Question

Java 鼠标监听器

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

public class Frame extends JFrame{
static JFrame frame = new JFrame("MyFrame");
public static void main(String[] args){
frame.setSize(314,314);
frame.setVisible(true);
JMenuBar();
}

public static void JMenuBar(){
JMenuBar menubar = new JMenuBar();//菜单初始化
frame.setJMenuBar(menubar);//建立菜单
JMenu startFile = new JMenu("开始");
JMenu helpFile = new JMenu("帮助");
JMenu aboutFile = new JMenu("关于");
menubar.add(startFile);
menubar.add(helpFile);
menubar.add(aboutFile);

JMenuItem againItem = startFile.add("再玩一次");//建立子菜单
JMenuItem heroItem = startFile.add("英雄榜");
JMenuItem howItem = helpFile.add("如何游戏");
JMenuItem writerItem = aboutFile.add("制作组成员");
JMenuItem callItem = aboutFile.add("联系方式");

againItem.addActionListener(new ActionHandler());//建立鼠标监听器

class ActionHandler implements ActionListener{
public void actionPerformed(ActionEvent event){
JOptionPane.showMessageDialog(null,"Hello world!","Display",JOptionPane.INFORMATION_MESSAGE);
}
}
}
}

编译总说31行找不到符号 求解（againItem.addActionListener(new ActionHandler());//建立鼠标监听器 这一行）

Answer 1

JMenuItem againItem = startFile.add("再玩一次");//建立子菜单
JMenuItem heroItem = startFile.add("英雄榜");
JMenuItem howItem = helpFile.add("如何游戏");
JMenuItem writerItem = aboutFile.add("制作组成员");
JMenuItem callItem = aboutFile.add("联系方式");

againItem.addActionListener(new ActionHandler());//建立鼠标监听器

}
}

class ActionHandler implements ActionListener{
public void actionPerformed(ActionEvent event){
JOptionPane.showMessageDialog(null,"Hello world!","Display",JOptionPane.INFORMATION_MESSAGE);
}
}

或者：

JMenuItem againItem = startFile.add("再玩一次");//建立子菜单
JMenuItem heroItem = startFile.add("英雄榜");
JMenuItem howItem = helpFile.add("如何游戏");
JMenuItem writerItem = aboutFile.add("制作组成员");
JMenuItem callItem = aboutFile.add("联系方式");

againItem.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent event){
JOptionPane.showMessageDialog(null,"Hello world!","Display",JOptionPane.INFORMATION_MESSAGE);
}
}
);//建立鼠标监听器

}
}

Answer 2

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