containereventdemo.java

《java事件处理指南》一书的代码,好东西

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

public class ContainerEventDemo extends JFrame 
                      implements ContainerListener, ActionListener
{
   private JButton addButton;
   private JTextField jtf;
   private JPanel southPanel, centerPanel;
   private int count;

   public ContainerEventDemo()
   {
      count = 0; 

/*  A JButton and a JTextField are added to a JPanel.         */
/*  The JPanel is placed in the South quadrant of the frame.  */

      addButton = new JButton("add");
      addButton.addActionListener(this);

      jtf = new JTextField(20);
      jtf.setEditable(false);

      southPanel = new JPanel();
      southPanel.add(addButton);
      southPanel.add(jtf);

/*  The centerPanel registers a ContainerListener.            */
/*  The ContainerEventDemo class itself serves as the         */
/*  ContainerListener so the addContainerListener() method    */
/*  is passed the "this" reference.                           */

      centerPanel = new JPanel();
      centerPanel.addContainerListener(this);

      getContentPane().add(southPanel, BorderLayout.SOUTH);
      getContentPane().add(centerPanel, BorderLayout.CENTER);

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 500, 200);
      setVisible(true);
   }

/*  When the "add" button is pressed, a new JButton is placed     */
/*  on the centerPanel.  This action generates a ContainerEvent   */
/*  which is sent to the componentAdded() method.                 */

   public void actionPerformed(ActionEvent event)
   {
      centerPanel.add(new JButton("Button "+count));
      centerPanel.revalidate();//使生效
      ++count;
   }

/*  The componentAdded() method obtains a reference to the JButton  */
/*  that was added to the centerPanel and updates the JTextField    */
/*  to indicate which button was added.                             */  

   public void componentAdded(ContainerEvent event)
   {
      JButton button = (JButton)event.getChild();
      jtf.setText(button.getText()+" was added");
   }

/*  The componentRemoved() method is not used in this example but   */
/*  an implementation must be provided anyway.  It is implemented   */
/*  as a stub method.  This could have been avoided if the          */
/*  ContainerAdapter class had been used.                           */

   public void componentRemoved(ContainerEvent event) {}

   public static void main(String args[])
   {
      ContainerEventDemo adj = new ContainerEventDemo();
   }
}