how can we get online user to gmail chat?

i am developing gmail chat application in android...anybody know how can we get the online user? i would login from my gmail id...i want to s开发者_如何学JAVAhow the my friends who is online from chat list...

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EDIT:

http://developer.android.com/reference/android/provider/ContactsContract.html

This section of the API looks like a good starting point.