Udacity offers great content for Android Programming in their Nanodegree programs. If you don't have the money you can take same of the courses for free (but without certificate). The skills you learn in this Nanodegree program will accelerate your journey to becoming a working Android Developer. this program teaches the tools, principles, and patterns that underlie all Android development.

1. Java Programming Basics
   TicTacToe
2. Object Oriented Programming in Java
3. Kotlin Bootcamp for Programmers
4. Developing Android Apps with Kotlin
5. Advanced Android with Kotlin
6. Kotlin for Android Developers
7. How to Install Android Studio
8. Android Basics: User Interface
9. Android Basics: User Input
10. Android Basics: Multi-screen Apps
    Custom Adapter Sample App
    ViewPager Sample App
    Miwok App
11. Android Basics: Networking
    Did You Feel It? App
    Soonami App
    Quake Report App
12. Android Basics: Data Storage
    Pets App
13. Developing Android Apps
    Toy App Exercise
    Sunshine App
14. Advanced Android App Development
    Old Sample Apps
    ClassicalMusicQuiz
    ShushMe
    Emojify
    Squawker
    TeaTime
    My Garden
15. Gradle for Android and Java
16. Android Performance
17. Material Design for Android Developers
18. Mobile Design and Usability
19. UX Design for Mobile Developers
20. Add Google Maps to your Android App
21. Google Location Services on Android
22. Add Google Sign-In to your Android Apps
23. Passwordless Login Solutions for Android
24. Firebase in a Weekend (Android)
25. Firebase Analytics: Android
26. Android Wear Development
27. Android Interview Prep
28. How to Make a Platformer Using libGDX
29. 2D Game Development with libGDX

1. Data Binding
2. ViewModel , Lifecycle , LiveData
3. ViewModelProvider.Factory
4. Room database
5. Room, LiveData, and ViewModel
6. Google Gson
7. Retrofit
8. RXJava
9. Retrofit with RXJava
10. Fundamentals of dependency injection
11. Dependency injection, Dagger 2 Simple Examples
12. Official Dagger Documentation
13. New Android Injector with Dagger 2