CommonsWare is here to help you through the challenges of Android app development, whether you are new to the platform or are deep into a project!
The Busy Coder's Guide to Android Development offers over 200 chapters of Android knowledge, from the very basics through highly advanced topics. It covers Android Studio 3.1 and the latest Android SDKs, including Android 9.0.
Not only does subscribing (only $20!) give you that book plus six months' worth of updates, but you also get three additional books and six months' work of their updates:
Android's Architecture Components, for a deep dive into this important set of Android libraries, and Android app architecture in general
Exploring Android, a series of hands-on tutorials for creating an Android app from scratch
GraphQL for Android, for accessing GraphQL-powered Web services from your Android app