Java Swing密钥处理程序偶尔不起作用

Question

I am developing a Java Swing based video game. I am having a problem with detecting keystrokes- the 'A' (move left) and 'D' keys (move right), where it almost seems they are not firing (but happens rarely). Almost as if they have become unregistered. Now, I have setup log files to capture the keyboard events, and again one of the keyHandlers at some point does not fire. Now when this does happen, if I click into the main screen of the game with my mouse, the keyHandler that somehow got lost seems to work again. Almost as if the "Focus" was inadvertantly transferred to some other widget in the game.

Here is the code to setup the Action Maps:

    topStatusPanel.getInputMap().put(KeyStroke.getKeyStroke("pressed A"),
            "aCharKeyPressed");
    topStatusPanel.getActionMap().put("aCharKeyPressed", aKeyActionPressed);


    topStatusPanel.getInputMap().put(KeyStroke.getKeyStroke("released A"), 
            "aCharKeyReleased");
    topStatusPanel.getActionMap().put("aCharKeyReleased", aKeyActionReleased);



    topStatusPanel.getInputMap().put(KeyStroke.getKeyStroke("pressed D"), 
            "dCharKeyPressed");
    topStatusPanel.getActionMap().put("dCharKeyPressed", dKeyActionPressed);

    topStatusPanel.getInputMap().put(KeyStroke.getKeyStroke("released D"), 
            "dCharKeyReleased");
    topStatusPanel.getActionMap().put("dCharKeyReleased", dKeyActionReleased);

    MoveSubLeftActionStart aKeyActionPressed= new MoveSubLeftActionStart();
    MoveSubLeftActionStop aKeyActionReleased= new MoveSubLeftActionStop();
    MoveSubRightActionStart dKeyActionPressed= newMoveSubRightActionStart();
    MoveSubRightActionStop dKeyActionReleased= new MoveSubRightActionStop();

Would really appreciate any ideas on this. Is there a way to force focus to a specific widget?- would I then for every other widget in the game have to set it to "unfocusable?" Could this be the issue? Appreciate any help here.

Answer 1

Here's an in-depth treatment on focus management and keyboard event handling. If your JPanel contains other components, they might get the focus and not propagate the key events up the component chain.

http://docs.oracle.com/javase/6/docs/api/java/awt/doc-files/FocusSpec.html#RequestingFocus