如何动态构建 JMenu?

问题描述

我试图在点击它时动态构建一个 JMenu(我只得到一个空菜单)，下面是我的代码.

I am trying to build a JMenu dynamically right when clicking in it (I'm only getting an empty menu), below is my code.

    final JMenu JMWindows = new JMenu("Opened Windows");                
    JMWindows.addActionListener(new ActionListener() {          
        @Override
        public void actionPerformed(ActionEvent e) {
            for(JInternalFrame ji : desktop.getAllFrames())
            {
                JMWindows.add(ji.getTitle());
            }               
        }
    });

我意识到 actionperformed 从未被调用，JMenu 位于 JMenuBar 内.可能是什么问题?

I've realized that the actionperformed is never called, the JMenu is inside a JMenuBar. What could be the problem ?

推荐答案

• 您将 ActionListener 添加到 JMenu 这不能为 JMenu 使用 MenuListener 并通过 JMenu#addMenuListener(..)

  • You add ActionListener to JMenu this cannot be done for JMenu use MenuListener and set it via JMenu#addMenuListener(..)

    此外，在添加/删除组件后，您还需要在 JMenu 实例上调用 revalidate() 和 repaint() 或更改不会被反映(我们也可以在容器实例上调用它，即 JMenuBar 或 JFrame，但我们知道只有 1 个特定的 JMenu 会改变所以不需要 IMO).

    Also you need to call revalidate() and repaint() on JMenu instance after adding/removing components from it or the changes will not be reflected (we could also call this on the containers instance i.e JMenuBar or JFrame, but we know only 1 specific JMenu will change so no need IMO).

    请注意你的变量命名方案 JMWindow 应该是 jmWindow/jMWindow 变量总是以无大写开头和第一个字母此后的每个新单词都会大写(除了常量和 enums).

    Please watch your variable naming schemes JMWindow should be jmWindow/jMWindow variables always begin with no caps and the 1st letter of every new word thereafter gets capitalized (besides for constants and enums).

    这是一个使用 MenuListener 的例子:

    Here is an example using MenuListener:

    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.JDesktopPane;
    import javax.swing.JFrame;
    import javax.swing.JInternalFrame;
    import javax.swing.JMenu;
    import javax.swing.JMenuBar;
    import javax.swing.JMenuItem;
    import javax.swing.SwingUtilities;
    import javax.swing.event.MenuEvent;
    import javax.swing.event.MenuListener;
    
    public class Test {
    
        private JDesktopPane jdpDesktop;
        private static int openFrameCount = 0;
        final JFrame frame = new JFrame("JInternalFrame Usage Demo");
    
        public Test() {
    
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
            // A specialized layered pane to be used with JInternalFrames
            jdpDesktop = new JDesktopPane() {
                @Override
                public Dimension getPreferredSize() {
                    return new Dimension(500, 500);
                }
            };
    
    
            for (int i = 0; i < 3; i++) {
                createFrame(); // Create first window
            }
    
            frame.setContentPane(jdpDesktop);
    
            frame.setJMenuBar(createMenuBar());
    
            // Make dragging faster by setting drag mode to Outline
            jdpDesktop.putClientProperty("JDesktopPane.dragMode", "outline");
    
            frame.pack();
            frame.setVisible(true);
        }
    
        protected JMenuBar createMenuBar() {
            JMenuBar menuBar = new JMenuBar();
            JMenu menu = new JMenu("Frame");
            menu.setMnemonic(KeyEvent.VK_N);
            JMenuItem menuItem = new JMenuItem("New IFrame");
            menuItem.setMnemonic(KeyEvent.VK_N);
            menuItem.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    createFrame();
                }
            });
            menu.add(menuItem);
            menuBar.add(menu);
    
    
            final JMenu jmWindows = new JMenu("Opened Windows");
            jmWindows.addMenuListener(new MenuListener() {
                @Override
                public void menuSelected(MenuEvent me) {
                    jmWindows.removeAll();//remove previous opened window jmenuitems
                    for (JInternalFrame ji : jdpDesktop.getAllFrames()) {
                        JMenuItem menuItem = new JMenuItem(ji.getTitle());
                        jmWindows.add(menuItem);
                    }
    
                    jmWindows.revalidate();
                    jmWindows.repaint();
                    jmWindows.doClick();
    
                }
    
                @Override
                public void menuDeselected(MenuEvent me) {
                }
    
                @Override
                public void menuCanceled(MenuEvent me) {
                }
            });
            menuBar.add(jmWindows);
    
    
            return menuBar;
        }
    
        protected void createFrame() {
            Test.MyInternalFrame frame = new Test.MyInternalFrame();
            frame.setVisible(true);
            // Every JInternalFrame must be added to content pane using JDesktopPane
            jdpDesktop.add(frame);
            try {
                frame.setSelected(true);
            } catch (java.beans.PropertyVetoException e) {
            }
        }
    
        public static void main(String[] args) {
            SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    new Test();
                }
            });
        }
    
        class MyInternalFrame extends JInternalFrame {
    
            static final int xPosition = 30, yPosition = 30;
    
            public MyInternalFrame() {
                super("IFrame #" + (++openFrameCount), true, // resizable
                        true, // closable
                        true, // maximizable
                        true);// iconifiable
                setSize(300, 300);
                // Set the window's location.
                setLocation(xPosition * openFrameCount, yPosition
                        * openFrameCount);
            }
        }
    }
    

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