KeyListener in Java

Question

Hello everyone I am new to Java so i think the answer to this question is very easy but I can't find out what part i'm doing wrong.. I added a keyListener to my pacman game but somehow it won't work.. i've used the following code:

package h04PacMan;

import java.awt.event.*;

import javax.swing.*;

public class PacManBediening extends JPanel implements ActionListener, KeyListener {

private JButton links, rechts, boven, beneden;
PacMan pacman;

public PacManBediening(PacMan pacman) {

    this.pacman = pacman;

    links = new JButton("<");
    links.addActionListener(this);
    add(links);

    rechts = new JButton(">");
    rechts.addActionListener(this);
    add(rechts);

    boven = new JButton("^");
    boven.addActionListener(this);
    add(boven);

    beneden = new JButton("v");
    beneden.addActionListener(this);
    add(beneden);

}

/*
 * bediening bij een klik
 */

@Override
public void actionPerformed(ActionEvent e) {

    if(e.getSource() == links) {

        pacman.setRichtingEnSnelheid( -10 );
        pacman.setBesturing(0);
        pacman.setView(180);
        //System.out.println("links");
    }
    else if(e.getSource() == rechts) {
        pacman.setRichtingEnSnelheid( +10 );
        pacman.setBesturing(0);
        pacman.setView(0);
        //System.out.println("rechts");
    }
    else if(e.getSource() == boven) {
        pacman.setRichtingEnSnelheid( -10);
        pacman.setBesturing(1);
        pacman.setView(90);
        //System.out.println("boven");
    }
    else {
        pacman.setRichtingEnSnelheid( +10);
        pacman.setBesturing(1);
        pacman.setView(270);
        //System.out.println("beneden");
    }


}

@Override
public void keyPressed(KeyEvent e) {

    int key = e.getKeyCode();

    if(key == KeyEvent.VK_LEFT) {
        pacman.setRichtingEnSnelheid( -10 );
        pacman.setBesturing(0);
        pacman.setView(180);
        System.out.println("links");
    }
    else if(key == KeyEvent.VK_RIGHT) {
        pacman.setRichtingEnSnelheid( +10 );
        pacman.setBesturing(0);
        pacman.setView(0);
        System.out.println("rechts");
    }
    else if(key == KeyEvent.VK_UP) {
        pacman.setRichtingEnSnelheid( -10);
        pacman.setBesturing(1);
        pacman.setView(90);
        System.out.println("boven");
    }
    else if(key == KeyEvent.VK_DOWN) {
        pacman.setRichtingEnSnelheid( +10);
        pacman.setBesturing(1);
        pacman.setView(270);
        System.out.println("beneden");
    }

}

@Override
public void keyReleased(KeyEvent arg0) {
    // TODO Auto-generated method stub

}

@Override
public void keyTyped(KeyEvent arg0) {
    // TODO Auto-generated method stub

}

}

can someone tell me what to add or do different?

well if i use my arrow controls nothing happens and i also don't see the system.out.prinln I wrote under the controls so the whole method is not called i think — Reshad, Oct 12 '12 at 14:38
I can only guess. You need to add a key listener to the component that has focus, otherwise the event will not fire. — jjnguy, Oct 12 '12 at 14:41

score 2 · Accepted Answer · answered Oct 12 '12 at 14:45

2

You're missing a couple of lines in your PacManBediening constructor.

this.pacman = pacman;
this.setFocusable(true);
this.addKeyListener(this);

answered Oct 12 '12 at 14:45

Gilbert Le Blanc

50,182
6
67
111

Thanks alot this were the lines i missed! – Reshad Oct 12 '12 at 14:49

score 2 · Answer 2 · edited May 23 '17 at 11:43

2

KeyListener isn't designated for Swing JComponents, I wouldn't going this way,
I think there is simple and possible to lost the Focus from focusable JComponents
use KeyBindings as most scallable workaround, rather that "catching or hunting for Focus" for KeyListener
for Swing JComponents are all internal short_cuts, key shortcuts, built_in methods, notifiers, based on KeyBindings
code example

edited May 23 '17 at 11:43

Community

1
1

answered Oct 12 '12 at 15:24

mKorbel

109,525
20
134
319

as i mentioned i am new to Java so I am just trying stuff out by creating this pacman game. I experienced the problem of KeyListener and I took a look at the code example but I can't understand everything that is in the code yet so I don't know what it does or what parts are relevant yet.. :( – Reshad Oct 12 '12 at 16:04
@Reshad no problem with you nor personally, my answer here is to ---> `can someone tell me what to add or do different?` – mKorbel Oct 12 '12 at 16:07
ah I understand! :) well I will try to redesign my code to work with keyBindings but can't promise it'll work! – Reshad Oct 12 '12 at 21:55

KeyListener in Java

2 Answers2