Keyboard input with KeyAdapter

Question

I'm trying to make a simple game in java where you can move the player (Defender) in the 4 directions. I tried to make the key detecting with a key adapter, but it doesn't work. What could be the problem (I tried to do a System.out.println at the key press to make sure that the problem isn't at the Defender)? Code:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class DefenderComponent extends JPanel implements ActionListener {
    private static final long serialVersionUID = 1L;

    private static final int WIDTH = 160;
    private static final int HEIGHT = 120;
    private static final int SCALE = 4;

    Defender player = new Defender();

    public DefenderComponent() {
        Dimension size = new Dimension(WIDTH * SCALE, HEIGHT * SCALE);
        setMinimumSize(size);
        setMaximumSize(size);
        setPreferredSize(size);

        addKeyListener(new TKeyListener());

        Timer timer = new Timer(5, this);
                timer.start();
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Test2");
        frame.add(new DefenderComponent());
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        frame.setFocusable(true);

        new DefenderComponent();
    }


    public void paintComponent(Graphics g){
        Graphics2D g2d = (Graphics2D) g;
        Image i = player.getImage();
        g2d.drawImage(i, player.getX(), player.getY(), i.getWidth(this) * SCALE, i.getHeight(this) * SCALE, this);
    }

    public void actionPerformed(ActionEvent e) {
        player.move();
        repaint();  
    }
}

Answer 1

KeyEvents are only generated for the component that has focus. A JPanel is not focusable by default.

Don't use a KeyListener. Instead you should be using Key Bindings which are more flexible.

See Motion Using the Keyboard for more information and examples.