Implement Google Login In Android Client/server App

The app I am working on consist two parts: Native android app Web service I want to implement a login procedure between the app and the webservice that is based on the user's Goo

Solution 1:

For verifying the app user, check out this post: Verifying Back-End Calls from Android Apps

1. In the app you can simply receive a Google token-id via the Google Play Services, which is really easy.
2. Then you send this token to your backend, where you validate it against a Google API. There are libraries for handling this for you (e.g. for PHP). The payload in this answer also contains the user's email and id if you want to deal with this.