Android MVI Architecture

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Modern Android MVI architecture example with Jetpack Compose, Koin, and Navigation.

Tech Stack

Component	Version	Purpose
Kotlin	1.9.20	Language
Compose BOM	2023.10.01	UI Framework
Material3	BOM	Design System
Navigation Compose	2.7.6	Navigation
Koin	3.5.0	Dependency Injection
StateFlow	-	State Management
Gradle KTS	8.5	Build System

Project Structure

com.hao.mvi/
│
├── MainActivity.kt                 # App entry, Compose + Navigation
├── App.kt               # Koin initialization
│
├── core/                           # 🔧 Core layer (shared across features)
│   ├── base/                       # MVI infrastructure
│   │   ├── BaseViewModel.kt        # Generic ViewModel<State, Event, Effect>
│   │   ├── MviContract.kt          # IViewState / IViewEvent / IViewEffect
│   │   ├── ObserveAsEvents.kt      # Lifecycle-safe Effect collector
│   │   └── UiState.kt              # Loading/Success/Error wrapper
│   ├── navigation/
│   │   ├── Screen.kt               # Route definitions
│   │   └── AppNavGraph.kt          # NavHost configuration
│   └── ui/theme/
│       ├── Color.kt
│       ├── Theme.kt
│       └── Type.kt
│
├── di/                             # 💉 Dependency Injection
│   └── AppModule.kt                # Koin modules
│
└── feature/                        # 📦 Feature modules
    ├── counter/
    │   ├── data/
    │   │   └── CounterRepository.kt
    │   ├── domain/
    │   │   └── CounterUseCases.kt
    │   └── presentation/
    │       ├── CounterContract.kt
    │       ├── CounterScreen.kt
    │       └── CounterViewModel.kt
    └── detail/
        └── presentation/
            └── DetailScreen.kt

Architecture

MVI Flow

User Action → Event → ViewModel.handleEvent() → setState() → State → UI
                                              ↘ setEffect() → Effect → Toast/Navigation

Layer Responsibilities

Layer	Package	Responsibility
Core	core.base	MVI abstractions
Navigation	core.navigation	Routes + NavGraph
DI	di	Koin module definitions
Data	feature.*.data	Repository interface + impl
Domain	feature.*.domain	UseCase business logic
Presentation	feature.*.presentation	Screen + ViewModel + Contract

Key Components

BaseViewModel

abstract class BaseViewModel<State : IViewState, Event : IViewEvent, Effect : IViewEffect>(
    private val mainDispatcher: CoroutineDispatcher = Dispatchers.Main
) : ViewModel() {

    abstract fun createInitialState(): State
    abstract fun handleEvent(event: Event)

    protected fun setState(reduce: State.() -> State)
    protected fun setEffect(effect: Effect)
}

Contract Pattern

// State - UI state, survives configuration changes
data class CounterState(
    val count: Int = 0,
    val isLoading: Boolean = false
) : IViewState

// Event - User intents
sealed class CounterEvent : IViewEvent {
    data object Increment : CounterEvent()
    data object Decrement : CounterEvent()
}

// Effect - One-time side effects
sealed class CounterEffect : IViewEffect {
    data class ShowToast(val message: String) : CounterEffect()
    data class NavigateToDetail(val count: Int) : CounterEffect()
}

Lifecycle-safe Effect Collection

@Composable
fun <T> ObserveAsEvents(flow: Flow<T>, onEvent: (T) -> Unit) {
    val lifecycleOwner = LocalLifecycleOwner.current
    LaunchedEffect(flow, lifecycleOwner.lifecycle) {
        lifecycleOwner.repeatOnLifecycle(Lifecycle.State.STARTED) {
            flow.collect(onEvent)
        }
    }
}

Adding New Feature

1. Create feature package:

feature/newfeature/
├── data/
│   └── NewFeatureRepository.kt
├── domain/
│   └── NewFeatureUseCases.kt
└── presentation/
    ├── NewFeatureContract.kt
    ├── NewFeatureScreen.kt
    └── NewFeatureViewModel.kt

2. Register in Koin (di/AppModule.kt)
3. Add route in core/navigation/Screen.kt
4. Add composable in core/navigation/AppNavGraph.kt

License

MIT