docs: public void onHostActivityPaused() {
          Log.i(TAG, "onHostActivityPaused");
          synchronized (mReadyForFrameFence) {
              // Pause the GLSurfaceView's Renderer thread
              if (mDisplayView != null)
                  mDisplayView.onPause();
              // Release camera if we're not recording
              if (!mRecording && mSurfaceTexture != null) {
                  if (VERBOSE) Log.i("CameraRelease", "Releasing camera");
                  if (mDisplayView != null)
                      releaseDisplayView();
                  mHandler.sendMessage(mHandler.obtainMessage(MSG_RELEASE_CAMERA));
              }
          }
      }