您可能在 Google 的 API 控制台作为已安装的应用程序类型为 Android.这仅适用于 AuthenticationManager.如果您想自己实施流程，请使用应用程序类型其他，您将获得所需的客户端密钥.

You probably created your client ID in Google's API Console as Installed Application with Application Type Android. This is only meant for use with AuthenticationManager. If you want to implement the flow yourself, use Application Type Other an you'll get the client secret you need.