鼠标拖动画图的问题？？？？///

下面的程序中，我想实现在鼠标的拖动中，圆随着鼠标的拖动而移动，但我怎么也实现
不了，希望各位大哥给点看法，谢谢！！

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

public class MyGame
{
public static void main(String[] args)
{
JFrame mygame=new MyGameFrame();
mygame.show();
}
}

class MyGameFrame extends JFrame
{
public MyGameFrame()
{
setTitle("游戏");
setSize(350,350);
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
dispose();
System.exit(0);
}
});
Container contentPane=getContentPane();
contentPane.add(new MyPanel());
}
}

class MyPanel extends JPanel implements MouseMotionListener
{

private int curx=10,cury=10,newx,newy;
private Graphics g;

public MyPanel()
{

addMouseMotionListener(this);

}


public boolean isFocusTraversable()
{
return(true);
}

public void update(Graphics g)
{

movepaint(g,curx,cury);
movepaint(g,newx,newy);
curx=newx;
cury=newy;
}

public void paint(Graphics g)
{
//g.setPaintMode();
//g.setColor(Color.black);
movepaint(g,curx,cury);
}

private void movepaint(Graphics g,int x,int y)
{
g.setXORMode(Color.white);
g.setColor(Color.black);
g.fillOval(x,y,25,25);

}



public void mouseDragged(MouseEvent e)
{
System.out.println("Dragged");
newx = e.getX();
newy = e.getY();
//System.out.println(newx+" "+newy);
repaint();


}

public void mouseMoved(MouseEvent e) {}


}