code: public static void tick() {
          sumFrames++;
          if (startTime == 0) {
              startTime = SystemClock.uptimeMillis();
          }
  
          ++frames;
          long currentTime = System.currentTimeMillis();
          if (currentTime - startTimeMillis >= interval) {
              int fps = (int) (frames * 1000 / interval);
              Log.v("FPSCounter", "FPS : " + fps);
              frames = 0;
              startTimeMillis = currentTime;
          }
      }
docs: This method should be called every frame in {@link org.gearvrf.GVRMain#onStep}
  to do FPS calculation.
  If main debug subsystem is enabled the FPS measurements will be printed out each frame.