根据API的需求，这些都是可以添加在你的build.gradle正确的版本。

These are the correct version that you can add in your build.gradle according to the API needs.

API 21：

compile 'com.android.support:appcompat-v7:21.0.1'
compile 'com.android.support:recyclerview-v7:21.0.1'

或

compile 'com.android.support:appcompat-v7:21.0.2'
compile 'com.android.support:recyclerview-v7:21.0.2'

或

compile 'com.android.support:appcompat-v7:21.0.3'
compile 'com.android.support:recyclerview-v7:21.0.3'

API 22：

compile 'com.android.support:appcompat-v7:22.0.0'
compile 'com.android.support:recyclerview-v7:22.0.0'