Detecting physical Menu key press in Android

I’d look for an up key event, rather than a down event, with onKeyUp.

public boolean onKeyUp(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_MENU) {
        // ........
        return true;
    }
    return super.onKeyUp(keyCode, event);
}

We return true because we’re handling the event; return false if you want the system to handle the event too.

You can do all of this in your Activity instance too because Activity is a known indirect subclass of KeyEvent.