Java KeyListener

Java KeyListener:

Java KeyListener listens for key events. They are represented by objects implementing the KeyListener interface (located in the java.awt.event package). KeyListener specifies three methods that must be implemented by a KeyListener’s class. These methods have the following signatures.

• public abstract void keyPressed (KeyEvent e)
• public abstract void keyReleased (KeyEvent e)
• public abstract void keyTyped (KeyEvent e)

The keyPressed method is called when a key-pressed event occurs, the keyReleased method is called when a key-released event occurs, and the keyTyped method is called when a key-typed event occurs. To register with a key source, a KeyListener must call the source’s addKeyListener method. (To de-register, a KeyListener would call the source’s removeKeyListener method).

Sample Code for Java KeyListener:

Download the image from here and paste it into the java project folder.

Output: Moveable image. Press keys a, w, s, and d.

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

public class Key_listener extends JFrame implements KeyListener{
	
	JLabel label;
	ImageIcon icon;
	
	Key_listener(){
		

		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		this.setSize(400,400);
		this.setLayout(null);
		this.addKeyListener(this);
		
		icon = new ImageIcon("rocket_icon.jpg");
		
		label = new JLabel();
		label.setBounds(0, 0, 100, 100);
		label.setIcon(icon);
		//label.setBackground(Color.GREEN);
		//label.setOpaque(true);
		
		this.getContentPane().setBackground(Color.WHITE);
		this.add(label);
		this.setVisible(true);
	
	}
	
	
    @Override
	public void keyTyped(KeyEvent e) {
		// TODO Auto-generated method stub
    	
    	switch(e.getKeyChar()) {
		  case 'a': label.setLocation(label.getX()-10, label.getY());
		    break;
		  case 'w': label.setLocation(label.getX(), label.getY()-10);
		    break;
		  case 's': label.setLocation(label.getX(), label.getY()+10);
		    break;
		  case 'd': label.setLocation(label.getX()+10, label.getY());
		    break;
		    
    	}
		
	}


	@Override
	public void keyPressed(KeyEvent e) {
		// TODO Auto-generated method stub
		
		switch(e.getKeyCode()) {
		  case 37: label.setLocation(label.getX()-10, label.getY());
		    break;
		  case 38: label.setLocation(label.getX(), label.getY()-10);
		    break;
		  case 39: label.setLocation(label.getX()+10, label.getY());
		    break;
		  case 40: label.setLocation(label.getX(), label.getY()+10);
		    break;
		}
		
	}


	@Override
	public void keyReleased(KeyEvent e) {
		// TODO Auto-generated method stub
		
		System.out.println("You released key char: " + e.getKeyChar());
		System.out.println("You released key code: " + e.getKeyCode());
		
	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub
    new Key_listener();


	}

}