java - JMenuItem 和 ENTER 键释放

Question

我有一个 JMenuItem，我想接收用户输入。用户必须能够通过鼠标或键盘启动项目的功能。

该项目的功能包含要打开的 JDialog。此对话框监听释放的 ENTER 键并在释放 ENTER 时启动其自身的功能。

当用户使用 ENTER(按下键)点击 JMenuItem 时，他将打开对话框。当他放开 ENTER 时，他将 - 这就是问题所在 - 导致对话框的功能启动。 (当用户松开 ENTER 键时，他将向现在打开的 JDialog 触发一个事件。我不想那样。我想要两个单独的步骤:第 1 步:选择 JMenuItem 通过使用 ENTER(完整笔划或释放 ENTER)，第二:通过使用 ENTER(完整笔划或释放 ENTER)在 JDialog 中启动新功能。

到目前为止，我已经尝试了几件事，但我无法让 JMenuItem 接收 key 发布事件。这似乎是我目前无法解决的一些焦点问题。

如何解决这个问题？

如果解释有点困惑，可以这样总结:

I want a JMenuItem to receive ENTER-key-released-events and react to it, I do not want it to react to ENTER-key-pressed-events.

一个小代码示例可能会显示我的问题:

编辑

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JRootPane;
import javax.swing.KeyStroke;
import javax.swing.MenuElement;
import javax.swing.MenuSelectionManager;

public class MenuItemProblem {
    public static void openDialog(JFrame frame){
        Action enterReleasedAction = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // This action shall be triggered by releasing
                // the enter key in the JDialog.
                // (There are two times events of the released enter key shall be
                // evaluated during the application runs, of which this is the second one.)
                // But: It is triggered by the first release of enter in the application,
                // which is the one to choose the menu item.
                System.out.println("Dialog: Enter was released!");
            }
        };
        JDialog dialog = new JDialog(frame, "My dialog", true);
        JRootPane rootPane = dialog.getRootPane();
        ActionMap actionMap = rootPane.getActionMap();
        String enterReleased = "my_enter_released_function";
        actionMap.put(enterReleased, enterReleasedAction);
        InputMap inputMap = rootPane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);    
        // Keystroke for releasing the enter key
        inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0, true), enterReleased);

        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
        dialog.setMinimumSize(new Dimension(260, 300));
        dialog.setResizable(true);
        dialog.pack();
        dialog.setLocationRelativeTo(frame);
        dialog.setVisible(true);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("My App");
        JMenuItem item = new JMenuItem("My item");
        item.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // By releasing enter (and mouse clicks, space and so on)
                // this action shall be triggered.
                // It shall not be triggered by enter key pressed,
                // for this would cause the action of the called dialog
                // do be triggered.
                // But: It is triggered by enter pressed!
                // (There are two times events of the released enter key shall be
                // evaluated during the application runs, of which this is the first one.)
                System.out.println("Choosing the menu item");
                openDialog(frame);
            }
        });

        JMenu menu = new JMenu("My menu");
        menu.add(item);
        JMenuBar bar = new JMenuBar();
        bar.add(menu);

        // Register alt key to be caught
        Action altAction = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                MenuElement[] elements = MenuSelectionManager.defaultManager().getSelectedPath();
                if(elements.length > 0){
                    MenuSelectionManager.defaultManager().clearSelectedPath();
                } else{
                    menu.doClick();
                }
            }
        };
        JRootPane rootPane = frame.getRootPane();
        ActionMap actionMap = rootPane.getActionMap();
        String altActionKey = "alt_key_for_menu";
        actionMap.put(altActionKey, altAction);
        InputMap inputMap = rootPane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        KeyStroke ks = KeyStroke.getKeyStroke(KeyEvent.VK_ALT, 0, true);
        inputMap.put(ks, altActionKey);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setJMenuBar(bar);
        frame.setSize(350, 250);
        frame.setVisible(true);
    }
}

是的，如果你们能指出我正确的方向，我会很高兴。在此先感谢您所做的一切努力!

Answer 1

好的，问题解决了。我没有尝试调整 API，而是调整了对话框功能的触发方式。详细地说，我将触发器从 ENTER released 更改为 ENTER typed。一些示例代码来理解我做了什么:

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JRootPane;
import javax.swing.KeyStroke;
import javax.swing.MenuElement;
import javax.swing.MenuSelectionManager;

public class MenuItemSolution {
    public static void openDialog(JFrame frame){
        Action enterTypedAction = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Dialog: Enter was typed!");
            }
        };
        JDialog dialog = new JDialog(frame, "My dialog", true);
        JRootPane rootPane = dialog.getRootPane();
        ActionMap actionMap = rootPane.getActionMap();
        String enterTyped = "my_enter_typed_function";
        actionMap.put(enterTyped, enterTypedAction);
        InputMap inputMap = rootPane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);    
        // This is the point of change: I just created a KeyStroke to
        // deal with ENTER key typed instead of ENTER key released.
        // Only problem left (which doesn't matter in my use case):
        // Key typed events can occur several time when holding down the ENTER key.
        inputMap.put(KeyStroke.getKeyStroke('\n'), enterTyped);
        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
        dialog.setMinimumSize(new Dimension(260, 300));
        dialog.setResizable(true);
        dialog.pack();
        dialog.setLocationRelativeTo(frame);
        dialog.setVisible(true);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("My App");
        JMenuItem item = new JMenuItem("My item");
        item.addActionListener((ActionEvent e) -> {
            openDialog(frame);
        });
        JMenu menu = new JMenu("My menu");
        menu.add(item);
        JMenuBar bar = new JMenuBar();
        bar.add(menu);

        // Register alt key to be caught
        Action altAction = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                MenuElement[] elements = MenuSelectionManager.defaultManager().getSelectedPath();
                if(elements.length > 0){
                    MenuSelectionManager.defaultManager().clearSelectedPath();
                } else{
                    menu.doClick();
                }
            }
        };
        JRootPane rootPane = frame.getRootPane();
        ActionMap actionMap = rootPane.getActionMap();
        String altActionKey = "alt_key_for_menu";
        actionMap.put(altActionKey, altAction);
        InputMap inputMap = rootPane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        KeyStroke ks = KeyStroke.getKeyStroke(KeyEvent.VK_ALT, 0, true);
        inputMap.put(ks, altActionKey);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setJMenuBar(bar);
        frame.setSize(350, 250);
        frame.setVisible(true);
    }
}

感谢大家的关注，尤其是@MadProgrammer 和@mKorbel!

编辑

据我所知，还有一些更好的方法。
第一种方法:
设置一个计时器以响应新打开的对话框上的 ENTER 键释放事件。
第二种方法:
在处理 ENTER 键释放事件之前，在新打开的对话框中强制执行 ENTER 键按下事件。