关键侦听器在JApplet中不起作用

Question

This is a break the brick type of game where the user cannot let the ball fall below the paddle. By the way paddle_x is sets the x coordinate of the paddle. I have a MouseListener that works very well however, the KeyListener does not. I am wondering what I am doing wrong and if anyone has any suggestions.

public PaintSurface() {
    addMouseMotionListener(new MouseMotionAdapter() 
    {
        public void mouseMoved(MouseEvent e)
        {
            if (e.getX() - 30 - paddle_x > 5)
                english  = 1.5f;
            else if(e.getX() - 30 - paddle_x < -5)
                english = - 1.5f;
            else
                english = 1.0f;
            paddle_x = e.getX() - 30;
        }
    });
    addKeyListener(new KeyListener() {

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

        }

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

        }

        @Override
        public void keyPressed(KeyEvent e) {
            // TODO Auto-generated method stub
            if(e.getID() == KeyEvent.KEY_TYPED){
                if(e.getKeyChar() == KeyEvent.VK_RIGHT){
                    paddle_x += 30;
                }
                else if (e.getKeyChar() == KeyEvent.VK_LEFT){
                    paddle_x -= 30;
                }
            }
        }
    });


    ball = new Ball(20);

}

Answer 1

The Component which has a registered KeyListener must have focus for the KeyListener to fire. Call requestFocus on the Component to request that the component has focus, or use KeyBindings (recommended)

In addition, the keyPressed method has a conditional that checks the ID against KeyEvent.KEY_TYPED events (which will never happen).