使用箭头键移动JLabel

Question

Sorry, for double posting, already posted this question once, but I realized I weren't explicit enough. I still haven't managed to find an answer to my question so I'll try to better describe my problem here:

I have the following classes:

public class Paddle extends JLabel {}
public class Canvas extends JPanel implements Runnable {}

Now, when I start the thread described in Canvas, I want an infinite loop (loops while program is exited). In this loop I've got a DIRECTION variable. When the left arrowkey is pressed I'd like this to be set -1. If right arrow key is pressed I'd like +1 to be it's value. If neither of the above cases is true, it's value should default 0.

I hope I was more explicit this time. If not please tell.

Answer 1

Well, to get the keystrokes you need to have a class that implements KeyListener

Like this:

public class MyKeyListener implements KeyListener, MouseListener{
   int direction = 0;

    public void keyPressed(KeyEvent e) {
        if(e.getKeyCode()  == KeyEvent.VK_LEFT) direction = -1;
        else if(e.getKeyCode()  == KeyEvent.VK_RIGHT) direction = 1;
    }

    public void keyReleased(KeyEvent e) {
        direction = 0;
    }
}

Then in your initialization code (for example, in the constructor of your JPanel derived class) you set the key listener to an instance of your MyKeyListener class

   MyKeyListener  mk = new MyKeyListener();
   this.addKeyListener(mk);

In your loop, you just look at the direction feild of mk;