问题
How can I check if user has +1'ed external page from my own page if I know his credentials?
回答1:
There is no way to do this with the current APIs.
There is, however, an active feature request. If you star the issue, you will be notified when it is updated.
来源：https://stackoverflow.com/questions/11761486/how-to-check-if-custom-url-is-1ed-with-google-plus-api