我已经试了一个小时，想要测试一个简单的程序，在点击时改变球的颜色，但是当我尝试使用myPanel.addActionListener(new BallListener())时，我在编译时遇到了一个错误。
请帮我找出错误所在？
myPanel.addActionListener(new BallListener());
^
symbol: method addActionListener(Ball.BallListener)
location: variable myPanel of type MyPanel
1 error
//first Java Program on the new VM
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
public class Ball{
private MyFrame myFrame;
private MyPanel myPanel;
public static void main(String[] args)
{
Ball ball=new Ball();
ball.go();
}//main ends
public class BallListener implements ActionListener{
public void actionPerformed(ActionEvent e)
{
myFrame.repaint();
}
}//listener ends
public void go()
{
myPanel=new MyPanel();
//myPanel.addActionListener(new BallListener());
myFrame=new MyFrame();
myFrame.add(BorderLayout.CENTER,myPanel);
myFrame.setVisible(true);
}
}//class ends
//ball panel
class MyPanel extends JPanel
{
public void paintComponent(Graphics g)
{
Graphics2D g2d=(Graphics2D)g;
Ellipse2D ellipse=new Ellipse2D.Double(200,200,400,400);
int r=(int)Math.random()*256;
int b=(int)Math.random()*256;
int g1=(int)Math.random()*256;
Color color=new Color(r,g1,b);
g2d.setPaint(color);
g2d.fill(ellipse);
}
}//Class ends
//a simple JFrame
class MyFrame extends JFrame{
public MyFrame()
{
setSize(600,600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(false);
}
}//class ends