rotation overlay

overlay.cs

var centerImg = new UIImageView (UIImage.FromBundle ("findme_fab"));
			centerImg.Frame = new RectangleF (
				centerX - (centerImg.Frame.Width / 2) ,
				centerY - centerImg.Frame.Height - 20 ,
				centerImg.Frame.Width ,
				centerImg.Frame.Height);
			var animation = CABasicAnimation.FromKeyPath("transform.rotation.z");
			animation.From = NSNumber.FromFloat (0.0f);
			animation.To = NSNumber.FromFloat (2f * (float)Math.PI);
			animation.Duration = 1f;
			animation.RepeatCount = float.MaxValue;
			centerImg.Layer.AddAnimation (animation, "spinAnimation");
			AddSubview (centerImg);