Project -> clean

refresh

In order to run the sample, make sure you do the necessary preperations in the Google API console, 
and provide your OAuth 2.0 details in https://github.com/gerdmestdagh/AndroidOauth2GoogleApiJavaClient/blob/master/src/com/ecs/android/sample/oauth2/OAuth2ClientCredentials.java

I've updated the sample to include the libraries in Git. You should be able to checkout / build / run without worrying about dependencies.