我认为你应该仔细阅读(或重新阅读)描述的所有过程 这里.如果您在从头开始学习本教程后需要更多帮助，请添加评论.

I think you should carefully read (or re-read) all the procedure described here. Add a comment if you need more help on this after you followed the tutorial from the scratch again.

90% 的问题与以下问题有关:错误的 sha1 签名证书、错误的应用程序包名称、缺少客户端 ID 等等......

90% of problems with this are related to: wrong sha1 signed certificate, wrong app package name, missing client ID and something like those...

PS:这里你可以找到所有的工作样品

PS: here you can find all the working samples