Java JMenuItem ActionListener [英] Java JMenuItem ActionListener

问题描述

我的JMenuBar上的ActionListener需要帮助。

I need some help with my ActionListener on my JMenuBar.

没有错误；但是，每次我单击JMenuItem时，它都会触发与JMenuItem相关的所有动作。我的问题是：我是否在ActionListener代码中正确执行此操作？我不太了解我的ActionListener类。我正在尝试将ActionListener与Button逻辑分开。

There's no error; however every time I click on a JMenuItem, it triggers all the action associated with the JMenuItem. My question is: am I doing it right in my ActionListener code? I'm not too sure about my ActionListener class. I'm trying to separate my ActionListener from my Button logic.

如果有人对我可能做错的事情有任何想法，请指出。

If anyone has any ideas on what I may be doing wrong, please point it out.

这里是我的代码：

package MenuBar;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class SimpleMenuBar{
    private static final LayoutManager grid = new GridLayout(0, 1);
    public JMenuBar MenuBar;
    public JMenu MenuFile, MenuEdit, MenuOption;
    public JMenuItem ItemNew, ItemOpen, ItemSave, ItemExit, ItemCopy, ItemCut, ItemPaste;
    ButtonGroup direction;
    JRadioButtonMenuItem forwardradio, backwardradio;
    JCheckBoxMenuItem CheckCase;
    String input = null;
    public void Design()
    {
        JFrame frame = new JFrame("Simple Menubar");
        frame.setSize(320, 320);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);

        MenuBar = new JMenuBar();
        frame.setJMenuBar(MenuBar);
        MenuBar.setLayout(grid);

        //Menus
        MenuFile = new JMenu("File");
        MenuFile.setMnemonic(KeyEvent.VK_F);
        MenuBar.add(MenuFile);

        //sub Menus
        ItemNew = new JMenuItem("New", KeyEvent.VK_N);
        MenuFile.add(ItemNew);
        ItemNew.setActionCommand("New");
        ItemNew.addActionListener(new MenuBarMethod());

        ItemOpen = new JMenuItem("Open", KeyEvent.VK_O);
        MenuFile.add(ItemOpen);
        ItemOpen.setActionCommand("Open");
        ItemNew.addActionListener(new MenuBarMethod());
        MenuFile.addSeparator();


        ItemSave = new JMenuItem("Save", KeyEvent.VK_S);
        MenuFile.add(ItemSave);
        MenuFile.addSeparator();

        ItemExit = new JMenuItem("Exit", KeyEvent.VK_X);
        MenuFile.add(ItemExit);

        MenuEdit = new JMenu("Edit");
        MenuFile.setMnemonic(KeyEvent.VK_E);
        MenuBar.add(MenuEdit);

        ItemCopy = new JMenuItem("Copy", KeyEvent.VK_C);
        KeyStroke ctrlCKeyStroke = KeyStroke.getKeyStroke("control C");
        ItemCopy.setAccelerator(ctrlCKeyStroke);
        MenuEdit.add(ItemCopy);

        ItemCut = new JMenuItem("Cut", KeyEvent.VK_V);
        KeyStroke ctrlVKeyStroke = KeyStroke.getKeyStroke("control V");
        ItemCut.setAccelerator(ctrlVKeyStroke);
        MenuEdit.add(ItemCut);

        ItemPaste = new JMenuItem("Paste", KeyEvent.VK_Y);
        KeyStroke ctrlYKeyStroke = KeyStroke.getKeyStroke("control Y");
        ItemPaste.setAccelerator(ctrlYKeyStroke);
        ItemPaste.setEnabled(false);
        MenuEdit.add(ItemPaste);
        MenuEdit.addSeparator();

        MenuOption = new JMenu("Option");
        Icon atIcon = new ImageIcon("option.png");
        MenuOption.setIcon(atIcon);
        MenuOption.setMnemonic(KeyEvent.VK_O);

        direction = new ButtonGroup();
        forwardradio = new JRadioButtonMenuItem("Forward Me", true);
        forwardradio.setMnemonic(KeyEvent.VK_F);
        MenuOption.add(forwardradio);
        direction.add(forwardradio);
        MenuEdit.add(MenuOption);

        backwardradio = new JRadioButtonMenuItem("Backward Me");
        backwardradio.setMnemonic(KeyEvent.VK_B);
        MenuOption.add(backwardradio);
        direction.add(backwardradio);

        MenuOption.addSeparator();

        CheckCase = new JCheckBoxMenuItem("Case Sensitive");
        MenuOption.add(CheckCase);
        direction.add(CheckCase);
        MenuEdit.add(MenuOption);

    }
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable(){
            public void run()
            {
                SimpleMenuBar MyMenu = new SimpleMenuBar();
                MyMenu.Design();

            }
        });
    }
}

仅用于菜单栏的代码很多。我还没有完全实现ActionListener。出于测试目的，我仅针对两个项目实现了该项目： ItemNew 和 ItemOpen 。不幸的是，每次我单击 ItemNew 菜单项时，它都会触发 ItemNew 和 ItemOpen 。

It's an awful lot of code for just a menu bar. I haven't fully implemented the ActionListener. For testing purposes, I've only implemented it for two items: ItemNew and ItemOpen. Unfortunately, every time I click on the ItemNew menu item, it triggers the actions of both ItemNew and ItemOpen.

以下是我的动作监听器的代码：

Here are is code for my action listener:

package MenuBar;
import java.awt.event.*;

import javax.swing.JOptionPane;
public class MenuBarMethod implements ActionListener{
    public void actionPerformed(ActionEvent e)
    {
        if("New".equals(e.getActionCommand())){
            JOptionPane.showMessageDialog(null, "Selected Item: " + e.getActionCommand());
        }
        if("Open".equals(e.getActionCommand())){
            JOptionPane.showMessageDialog(null, "Selected Item: " + e.getActionCommand());
        }
    }

}

推荐答案

根据个人喜好，我更喜欢使用动作 API

As a matter of personal preference, I prefer to use the Action API

主要原因是

• 它集中与特定动作相关的逻辑，包括名称，按键，快捷方式，图标等


• 可重复使用。创建 Action 对象要容易得多，然后重新创建菜单项&工具栏项目&弹出菜单项


• 其他Swing组件都很好地支持了该菜单项。大多数支持 ActionListener API的Swing组件通常也提供提供 Action 的方法（ JMenu.add（Action）， JMenu（Action）等）


• 这使您的代码更容易易于阅读，更容易阅读 Action 类的单个 ActionPerformed 方法，然后尝试浏览多个 if 语句

• It centralise logic associated with a particular action, including name, key stroke, short cuts, icons etc
• It's reusable. It's much easier to create an Action Object then it's to have recreate the menu item & the tool bar item & the popup menu item
• It's well supported by other Swing components. Most Swing components that support the ActionListener API generally provide the means to supply an Action as well (JMenu.add(Action), JMenu(Action) etc)
• It makes your code easier to read, much easier to read a single ActionPerformed method of an Action class then try and skim through multiple if statements

看看如何使用操作

恕我直言

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