使用MouseMotionListener为JLabel设置SetLocation

Question

无法让JLabel出现并移动

我正在尝试制作一个钓鱼游戏，而我正在尝试使用mouseMoved（MouseEvent evt）让JLabel鱼移动。但是，图像不会出现在图像上。怎么了？

 import java.awt.*;
 import javax.swing.*; 
 import java.awt.event.*;
 import sun.audio.*;
 import java.io.*;
 import java.util.Timer;
 import java.util.TimerTask;
 import java.awt.event.MouseEvent;
 public class playFishGame extends JPanel implements MouseMotionListener
{
    private JFrame board;//the main board
    private JLabel fish;
    private ImageIcon fishPic;
  public static void main(String args[])
{
    playFishGame play= new playFishGame();
}

  public playFishGame()
{
    board= new JFrame("Play Fish Game");
    board.setSize(1200,750);
    board.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    board.add(this);//adds JLabel to JFrame
    this.addMouseMotionListener(this);
    board.setVisible(true);
    ImageIcon fishPic= new ImageIcon("fishLarge4.png");
    fish=new JLabel (fishPic);
    this.add(fish);
    fish.setLocation(10,10);
}

public void mouseMoved(MouseEvent evt)
{
    System.out.println(evt.getPoint().x + ", " + evt.getPoint().y);
    fish.setLocation(evt.getPoint().x,evt.getPoint().y);
}

public void mouseDragged(MouseEvent evt)
{
}
}