697: Sidetrip

You may, if you wish, create a subclass of the ApplicationClosingWindowListener that alters or supplements the behavior of the superclass. For example, suppose that you want your users to be told when Java is about to exit from an application. Then, you could define the following PausingWindowListener subclass. There is no need to define most of the methods required by the WindowListener interface, because all but one of those methods is defined adequately in the superclass. You do, however, wish to define windowClosing such that it pops up a message window, arranged by the JOptionPane class method, showMessageDialog. After you click your acknowledgement, windowClosing calls the windowClosing method in the ApplicationClosingWindowListener superclass, which shuts down the application.

import javax.swing.*; 
import java.awt.event.*; 
public class PausingWindowListener 
       extends ApplicationClosingWindowListener { 
 private MovieApplication application; 
 public PausingWindowListener (MovieApplication a) { 
  application = a; 
 } 
 public void windowClosing(WindowEvent e) { 
  JOptionPane.showMessageDialog(application, "Shutting down..."); 
  super.windowClosing(e); 
 } 
}