This is an Android nanodegree I'm currently doing at Udacity to sharpen my Android knowledge and skills https://www.udacity.com/course/android-developer-nanodegree-by-google--nd801
This course includes:
- Developing Android Apps
- Advanced Android App Development
- Gradle for Android and Java
- Material Design for Android Developers
- (additional) Android Performance
Disclaimer: I did all of the free courses that made up this Android Developer nanodegree. The only difference between paid and free versions is the lack of project reviews and feedback. However, considering my previous experience with Android Devolopment, I didn't face any problems while following these courses or building projects.