问题
I see everywhere that google plus api is readonly. But i saw this app screenshot.

How did they do then? Even the docs say its read only.
回答1:
The API is indeed still read-only. We worked directly with SXSW on this year's mobile app to enable sharing... it's not a feature that is generally available at this time.
回答2:
The note at the top of the REST API documentation page seems to answer both questions at once:
Note: The Google+ API currently provides read-only access to public data. All API calls require either an OAuth 2.0 token or an API key.
来源:https://stackoverflow.com/questions/9806118/is-google-plus-api-still-read-only