Architecting Android Apps the Clean Way (DevFest Lagos 2018)

As your android applications grow in size, using the default structure android provides would lead to classes having more than one responsibility, which makes code difficult to maintain, test, and read.

To solve this problem, there is need for an architecture which will help bring "separation of concerns" to your code, making it easily maintainable, testable, and readable.

In this talk, you will learn how to architecture your android applications in a clean way by leveraging concepts of Clean Architecture, Android Architecture Components, and some Software Design Principles/Patterns.

Transcript

1. Chizoba Ogbonna, Paylater @techietoby Lagos Architecting Android Apps the Clean Way
2. Back Story
3. Things you would learn Clean Architecture Android Architecture Components Software Design Principles and Patterns
4. Clean Architecture Location DevFest GDG Lagos
5. The Principles
6. The application code is separated into layers
7. The layers should follow a strict dependency rule
8. The Layers
9. Presentation Layer • Views - Activities and Fragments MVC | MVP | MVVM ViewModel LiveData 3 LiveData 3 LiveData 3 Activity/Fragment • ViewModel with LiveData(s)
10. // MainActivity.kt override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) viewModel = ViewModelProviders.of(this).get(MainViewModel::class.java) makeGithubSearchQuery() } private fun makeGithubSearchQuery() { viewModel!!.users.observe(this, Observer { users -> // Update UI }) }
11. // MainViewModel.kt class MainViewModel(val repository : GitHubRepository) : ViewModel() { private var users = MutableLiveData<List<UserDataLayerModel>>() get() { GetUsersUseCase(repository).invoke(this) return users } }
12. Presentation Layer • Views - Activities and Fragments MVC | MVP | MVVM ViewModel LiveData 3 LiveData 3 LiveData 3 Activity/Fragment • ViewModel with LiveData(s)
13. Proprietary + Confidential Feature’s Y ViewModel Data X’s LiveData Data Y’s LiveData Dashboard Shows data from feature X Shows data from feature Y Dashboard’s ViewModel Feature’s X ViewModel
14. // MainViewModel.kt class MainViewModel : ViewModel() { private var usersLiveData: UsersLiveData private var viewModelResult: LiveData<List<UserUILayerModel>> val users: LiveData<List<UserUILayerModel>> get() { usersLiveData.loadData() return viewModelResult } init { usersLiveData = UsersLiveData(GitHubRepository(NetworkDataSource())) viewModelResult = Transformations.map(usersLiveData) { data -> convertDataToUIModel(data) } } }
15. // UsersLiveData.kt (Custom Live Data) class UsersLiveData(val repository: GitHubRepository) : MutableLiveData<UserDataLayerModel>() { init { loadData() } fun loadData() { GetUsersUseCase(repository).invoke(this) } }
16. • Lifecycle Aware Data Loading with Architecture Components - Ian Lake • LiveData beyond the ViewModel - Reactive patterns using Transformations and MediatorLiveData - Jose Alcérreca • LiveData with SnackBar, Navigation and other events (the SingleLiveEvent case) - Jose Alcérreca Learn more
17. Domain Layer • Entities Business Logic Entities
18. // Entity data class UserDataLayerModel(val total_count: Int, val incomplete_results: Boolean, val items: List<Items>)
19. Domain Layer • Entities Business Logic • Use cases Entities Use cases
20. // UseCase class GetUsersUseCase(private val gitHubRepository: GitHubRepository) { fun execute(): UserDataLayerModel { return gitHubRepository.lagosJavaDevs } }
21. Data Layer
22. Data Layer • Cache • Local Database • Remote Database Repository Repository Cache Local DB Cloud DB
23. class GitHubRepository(private val networkDataSource: GitHubDataSource){ lateinit var userDataLayerModel: UserDataLayerModel? = null fun getLagosJavaDevs(): UserDataLayerModel? { try { userDataLayerModel = RetrofitUtil.createService().javaDevsInLagos.execute().body() } catch (e: IOException) { e.printStackTrace() } return userDataLayerModel } }
24. High-level modules should not depend on low-level modules. Both should depend on abstractions.
25. Abstractions should not depend on details. Details should depend on abstractions.
26. Data Layer • Cache • Local Database • Remote Database Repository Repository Cache Local DB Cloud DB
27. class GitHubRepository(private val networkDataSource: GitHubDataSource){ fun getLagosJavaDevs(): UserDataLayerModel { return networkDataSource.getLagosJavaDevs("lagos", "java") } } interface GitHubDataSource { fun getLagosJavaDevs(location: String, language: String): UserDataLayerModel }
28. class NetworkDataSource : GitHubDataSource { override fun getLagosJavaDevs(location: String, language: String): UserDataLayerModel? { var userDataLayerModel: UserDataLayerModel? = null try { userDataLayerModel = RetrofitUtil.createService().javaDevsInLagos.execute().body() } catch (e: IOException) { e.printStackTrace() } return userDataLayerModel } }
29. Dependency Rule
30. Proprietary + Confidential The Dependency Rule Source: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis non erat sem Presentation Data Domain
31. // build.gradle // Presentation layer dependencies { implementation project(':data') implementation project(':domain') } // Data Layer dependencies { implementation project(':domain') } // Domain layer dependencies { }
32. Proprietary + Confidential Presentation Data Domain Dependency Flow vs Data Flow Source: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis non erat sem Presentation Data Domain
33. Proprietary + Confidential ViewModel with LiveData Activity/Fragment Use cases Entities Repository DataSources Presentation Layer Domain Layer Data Layer <I> <I>
34. Proprietary + Confidential ViewModel with LiveData Activity/Fragment Use cases Entities Repository DataSources Presentation Layer Domain Layer Data Layer
35. Proprietary + Confidential 35
36. Crazy Overhead Right?
37. My Advice Presentation layer (MVVM, MVP, MVC) Lagos Presentation + Data layer (Repository) Presentation + Domain (Use cases) + Data layer
38. There’s More...
39. More tools... App Bundle (Dynamic features) Dependency Injection Data Binding Library etc. Lagos
40. • The Principles of Clean Architecture - Robert C. Martin • Guide to app architecture - Android Docs • Google I/O 2018 app - Architecture and Testing • Clean Architecture for Android with Kotlin - Antonio Leiva Further Reading
41. Lagos Thank you! Chizoba Ogbonna, Paylater @techietoby