WebView fails to download files from the site.

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You need to create a custom renderer for webview in Xamarin Android.

Then make sure WebView has enabled javascript and the WebViewClient is set correctly.

   web.Settings.JavaScriptEnabled = true;  
   web.SetWebViewClient(new WebviewClient());  

Then set a SetDownloadListener for Android.Webkit.WebView, Then use DownloadManager to download the file. Due to the Android 11 storage limitation. I store download file to the application's top-level directory with Xamarin.Essentials: File System Helpers.

   [assembly: ExportRenderer(typeof(Xamarin.Forms.WebView), typeof(MyWebviewCustomRenderer))]  
   namespace App11.Droid  
   {  
       internal class MyWebviewCustomRenderer : WebViewRenderer  
       {  
           public MyWebviewCustomRenderer(Context context) : base(context)  
           {  
           }  
           protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)  
           {  
                   base.OnElementChanged(e);  
                   var webView = new global::Android.Webkit.WebView(Android.App.Application.Context);  
                   webView.Settings.JavaScriptEnabled = true;  
                   webView.SetWebViewClient(new WebViewClient());  
                   webView.SetWebChromeClient(new WebChromeClient());  
                   webView.SetDownloadListener(new CustomDownloadListener());  
                   this.SetNativeControl(webView);  
                   var source = e.NewElement.Source as UrlWebViewSource;  
                   if (source != null)  
                   {  
                       webView.LoadUrl(source.Url);  
                   }  
                
           }  
       }  
       public class CustomDownloadListener : Java.Lang.Object, IDownloadListener  
       {  
           public void OnDownloadStart(string url, string userAgent, string contentDisposition, string mimetype, long contentLength)  
           {  
     
               try  
               {  
                   DownloadManager.Request request = new DownloadManager.Request(Android.Net.Uri.Parse(url));  
                   request.AllowScanningByMediaScanner();  
                   request.SetNotificationVisibility(DownloadVisibility.VisibleNotifyCompleted);  
     
                   // if this path is not create, we can create it.  
                   string thmblibrary = FileSystem.AppDataDirectory + "/download";  
                   if (!Directory.Exists(thmblibrary))  
                       Directory.CreateDirectory(thmblibrary);  
     
                   request.SetDestinationInExternalFilesDir(Android.App.Application.Context, FileSystem.AppDataDirectory, "download");  
                   DownloadManager dm = (DownloadManager)Android.App.Application.Context.GetSystemService(Android.App.Application.DownloadService);  
                   dm.Enqueue(request);  
                    
               }  
               catch (Exception)  
               {  
                   throw;  
               }  
                
           }  
       }  
   }  

Best Regards,

Leon Lu

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