Setting WebView AllowFileAccess property in Xamarin Forms Shared Project

Question

Hi,

How can I want to set below webview settings in shared project

webView.Settings.AllowContentAccess = true;
webView.Settings.AllowFileAccess = true;

Below is the XAML part

<WebView x:Name="webView" Navigating="webView_Navigating" Navigated="webView_Navigated" ></WebView>

Tried custom renderer, but renderer OnElementChanged calls after webview source has been set

Thanks.

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

You can create a custom webview add two BindableProperty in the background code.

   public class MyWebview:WebView  
       {  
           public static BindableProperty AllowContentAccessProperty =  
                        BindableProperty.Create(nameof(AllowContentAccess),  
                        typeof(bool),  
                        typeof(MyWebview),  
                        null);  
     
          
           public bool AllowContentAccess  
           {  
               get => (bool)GetValue(AllowContentAccessProperty);  
               set => SetValue(AllowContentAccessProperty, value);  
           }  
     
     
     
           public static BindableProperty AllowFileAccessProperty =  
                       BindableProperty.Create(nameof(AllowFileAccess),  
                       typeof(bool),  
                       typeof(MyWebview),  
                       null);  
     
     
           public bool AllowFileAccess  
           {  
               get => (bool)GetValue(AllowFileAccessProperty);  
               set => SetValue(AllowFileAccessProperty, value);  
           }  
       }  

Then use it in the xaml.

   <customwebviewdemo:MyWebview AllowContentAccess="True" AllowFileAccess="True" Source="https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/custom-renderer/entry" WidthRequest="100" HeightRequest="100" ></customwebviewdemo:MyWebview>  

In the android customrenderer, you can set the Bindable value.

   [assembly: ExportRenderer(typeof(MyWebview), typeof(MyWebviewRenderer))]  
   namespace CustomWebviewDemo.Droid  
   {  
       class MyWebviewRenderer : WebViewRenderer  
       {  
           Context context;  
           public MyWebviewRenderer(Context context) : base(context)  
           {  
               this.context = context;  
           }  
     
           protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)  
           {  
               base.OnElementChanged(e);  
     
               if (e.OldElement != null || Element == null)  
               {  
                   return;  
               }  
     
               var webView = (global::Android.Webkit.WebView)Control;  
     
               MyWebview myWebview= e.NewElement as MyWebview;  
                
     
                
     
               webView.Settings.AllowContentAccess = myWebview.AllowContentAccess;  
               webView.Settings.AllowFileAccess = myWebview.AllowFileAccess;  
     
                
           }  
       }  
   }  

Best Regards,

Leon Lu

---

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Answer 2

Hi Leon Lu,

Thank you for detailed code. I tried implement it same way, but it still gives same error.

Apparently, webview goes to renderer after webview has been initialized, i.e. first it has called protected override void OnAppearing() {}, then protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e) {}

This happening at random - for. e.g. If I open browser (navigation.PushModalAsync) 10 time (same url), it will give error randomly 2 to 3 times, other it will load page perfectly.

Error :

Webpage not available

The webpage at
file:///data/user/0/com.test.xamarin/files/webpage.html
could not be loaded because:

net:ERR_ACCESS_DENIED

Below is my implementation :

Custom Control (WebViewCustom) = same as yours.
Rendererer = same as yours

Below is WebBrowser Page XML that uses WebViewCustom

<ContentPage.Content>
    <StackLayout HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
        <controls:WebViewCustom x:Name="wvBrowser" AllowContentAccess="True" AllowFileAccess="True" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"  ></controls:WebViewCustom>
    </StackLayout>
</ContentPage.Content>

WebBrowser CS

public partial class WebViewBrowser : ContentPage
{
    string url;
    public WebViewBrowser(string url)
    {
        InitializeComponent();
        this.url = url;
    }

    protected override void OnAppearing()
    {
        base.OnAppearing();
        wvBrowser.Source = new UrlWebViewSource { Url = this.url };
    }
}

}

Answer 3

Hi Leon Lu,

Thank you for detailed code. I tried implement it same way, but it still gives same error.

Apparently, webview goes to renderer after webview has been initialized, i.e. first it has called protected override void OnAppearing() {}, then protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e) {}

Below is my implementation

Custom Control (WebViewCustom) = same as yours.
Rendererer = same as yours

Below is WebBrowser Page XML that uses WebViewCustom

<ContentPage.Content>
    <StackLayout HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
        <controls:WebViewCustom x:Name="wvBrowser" AllowContentAccess="True" AllowFileAccess="True" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"  ></controls:WebViewCustom>
    </StackLayout>
</ContentPage.Content>

WebBrowser CS

public partial class WebViewBrowser : ContentPage
{
    string url;
    public WebViewBrowser(string url)
    {
        InitializeComponent();
        this.url = url;
    }

    protected override void OnAppearing()
    {
        base.OnAppearing();
        wvBrowser.Source = new UrlWebViewSource { Url = this.url };
    }
}

}

Answer 4

After doing all the custom renderer and configuration stuff, what solved the problem for me was adding android:usesCleartextTraffic="true" at <application> tag in AndroidManifest File.

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