java - 使用 MouseMotionListener 为 JLabel 设置位置

Question

无法让 JLabel 出现和移动

我正在尝试制作钓鱼游戏，并且正在尝试使用 mouseMoved(MouseEvent evt) 让 JLabel 鱼移动。但是，图像不会出现在框架上。怎么了？

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 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)
{
}
}