WKWebView fails to load images and CSS using loadHTMLString(_, baseURL:)

Question

Apple\'s recommendation:

In apps that run in iOS 8 and later, use the WKWebView class instead of using UIWebView.

Thus, I have r

Answer 1

I know this is quite old already, but I ran into the exact same problem and it took me hours of trials and even to find this thread with the same problem (Xamarin Forms App)

My issue was: parsing remote HTML content into a string and also adding locally saved images (also downloaded dynamically, no resource of the app). On the simulator all works well, but on acutal device the local images are not showing (also no ? or anything indicating an error, just a blank frame). The Xamarin webview also offers the "BaseURL" option which didn't help, also not to use the BaseURL on the custom iOS wkWebView.

The only working solution as pointed out by Scott above, is to write the HTML into a file and then use the "LoadFileUrl" function and allow read access to the base directory. This also works with absolute file paths for images in the HTML (not only relative to the basedir, but of course somewhere within the basedir).

My custom webview renderer to load web and local content looks like this now:

protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
    base.OnElementPropertyChanged(sender, e);
    NSUrl baseURL = new NSUrl(App.dirNews, true);
    string viewFile = Path.Combine(App.dirNews, "view.html");
    NSUrl fileURL = new NSUrl(viewFile, false);

    switch (e.PropertyName) {
        case "Url":
            System.Console.WriteLine("--- Loading Web page ---");
            System.Console.WriteLine("--- " + Element.Url + " ---");
            NSUrlRequest myRequest = new NSUrlRequest(new NSUrl(Element.Url), NSUrlRequestCachePolicy.ReloadIgnoringLocalAndRemoteCacheData, 120);
            Control.LoadRequest(myRequest);
            break;

        case "HTML":
            System.Console.WriteLine("--- Showing HTTP content ---");
            File.WriteAllText(viewFile, Element.HTML, System.Text.Encoding.UTF8);
            Control.LoadFileUrl(fileURL, baseURL);
            break;
    }
}