Xamarin Webview link is opening twice in Android

Question

Hello, I want to open urls in a browser and I found some discussions about:

https://stackoverflow.com/questions/53704452/how-can-i-modify-a-webview-in-xamarin-forms-to-open-links-in-a-browser-on-the-de
https://forums.xamarin.com/discussion/38243/webview-open-external-browser

Then, my solution was to
a) use Browser.OpenAsync to open it the browser
b) use e.Cancel = true to avoid the opening in the webview

Expected: touch link and open the browser.
What happend: touch link, open url in webview and then open url in the browser. If I try to goback it show the webview with the url content.

How can I avoid to open the url first in webview?

Information about my project

• Visual Studio 2019 Version 16.8.3 on Windows
• Android target version: 10.0 (Q)
• Minimum android version: 4.4
• Xamarin Forms version: 4.6.0.1141
• Xamarin Essentials version: 1.5.0

The Navigation event in code-behind

        public void OnNavigating(object sender, WebNavigatingEventArgs e)  
        {  
            if (e.Url.StartsWith("http") && !e.Url.Equals(URL))  
            {  
                try  
                {  
                    var uri = new Uri(e.Url);  
                    Browser.OpenAsync(uri);  
                }  
                catch (Exception)  
                {  
                }  
  
                e.Cancel = true;  
            }  
        }  

If it helps to understand o problem, I also implemented and webview renderer for android and its method OnElementChanged. Also, methods OnPageFinished and OnPageStarted were overridden in WebViewClient.

OnElementChanged implementation:

        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)  
        {  
            base.OnElementChanged(e);  
            Control.VerticalScrollBarEnabled = false;  
            Control.Settings.JavaScriptEnabled = true;  
            Control.Settings.SetGeolocationEnabled(true);  
            Control.Settings.DomStorageEnabled = true;  
            Control.Settings.SetAppCacheEnabled(true);  
            Control.Settings.JavaScriptCanOpenWindowsAutomatically = true;  
            Control.Settings.SetGeolocationDatabasePath(Control.Context.FilesDir.Path);  
  
            Control.Settings.CacheMode = CacheModes.CacheElseNetwork;  
  
            if (Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.Kitkat)  
            {  
                Control.SetLayerType(Android.Views.LayerType.Hardware, null);  
            }  
            else  
            {  
                Control.SetLayerType(Android.Views.LayerType.Software, null);  
            }  
  
            Control.SetWebChromeClient(new GeoWebClient());  
  
            if (Control != null)  
            {  
                Control.SetWebViewClient(new WebClient(this));  
            }  
        }  

WebViewClient implementation:

    class WebClient : WebViewClient  
    {  
        GeoWebViewRenderer _renderer;  
  
        public WebClient(GeoWebViewRenderer renderer)  
        {  
            _renderer = renderer ?? throw new ArgumentNullException("renderer");  
        }  
  
        public override void OnPageFinished(Android.Webkit.WebView view, string url)  
        {  
            base.OnPageFinished(view, url);  
  
            var source = new UrlWebViewSource { Url = url };  
            var args = new WebNavigatedEventArgs(WebNavigationEvent.NewPage, source, url, WebNavigationResult.Success);  
            _renderer.ElementController.SendNavigated(args);  
        }  
  
        public override void OnPageStarted(Android.Webkit.WebView view, string url, Bitmap favicon)  
        {  
            base.OnPageStarted(view, url, favicon);  
  
            var args = new WebNavigatingEventArgs(WebNavigationEvent.NewPage, new UrlWebViewSource { Url = url }, url);  
            _renderer.ElementController.SendNavigating(args);  
        }  
    }  

Answer 1

I tested your proposal and it doesn't work for me. However, I solved my problem by removing the class WebClient and its instance of the OnElementChanged function. I hope this help someone in the future. Thanks a lot @JarvanZhang !

Answer 2

Hello,​

Welcome to our Microsoft Q&A platform!

The navigating event will be triggered twice when opening a url, you could add a breakpoint to check that. When the event is called for the second time, the Url has been added a '/' at the end. That should the cause.

   private void browser_Navigating(object sender, WebNavigatingEventArgs e)  
   {  
       var str = e.Url;  
   }  

To fix the issue, try adding another condition sentence like below:

   private void browser_Navigating(object sender, WebNavigatingEventArgs e)  
   {  
       if (e.Url.StartsWith("http") && !e.Url.Equals("https://www.google.com") && !e.Url.Equals("https://www.google.com/"))  
       {  
           try  
           {  
               var uri = new Uri(e.Url);  
               Browser.OpenAsync(uri);  
           }  
           catch (Exception)  
           {  
           }  
     
           e.Cancel = true;  
       }  
   }  

Best Regards,

Jarvan Zhang

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