SWING - ContainerListener Interface

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Introduction

The interface ContainerListener is used for receiving container events. The class that processes container events needs to implements this interface.

Class Declaration

Following is the declaration for java.awt.event.ContainerListener interface −

public interface ContainerListener
extends EventListener

Interface Methods

Sr.No.	Method & Description
1	void componentAdded(ContainerEvent e) Invoked when a component has been added to the container.
2	void componentRemoved(ContainerEvent e) Invoked when a component has been removed from the container.

Methods Inherited

This class inherits methods from the following interfaces −

• java.awt.event.EventListener

ContainerListener Example

Create the following Java program using any editor of your choice in say D:/ > SWING > com > tutorialspoint > gui >

SwingListenerDemo.java

package com.tutorialspoint.gui;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class SwingListenerDemo {
   private JFrame mainFrame;
   private JLabel headerLabel;
   private JLabel statusLabel;
   private JPanel controlPanel;

   public SwingListenerDemo(){
      prepareGUI();
   }
   public static void main(String[] args){
      SwingListenerDemo  swingListenerDemo = new SwingListenerDemo();  
      swingListenerDemo.showContainerListenerDemo();
   }
   private void prepareGUI(){
      mainFrame = new JFrame("Java SWING Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));

      headerLabel = new JLabel("",JLabel.CENTER );
      statusLabel = new JLabel("",JLabel.CENTER);        
      statusLabel.setSize(350,100);
      
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }        
      });    
      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);  
   }
   private void showContainerListenerDemo(){
      headerLabel.setText("Listener in action: ContainerListener");      

      JPanel panel = new JPanel();      
      panel.setBackground(Color.magenta);            
      panel.addContainerListener(new CustomContainerListener());  

      JLabel msglabel = new JLabel("Welcome to TutorialsPoint SWING Tutorial."
         ,JLabel.CENTER);        
      panel.add(msglabel);

      controlPanel.add(panel);
      mainFrame.setVisible(true);  
   }
   
   class CustomContainerListener implements ContainerListener {
      public void componentAdded(ContainerEvent e) {
         statusLabel.setText(statusLabel.getText() 
            + e.getComponent().getClass().getSimpleName() + " added. ");
      }
      public void componentRemoved(ContainerEvent e) {
         statusLabel.setText(statusLabel.getText() 
            + e.getComponent().getClass().getSimpleName() + " removed. ");
      }
   }
}

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

D:\SWING>javac com\tutorialspoint\gui\SwingListenerDemo.java

If no error occurs, it means the compilation is successful. Run the program using the following command.

D:\SWING>java com.tutorialspoint.gui.SwingListenerDemo

Verify the following output.