JavaFX KeyTypedEvent conflit with KeyPressed and KeyReleasedEvent

Question

    scene.setOnKeyPressed(new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent ke) {
            if (ke.getCode() == KeyCode.SPACE) {
                System.out.println("space pressed");
            }
        }
    });
    scene.setOnKeyReleased(new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent ke) {
            if (ke.getCode() == KeyCode.SPACE) {
                System.out.println("space released");
            }
        }
    });
    scene.setOnKeyTyped(new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent ke) {
            if (ke.getCode() != KeyCode.SPACE) {
                System.out.println("typed");
            }
        }
    });

JavaFX KeyTypedEvent conflit with KeyPressed and KeyReleasedEvent.

Why I press SPACE key, also print "Typed", It's strange.

Thanks!

Answer 1

To quote the Java Documentation:

"Key typed" events are higher-level and generally do not depend on the platform or keyboard layout. They are generated when a Unicode character is entered, and are the preferred way to find out about character input. In the simplest case, a key typed event is produced by a single key press (e.g., 'a'). Often, however, characters are produced by series of key presses (e.g., SHIFT + 'a'), and the mapping from key pressed events to key typed events may be many-to-one or many-to-many. Key releases are not usually necessary to generate a key typed event, but there are some cases where the key typed event is not generated until a key is released (e.g., entering ASCII sequences via the Alt-Numpad method in Windows). No key typed events are generated for keys that don't generate Unicode characters (e.g., action keys, modifier keys, etc.).

The char variable always contains a valid Unicode character or CHAR_UNDEFINED. Character input is reported by key typed events; key pressed and key released events are not necessarily associated with character input. Therefore, the char variable is guaranteed to be meaningful only for key typed events.

For key pressed and key released events, the code variable contains the event's key code. For key typed events, the code variable always contains KeyCode.UNDEFINED.

"Key pressed" and "key released" events are lower-level and depend on the platform and keyboard layout. They are generated whenever a key is pressed or released, and are the only way to find out about keys that don't generate character input (e.g., action keys, modifier keys, etc.). The key being pressed or released is indicated by the code variable, which contains a virtual key code.

Basically said, "Key typed" events are input events while "Key pressed" and "Key released" events are keyboard events.