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.

Answer 1

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.

Answer 2

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));
        }
    }