What is MVI Architecture? A Guide for Android Developers

As Android applications become richer and more interactive, managing UI state, user intent, and data flow becomes increasingly complex. Over the years, several architectural patterns have emerged to address this challenge—MVC, MVP, MVVM, and more recently, MVI.

MVI (Model–View–Intent) is a reactive, predictable, and test-friendly architectural pattern built around unidirectional data flow. It eliminates ambiguity around how data moves through an application and how UI updates occur, which makes it particularly well-suited for modern Android development with Jetpack Compose.

In this guide, we will explore what MVI is, how it differs from MVVM and MVP, why it is gaining traction, and how to implement it effectively in real-world Android applications.

What is MVI Architecture?

Model–View–Intent (MVI) is an architectural pattern where:

• Users express Intents (actions or events)
• A ViewModel (Reducer) processes those intents
• A new State is produced
• The UI renders purely based on that state

The key idea is that the UI is a pure function of state. Whenever the state changes, the UI re-renders automatically. This approach enforces a single direction of data flow and a single source of truth.

Unidirectional Data Flow

User Action → Intent → ViewModel (Reducer) → New State → UI Render

• Events flow upward (UI → Intent → ViewModel)
• State flows downward (ViewModel → UI)

This predictability is one of the primary reasons MVI pairs so naturally with Jetpack Compose.

MVI vs MVP vs MVVM

In MVVM, it is common to expose multiple observable fields:

val name = MutableStateFlow("")

val isLoading = MutableStateFlow(false)

val error = MutableStateFlow<String?>(null)

val items = MutableStateFlow(emptyList<Item>())

This approach can lead to:

• Inconsistent UI states
• Missed updates
• Hard-to-reproduce bugs

MVI addresses this by modeling the entire screen with a single immutable state object:

data class ScreenState(
    val name: String,
    val isLoading: Boolean,
    val error: String?,
    val items: List<Item>
)

At any moment, the UI reflects one well-defined state snapshot.

Core Principles of MVI

1. Unidirectional Data Flow

All interactions follow a single loop:

Intent → Reducer → New State → UI

2. Single Source of Truth

The entire UI is derived from one immutable state object.

3. Immutability

State objects are never modified directly. New instances are created using copy(), ensuring deterministic and reproducible UI updates.

A Practical MVI Example (Jetpack Compose)

To ground these concepts, we will start with a simple counterexample before moving to a more realistic use case.

Step 1: Define State

data class CounterState(
    val count: Int = 0
)

Step 2: Define Intents

sealed class CounterIntent {
    object Increment : CounterIntent()
    object Decrement : CounterIntent()
    object Reset : CounterIntent()
}

Step 3: ViewModel (Reducer)

class CounterViewModel : ViewModel() {

    private val _state = MutableStateFlow(CounterState())
    val state = _state.asStateFlow()
    fun handleIntent(intent: CounterIntent) {
        when (intent) {
            CounterIntent.Increment ->
                _state.value = _state.value.copy(count = _state.value.count + 1)

            CounterIntent.Decrement ->
                _state.value = _state.value.copy(count = _state.value.count - 1)

            CounterIntent.Reset ->
                _state.value = _state.value.copy(count = 0)
        }
    }
}

Each intent results in a new state derived from the previous one.

Step 4: Compose UI

@Composable
fun CounterScreen(viewModel: CounterViewModel = viewModel()) {
    val state by viewModel.state.collectAsState()

    Column(horizontalAlignment = Alignment.CenterHorizontally) {
        Text(text = "Count: ${state.count}")

        Row {
            Button(onClick = { viewModel.handleIntent(CounterIntent.Decrement) }) {
                Text("-")
            }
            Button(onClick = { viewModel.handleIntent(CounterIntent.Increment) }) {
                Text("+")
            }
        }

        Button(onClick = { viewModel.handleIntent(CounterIntent.Reset) }) {
            Text("Reset")
        }
    }
}