Question

在我的应用程序中，我使用jmenuitem执行一些操作来通过套接字编程连接特定端口。现在，我想点击“连接”菜单项，将其名称和操作更改为“断开连接”。我的“连接”菜单项代码是这样的：

connect = new JMenuItem("Connect");
    connect.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            loginForm login = new loginForm();
            login.setVisible(true);

        }
    });
 jpopupMenu.insert(connect, 0);

和“断开”代码是这样的：

disconnect = new JMenuItem("Disonnect");
    disconnect.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            try {
                client.disconnect();
            } catch (IOException ex) {
                Logger.getLogger(systemTray.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    });
jpopupMenu.insert(disconnect, 0);

但此代码会导致重复项目添加到菜单。我找不到有关如何检测菜单项是否存在或替换菜单项的任何帮助！

Answer 1

您的问题标题说明了所有内容（例如Action，但您使用的是ActionListener/JMenuItem）。使用Action（我们可以使用而不是JMenuItem），我们可以简单地覆盖NAME值，这是菜单项名称中显示的值。这是一个例子。

请注意menu.add(Action)而不是menu.add(JMenuItem)

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

public class TestMenu {
    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setSize(300, 300);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);

        JMenuBar menuBar = new JMenuBar();
        JMenu menu = new JMenu("Menu");

        Action menuAction = new AbstractAction("Connect") {
            private boolean connected = false;
            @Override
            public void actionPerformed(ActionEvent e) {
                if (!connected) {
                    JOptionPane.showMessageDialog(null, "Connected");
                    putValue(NAME, "Disonnect");
                    connected = true;
                } else {
                    JOptionPane.showMessageDialog(null, "Disconnected");
                    putValue(NAME, "Connect");
                    connected = false;
                }     
            }  
        };

        menuBar.add(menu);
        menu.add(menuAction);
        f.setJMenuBar(menuBar);
        f.setVisible(true);
    }
}

请参阅How to Use Actions
和How to use Menus（将使用操作）
请参阅Action API for all action keys

Answer 2

我想你可以做这样的事情，它允许你对这两个动作使用单个菜单项，并根据客户端是否连接来改变其动作/文本。

private JMenuItem connect = new JMenuItem("Connect");

// ...

connect.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        if (client.isConnected()) {
            disconnect();
        } else {
            connect();
        }
    }
});

// ...

private void connect() {
    loginForm login = new loginForm();
    login.setVisible(true);
    // TODO: You should change the label only if connection actually succeeds
    connect.setText("Disconnect");
}

private void disconnect() {
    try {
        client.disconnect();
        connect.setText("Connect");
    } catch (IOException ex) {
        Logger.getLogger(systemTray.class.getName()).log(Level.SEVERE, null, ex);
    }
}

Answer 3

也许这也会对你有所帮助我把它全部放在了一个jpopupmenu

上

public class Test {

    JPopupMenu popmenu;
    public boolean isConnected = false;

    public Test() {
        JFrame frame = new JFrame();
        frame.setSize(200, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);

        popmenu = new JPopupMenu();
        final JMenuItem connect = new JMenuItem("connect");
        connect.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        if (!isConnected) {
                            System.out.println("connect action");

                            connect();

                            isConnected = true;
                        } else {
                            System.out.println("disconnect action");

                            disconnect();

                            isConnected = false;
                        }
                    }
                });

            }
        });

        popmenu.insert(connect, 0);

        frame.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseReleased(MouseEvent e) {
                if (e.isPopupTrigger()) {
                    popmenu.show(e.getComponent(), e.getX(), e.getY());
                }
            }
        });
        frame.setVisible(true);
    }

    private void connect() {
        loginForm login = new loginForm();
        login.setVisible(true);
        // TODO: You should change the label only if connection actually
        // succeeds
        connect.setText("Disconnect");
    }

    private void disconnect() {
        try {
            client.disconnect();
            connect.setText("Connect");
        } catch (IOException ex) {
            Logger.getLogger(systemTray.class.getName()).log(Level.SEVERE,
                    null, ex);
        }
    }

    public static void main(String[] args) {
        new Test();
    }
}

如何改变＆＃34; JMenuItem＆＃34;和它的＆＃39; java中的动作

3 个答案: