Handling Events - Beginning Java 2 SDK - page 737

FocusAdapter WindowAdapter KeyAdapter

MouseAdapter MouseMotionAdapter MouseInputAdapter

The WindowAdapter class implements all of the methods defined in the WindowListener ,
WindowFocusListener , and WindowStateListener interfaces. The other five each implement the
methods in the corresponding listener interface.

To handle the window closing event for the Sketcher application, we could derive our own class from
the WindowAdapter class and just implement the windowClosing() method. If we also make it an
inner class for the class Sketcher , it will automatically have access to the members of the Sketcher
object, regardless of their access specifiers.

Try It Out - Implementing an Adapter Class
The version of the Sketcher class to implement this will be as follows, with changes to the previous
version highlighted:

// Sketching application
import java.awt.Dimension;
import java.awt.Toolkit;

import java.awt.event.WindowEvent;
import java.awt.event.WindowAdapter;

public class Sketcher {
public static void main(String[] args) {
theApp = new Sketcher(); // Create the application object
theApp.init(); // ...and initialize it
}

// Initialization of the application
public void init() {
window = new SketchFrame("Sketcher");
Toolkit theKit = window.getToolkit(); // Get the window toolkit
Dimension wndSize = theKit.getScreenSize(); // Get screen size

// Set the position to screen center & size to 2/3 screen size
window.setBounds(wndSize.width/6, wndSize.height/6, // Position
2*wndSize.width/3, 2*wndSize.height/3); // Size

window.addWindowListener(new WindowHandler()); // Add window listener
window.setVisible(true); // Display the window
}

// Handler class for window events
class WindowHandler extends WindowAdapter {
// Handler for window closing event
public void windowClosing(WindowEvent e) {
window.dispose(); // Release the window resources
System.exit(0); // End the application
}