code: private void updatePreview(CameraCaptureSession session ) {
  		if (null == open.mCameraDevice) {
  			return;
  		}
  		open.mLock.lock();
  		try {
  			mPreviewSession = session;
  			mPreviewSession.setRepeatingRequest(open.mPreviewRequestBuilder.build(), null, mBackgroundHandler);
  		} catch (CameraAccessException e) {
  			e.printStackTrace();
  		} finally {
  			open.mLock.unlock();
  		}
  
  	}
docs: Update the camera preview. {@link #startPreview()} needs to be called in advance.