SnackbarChannel

1.0.7indexed

Lightweight, lifecycle-safe snackbar event dispatcher solves common pitfalls with StateFlow and SharedFlow, ensuring reliable event emission without duplicates or manual state management. Offers a simple API and is lifecycle-aware.

AndroidJVMNativeWasm·AungThiha/SnackbarChannel

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SnackbarChannel

⚠️ Limitation (and Upcoming Fix)
Thanks to the community feedback, I learned that this solution can lose the Snackbar if a configuration change happens right after the event is delivered to the collector but before the Snackbar is dismissed. As a result, the Snackbar won't be shown again even if the user hasn't grasped the message yet. Therefore, I'll switch back to StateFlow<List<Event>> but will abstract out the details to make it easy for the developers. The update should be available before September 2025.

A lightweight, lifecycle-safe snackbar event dispatcher for Compose Multiplatform that addresses common pitfalls of using SharedFlow and StateFlow.

⚠️ Using Jetpack Compose for Android only?
This library relies on StringResource and getString from org.jetbrains.compose.resources, which are not supported in pure Android projects. Please refer to the Android-specific version instead: AndroidSnackbarChannel.

Why use SnackbarChannel?

SnackbarChannel addresses the common pitfalls of using StateFlow, SharedFlow, or even StateFlow<List<Event>>.

StateFlow re-emits on config changes, leading to duplicate snackbars.
SharedFlow(replay = 0) may drop events when no collector is active.
SharedFlow(replay = 1) can treat each lifecycle change as a new subscription, re-emitting events.
List-based workarounds (e.g., StateFlow<List<String>>) require manual state updates to remove consumed items, adding extra complexity and visual noise to the .

SnackbarChannel avoids these issues:

Emits events reliably even across lifecycle changes.
No risk of duplicates or dropped events.
No manual list mutation or bookkeeping required.

It’s a focused solution that keeps your snackbar logic clean, lifecycle-aware, and easy to use.

Features

One-liner API for triggering snackbars from your ViewModel
No more missed or duplicated snackbars
Lifecycle-aware: events are only collected when the UI is active
Works seamlessly with SnackbarHostState.showSnackbar(...)
No brittle base classes - favors composition over inheritance using Kotlin delegation
Supports all original showSnackbar parameters (action labels, duration, callbacks, etc.)
Compose Multiplatform support

Installation

commonMain.dependencies {
    implementation("io.github.aungthiha:snackbar-channel:1.0.7")
}

Setup

1. Add `SnackbarChannel` to your `ViewModel`

By default, SnackbarChannel uses Channel.UNLIMITED and BufferOverflow.SUSPEND to ensure no snackbar events are dropped.

import io.github.aungthiha.snackbar.SnackbarChannel
import io.github.aungthiha.snackbar.SnackbarChannelOwner

class MyViewModel(
    private val snackbarChannel: SnackbarChannel = SnackbarChannel() // Default: Channel.UNLIMITED
) : ViewModel(), SnackbarChannelOwner by snackbarChannel {

    fun showSimpleSnackbar() {
        showSnackBar(message = Res.string.hello_world)
    }
}

While the defaults are recommended for most use cases, both the channel capacity and onBufferOverflow strategy are configurable:

SnackbarChannel(
    capacity = Channel.RENDEZVOUS, // Or Channel.BUFFERED, etc.
    onBufferOverflow = BufferOverflow.DROP_OLDEST, // Or BufferOverflow.DROP_LATEST
)

2. Observe snackbars in your Composable

import androidx.compose.material3.Scaffold
import androidx.compose.material3.SnackbarHost
import androidx.compose.material3.SnackbarHostState
import io.github.aungthiha.snackbar.collectWithLifecycle
import io.github.aungthiha.snackbar.showSnackbar

@Composable
fun MyScreen(viewModel: MyViewModel = viewModel()) {
    val snackbarHostState = remember { SnackbarHostState() }

    viewModel.snackbarFlow.observeWithLifecycle {
        snackbarHostState.showSnackbar(it)
    }

    Scaffold(snackbarHost = { SnackbarHost(snackbarHostState) }) {
        Button(onClick = { viewModel.showSimpleSnackbar() }) {
            Text()
        }
    }
}

API Overview

Use showSnackBar(...) from your ViewModel. You can pass string resources, string literals, or even mix both using SnackbarString.

// All parameters
showSnackBar(
    message = Res.string.hello_world, // can be either StringResource or String
    actionLabel = "ok", // can be either StringResource or String
    withDismissAction = true,
    duration = SnackbarDuration.Indefinite,
    onActionPerform = { /* handle action */ },
    onDismiss = { /* handle dismiss */ }
)

// Using a string resource
showSnackBar(
    message = Res.string.hello_world,
    actionLabel = Res.string.ok
)


showSnackBar(
    message = ,
    actionLabel = 
)


showSnackBar(
    message = ,
    actionLabel = Res.string.ok
)

showSnackBar(
    message = Res.string.hello_world,
    actionLabel = 
)

All parameters are optional except the message.
For more example usages, see AppViewModel.kt

Unit Testing

You can test snackbar emissions using runTest and collecting from snackbarFlow.

class MyViewModelTest {

    private val viewModel = MyViewModel()

    @Test
    fun snackbar_is_emitted() = runTest {
        viewModel.showSimpleSnackbar()

        val snackbarModel = viewModel.snackbarFlow.first()

        assertEquals(
            SnackbarString(Res.string.hello_world),
            snackbarModel.message
        )
    }
}