Possible Duplicate:
How to find Gmail account associated with Android Market?
In Android, is there an easy way in code to detect if the user has linked their phone to Google Market using a gmail address?
Possible Duplicate:
How to find Gmail account associated with Android Market?
In Android, is there an easy way in code to detect if the user has linked their phone to Google Market using a gmail address?
It seems to me like the right thing to ask at this point is, "What are you really trying to do?"
The most obvious use case I can think of is to verify that the user is legitimately using your app, in which case you might find the right answer in Application Licensing: http://developer.android.com/guide/google/play/licensing/index.html
The next most obvious use case I can think of is you want to help the user install something, in which case maybe your answer is in Linking to your Application: http://developer.android.com/distribute/googleplay/promote/linking.html
For other cases, the answer may begin with Account Manager. Try here: http://developer.android.com/training/id-auth/identify.html