Mac 上的 Java：屏幕菜单栏中的键盘命令未执行

Question

Using Java 8 with Swing on a Mac, I'm having a JMenuBar in a JFrame which is placed as a screen menu bar using the system property apple.laf.useScreenMenuBar .

When I open a child dialog inside this JFrame, I should be able to access my menu commands via their shortcuts. When hitting my shortcut (Command +Z) The menubar flashes, but the command is not executed. Any suggestions?

Here a code snippet to run the problem. Pressing Command+Z in the main JFrame works and executes the action. Pressing Command +Z inside the child window doesn't work.

public class TestClass {

    static class MyFrame extends JFrame {

        public MyFrame() throws HeadlessException {
            JMenuBar menuBar = new JMenuBar();
            JMenu menu = new JMenu("menu");
            JMenuItem menuItem = new JMenuItem(new AbstractAction("action") {
                {
                    putValue(AbstractAction.ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_Z, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
                }

                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("action executed!");
                }
            });
            menu.add(menuItem);
            menuBar.add(menu);
            setJMenuBar(menuBar);
            JButton button = new JButton("open dialog");
            add(button);
            button.addActionListener((e) -> {
                JDialog dlg = new JDialog(MyFrame.this);
                dlg.setSize(300, 300);
                dlg.setVisible(true);
            });
        }

    }

    public static void main(String[] args) {
        System.setProperty("apple.laf.useScreenMenuBar", "true");
        MyFrame f = new MyFrame();
        f.setSize(400, 400);
        f.setVisible(true);
    }


}

Answer 1

I encountered the same issue with a JFrame on macOS (jdk1.8.0_201). Symptoms:

• menus work fine with a mouse, and menu shortcuts are visible on the menu items
• when the shortcut keys are pressed, the menu heading flashes but no ActionEvent is triggered

I eventually figured out the issue was caused by overriding java.lang.Object 's hashCode() method on the JFrame. Why this causes keyboard shortcuts to fail is unknown to me, but it is definitively the root cause in my case.