📢 Blog 2: Event Handling in Android with Channel vs SharedFlow

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# ⚡ Channel vs SharedFlow: Handling One-Time Events in Android

One-time events—like showing a Toast, navigating to another screen, or displaying a Snackbar—are hard to get right in Android. While LiveData often leads to "sticky" or repeated events, Kotlin’s `SharedFlow` and `Channel` offer better options.

In this blog, we’ll compare:

- What are SharedFlow and Channel?
- Key differences
- Code examples
- Which one should you use?
- Best practices

---

## 🔄 What is SharedFlow?

`SharedFlow` is a **hot, multicast** coroutine-based stream. It emits data to all active collectors and is ideal for broadcasting events.

```kotlin
private val _eventFlow = MutableSharedFlow<String>()
val eventFlow = _eventFlow.asSharedFlow()

viewModelScope.launch {
    _eventFlow.emit("Show Toast")
}

📬 What is Channel? A Channel is a cold, single-consumer stream that behaves like a queue. Only one collector can consume data from it at a time.

kotlin Copy Edit private val _channel = Channel() val channel = _channel.receiveAsFlow()

viewModelScope.launch { _channel.send(“Show Toast”) } 🆚 Key Differences

Feature SharedFlow Channel Multicast ✅ Yes ❌ No (single consumer) Lifecycle-safe ❌ (requires coroutine) ❌ (requires coroutine) Backpressure ✅ With buffer settings ⚠️ Risk of dropped values Replay support ✅ Yes (optional) ❌ No Ideal for UI Events (toasts, nav) One-time messages 📦 Use Case: Snackbar Event Using SharedFlow kotlin Copy Edit // ViewModel val _snackbar = MutableSharedFlow() val snackbar = _snackbar.asSharedFlow()

fun showSnackbar() { viewModelScope.launch { _snackbar.emit(“Hello from SharedFlow!”) } }

// UI lifecycleScope.launchWhenStarted { viewModel.snackbar.collect { message -> showSnackbar(message) } } Using Channel kotlin Copy Edit // ViewModel private val _eventChannel = Channel() val eventFlow = _eventChannel.receiveAsFlow()

fun sendEvent() { viewModelScope.launch { _eventChannel.send(“Hello from Channel!”) } }

// UI lifecycleScope.launchWhenStarted { viewModel.eventFlow.collect { message -> showSnackbar(message) } } 🧠 Which One Should You Use?

Scenario Recommendation Multiple collectors ✅ SharedFlow Single-use messages ✅ Channel Events with replay ✅ SharedFlow Lightweight fire-and-forget ✅ Channel 📌 Best Practices For one-time UI events → prefer SharedFlow(replay = 0)

Avoid using StateFlow for transient events

Always collect in appropriate lifecycle (e.g. launchWhenStarted)

Limit Channel usage for internal messaging or one-shot events

🧠 Final Thoughts Both SharedFlow and Channel are powerful tools when used correctly. For most modern Android UI patterns, SharedFlow is more flexible and safer—especially when working with Jetpack Compose or multiple collectors.

TL;DR: Use StateFlow for state, SharedFlow for events, and Channel for isolated, one-time, fire-and-forget messaging.