Having trouble retrieving headers from Xamarin.Forms Android webview using ShouldOverrideUrlLoading, always (null)

Question

I am using a custom webview client CustomWebviewClient : FormsWebViewClient

In the overridden function ShouldOverrideUrlLoading(Android.Webkit.WebView webView, IWebResourceRequest request) I can see the request object, but the RequestHeaders are null.

In my HybridWebViewRenderer : WebViewRenderer I'm adding additional headers for my app version like so:

Dictionary<string, string> headers = new Dictionary<string, string>
                {
                    {Constants.AppHeader, Constants.AppVersion }
                };

Control.LoadUrl(uri, headers);

I can see these headers on my site when I dump them, but the IWebResourceRequest.RequestHeaders are always null

Am I missing something here on the Android side?

I've noticed a couple times on the iOS side that I need to force cast certain objects in order to access their properties/methods like so:

var thisresponse = (NSHttpUrlResponse)navigationResponse.Response;

var allOfThem = thisresponse.AllHeaderFields;

Thanks for the help!

Answer 1

You could try the code below. CustomHeaderValue is the BindableProperty of my CustomHeaderWebView.

  [assembly: ExportRenderer(typeof(CustomHeaderWebView), typeof(CustomHeaderWebViewRenderer))]
namespace App14.Droid
{
public class CustomHeaderWebViewRenderer : ViewRenderer<CustomHeaderWebView, Android.Webkit.WebView>
{
    Context _localContext;

    public CustomHeaderWebViewRenderer(Context context) : base(context)
    {
        _localContext = context;
    }

    protected override void OnElementChanged(ElementChangedEventArgs<CustomHeaderWebView> e)
    {
        base.OnElementChanged(e);

        Android.Webkit.WebView webView = Control as Android.Webkit.WebView;

        if (Control == null)
        {
            webView = new Android.Webkit.WebView(_localContext);
            SetNativeControl(webView);
        }

        if (e.NewElement != null)
        {
            Dictionary<string, string> headers = new Dictionary<string, string>
            {
                ["Authorization"] = Element.CustomHeaderValue // Change this string for a different header key
            };

            webView.Settings.JavaScriptEnabled = true;

            webView.Settings.BuiltInZoomControls = true;
            webView.Settings.SetSupportZoom(true);

            webView.ScrollBarStyle = ScrollbarStyles.OutsideOverlay;
            webView.ScrollbarFadingEnabled = false;

            webView.SetWebViewClient(new CustomWebViewClient(headers));
            UrlWebViewSource source = Element.Source as UrlWebViewSource;
            webView.LoadUrl(source.Url, headers);
        }
    }
}

public class CustomWebViewClient : Android.Webkit.WebViewClient
{
    public Dictionary<string, string> headers { get; set; }

    public CustomWebViewClient(Dictionary<string, string> requestHeaders)
    {
        headers = requestHeaders;
    }
}
}