使用 ActionListener 退出菜单不起作用

问题描述

我正在尝试使用 ActionListener 退出菜单，但是我的代码无法正常工作并且“退出程序”按钮没有任何作用。代码如下：

import java.awt.*;
 import java.awt.event.*;
 import javax.swing.JMenu;
 import javax.swing.JMenuItem;
 import javax.swing.JCheckBoxMenuItem;
 import javax.swing.JRadioButtonMenuItem;
 import javax.swing.ButtonGroup;
 import javax.swing.JMenuBar;
 import javax.swing.Keystroke;
 import javax.swing.ImageIcon;
 import javax.swing.JPanel;
 import javax.swing.JTextArea;
 import javax.swing.JScrollPane;
 import javax.swing.JFrame;

 public class testCoinSorterGUI extends testCoinSorter{

JTextArea output;
JScrollPane scrollPane;

public JMenuBar createMenuBar() {
    JMenuBar menuBar;
    JMenu menu,submenu;
    JMenuItem menuItem;
    JRadioButtonMenuItem rbMenuItem;
    JCheckBoxMenuItem cbMenuItem;

    //Create the menu bar.
    menuBar = new JMenuBar();

    //Build the first menu.
    menu = new JMenu("Calculator");
    menu.setMnemonic(KeyEvent.VK_A);
    menu.getAccessibleContext().setAccessibleDescription(
            "The only menu in this program that has menu items");
    menuBar.add(menu);
    
    menuItem = new JMenuItem("Coin calculator");
    menu.add(menuItem);
    
    menuItem = new JMenuItem("Multi Coin calculator");
    menu.add(menuItem);

    //Build second menu in the menu bar.
    menu = new JMenu("Print coin list");
    menu.setMnemonic(KeyEvent.VK_N);
    menu.getAccessibleContext().setAccessibleDescription("This menu does nothing");
    menuBar.add(menu);

    //Build third menu in the menu bar.
    menu = new JMenu("Set details");
    menuBar.add(menu);

    menuItem = new JMenuItem("Set currency");
    menu.add(menuItem);

    menuItem = new JMenuItem("Set minimum coin input value");
    menu.add(menuItem);

    menuItem = new JMenuItem("Set maximum coin input value");
    menu.add(menuItem);
    menu.addSeparator();

    menuItem = new JMenuItem("display program configurations");
    menu.add(menuItem);

    //Build fifth menu in the menu bar.
    menu = new JMenu("Quit the program");
    menuBar.add(menu);
    menu.addActionListener(
        new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        }
    );
    
    return menuBar;
}

public Container createContentPane() {
    //Create the content-pane-to-be.
    JPanel contentPane = new JPanel(new BorderLayout());
    contentPane.setopaque(true);

    //Create a scrolled text area.
    output = new JTextArea(5,30);
    output.setEditable(false);
    scrollPane = new JScrollPane(output);

    //Add the text area to the content pane.
    contentPane.add(scrollPane,BorderLayout.CENTER);

    return contentPane;
}

/** Returns an ImageIcon,or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
    java.net.URL imgurL = testCoinSorterGUI.class.getResource(path);
    if (imgurL != null) {
        return new ImageIcon(imgurL);
    } else {
        System.err.println("Couldn't find file: " + path);
        return null;
    }
}

/**
 * Create the GUI and show it.  For thread safety,* this method should be invoked from the
 * event-dispatching thread.
 */
private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("*** CoinSorterGUI ***");
    frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);

    //Create and set up the content pane.
    testCoinSorterGUI demo = new testCoinSorterGUI();
    frame.setJMenuBar(demo.createMenuBar());
    frame.setContentPane(demo.createContentPane());

    //display the window.
    frame.setSize(680,480);
    frame.setVisible(true);
}

public static void main(String[] args) {
    //Schedule a job for the event-dispatching thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokelater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    });
}
}

目前我只想测试“退出程序”按钮，所以请忽略所有其他菜单。任何帮助将不胜感激，尽管我认为我已将代码按正确顺序排列，但我真的很困惑。

解决方法

您可以使用它代替 ActionListener，后者应该用于不同范围的控件：

JMenu quitProgramMenu = new JMenu("Quit the program");

quitProgramMenu.addMenuListener(
 new MenuListener() {

  @Override
  public void menuSelected(MenuEvent e) {
   System.exit(0);
  }

  @Override
  public void menuDeselected(MenuEvent e) {}

  @Override
  public void menuCanceled(MenuEvent e) {}
 }
);
menuBar.add(quitProgramMenu);