Support virtual files on Android

[dantman]

Files provided by document providers on Android can be "Virtual", meaning it doesn't have a binary representation of its own you can call openInputStream on, but if supported can be converted to a binary representation of various mime types. Instead when you know the file is virtual you use getStreamTypes(uri, mimeTypeFilter) to negotiate a valid alternate mime type ("*/*" is a valid filter to make the provider choose the best representation from anything) and then use resolver.openTypedAssetFileDescriptor(uri, mimeType, ...) to get an InputStream.

https://developer.android.com/guide/topics/providers/document-provider.html#virtual

Is there any plan to support virtual files?

[dantman]

Virtual files also may not have a filename, so PathResolver should generate a random name for temp files instead of returning null when the document doesn't have a filename.