GetFileFromApplicationUriAsync, CopyAsync, AsStreamForRead not implemented in Uno Platform. Workarounds? - uno-platform

Question

I tried to use the following methods, but all of them appeared as not implemented in Uno (Android). What can I do?
Is there any Xamarin.Essentials alternative?
Or other NuGet package?
Or should I use native implementations on each platform?
And is it even possible to implement it in Uno directly?
var pdfFile = StorageFile.GetFileFromApplicationUriAsync(..);
pdfFile.CopyAsync(..);
(await pdfFile.OpenReadAsync()).AsStreamForRead(); // AsStreamForRead() not implemented
I'm using v1.45.0 of Uno.UI.

Answer 1

As David Oliver pointed out in his answer,
Uno hasn't implemented most of the Windows.StorageFile APIs, as for
the most part there are alternatives available in System.IO, which
will work cross-platform.
So...
To open file from the app package we can set its build action to Embedded Resource instead of Content. And instead of StorageFile.GetFileFromApplicationUriAsync() method we can use this code:
public Stream GetStreamFromResourceFile(string filename, Type callingType = null)
{
var assembly = (callingType ?? GetType()).Assembly;
string foundResourceName = assembly.GetManifestResourceNames().FirstOrDefault(r => r.EndsWith(filename, StringComparison.InvariantCultureIgnoreCase));
if (foundResourceName == null)
throw new FileNotFoundException("File was not found in application resources. Ensure that the filename is correct and its build action is set to 'Embedded Resource'.", filename);
return assembly.GetManifestResourceStream(foundResourceName);
}
to copy a file
await pdfFile.CopyAsync(..);
we change to:
await pdfFile.CopyToAsync(newFile);
and to get a stream for read
(await pdfFile.OpenReadAsync()).AsStreamForRead();
we use:
File.OpenRead(pdfFile);
So in the end we have:
string filename = "File.pdf";
var pdfFile = GetStreamFromResourceFile(filename, GetType());
string newFilePath = Path.Combine(ApplicationData.Current.LocalFolder.Path, filename);
using (var newFile = File.Create(newFilePath))
{
await pdfFile.CopyToAsync(newFile);
}
var fileStream = File.OpenRead(newFilePath);

Answer 2

Uno hasn't implemented most of the Windows.StorageFile APIs, as for the most part there are alternatives available in System.IO, which will work cross-platform.
If you're trying to display a pdf, however, there's no cross-platform option currently. On Android the best way to display a pdf is to launch an intent, on iOS it's possible to display the pdf in a WebView.
Partial example code for Android:
public async Task Read(CancellationToken ct, string filePath)
{
var intent = new Intent(Intent.ActionView);
var file = new Java.IO.File(filePath);
var contentUri = Android.Support.V4.Content.FileProvider.GetUriForFile(ContextHelper.Current, _fileProviderAuthority, file);
intent.SetFlags(ActivityFlags.GrantReadUriPermission);
intent.SetDataAndType(contentUri, "application/pdf");
StartActivity(intent);
}
Partial example code for iOS:
<ios:WebView
Source="{Binding FilePath}"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch" />