public override void ViewDidLoad()
        {
            base.ViewDidLoad ();

            _activityIndicator = new UIActivityIndicatorView (UIActivityIndicatorViewStyle.Gray);

            View.AddSubview (_activityIndicator);

            _activityIndicator.SetStyleId ("sample-activity-indicator");

            _activityIndicator.StartAnimating ();

            View.SetStyleClass ("sample-background");
        }