Download PDF as byte stream then open in default Android application in Xamarin.Forms

Question

I'm using a post call to get a byte stream with all the data for a PDF, then I want to open the PDF using the default program in Android. Will later do for iOS.

Here's my code:

 async void OnItemSelected(object sender, SelectedItemChangedEventArgs e) { Publication p = (Publication)e.SelectedItem; Debug.WriteLine(p); if (p.folderID.Equals("-1")) { using (Stream respStream = await post(p.docNum)) { byte[] buffer = new byte[respStream.Length]; respStream.Read(buffer, 0, buffer.Length); string path = Environment.GetFolderPath(Environment.SpecialFolder.Personal); File.WriteAllBytes(path + "foo.pdf", buffer); Device.OpenUri(new Uri(path + "foo.pdf")); } } else { await Navigation.PushAsync(new PublicationsPage(p.folderID)); } } private async Task<Stream> post(string id) { Dictionary<string, string> dir = new Dictionary<string, string>(); dir.Add("LoginID", App.user.login_id); dir.Add("docID", id); var jsonReq = JsonConvert.SerializeObject(dir); Debug.WriteLine("req: " + (String)jsonReq); var content = new StringContent(jsonReq, Encoding.UTF8, "application/json"); var response = await client.PostAsync(url, content); var responseStream = await response.Content.ReadAsStreamAsync(); return responseStream; }

What I have now downloads the pdf as a byte stream then makes a window pop up then close. What should I do to fix? I'd rather not pay for any packages and ideally I'd like to have it prompt for what program to open with.

Robbit · Accepted Answer · 2018-02-23 02:21:21Z

The file system is different between Ios and Android. So, you need use DependencyService to save and load the PDF file on different platform.

Thanks @B.6242, in this issue, @B.6242 has implemented it in both Android and Ios with DependencyService, you can refer to it.

Here is an issue about how to use the file system on different platforms.

jwartofsky · Accepted Answer · 2018-02-23 18:49:47Z

Got it to work by following this: https://developer.xamarin.com/recipes/cross-platform/xamarin-forms/controls/display-pdf/

In the code above, change OnItemSelected to this, where PDFViewPage uses the customWebView described in the above link:

 async void OnItemSelected(object sender, SelectedItemChangedEventArgs e) { Publication p = (Publication)e.SelectedItem; Debug.WriteLine(p); if (p.folderID.Equals("-1")) { using (Stream respStream = await post(p.docNum)) { byte[] buffer = new byte[respStream.Length]; respStream.Read(buffer, 0, buffer.Length); string path = System.Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments); File.WriteAllBytes(path + "foo.pdf", buffer); await Navigation.PushAsync(new PDFViewPage(path + "foo.pdf")); //Device.OpenUri(new Uri(path + "foo.pdf")); } } else { await Navigation.PushAsync(new PublicationsPage(p.folderID)); } }

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