Xamarin.forms display PDF in webview not working

Question

I download a pdf stream from my server. In my app I save the bytearray to a the local folder as pdf. But when I open it in the webview, it just shows a white page.

I followed this example: https://developer.xamarin.com/recipes/cross-platform/xamarin-forms/controls/display-pdf .

Here is customwebview in my xaml:

<local:CustomWebView x:Name="customView" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" />

Here is my code of the custom view:

 public class CustomWebView : WebView
    {        
        public static readonly BindableProperty UriProperty = BindableProperty.Create(propertyName: "Uri",
       returnType: typeof(string),
       declaringType: typeof(CustomWebView),
       defaultValue: default(string));

        public string Uri
            {
                get { return (string)GetValue(UriProperty); }
                set { SetValue(UriProperty, value); }
            }
    }

This is my method to retrieve the pdf byte array and store it locally:

 private async void ReadPDF()
        {
            var response = CommonLibrary.Helpers.HTTPClientHelper.DownloadPDF(AccountBL.AccessToken, APISettings.APIURI("api/booking/pdf"));
            var streamContent = response.Content as System.Net.Http.StreamContent;
            var bytes = CommonLibrary.Helpers.FileHelper.ReadBytes(await streamContent.ReadAsStreamAsync());
            var dir = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
            var fileName = "test.pdf";
            CommonLibrary.Helpers.FileHelper.WriteFileFromByteArray(bytes, dir, fileName);

           customView.Uri = System.IO.Path.Combine(dir, fileName);            
        }

Am I missing something?

Answer 1

If I remember correctly, you can display a "remote" PDF in a webview on iOS. With Android there are some problems. I suggest to take a look to this repo OpenPDF . I use a CustomRenderer and a google tool to display the PDF. I have had some problems with some Android version... but you can take a look.(here a blog )

Otherwise there is @AdamPedley suggestion to use PDF JS Viewer Adam Pedley The code is here .

This is the CustomRenderer for Android

[assembly: ExportRenderer (typeof(CustomWebView), typeof(CustomWebViewRenderer))]
namespace DisplayPDF.Droid
{
    public class CustomWebViewRenderer : WebViewRenderer
    {
        protected override void OnElementChanged (ElementChangedEventArgs<WebView> e)
        {
            base.OnElementChanged (e);

            if (e.NewElement != null) {
                var customWebView = Element as CustomWebView;
                Control.Settings.AllowUniversalAccessFromFileURLs = true;
                Control.LoadUrl (string.Format ("file:///android_asset/pdfjs/web/viewer.html?file={0}", string.Format ("file:///android_asset/Content/{0}", WebUtility.UrlEncode (customWebView.Uri))));
            }
        }
    }
}

Answer 2

Following approach will allow you to view pdf in xamarin forms. If you are trying to open one from azure blob or you have valid URl.

WebView webView = new WebView();
var page = new ContentPage();
webView.Source = "https://docs.google.com/viewer?url=http://yourpdfurl.pdf";
page.Content = webView;
Navigation.PushModalAsync(page);