[Solved]how to add KeyListener to JPanel from another class

Newbie & Debugging Questions
#1

Hello,
i have a class that implements KeyListener (Control.java) and i want to use that KeyListener in a class that extends JPanel and implements Runnable (Screen.java)
how do i do that ?
notice that i have another class that extends JFrame (Frame.java) which i already added the panel into it

i hope what i said make sense :stuck_out_tongue:

thank you

#2

if i understand correctly, you want to add an instance of Control as KeyListener to an instance of Screen?
that would be


theScreenInstance.addKeyListener(theControlInstance);
#3

yes but it didn’t work :confused:
wont me to post the full code ?

#4

Maybe the culprit is focus. Try


mypanel.setFocusible(true);
#5

still doesn’t work :clue:
codes :

the panel :

import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JPanel;

public class Screen extends JPanel implements Runnable {
	Thread thread = new Thread(this);

	public static Ball ball;
	public static Player player;
	public static Control control;
	
	public static boolean isFirst = true;
	
	public static int screenWidth,screenHeight,screenX,screenY;

	public Screen() {
		thread.start();
		
		this.addKeyListener(control);
		this.setFocusable(true);
	}

	public void define() {
		control = new Control();
		ball = new Ball(ball.x, ball.y, ball.height, ball.width);
		player = new Player(player.x,player.y,player.width,player.height,player.speed);
		
		screenWidth = this.getWidth();
		screenHeight=this.getHeight();
		
		
	}

	public void paintComponent(Graphics g) {

		if (isFirst) {
			define();
		}
		g.setColor(new Color(0, 0, 0));
		g.fillRect(screenX, 0, screenWidth, screenHeight);

		g.setColor(new Color(250, 50, 0));
		ball.move(ball.x, ball.y);
		ball.draw(g);
		g.setColor(new Color(255,255,255));
		player.draw(g);
		

	}

	public void run() {
		// while is true
		while (true) {
			// do stuff

			if (!isFirst) {
				
			}

			repaint();
			
			try {
				// make the thread slee every 1 milliSecond
				// the try and catch are auto-generated
				Thread.sleep(5);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

}

the Key class

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;


public class Control implements KeyListener{

	@Override
	public void keyPressed(KeyEvent e) {
		// TODO Auto-generated method stub
		if(e.getKeyCode()==e.VK_RIGHT){
			System.out.println("Right");
		}else if(e.getKeyCode()==e.VK_LEFT){
			System.out.println("LEFT");
		}
		
	}

	@Override
	public void keyReleased(KeyEvent e) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void keyTyped(KeyEvent e) {
		if(e.getKeyCode()==e.VK_RIGHT){
			System.out.println("Right");
		}else if(e.getKeyCode()==e.VK_LEFT){
			System.out.println("LEFT");
		}
		
	}

}

the frame class

import java.awt.Dimension;

import javax.swing.JFrame;


public class Frame extends JFrame  {

	public static Dimension size = new Dimension(800,600);
	public static String title ="Pong2.0";

	public Frame(){
		
		this.setSize(size);
		this.setTitle(title);
		//this.setLocationRelativeTo(null);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		init();
		
	}
	
	public void init(){
		
		Screen screen = new Screen();

		this.add(screen);
		
	
		
		this.setVisible(true);
		
	}
	
	
	
	
	public static void main(String args[]){
		Frame frame = new Frame();
	}
	
}
#6

You are not initializing the [icode]control[/icode] variable!

Call [icode]define()[/icode] first before creating the thread. Remove the [icode]isFirst[/icode] part.

So the constructor becomes


public Screen()
{
    define();
    thread.start();
    addKeyListener(control);
    setFocusable(true);
}
#7

Thank you ;D