JMenuItem问题.我有五个.其中一个编译没有问题.其他人是相同的,但他们拒绝编译

Question

出于某种原因,我无法在Eclipse中编译它."退出"menuItem工作,没有其他menuItem工作.这是为什么？

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

public class GUI{

private JFrame frame;

public GUI(){
    makeFrame();
}

//This method makes the overall GUI and adds panels, labels,
//buttons, and everything else to the GUI.
public void makeFrame(){
    frame = new JFrame("Tower Defense");
    Container contentPane = frame.getContentPane();

    makeMenus();

    JButton shootButton = new JButton("Shoot");
    contentPane.add(shootButton);

    frame.pack();
    frame.setVisible(true);

}

//This method makes the menu and all of the items contained
//in the menu which is then called by the makeFrame() method.
//I also add the menuItem's various ActionLiteners here.
public void makeMenus(){
    JMenuBar menubar = new JMenuBar();
    frame.setJMenuBar(menubar);

    JMenu fileMenu = new JMenu("File");
    JMenu actionsMenu = new JMenu("Actions");
    JMenu buildMenu = new JMenu("Build");

    menubar.add(fileMenu);
    menubar.add(actionsMenu);
    menubar.add(buildMenu);

    JMenuItem sellItem = new JMenuItem("Sell");
    JMenuItem quitItem = new JMenuItem("Quit");

    JMenuItem turretsItem = new JMenuItem("Turrets");
    JMenuItem minesItem = new JMenuItem("Mines");
    JMenuItem workersItem = new JMenuItem("Workers");

    quitItem.addActionListener(new QuitActionListener());
    sellItem.addActionListener(new SellActionListener());
    turretsItem.addActionListener(new TurretsActionListener());
    minesItem.addActionListener(new MinesActionListener());
    workersItem.addActionListener(new WorkersActionListener());

    fileMenu.add(quitItem);
    actionsMenu.add(sellItem);
    buildMenu.add(turretsItem);
    buildMenu.add(minesItem);
    buildMenu.add(workersItem);
}

//Main method. It creates a new GUI.
public static void main(String args []){
    GUI gui = new GUI();
}

class QuitActionListener implements ActionListener{
    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

class SellActionListener{

    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

class TurretsActionListener{

    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

class MinesActionListener{

    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

class WorkersActionListener{

    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

class ShootActionListener{
    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

}

Answer 1

它没有编译,因为SellActionListener您正在提供的动作侦听器(例如,所有禁止退出操作)未实现ActionListener.该方法addActionListener需要一个实现的对象ActionListener.

这个:

class SellActionListener{

    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

需要变成这样:

class SellActionListener implements ActionListener{

    public void actionPerformed(ActionEvent e){
        System.exit(0);
    }
}

(以及其他动作监听器)

对于后代

通常可以从编译器反馈中找出这些错误.当eclipse说存在编译错误时,您应该能够看到错误详细信息.我想它会说像"类SellActionListener没有实现接口ActionListener"(或类似的东西).如果你谷歌那个错误信息,你可能能够更快地找到答案,等待某人回答你的具体问题.