Moving a rectangle in JPanel with arrow keys using KeyListener

Question

I have been trying to make a JPanel move with the arrow keys. It has not been working. I believe it is my inner class that extends the KeyAdapter. I'm also not sure about the ActionListener implemented were it is. The other class I have made does not matter since it is just the frame.

package jerryWorlds;

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

public class Jerry extends JPanel implements ActionListener{

int SizeX, SizeY, PosX, PosY, VelX, VelY;
Image img;
Timer time = new Timer(1, this);

public Jerry(){
    ImageIcon i = new ImageIcon();
    addKeyListener(new AL());
    time.start();
    img = i.getImage();
    PosX = 375;
    PosY = 250;
}

public void paint(Graphics g){
    Graphics2D g2d = (Graphics2D)g;
    g2d.fillRect(PosX, PosY, 50, 100);
}
public void actionPerformed(ActionEvent e) {
    PosX = PosX + VelX;
    repaint();
}

private class AL extends KeyAdapter{
    public void keyPressed(KeyEvent e) {
        int key = e.getKeyCode();
        System.out.println("YAY!");
        if(key == KeyEvent.VK_LEFT)
            VelX = -1;
        else if(key == KeyEvent.VK_RIGHT)
            VelX = 1;
    }

    public void keyReleased(KeyEvent e) {
        int key = e.getKeyCode();
        if(key == KeyEvent.VK_LEFT)
            VelX = 0;
        else if(key == KeyEvent.VK_RIGHT)
            VelX = 0;
    }
}

}

This post by @camickr, regarding [Motion Using the Keyboard](http://tips4java.wordpress.com/2013/06/09/motion-using-the-keyboard/), will definitely add something to your knowledge :-). Seems like your question is not written in the write sense, looking at the code it appears you wanted to draw a new rectangle as you press arrow keys, you really not moving your `JPanel` as stated in your title... — nIcE cOw, Jun 22 '13 at 01:30

score 5 · Answer 1 · edited May 23 '17 at 10:32

You will want to search this site for similar questions, as they usually have the same issue and same answer.
They will tell you that focus is one problem since a component's KeyListener won't work unless it has focus.
They will tell you that regardless you shouldn't use KeyListener at all but rather Key Bindings.
They will tell you not to override paint(...) but rather paintComponent(...) unless you are sure that you want to override painting of a component's borders and children (you don't).
They will tell you to be sure to call the super method inside of paintComponent(...).

Also please have a look at this animation and key bindings example.

Moving a rectangle in JPanel with arrow keys using KeyListener

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