FocusView.showFocusArea(android.graphics.Rect).CameraPreviewFragment.onResume() and CameraPreviewFragment.onPause()
to determine whether the creation of camera should be handled automatically.CameraPreviewCutoutFragment.showFailureFeedback(int)CameraPreviewCutoutFragment.onCameraOpenFailed(Throwable) which will only be called after overlay has
been generated (so don't need to handle uninitialised views).