code: private void vibrateIfEnabled() {
          final boolean enabled = styledAttributes.getBoolean(R.styleable.PinLock_vibrateOnClick, false);
          if(enabled){
              Vibrator v = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
              final int duration = styledAttributes.getInt(R.styleable.PinLock_vibrateDuration, 20);
              v.vibrate(duration);
          }
      }
docs: Vibrate device on each key press if the feature is enabled