Q:

Google authentication accessing api through custom service?

I have a web based service (running for years) that works with google apis.
Now I would like to create an android and iphone ui (using xamarin) that uses my web services which in turn talks to google apis.
Given that I don't talk directly to google apis from the phone, do I need to use a web browser control to let the user login, or can I authenticate my server and establish a session natively on the phone?
I'm afraid I need to use a browser window, and I don't think it's user friendly to have to login to a google account in a browser window on the phone.
(I want to keep the logic on the server, so that the phone apps and the web ui uses the exact same code for it's calculations.)
EDIT: It seems Cross-client identity is what I'm looking for.

A:

It can be done natively. See this video https://www.youtube.com/watch?v=9wAx39s10yw which explains all of the procedure using cross-platform authentication.

