Google OpenId and Google APIs - oauth-2.0

Question

I was trying to achieve an openID login with google and then get an acces token to access google apis (such google plus, or drive)
The first attemp was successful but with a big problem:
Make the openId stuff, and the user is redirected to google to identify himself, then return to my app identified.
Make the oAuth stuff with google apis, redirect the user again to identify himself and cameback with a code, then exchange the code for the access token needed to call google apis.
The user needs to identify twice. That's not good.
I read and tryed the google hybrid openId and oAuth. All links there points to the deprecated oAuth1 interface, and i cant make it work, i get the user identified but not request_token to continue the oAuth stuff.
So i have a couple of questions:
Is there a way to identify the user agains google openId and at the same time get the users consent to access google apis?
Is the hybrid protocol still working with oAuth2 and new google apis?
I'm on the good way or im missing something?
I need both openId and oAuth beacouse the application needs to be in the google marketplace and is a must to login users with openId, and i need to hit some APIs that need oAuth2 access_token.
Thanks!

Answer 1

Why do you need to work on both OpenID and OAuth side by side, and have two login screens? If you simply use OAuth 2.0 workflow, the user needs to key in his credentials just once and you can do anything that you want to.
Once the user consents to the login/permissions screen in the OAuth workflow, your app will get an access token. If you need any client info for, say, a welcome user screen - you just need to hit the https://www.googleapis.com/oauth2/v1/userinfo endpoint with the access token and it will give you the user's public information. So, in short you can do pretty much most of the things with the OAuth flow, and with the user logging in just once.
Good luck! Feel free to follow up with more questions.

Answer 2

OK, finally i have a working solution, and this is the "magic" url that make the trick for me:
String url = "https://accounts.google.com/o/oauth2/auth?"
+ "client_id="+ GoogleapiAuthHelper.CLIENT_ID +"&"
+ "response_type=code&"
+ "scope=openid%20profile%20https://www.googleapis.com/auth/plus.me&"
+ "redirect_uri="+GoogleapiAuthHelper.REDIRECT_URI+ "&"
+ "state=security_token%3Dasdalskjqwo91231029";
if( userService.getCurrentUser() != null ){
url += "&login_hint=" + userService.getCurrentUser().getEmail();
}
Steps:
First of all, identify the user with openId, the users go to login screen and type his credentials.
User return idenfied to the application
Redirect the user to the URL above. The param login_hint makes that the user dosen't need to idenfity again and the response to this url is a redirection with an oAuth code, wich you can easily exchange for the desirec access token.
After reading all Google Plus API, Google Drive API, oAuth2 and openId documentation, the doc that point me to the rigth direction was https://developers.google.com/accounts/docs/OAuth2Login?hl=es
I don't know if this is the best way to achieve openId + oAuth, but it works and i cant make it work in any other way. Hope this can help someone.