Graphical User Interfaces - Java - page 566

Figure 14-5. WindowListener, WindowAdapter, and my WindowCloser

Let's put this all together in some code examples. Class WindowDemo2 puts up a JFrame and
closes when you ask it to. The online source includes the older AWT Frame-based Win-
dowDemo .

public public class class WindowDemo2 WindowDemo2 extends extends JFrame {

public public static void main ( String [] argv ) {

JFrame f = new

static void

new WindowDemo2 ();
f . setVisible ( true true );

}
public

public WindowDemo2 () {
setSize ( 200 , 100 );
setDefaultCloseOperation ( WindowConstants . DO_NOTHING_ON_CLOSE );
addWindowListener ( new new WindowDemoAdapter ());

}

/** Named Inner class that closes a Window. */
class class WindowDemoAdapter WindowDemoAdapter extends extends WindowAdapter {

public public void void windowClosing ( WindowEvent e ) {

// whimsy - close randomly, ~ 1 times in 3
iif ( Math . random () > 0.666 ) {
System . out . println ( "Goodbye!" );
WindowDemo2 . this . setVisible ( false

false ); // window will close

WindowDemo2 . this . dispose (); // and be freed up.

System . exit ( 0 );

}
System . out . println ( "You asked me to close, but not to I chose." );

}

}

}

Because making a Window close—and optionally exit the program—is a common operation,
I've encapsulated this into a small class called WindowCloser , which is in my public pack-
age com.darwinsys.util . Most AWT and Swing books have similar classes. Example 14-5
contains my WindowCloser class. Note that the class is marked deprecated; this serves as a