https://github.com/rootrl/AndroidSamples/blob/master/docs/ConstraintLayout.md
https://github.com/rootrl/AndroidSamples/blob/master/docs/Memery.md
https://github.com/rootrl/AndroidSamples/blob/master/docs/HttpRequest.md
https://github.com/rootrl/AndroidSamples/blob/master/docs/UserDatabaseOrmWithLitePal.md