Activity View (Spinner) position iOS

On iOS devices the current plugin version does not center the activity view (Spinner) in its parent view. Instead its center is bound to the upper left corner. Only after some time (5 seconds) the activity view is centered in its parent view.
I already have fixed this bug by replacing the current positioning (via _activityView.center and _activityView.autoresizingMaks) with NSLayoutConstraint.