Tag: KeyListener

This post continues a serie of posts I’m writing about 2D game development in Java.
A simple example of an JPanel that implements KeyListener (and a little trick) to handle KeyEvents to move a white square.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class KeyPanel extends JPanel implements KeyListener{
    private int x=50,y=50;
    public KeyPanel() {
        JTextField textfield = new JTextField();
        textfield.addKeyListener(this);
        add(textfield);
        textfield.setPreferredSize(new Dimension(0,0));
    }

    public void keyTyped(KeyEvent e) {}

    public void keyReleased(KeyEvent e) {}

    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_LEFT)
            x-=5;
        if (e.getKeyCode() == KeyEvent.VK_RIGHT)
            x+=5;
        if (e.getKeyCode() == KeyEvent.VK_DOWN)
            y+=5;
        if (e.getKeyCode() == KeyEvent.VK_UP)
            y-=5;
        this.repaint();
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(Color.black);
        g.fillRect(0, 0, 500, 500);
        g.setColor(Color.white);
        g.fillRect(x, y, 50, 50);
    }
}

Download the complete NetBeans source project files: KeyTest.tar.bz2.