Problems with the interface when rotating the device horizontally - xaml

Question

The interface of my app is divided into a header (it is a webview) and absolute content, which among other things contains a second webview.
In vertical orientation it works and looks perfect.
But when I turn the device horizontally the header stops measuring 70 and measures something like 30 ....
The header reduces the height although it has a fixed height.
Why this happen? Any solution?
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:PruebaHeight"
x:Class="PruebaHeight.MainPage">
<ContentPage.Content>
<StackLayout Spacing="0">
<WebView x:Name="webview_header" HorizontalOptions="FillAndExpand" HeightRequest="70" BackgroundColor="Red"/>
<AbsoluteLayout HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" BackgroundColor="Black">
<!-- other things -->
<ScrollView AbsoluteLayout.LayoutBounds="0,0,1,1" AbsoluteLayout.LayoutFlags="All" BackgroundColor="Green">
<AbsoluteLayout HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" Padding="0" BackgroundColor="Purple">
<WebView x:Name="webview" AbsoluteLayout.LayoutBounds="0,0,1,1" AbsoluteLayout.LayoutFlags="All" BackgroundColor="Blue" />
</AbsoluteLayout>
</ScrollView>
</AbsoluteLayout>
</StackLayout>
</ContentPage.Content>

Answer 1

You could try to custom a view like following code.
XamWebView.cs
public class XamWebView: WebView
{
}
Then use it in your code.
var webview= new XamWebView();
webview.HorizontalOptions = LayoutOptions.Fill;
webview.VerticalOptions = LayoutOptions.StartAndExpand;
webview.WidthRequest = 70;
webview.HeightRequest = 70;
webview.Source = "https://www.google.com/";
Creating the Custom Renderer on Android(you could get the value of heightrequest when you running)
using WebView = Android.Webkit.WebView;
[assembly: ExportRenderer (typeof(XamWebView), typeof(XamWebViewRenderer))]
namespace Core.Droid
{
public class XamWebViewRenderer : WebViewRenderer
{
static XamWebView _xwebView = null;
WebView _webView;
public XamWebViewRenderer(Context context) : base(context)
{
}
class XamWebViewClient : Android.Webkit.WebViewClient
{
public override async void OnPageFinished(WebView view, string url)
{
if (_xwebView != null)
{
int i = 10;
while (view.ContentHeight == 0 && i-- > 0)
await System.Threading.Tasks.Task.Delay(100);
_xwebView.HeightRequest = view.ContentHeight;
}
}
}
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
{
base.OnElementChanged(e);
_xwebView = e.NewElement as XamWebView;
_webView = Control;
if (e.OldElement == null)
{
_webView.SetWebViewClient(new XamWebViewClient());
}
}
}
}