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.