🔁 Everything You Need to Know About StateFlow in Android

Modern Android apps are shifting toward Kotlin-first, coroutine-based architectures, and StateFlow is becoming a go-to solution for reactive, state-driven UI design. While LiveData is still widely used, StateFlow offers greater flexibility and power, especially in ViewModels.

In this post, we’ll cover:

• What is StateFlow?
• Why use StateFlow instead of LiveData?
• How StateFlow works
• Key differences: StateFlow vs SharedFlow vs LiveData
• Code examples
• Best practices
• Real-world use cases

💡 What is StateFlow?

StateFlow is a state-holder observable flow introduced in Kotlin Coroutines 1.3.6+. It is part of the kotlinx.coroutines.flow package and is designed to hold and emit the latest state to its collectors.

Think of StateFlow as a coroutine-native version of LiveData, with additional coroutine benefits and no dependency on Android lifecycle.

Key Features:

• Always has a current value (similar to a BehaviorSubject in RxJava)
• Emits the latest value to new collectors
• Works seamlessly with coroutines and ViewModelScope

🚀 Why Use StateFlow?

✅ Kotlin-first and lifecycle-independent

It’s part of Kotlin’s coroutines library and doesn’t depend on Android framework classes like LiveData.

🔄 Hot stream

StateFlow is a hot stream — it always stays active and emits the current state immediately to new collectors.

🧵 Coroutine compatibility

It works naturally with coroutine scopes (viewModelScope, lifecycleScope) and structured concurrency.

👁️‍🗨️ UI-friendly with Jetpack Compose

StateFlow integrates perfectly with Compose’s state-driven rendering and is often preferred over LiveData in Compose UIs.

🧬 Anatomy of StateFlow

You generally expose a read-only StateFlow and update it using a private MutableStateFlow in your ViewModel.

1
2
3
4
5
6
7
8
class MyViewModel : ViewModel() {
    private val _uiState = MutableStateFlow("Initial value")
    val uiState: StateFlow<String> = _uiState

    fun updateState(newValue: String) {
        _uiState.value = newValue
    }
}

Then collect in the UI:

lifecycleScope.launchWhenStarted { viewModel.uiState.collect { value -> textView.text = value } }

🔄 StateFlow vs SharedFlow vs LiveData

Feature StateFlow SharedFlow LiveData Lifecycle aware ❌ (needs manual handling) ❌ (same) ✅ Yes Hot/Cold stream 🔥 Hot 🔥 Hot 🧊 Cold Current value ✅ Yes ❌ No ✅ Yes Coroutine support ✅ Native ✅ Native ⚠️ Optional via LiveData-KTX Best for State updates Events (e.g. navigation) UI-bound state Integration with Compose ✅ Excellent ✅ Excellent ⚠️ Indirect 🔧 StateFlow in Compose StateFlow works beautifully with Jetpack Compose using collectAsState():

kotlin Copy Edit @Composable fun MyScreen(viewModel: MyViewModel) { val text by viewModel.uiState.collectAsState()

1
Text(text = text) } 📦 Real-World Example Here’s a simple counter ViewModel:

kotlin Copy Edit class CounterViewModel : ViewModel() { private val _count = MutableStateFlow(0) val count: StateFlow = _count

1
2
3
fun increment() {
    _count.value += 1
} } Usage in an Activity or Fragment:

kotlin Copy Edit lifecycleScope.launchWhenStarted { viewModel.count.collect { count -> textView.text = “Count: $count” } } 📌 Best Practices Expose only immutable StateFlow to the UI layer.

Use viewModelScope to update the flow.

Collect in the appropriate lifecycle-aware scope (lifecycleScope or Compose).

Prefer SharedFlow for events, like one-time navigation, toasts, or dialogs.

Avoid using StateFlow for large or complex data that doesn’t change often.

⚙️ Common Use Cases Managing UI state in MVVM (loading, content, error)

Observing user input (search queries, form state)

Real-time updates (e.g., timers, progress bars)

Reactive settings or preference changes

Integration with Room or other data sources

🧠 Final Thoughts StateFlow is the future of reactive state management in modern Android development. It’s powerful, lightweight, and coroutine-native, making it ideal for ViewModel state management, especially when working with Jetpack Compose or clean MVVM architecture.

While LiveData is still useful (especially for lifecycle-bound UI), learning and using StateFlow will prepare you for a more scalable, modern, and testable architecture.

If you’re building with Kotlin and Coroutines — StateFlow is a must-have in your toolkit.