java中JFrame的鼠标移动事件相关问题

你可以这样改
import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

public class MyPractice extends JFrame {
int x=100,y=100;
public MyPractice(){
addMouseMotionListener(new MouseMotionListener() {

@Override
public void mouseMoved(MouseEvent e) {
// TODO Auto-generated method stub
x=e.getX();
y=e.getY();
repaint();
}

@Override
public void mouseDragged(MouseEvent e) {
// TODO Auto-generated method stub

}
});
setSize(300,400);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}

public void paint(Graphics g){
super.paint(g);
//初始化小球
g.fillOval(x, y, 30, 30);
}

public static void main(String args[]){
new MyPractice();
}
}