Added PickiTonUriReturned() callback
IMPORTANT:
When selecting a file from Google Drive, for example, the Uri will be returned in onActivityResult before the file is even available. We first have to wait for Google Drive to download the file before we try and use it. That is why PickiTonUriReturned() callback was added. Applications like Dropbox display a ProgressBar (indicating the progress) for us(inside the picker), but there are many applications like Google Drive and OneDrive which will return the Uri before it is even usable. Unfortunately, there is no way of knowing the progress of the file being downloaded - Thus we can only let the user know (inside PickiTonUriReturned) that we are waiting for the file to be downloaded (This can actually take very long depending on the file size).
You can test this, go to:
Google Drive - App Info - Storage - Clear data
Then open your app (or the demo app) and select a file from Google Drive.