Java: handling combined keyboard input

Question

What is the correct way to separate between F1 and i.e. CTRL+F1 respective SHIFT-CTRL+F1 within an KeyListener registered behind i.e. a JButton?

public void keyPressed(KeyEvent event) {
    int key = event.getKeyCode();

    logger.debug("KeyBoard pressed char(" + event.getKeyChar() + ") code (" + key + ")");
}

.. always gives me 112 for F1, 113 for F2 and so on. I understand that I can handle it by taking care of the keyPressed() respective for keyReleased for CTRL / SHIFT / ALT / etc on my own, but I hope that there is a better way.

Many many thanks!!!

Answer 1

The Solution lies in the parent of KeyEvent (InputEvent)

1. Use the isAltDown,isControlDown,isShiftDown methods or
2. Use the getModifiers method

Answer 2

Since KeyEvent extends InputEvent, isControlDown, isShiftDown and isAltDown.

Answer 3

KeyEvents are probably a bit low-level when dealing with a Swing widget. Instead go through InputMap and ActionMap.

Answer 4

The key down event is called whenever a key is down, obviously. Its not a multiple key down event, and there is no such thing, so there is no keycode for multiple keys being down.

You are just going to have to use a variable to keep track of the crtl key being pressed. This means you are also going to have to use a key up event to keep track of when the control key is released.

In pusedo code:

// CRTLKeyCode is whatever the code is for the ctrl key
private boolean ctrlPressed = false;

 onKeyDown(KeyEvent event){
     int key = event.getKeyCode();
     if(key == CRTLKeyCode)
        ctrlPressed = true;
     else if(ctrlPressed && key == 112)
        //Perform your action
 }
 onKeyUp(KeyEvent event){
     int key = event.getKeyCode();
     if(key == CRTLKeyCode)
        ctrlPressed = false;
 }