Q:

Facebook authorization in my Android app

How can I check if a user has account on an Android device, not to check this in my program?
How can I check the authenticity if the device is software Facebook for Android?
Thank you!

A:

your english is a bit shakey but what i think you mean is:
How can I (being you the question giver) check if a Facebook account is already on an driod device instead of authentication through your application. 
That may require some work with the facebook api due to permissions you ask from the user. 
This however http://developer.android.com/reference/android/accounts/package-summary.html May help you atleast determine the account and perhaps use it for auto login so its just the Allow / Denny stage being handled within your app rather than requiring them to log in

