BorderLayout.CENTER, text);
     panel.add(BorderLayout.NORTH, warn);
     panel.add(BorderLayout.SOUTH, button);
   } //End Constructor
   public void actionPerformed(ActionEvent event){
        Object source = event.getSource();
        if (_clickMeMode) {
          text.setText("Button Clicked");
          button.setText("Click Again");
          _clickMeMode = false;
        } else {
          text.setText("I'm a Simple Program");
          button.setText("Click Me");
          _clickMeMode = true;
        }
   }
   public static void main(String[] args){
     SwingUI frame = new SwingUI();
     frame.setTitle("Example");
     WindowListener l = new WindowAdapter() {
       public void windowClosing(WindowEvent e) {
         System.exit(0);
       }
     };
     frame.addWindowListener(l);
     frame.pack();
     frame.setVisible(true);
  }
}