WindowListener in Java Using NetBeans IDE

Introduction

This article describes how a Window Listener can be used in Java. The NetBeans IDE is used for the development of the example.

What a Window Listener is

A Window Listener is used to listen for window events. It has the following seven methods:

windowOpened(WindowEvent e)
This method is called when the window is first made visible.
windowClosing(WindowEvent e)
This method is called when the user attempts to close the window.
windowClosed(WindowEvent e)
This method is called when the window gets closed.
windowIconified(WindowEvent e)
This method is called when the user minimizes the window.
windowDeiconified(WindowEvent e)
This method is just the opposite of the method windowIconified, this method is called when the window is changed from the minimized state to normal state.
windowActivated(WindowEvent e)
This method is called when the window is set to be active the window, only a dialog or a frame can be set to be an active window.
windowDeactivated(WindowEvent e)
This method is called when the window will no longer be the active window.

Packages imported

java.awt.*;

AWT stands for Abstract Window Toolkit, AWT is basically imported to use AWT components like label, frame and so on.

java.awt.event.*;

This package is basically imported to handle the action events.

Example

In this example; we implement a Window Listener in Java using the Netbeans IDE. There are certain steps in the Netbeans IDE that we need to follow as explained below.

Step 1

Open the Netbeans IDE and click on "File" -> "New project" then choose Java project then provide the name (for example "CloseFrame") then click on "Ok" then right-click on our project and choose "New" -> "Java class" and then provide your class name (CloseFrame.java) and click "Ok" then supply the following code for it.

Step 2

In the class use the following code (in this example only one method is shown, in other words windowClosing):

import java.awt.*;

import java.awt.event.*;

class CloseFrame extends Frame implements WindowListener

{

Label label;

CloseFrame(String title)

{

setTitle(title);

label=new Label("Close the frame");

addWindowListener(this);

}

void launchFrame()

{

setSize(300,300);

setVisible(true);

}

public void windowActivated(WindowEvent e)

{

}

public void windowClosed(WindowEvent e)

{

}

public void windowClosing(WindowEvent e)

{

System.exit(0);

}

public void windowDeactivated(WindowEvent e)

{

}

public void windowDeiconified(WindowEvent e)

{

}

public void windowIconified(WindowEvent e)

{

}

public void windowOpened(WindowEvent e)

{

}

public static void main(String[] args)

{

CloseFrame cd=new CloseFrame("Close Window");

cd.launchFrame();

}

Step 3

Now go to "CloseFrame" and right-click on that, click on "Run" from the menu bar as in the following:

Output

The output shows the window:

Now you can close the window by clicking on the close icon on the menu bar.