WebView on iOS using Navigating event fails with obj exception

Description

I have an anchor tag which when clicked, is supposed to call the navigating event, where I inspect the url and do different things and set cancel to true.

Completion handler passed to -[Microsoft_Maui_Platform_MauiWebViewUIDelegate webView:contextMenuConfigurationForElement:completionHandler:] was not called.

<WebView x:Name="WebBrowser" Navigating="WebBrowser_Navigating">
  <WebView.Source>
    <HtmlWebViewSource>
      <HtmlWebViewSource.Html>
<!-- html snipped for brevity, include a tag with a url in the href and some text -->
      </HtmlWebViewSource.Html>
    </HtmlWebViewSource>
  <WebView.Source>
</WebView>

private void WebBrowser_Navigating(object? sender, WebNavigatingEventArgs e)
{
    e.Cancel = true;
    // business logic here, snipped for brevity
}

Steps to Reproduce

1. Create new maui app
2. Add webview component with an html anchor tag in the xaml that points to any url
3. Hook into the navigating event - Navigating="WebBrowser_Navigating"
4. Create callback in the xaml.cs file and in the navigating event callback, set e.Cancel to true
5. Deploy to iOS device
6. Click the anchor tag in the web view
7. Crash

Version with bug

7.0 (current)

Last version that worked well

Unknown/Other

Affected platforms

iOS

Affected platform versions

iOS 13, 14, 15, 16

Did you find any workaround?

No

Relevant log output

Completion handler passed to -[Microsoft_Maui_Platform_MauiWebViewUIDelegate webView:contextMenuConfigurationForElement:completionHandler:] was not called.

Works fine on Windows and Android, no issue.

[anton-yashin]

This is because MauiWebViewUIDelegate.SetContextMenuConfiguration may not call completionHandler when no webView.Interactions is available. For workaround you should install WKView.UIDelegate where you going to call completion handler. Something like that:

sealed class MauiWebViewUIDelegate2 : MauiWebViewUIDelegate
    {
        public MauiWebViewUIDelegate2(IWebViewHandler handler) : base(handler)
        {
        }

        [SupportedOSPlatform("maccatalyst13.1")]
        [SupportedOSPlatform("ios13.0")]
        [UnsupportedOSPlatform("macos")]
        [UnsupportedOSPlatform("tvos")]
        public override void SetContextMenuConfiguration(WKWebView webView, WKContextMenuElementInfo elementInfo, Action<UIContextMenuConfiguration> completionHandler)
        {
            bool completionHandlerIsInvoked = false;

            base.SetContextMenuConfiguration(webView, elementInfo, cfg =>
            {
                completionHandlerIsInvoked = true;
                completionHandler(cfg);
            });

            if (completionHandlerIsInvoked == false)
                completionHandler(null!);
        }
    }

    sealed class WebViewHandler2 : WebViewHandler
    {
        WKUIDelegate? _delegate;

        public static void MapWKUIDelegate2(IWebViewHandler handler, IWebView webView)
        {
            if (handler is WebViewHandler2 platformHandler)
                handler.PlatformView.UIDelegate = platformHandler._delegate ??= new MauiWebViewUIDelegate2(handler);
        }
    }

    // at your application startup
   WebViewHandler.Mapper.Add(nameof(WKUIDelegate), WebViewHandler2.MapWKUIDelegate2);
   // when maui app is created
  app.ConfigureMauiHandlers(h => h.AddHandler<WebView, WebViewHandler2>());

[msftbot[bot]]

We’ve moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.