code: public void tryVibrate() {
          if (mVibrator != null) {
              long now = SystemClock.uptimeMillis();
              // We want to try to vibrate each individual tick discretely.
              if (now - mLastVibrate >= 125) {
                  mVibrator.vibrate(5);
                  mLastVibrate = now;
              }
          }
      }
docs: Try to vibrate. To prevent this becoming a single continuous vibration, nothing will
  happen if we have vibrated very recently.