android-clean-architecture

Android Clean Architecture

Clean Architecture patterns for Android and KMP projects. Covers module boundaries, dependency inversion, UseCase/Repository patterns, and data layer design with Room, SQLDelight, and Ktor.

When to Use

• Structuring Android or KMP project modules
• Implementing UseCases, Repositories, or DataSources
• Designing data flow between layers (domain, data, presentation)
• Setting up dependency injection with Koin or Hilt
• Working with Room, SQLDelight, or Ktor in a layered architecture

Module Structure

Recommended Layout

project/
├── app/                  # Android entry point, DI wiring, Application class
├── core/                 # Shared utilities, base classes, error types
├── domain/               # UseCases, domain models, repository interfaces (pure Kotlin)
├── data/                 # Repository implementations, DataSources, DB, network
├── presentation/         # Screens, ViewModels, UI models, navigation
├── design-system/        # Reusable Compose components, theme, typography
└── feature/              # Feature modules (optional, for larger projects)
    ├── auth/
    ├── settings/
    └── profile/

Dependency Rules

app → presentation, domain, data, core
presentation → domain, design-system, core
data → domain, core
domain → core (or no dependencies)
core → (nothing)

Critical: domain must NEVER depend on data, presentation, or any framework. It contains pure Kotlin only.

Domain Layer

UseCase Pattern

Each UseCase represents one business operation. Use operator fun invoke for clean call sites:

class GetItemsByCategoryUseCase(
    private val repository: ItemRepository
) {
    suspend operator fun invoke(category: String): Result<List<Item>> {
        return repository.getItemsByCategory(category)
    }
}

// Flow-based UseCase for reactive streams
class ObserveUserProgressUseCase(
    private val repository: UserRepository
) {
    operator fun invoke(userId: String): Flow<UserProgress> {
        return repository.observeProgress(userId)
    }
}