SWING - KeyListener Interface


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The class which processes the KeyEvent should implement this interface. The object of that class must be registered with a component. The object can be registered using the addKeyListener() method.

Interface Declaration

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

public interface KeyListener
   extends EventListener

Interface Methods

Sr.No. Method & Description
1

void keyPressed(KeyEvent e)

Invoked when a key has been pressed.

2

void keyReleased(KeyEvent e)

Invoked when a key has been released.

3

void keyTyped(KeyEvent e)

Invoked when a key has been typed.

Methods Inherited

This interface inherits methods from the following interfaces −

java.awt.EventListener

KeyListener 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.showKeyListenerDemo();
   }
   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 JTextField textField;
   private void showKeyListenerDemo(){
      headerLabel.setText("Listener in action: KeyListener");      
      textField  = new JTextField(10);
      textField.addKeyListener(new CustomKeyListener());
      JButton okButton = new JButton("OK");
      
      okButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            statusLabel.setText("Entered text: " + textField.getText());                
         }
      });
      controlPanel.add(textField);
      controlPanel.add(okButton);    
      mainFrame.setVisible(true);  
   }
   class CustomKeyListener implements KeyListener{
      public void keyTyped(KeyEvent e) {
      }
      public void keyPressed(KeyEvent e) {
         if(e.getKeyCode() == KeyEvent.VK_ENTER){
            statusLabel.setText("Entered text: " + textField.getText());
         }
      }
      public void keyReleased(KeyEvent e) {
      }   
   }
}

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.

SWING KeyListener
swing_event_listeners.htm

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