如何保证Java Swing JDialog将保持焦点并注册游戏中的所有按键？

Question

I am making a game. It uses a jDialog because one Stack Overflow question said I had to use a modal jDialog to always be in focus. My jDialog has an outgoing chat field and a game window. The game window is a jPanel, the field a jTextField. When I press the arrow keys, I want that to go to the jPanel. When I type on the keyboard, I want that to go to the jTextField. When I press enter, I want the jTextField to clear. I do not want to click on the jTextField to make it in focus to type stuff in it and then click on the game screen to to move again.

My code looks like this:

/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
    public void run() {
        jDialog_GUI.singleton_ = new jDialog_GUI(new javax.swing.JFrame(), true);
        singleton_.requestFocusInWindow();
        singleton_.setVisible(true);
        singleton_.addWindowListener(new java.awt.event.WindowAdapter() {
            @Override
            public void windowClosing(java.awt.event.WindowEvent e) {
                System.exit(0);
            }
        });
    }
});

Constructor:

public jDialog_GUI(java.awt.Frame parent, boolean modal) {
    super(parent, modal);
    initComponents(); // initializes all the components using Swing GUI builder code
    this.setModalityType(jDialog_GUI.ModalityType.APPLICATION_MODAL);
    if (this.getModalityType() != jDialog_GUI.ModalityType.APPLICATION_MODAL) {
        RunGame.printStackTraceAndCrashTheProgramBecause("Not modal.");
    }
}

One of the other StackOverflow questions told me that if I use a jDialog and make it modal, then it will maintain focus, but when I do:

SwingUtilities.invokeLater(new Runnable() {
    public void run() {
        if(! jDialog_GUI.get_GUI().isFocusOwner() ) {
            RunGame.printStackTraceAndCrashTheProgramBecause("JDialog must always be in focus.");
        }
    }
});

It crashes and prints "JDialog must always be in focus."

Even when I don't crash the program, none of the key presses will register in my jDialog's key listener.

addKeyListener(new java.awt.event.KeyAdapter() {
    public void keyPressed(java.awt.event.KeyEvent evt) {
        formKeyPressed(evt);
    }
    public void keyTyped(java.awt.event.KeyEvent evt) {
        formKeyTyped(evt);
    }
});

...

private void formKeyPressed(java.awt.event.KeyEvent evt) {     
    int keyCode = evt.getKeyCode();
    System.out.println(keyCode + " " + KeyEvent.getKeyText(keyCode));
}      
private void formKeyTyped(java.awt.event.KeyEvent evt) {
    char c = evt.getKeyChar();
    System.out.println(c);
}

...

Mouse presses register, and button presses register, but the key presses won't register. I even have a I want the focus to be on the frame and the frame to modify its components based on what keys are pressed rather than having one of the components hog all the key input from the other components. How do I fix this?

There is also a formWindowFocused listener that goes off when I run the program, but my jDialog's formFocusGained listener does not.

Answer 1

KeyEvents are dispatched to the component that has focus, so using a KeyListener is not a good solution.

For more flexibility in handling KeyStrokes you need to use Key Bindings . You can map a KeyStroke to an Action even when a component doesn't have focus.

Read the section from the Swing tutorial on How to Use Key Bindings for more information and examples.