LoadingServiceiOS.cs

[assembly: Xamarin.Forms.Dependency (typeof(LoadingService))]
namespace YOURNAMESPACE.iOS
{
        public class LoadingService : ILoadingService
        {
                public LoadingService ()
                {
                    BTProgressHUD.ForceiOS6LookAndFeel = true;
                }

                #region ILoadingService implementation

                public void Show (string message = "Loading")
                {
                    BTProgressHUD.Show (maskType: ProgressHUD.MaskType.Gradient);

                }

                public void Hide ()
                {
                    BTProgressHUD.Dismiss ();
                }

                #endregion
        }
}