mobiai-android-architecture

Android Architecture

Common architecture patterns and project structures in Android apps.

When to Use

• Navigating an unfamiliar Android codebase
• Understanding where to make changes for a bug fix
• Writing code that follows the project's existing patterns

Detecting the Architecture

Check project structure

# Find the main source directory
find app/src/main -type d | head -30

# Look for common architecture indicators
grep -r "ViewModel\|UseCase\|Repository\|Interactor\|Presenter" app/src/main --include="*.kt" -l | head -20

Common Patterns

Pattern	Indicator Files	Layer Structure
MVVM + Clean	*ViewModel.kt, *UseCase.kt, *Repository.kt	UI → ViewModel → UseCase → Repository → DataSource
MVI	*Intent.kt, *State.kt, *Reducer.kt	UI → ViewModel (reducer) → Repository
MVP	*Presenter.kt, *View.kt (interface)	View → Presenter → Model
Simple MVVM	*ViewModel.kt, no UseCases	UI → ViewModel → Repository

Clean Architecture (Most Common)

Layer Structure

feature/
  presentation/        # UI Layer
    MyFragment.kt         # Fragment (XML) or Screen (Compose)
    MyViewModel.kt        # ViewModel — UI state + user actions
    MyUiState.kt          # State model for the UI
  domain/              # Business Logic Layer
    usecase/
      GetItemsUseCase.kt  # Single-purpose business operation
    model/
      Item.kt              # Domain model (plain Kotlin)
    repository/
      ItemRepository.kt   # Interface — defined here, implemented in data layer
  data/                # Data Layer
    repository/
      ItemRepositoryImpl.kt  # Implementation of domain interface
    local/
      ItemDao.kt           # Room DAO
      ItemEntity.kt        # Database entity
    remote/
      ItemApi.kt           # Retrofit API interface
      ItemDto.kt           # Network response model
    mapper/
      ItemMapper.kt        # DTO ↔ Entity ↔ Domain model mapping