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
   

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2. Christopher Alexander
   “It is the first steps in a design
   process which count for most. The
   first few strokes, creates the form.”
   

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3. Challenges
   

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4. Challenges
   • Independence: be able to work in a feature without
   impacting other developers.
   

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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.
   

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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.
   

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7. Module by Layer
   In Module by Layer, the highest level modules
   reflect the various application "layers", instead of
   features.
   

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8. :app
   

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9. :app
   :ui
   

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10. :app
    :domain
    :ui
    DI injects use case in
    the presentation.
    

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11. :app
    :domain
    :ui
    :data
    DI injects repository
    implementation in the domain.
    DI injects use case in
    the presentation.
    

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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.
    

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13. Challenges
    

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14. Challenges
    • Independence: features has its implementation spread out
    over multiple modules.
    

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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.
    

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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.
    

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17. This results in modules with low
    cohesion with high coupling
    between each other.
    

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18. The fundamental flaw with Module by
    Layer is that it puts implementation
    details ahead of high level abstractions.
    

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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.
    

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20. What is a feature?
    

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21. What is a feature?
    A feature is fully independent, fine-grained and self
    contained service those messages are delivered
    over Intent by URLs.
    

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22. :app
    

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23. :app
    :feature1
    

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24. :app
    :feature1 :feature2
    

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25. :app
    :feature1 :feature2 :feature3
    

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26. :app
    :feature1 :feature2 :feature3 :feature4
    

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27. Challenges
    

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28. Challenges
    • Independence: all items needed for a given feature are in
    the same module.
    

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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.
    

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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.
    

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31. This results in modules with high
    cohesion and low coupling
    between each other.
    

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32. Micro-Module Architecture
    

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33. :app
    

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34. :app
    :feature1
    

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35. :app
    :feature2
    :feature1
    

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36. :app
    :feature2
    :feature1
    :component1
    

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37. :app
    :feature2
    :common
    :feature1
    :component1
    :design :testing
    

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38. :app
    :feature2
    :common
    :feature3
    :feature1
    :component1
    :design :testing
    

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39. :app
    :feature2
    :component2
    :common
    :feature3
    :feature1
    :component1
    :design :testing
    

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40. Module Structure
    

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41. :module
    

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42. :module
    ui
    

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43. :module
    ui
    activity
    fragment
    viewmodel
    

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44. :module
    domain
    ui
    activity
    fragment
    viewmodel
    

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45. :module
    domain
    ui
    model
    usecase
    

    repository
    activity
    fragment
    viewmodel
    

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46. :module
    domain
    data
    ui
    model
    usecase
    

    repository
    activity
    fragment
    viewmodel
    

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47. :module
    domain
    data
    ui
    model
    usecase
    

    repository
    activity
    fragment
    viewmodel repository
    

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48. :module
    domain
    data
    ui
    model
    usecase
    

    repository
    activity
    fragment
    viewmodel
    store
    repository
    local
    remote
    

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49. Thank you.
    

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