iOS web view renderer doesn't update its value - xamarin.forms

Question

I have implemented WebViewRenderer it works well on Android but it doesn't work on iOS. It displays the value, but then user clicks next button and the value doesn't update. I have tried the the example on ms website, but that displayed no text, I don't have the values from URL. I have also tried several post here.
[assembly: ExportRenderer(typeof(ExtendedWebView), typeof(ExtendedWebViewRenderer))]
namespace MyApp.iOS.Renderers
{
public class ExtendedWebViewRenderer : ViewRenderer<ExtendedWebView, WKWebView>
{
WKWebView _wkWebView;
static ExtendedWebView _xwebView = null;
protected override void OnElementChanged(ElementChangedEventArgs<ExtendedWebView> e)
{
base.OnElementChanged(e);
if (Control == null)
{
WKWebViewConfiguration config = new WKWebViewConfiguration();
_wkWebView = new WKWebView(Frame, config);
_wkWebView.NavigationDelegate = new CustomWKNavigationDelegate(this);
SetNativeControl(_wkWebView);
}
if (e.NewElement != null)
{
HtmlWebViewSource source = (Xamarin.Forms.HtmlWebViewSource)Element.Source;
string html = source.Html;
_wkWebView.LoadHtmlString(html, baseUrl: null);
_wkWebView.ScrollView.ScrollEnabled = false;
_wkWebView.SizeToFit();
}
}
}
public class CustomWKNavigationDelegate : WKNavigationDelegate
{
ExtendedWebViewRenderer _webViewRenderer;
public CustomWKNavigationDelegate(ExtendedWebViewRenderer webViewRenderer)
{
_webViewRenderer = webViewRenderer;
}
public override async void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
{
var wv = _webViewRenderer.Element as ExtendedWebView;
if (wv != null)
{
await System.Threading.Tasks.Task.Delay(100); // wait here till content is rendered
wv.HeightRequest = (double)webView.ScrollView.ContentSize.Height;
}
}
}
}
[assembly: ExportRenderer(typeof(ExtendedWebView), typeof(ExtendedWebViewRenderer))]
namespace MyApp.Droid.Renderers
{
public class ExtendedWebViewRenderer : WebViewRenderer
{
public static int _webViewHeight;
static ExtendedWebView _xwebView = null;
public WebView _webView;
bool isScroll;
[Obsolete]
public ExtendedWebViewRenderer(Context context) : base(context)
{
}
class ExtendedWebViewClient : WebViewClient
{
WebView _webView;
public async override void OnPageFinished(WebView view, string url)
{
try
{
_webView = view;
if (_xwebView != null)
{
view.Settings.JavaScriptEnabled = true;
await Task.Delay(100);
string result = await _xwebView.EvaluateJavaScriptAsync("(function(){return document.body.scrollHeight;})()");
_xwebView.HeightRequest = Convert.ToDouble(result);
}
base.OnPageFinished(view, url);
}
catch (Exception ex)
{
Console.WriteLine($"{ex.Message}");
}
}
public override bool ShouldOverrideUrlLoading(Android.Webkit.WebView view, IWebResourceRequest request)
{
return true;
}
}
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
{
base.OnElementChanged(e);
_xwebView = e.NewElement as ExtendedWebView;
_webView = Control;
if (e.OldElement == null)
{
_webView.SetWebViewClient(new ExtendedWebViewClient());
}
}
}
}
public class ExtendedWebView : WebView
{
public ExtendedWebView()
{
}
}
XAML
<controls:ExtendedWebView
VerticalOptions="FillAndExpand" Grid.RowSpan="2"
x:Name="enView"
Opacity="1"
Source="{Binding CZ, Mode=TwoWay}"/>
private static HtmlWebViewSource htmlSourceExplanation = new HtmlWebViewSource();
public HtmlWebViewSource Cz
{
get { return _cz; }
set
{
_cz = value;
NotifyPropertyChanged(nameof(Cz));
}
}
private void SetExplanationDetail(string text, string text2)
{
htmlSourceExplanation.Html = _style + "<div class=\"text\"><div>" + text + "</div><div>" + text2 + "</div></div>";
_cz = htmlSourceExplanation;
NotifyPropertyChanged("Cz");
}
I expect the value to change once to user cliks the button. `