Xamarin Forms custom webView renderer with activity load

gistfile1.cs

***
In Shared code:

	public class WebViewPage : ContentPage
	{
	}

...

await Navigation.PushAsync (new WebViewPage());

***

using System;

using ViewRSS;
using Xamarin.Forms;
using ViewRSS.iOS;
using Xamarin.Forms.Platform.iOS;

using Foundation;
using UIKit;
using CoreGraphics;

using System.Threading;
using System.Threading.Tasks;

[assembly: ExportRenderer (typeof (WebViewPage), typeof (WebViewPageRenderer))]

namespace ViewRSS.iOS
{
	public class WebViewPageRenderer : PageRenderer
	{
		UIWebView webView;
		LoadingOverlay loadingOverlay;

		public WebViewPageRenderer ()
		{
		}

		public override void ViewDidAppear (bool animated)
		{
			base.ViewDidAppear (animated);

			App.Debug ("ViewDidAppear");

			var url = new NSUrlRequest (new NSUrl (ItemsPage._item.Link), NSUrlRequestCachePolicy.UseProtocolCachePolicy, 15.0);
			webView.LoadRequest (url);
		}

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

			App.Debug ("ViewDidLoad");

			webView = new UIWebView (View.Bounds);
			webView.WeakDelegate = this;
			webView.ScalesPageToFit = true;
			View.AddSubview(webView);

			bool didStart = false;
			bool didFinish = false;

			loadingOverlay = new LoadingOverlay(webView.Bounds);
			webView.Add(loadingOverlay);
			UIApplication.SharedApplication.NetworkActivityIndicatorVisible = true;

			//When the web view is finished loading
			webView.LoadFinished += (object sender, EventArgs e) => {
				if (didFinish == false)
				{
					loadingOverlay.Hide();
					UIApplication.SharedApplication.NetworkActivityIndicatorVisible = false;
					didStart = false;
					didFinish = true;
				}
			};

			//If there is a load error
			webView.LoadError += (object sender, UIWebErrorArgs e) => {
				if (didFinish == false)
				{
					loadingOverlay.Hide();
					UIApplication.SharedApplication.NetworkActivityIndicatorVisible = false;
					didStart = false;
					didFinish = true;
				}
			};
		}
	}

	public class LoadingOverlay : UIView {
		// control declarations
		UIActivityIndicatorView activitySpinner;
		UILabel loadingLabel;

		public LoadingOverlay (CGRect frame) : base (frame)
		{
			// configurable bits
			BackgroundColor = UIColor.Black;
			Alpha = 0.75f;
			AutoresizingMask = UIViewAutoresizing.FlexibleDimensions;

			nfloat labelHeight = 22;
			nfloat labelWidth = Frame.Width - 20;

			// derive the center x and y
			nfloat centerX = Frame.Width / 2;
			nfloat centerY = Frame.Height / 2;

			// create the activity spinner, center it horizontall and put it 5 points above center x
			activitySpinner = new UIActivityIndicatorView(UIActivityIndicatorViewStyle.WhiteLarge);
			activitySpinner.Frame = new CGRect (
				centerX - (activitySpinner.Frame.Width / 2) ,
				centerY - activitySpinner.Frame.Height - 20 ,
				activitySpinner.Frame.Width ,
				activitySpinner.Frame.Height);
			activitySpinner.AutoresizingMask = UIViewAutoresizing.FlexibleMargins;
			AddSubview (activitySpinner);
			activitySpinner.StartAnimating ();

			// create and configure the "Loading Data" label
			loadingLabel = new UILabel(new CGRect (
				centerX - (labelWidth / 2),
				centerY + 20 ,
				labelWidth ,
				labelHeight
			));
			loadingLabel.BackgroundColor = UIColor.Clear;
			loadingLabel.TextColor = UIColor.White;
			loadingLabel.Text = "Loading Data...";
			loadingLabel.TextAlignment = UITextAlignment.Center;
			loadingLabel.AutoresizingMask = UIViewAutoresizing.FlexibleMargins;
			AddSubview (loadingLabel);
		}

		/// <summary>
		/// Fades out the control and then removes it from the super view
		/// </summary>
		public void Hide ()
		{
			UIView.Animate (
				0.5, // duration
				() => { Alpha = 0; },
				() => { RemoveFromSuperview(); }
			);
		}
	};
}