Help making a ball move

Question

Hi all.
I'm trying to make a ball (in a panel) move left and right when I press down left and right keys, but I cant seem to get it working. Can someone please advise me where I might be getting it wrong.
Here is my code:
Frame/Panel class
package movingball;
import java.awt.Graphics;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
public  class  MovingBall  extends  JFrame
    protected  final  int  FRAME_WIDTH  = 240;
    protected  final  int  FRAME_HEIGHT  = 320;
    private BallPanel myPanel;
    public  MovingBall  (String  title)
        super(title);  
        setSize(FRAME_WIDTH,  FRAME_HEIGHT);
        setLocation(400,400);
        setResizable(false);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        myPanel = new BallPanel();        
        add(myPanel);
    private class BallPanel extends JPanel
        private Ball ball;
        public BallPanel()
            ball = new Ball(FRAME_WIDTH, FRAME_HEIGHT);
            addKeyListener(new BallWatcher());
        public void paintComponent(Graphics g)
            super.paintComponent(g);
            ball.paint(g);
        private class BallWatcher extends KeyAdapter
            public void keyPressed(KeyEvent k)
                if (k.getKeyCode()==KeyEvent.VK_LEFT)
                    ball.moveLeft();
                if (k.getKeyCode()==KeyEvent.VK_RIGHT)
                    ball.moveRight();
                repaint();
            } // end keypressed
        } // end ballwatcher
    } // end ball panel
} // end moving ballBall class:
package movingball;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
public class Ball
    private  final  int  RADIUS  = 10;
    private  int move;
    private  Point  pos;
    private  Color  ballColour;
    private  int  height,  width;
    public  Ball  (int  frameWidth,  int  frameHeight)
        move = 3;
        ballColour = Color.RED;
        width  = frameWidth;
        height  = frameHeight;
        pos  =  new  Point();
        pos.x  = 0 + RADIUS;
        pos.y  = 0 + RADIUS;
    public void moveLeft()
        if(pos.x - RADIUS > 0)
            pos.x = pos.x + move;
    public void moveRight()
        if(pos.x + RADIUS < width)
            pos.x = pos.x + move;
    public void paint(Graphics  g)
        g.setColor(ballColour);
        g.fillOval(pos.x,  pos.y,  2*RADIUS, 2*RADIUS);
}Many thanks in advance,

Answer 1

JPanel are not focusable by default and key events are sent to the focused component. Use JPanel#setFocusable(true) to make it focusable or use keybinding on the JFrame (search on "java keybinding tutorial").