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AWT ComponentListener Interface

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componentlistener

In this topic, we will discuss ComponentListener in the AWT interface. The object of that class must be registered with a component. The object can be registered using the addComponentListener() method. Component events are raised for information only.

Interface declaration

Following is the declaration for java.awt.event.ComponentListener interface:

public interface ComponentListener
   extends EventListener

Interface methods

S.N.Method & Description
1void componentHidden(ComponentEvent e)Invoked when the component has been made invisible.
2void componentMoved(ComponentEvent e)Invoked when the component’s position changes.
3void componentResized(ComponentEvent e)Invoked when the component’s size changes.
4void componentShown(ComponentEvent e)Invoked when the component has been made visible.

Methods inherited

This interface inherits methods from the following interfaces:

  • java.awt.EventListener

ComponentListener Example

Create the following java program using any editor of your choice in say D:/ > AWT > com > adglob > gui >AwtListenerDemo.java

package com.adglob.gui;

import java.awt.*;
import java.awt.event.*;

public class AwtListenerDemo {
   private Frame mainFrame;
   private Label headerLabel;
   private Label statusLabel;
   private Panel controlPanel;

   public AwtListenerDemo(){
      prepareGUI();
   }

   public static void main(String[] args){
      AwtListenerDemo  awtListenerDemo = new AwtListenerDemo();  
      awtListenerDemo.showComponentListenerDemo();
   }

   private void prepareGUI(){
      mainFrame = new Frame("Java AWT Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }        
      });    
   
      headerLabel = new Label();
      headerLabel.setAlignment(Label.CENTER);
      statusLabel = new Label();        
      statusLabel.setAlignment(Label.CENTER);
      statusLabel.setSize(350,100);

      controlPanel = new Panel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);  
   }

   private void showComponentListenerDemo(){
      headerLabel.setText("Listener in action: ComponentListener");      

      ScrollPane panel = new ScrollPane();      
      panel.setBackground(Color.magenta);            

      Label msglabel = new Label();
      msglabel.setAlignment(Label.CENTER);
      msglabel.setText("Welcome to Adglob AWT Tutorial.");
      panel.add(msglabel);

      msglabel.addComponentListener(new CustomComponentListener());      
      controlPanel.add(panel);
      mainFrame.setVisible(true);  
   }

   class CustomComponentListener implements ComponentListener {

      public void componentResized(ComponentEvent e) {
         statusLabel.setText(statusLabel.getText() 
         + e.getComponent().getClass().getSimpleName() + " resized. ");
      }

      public void componentMoved(ComponentEvent e) {
         statusLabel.setText(statusLabel.getText() 
         + e.getComponent().getClass().getSimpleName() + " moved. ");
      }

      public void componentShown(ComponentEvent e) {
         statusLabel.setText(statusLabel.getText() 
         + e.getComponent().getClass().getSimpleName() + " shown. ");
      }

      public void componentHidden(ComponentEvent e) {
         statusLabel.setText(statusLabel.getText() 
         + e.getComponent().getClass().getSimpleName() + " hidden. ");
      }
   }
}

Compile the program using command prompt. Go to D:/ > AWT and type the following command.

D:\AWT>javac com\adglob\gui\AwtListenerDemo.java

If no error comes that means compilation is successful. Run the program using the following command.

D:\AWT>java com.adglob.gui.AwtListenerDemo

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