how to get a skill to improve with sample code on android

https://blog.aritraroy.in/20-awesome-open-source-android-apps-to-boost-your-development-skills-b62832cf0fa4

http://www.kmshack.kr/2017/03/%EC%95%88%EB%93%9C%EB%A1%9C%EC%9D%B4%EB%93%9C-%EA%B0%9C%EB%B0%9C-%EC%8A%A4%ED%82%AC%EC%9D%84-%ED%96%A5%EC%83%81%EC%8B%9C%ED%82%A4%EB%8A%94-%EC%98%A4%ED%94%88%EC%86%8C%EC%8A%A4-%EC%95%B1-20%EA%B0%80/