Activities and fragments are not MVx views. Extracting UI logic into standalone classes separated from activities allows for easier development and maintenance. It provides advantages such as outsourcing UI development, enabling A/B testing through alternative view implementations, and defining the activity's natural role as a controller. However, this approach requires an initial ramp-up and more code, and discipline must be maintained.

1. Activities and Fragments are
not MVxViews
Vasiliy Zukanov
Consultant, developer, blogger

2. MVx:
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Family of architectural patterns featuring concerns
separation for GUI applications
Model : application state + business logic (optional)
View : application user interface
x : application logic + business logic (optional)

3. How I became an Android developer:
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Official documentation Blogs

4. After a short while:
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Fragments of 500+ lines of code are the norm!?

5. Google for “android application architecture”:
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Exactly what I looked for… said no one ever.

6. The best place to hide a dead body is page 2 of
Google search results
I saw pages 2, 3, 4…

7. Android Architecture: Message-based MVC[1]
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View Controller Model
Activity

8. Tremendous improvement…
… but still didn’t feel quite right.

9. Android Architecture [in 10 parts][2]
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10. Joshua Musselwhite’s Breakthrough:
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View Controller Model
Activity

11. What’s the main advantage of any MVx
architecture?
Decoupled UI logic!

12. UI logic characteristics:
Much higher rate of change in most cases
Not directly related to core functionality in most cases
Unreadable - verbose, messy, hacky, etc.
Easiest to test manually
Hardest to test automatically
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development and maintenance
testing

13. Why not decouple UI logic by encapsulation
inside Activity?
Project advantage!

14. Outsourcing:
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UI isn’t directly related to
core functionality
Detailed UI specification
MyActivity
<<interface>>
MyViewMvc

15. The whole picture:
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MyActivity
<<interface>>
MyViewMvc
Lifecycle
Screens navigation
Runtime permissions
Loaders
Dependency injection
Fragments
Dialogs
More…
* this coupling exists even when developing in-house
UI logic

16. Outsourcing UI development is hard when UI
logic resides in Activities.

17. A/B testing:
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BUY

18. A/B testing – approach 1:
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MyActivity.java
Different XML layout
Different product data
Read code… Add test code… Remove test code… Bugs…

19. MyActivity2.java
A/B testing – approach 2:
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MyActivity.java
Duplication hell…
MyActivity3.java
Bug fix 1 Bug fix 1 Bug fix 1
Bug fix 2 Bug fix 2

20. Can we do better than this?
Yes!

21. Extract UI logic into standalone classes:
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MyViewMvcImplMyActivity
<<interface>>
MyViewMvc
Composition instead of inheritance
Controller
UI logic

22. Activity only aware of simple interfaces:
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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())

23. Project advantages:
Outsource development of implementations of MVC views
Inject alternative implementations during A/B testing
More…
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24. Disadvantages:
Different mental model
Initial ramp-up
More code
Requires discipline
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25. Summary:
Extracting UI logic from Activities allows for easier
development and maintenance
Advantages up to project and business level
Activity can take on its natural role – controller
Mature and documented[3]
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26. But what about Fragments?
Replace “activity” with “fragment” and re-read the
presentation.

27. Questions
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28. Thank you!
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www.TechYourChance.com

29. 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. Activities in Android are not UI Elements - https://www.techyourchance.com/activities-
android/
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