Window Listener Event in Advanced Java Programming

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The WindowListener interface defines seven methods for handling window events. An application of the WindowListener interface is to close a Frame window. The seven methods of the WindowListener interface are:

1. void windowActivated(WindowEvent we) Is invoked when a window is activated.
2. void windowDeactivated(WindowEvent we) Is invoked when a window is deactived.
3. void windowOpened(WindowEvent we) Is invoked when a window is opened.
4. void windowClosed(WindowEvent we) Is invoked when a window is closed.
5. void windowClosing(WindowEvent we) Is invoked when a window is closing
6. void windowIconified(WindowEvent we) Is invoked when a window minimized.
7. void windowDeiconfied(WindowEvent we) Is invoked when a window is restored.

The addWindowListener() method enables monitoring a window for the occurrence of a window event. The following program code shows how to implement the WindowListener interface:

Implementing the WindowListener Interface:
/* =========================================================== File Name : WindowListenerTest.java WebSite : http://javaproglang.blogspot.in/ Facebook : https://www.facebook.com/AdvanceJavaProgramming Twitter ID : https://twitter.com/AdvanceJava Created By : Bintu Chaudhary =========================================================== */ import java.awt.*; import java.applet.*; import java.awt.event.*; public class WindowListenerTest extends Frame implements WindowListener { Label l1,l2; TextField t1,t2; Button b1; public WindowListenerTest() { super("Implementing Window Listener"); setLayout(new GridLayout(4,2)); l1=new Label("Name"); l2=new Label("Password"); t1=new TextField(10); t2=new TextField(10); t2.setEchoChar('*'); b1=new Button("Send"); add(l1); add(t1); add(l2); add(t2); add(b1); addWindowListener(this); } public static void main(String args[]) { WindowListenerTest d=new WindowListenerTest(); d.setSize(400,400); d.setVisible(true); } public void windowClosing(WindowEvent we) { this.setVisible(false); System.exit(0); } public void windowActivated(WindowEvent we) { } public void windowDeactivated(WindowEvent we) { } public void windowOpened(WindowEvent we) { } public void windowClosed(WindowEvent we) { } public void windowIconified(WindowEvent we) { } public void windowDeiconified(WindowEvent we) { } }

The above code shows closing a Frame window using the WindowListener interface. the windowClosing() method uses the setVisible method to close the frame window. The System.exit(0) method stop the program from runing and code will be stored in the file called WindowListenerTest.java, which on compilation will crate a class file called WindowListenerTest.class. Now compile this file using below commands in the DOS mode:

C:\>jdk1.4\bin>javac WindowListenerTest.java
C:\>jdk1.4\bin>java WindowListenerTest

"Output of WindowListenerTest.java"

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