I have to say, Facebook on Android does it best. They publish an open source library on GitHub. You use that, and it will even check if the user is already logged in on that phone and reuse that.

I have no problem with Twitter, personally. I even provided the sample source code for using a common open source third party Twitter library to login on Android by OAuth for a book out there. But people say it just isn't as easy.

In this case the third party library does require other dependencies, some of which can break it, and other complexities. It also requires using either the Browser, or an internal web control to login and then return the token to the app. So it isn't as low fiction as Facebook for users, and I hear complaints from developers as well.