Vasiliy Zukanov - Activities and Fragments are not MVxViews

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1. Activities and Fragments are not MVxViews Vasiliy Zukanov Freelancer, blogger, online instructor www.TechYourChance.com
2. How I became an Android developer: @VasiliyZukanov 2 Official documentation Blogs
3. After a short while: @VasiliyZukanov 3 Activities and Fragments of 500+ lines of code
4. Google for “android application architecture”: @VasiliyZukanov 4 Exactly what I looked for… said no one ever.
5. The best place to hide a dead body is page 2 of Google search results I saw pages 2, 3, 4…
6. MVx in a nutshell: @VasiliyZukanov 6 Family of architectural patterns featuring separation of concerns for GUI applications Model : state and/or business logic and/or data structures View : application user interface x : flow control logic and/or state and/or business logic and/or data structures
7. Android Architecture: Message-based MVC[1] @VasiliyZukanov 7 View Controller Model Activity
8. Tremendous improvement… … but still didn’t feel quite right.
9. Android Architecture [in 10 parts][2] @VasiliyZukanov 9
10. Joshua Musselwhite’s Breakthrough: @VasiliyZukanov 10 View Controller Model Activity
11. What’s the main advantage of any MVx architectural pattern? Decoupled UI logic!
12. UI logic responsibilities: Define application’s UI Notify the application about user’s interactions with UI @VasiliyZukanov 12
13. Decoupled UI logic seems to be the only common denominator of all MVx
14. UI logic characteristics: Detailed and accurate requirements (UI mockups) Much higher rate of change in most cases Unreadable - verbose, messy, hacky, etc. Easiest to test manually Hardest to test automatically @VasiliyZukanov 14
15. Why not decouple UI logic by encapsulation inside Activity?
16. Outsourcing: @VasiliyZukanov 16 UI logic should be decoupled from the rest of the application Detailed UI specification MyActivity <<interface>> MyViewMvc Would you integrate this class into your app “as is”?
17. The whole picture: @VasiliyZukanov 17 MyActivity <<interface>> MyViewMvc Life-cycle Screens navigation Runtime permissions Loaders Dependency injection Fragments Dialogs More… UI logic
18. Activity is God Object with many responsibilities… … therefore, it’s impossible to decouple UI logic if it resides inside Activity!
19. Can we do better than this? Yes!
20. Extract UI logic into standalone class: @VasiliyZukanov 20 MyViewMvcImpl MyActivity <<interface>> MyViewMvc Composition instead of inheritance controller UI logic
21. Activity only aware of simple interfaces: @VasiliyZukanov 21 public interface ViewMvc { View getRootView(); } public interface MyViewMvc extends ViewMvc { interface Listener { void onBuyClicked(); } void bindProduct(Product product); void registerListener(Listener listener); void unregisterListener(Listener listener); } setContentView(mViewMvc.getRootView())
22. Pros: Decoupled UI logic (tremendous advantage) Modularity and reusability No need for ViewHolder in ListView More natural implementation of RecyclerView Same level of abstraction across the entire UI hierarchy @VasiliyZukanov 22
23. Cons: Different mental model Initial ramp-up More code Requires discipline @VasiliyZukanov 23
24. Is this another “New and Shiny Android Architecture of the Month”?
25. 2010: Ivan proposed MVC on Android 2012: Josh realized that Activity is controller 2014: Vasiliy added explicit view interface The most mature architectural pattern for Android development!
26. Android MVP for beginners[3] @VasiliyZukanov 26
27. MVC or MVP or MVVM or … ? Doesn’t matter!
28. Summary: Extracting UI logic from Activities is the only way to make it truly decoupled MVx View is the natural abstraction level for UI logic in Android Activity can take on its natural role – controller Mature and documented[4] @VasiliyZukanov 28
29. But what about Fragments? Replace “Activity” with “Fragment” and re-read the presentation.
30. @VasiliyZukanov 30 Professional Android Unit Testing Android Dependency Injection with Dagger 2 Special coupon code: DROIDCON_DE My courses on Udemy
31. Questions @VasiliyZukanov 31
32. Thank you! @VasiliyZukanov 32
33. References 1. Android Architecture: Message-based MVC - http://mindtherobot.com/blog/675/android- architecture-message-based-mvc/ 2. Android Architecture [in 10 parts] - http://www.therealjoshua.com/2011/11/android- architecture-part-1-intro/ 3. Android MVP for Beginners - https://android.jlelse.eu/android-mvp-for-beginners- 25889c500443 4. Activities in Android are not UI Elements - https://www.techyourchance.com/activities- android/ @VasiliyZukanov 33