browser retrieve facebook credentials from facebook app

Question

I'm developing a web-app that at the start connect to facebook, but before asking user credentials I'd like to try to retrieve these credentials from official Facebook Application (Android, IOS or MAC app).

Is this possible?

Answer 1

The user must accept the applications permissions BEFORE anything is displayed. The easiest way is just printing their details from them to view once they're signed in, but following Facebook's Guidelines, you can't view a user's profile information without.