Android Modular Architecture

Building a quality software is a complex task. This isn't just a matter of satisfying the business requirements. The software needs to be robust, easy-to-maintain, testable, and flexible to adapt to the various changes that an agile team needs to face.

In this presentation, I will walk you through planning and refactoring of a modern Android application built for a large-scale user base.

Transcript

1. Android Modular Architecture
2. Christopher Alexander “It is the first steps in a design process which count for most. The first few strokes, creates the form.”
3. Challenges
4. Challenges • Independence: be able to work in a feature without impacting other developers.
5. Challenges • Independence: be able to work in a feature without impacting other developers. • Encapsulation: effective use of access modifiers to hide information from different modules.
6. Challenges • Independence: be able to work in a feature without impacting other developers. • Encapsulation: effective use of access modifiers to hide information from different modules. • Growth: a module should not increase size without bounds.
7. Module by Layer In Module by Layer, the highest level modules reflect the various application "layers", instead of features.
8. :app
9. :app :ui
10. :app :domain :ui DI injects use case in the presentation.
11. :app :domain :ui :data DI injects repository implementation in the domain. DI injects use case in the presentation.
12. :app :domain :ui :data DI injects repository implementation in the domain. DI injects use case in the presentation. :app knows about all modules, and need to set up the DI.
13. Challenges
14. Challenges • Independence: features has its implementation spread out over multiple modules.
15. Challenges • Independence: features has its implementation spread out over multiple modules. • Encapsulation: modules contains items that usually aren't closely related to each other.
16. Challenges • Independence: features has its implementation spread out over multiple modules. • Encapsulation: modules contains items that usually aren't closely related to each other. • Growth: As an application grows, the number of modules remains the same, while the number of classes in each module will increase without bound.
17. This results in modules with low cohesion with high coupling between each other.
18. The fundamental flaw with Module by Layer is that it puts implementation details ahead of high level abstractions.
19. Module by Feature Module by Feature uses modules to reflect the feature set. It tries to place all items related to a single feature (and only that feature) into a single module.
20. What is a feature?
21. What is a feature? A feature is fully independent, fine-grained and self contained service those messages are delivered over Intent by URLs.
22. :app
23. :app :feature1
24. :app :feature1 :feature2
25. :app :feature1 :feature2 :feature3
26. :app :feature1 :feature2 :feature3 :feature4
27. Challenges
28. Challenges • Independence: all items needed for a given feature are in the same module.
29. Challenges • Independence: all items needed for a given feature are in the same module. • Encapsulation: allows classes to decrease their scope from public to internal.
30. Challenges • Independence: all items needed for a given feature are in the same module. • Encapsulation: allows classes to decrease their scope from public to internal. • Growth: the number of classes within each package remains limited to the items related to a specific feature.
31. This results in modules with high cohesion and low coupling between each other.
32. Micro-Module Architecture
33. :app
34. :app :feature1
35. :app :feature2 :feature1
36. :app :feature2 :feature1 :component1
37. :app :feature2 :common :feature1 :component1 :design :testing
38. :app :feature2 :common :feature3 :feature1 :component1 :design :testing
39. :app :feature2 :component2 :common :feature3 :feature1 :component1 :design :testing
40. Module Structure
41. :module
42. :module ui
43. :module ui activity fragment viewmodel
44. :module domain ui activity fragment viewmodel
45. :module domain ui model usecase <interface>
 repository activity fragment viewmodel
46. :module domain data ui model usecase <interface>
 repository activity fragment viewmodel
47. :module domain data ui model usecase <interface>
 repository activity fragment viewmodel repository
48. :module domain data ui model usecase <interface>
 repository activity fragment viewmodel store repository local remote
49. Thank you.