Snackbars are an essential UI element in Android applications, providing quick feedback about app processes without disrupting the user’s flow. Jetpack Compose, Google's modern toolkit for building native UIs, offers a simplified yet powerful way to implement Snackbars. However, managing multiple Snackbars effectively in a Compose environment can be challenging, especially when dealing with complex scenarios like concurrent triggers or overlapping messages.
In this blog post, we’ll explore best practices for handling multiple Snackbars in Jetpack Compose, delving into advanced concepts and practical examples to help intermediate and advanced developers master this aspect of app development.
Understanding Snackbars in Jetpack Compose
Jetpack Compose provides a Snackbar and SnackbarHost as part of its Material Design components. The SnackbarHost is responsible for displaying Snackbar instances, and it is typically controlled by a SnackbarHostState. To trigger a Snackbar, you use the SnackbarHostState.showSnackbar function, which suspends until the Snackbar is dismissed.
Here’s a basic example:
val snackbarHostState = remember { SnackbarHostState() }
LaunchedEffect(Unit) {
snackbarHostState.showSnackbar(
message = "This is a simple Snackbar",
actionLabel = "Retry"
)
}
Scaffold(
snackbarHost = { SnackbarHost(hostState = snackbarHostState) }
) { paddingValues ->
// Your content here
}While this works well for simple use cases, handling multiple Snackbars requires a more robust approach.
Challenges with Multiple Snackbars
Concurrency Issues: Multiple events triggering Snackbars simultaneously can result in unintended behaviors like skipped messages or overlapping Snackbars.
Message Prioritization: Not all Snackbars are equally important. Some might need higher priority based on the context.
State Management: Managing Snackbar state across different components or ViewModels can become cumbersome.
To address these challenges, let’s look at some best practices and patterns.
Best Practices for Handling Multiple Snackbars
1. Use a Centralized Snackbar Manager
A centralized manager ensures that all Snackbar requests are funneled through a single source, allowing for better control and coordination.
Here’s an example implementation:
class SnackbarManager {
private val _messages = MutableSharedFlow<SnackbarMessage>()
val messages: SharedFlow<SnackbarMessage> = _messages
suspend fun showMessage(message: SnackbarMessage) {
_messages.emit(message)
}
}
data class SnackbarMessage(
val message: String,
val actionLabel: String? = null,
val duration: SnackbarDuration = SnackbarDuration.Short
)In your Composable, collect messages from the SnackbarManager and display them using SnackbarHostState:
val snackbarHostState = remember { SnackbarHostState() }
val snackbarManager = remember { SnackbarManager() }
LaunchedEffect(snackbarManager) {
snackbarManager.messages.collect { message ->
snackbarHostState.showSnackbar(
message = message.message,
actionLabel = message.actionLabel,
duration = message.duration
)
}
}
Scaffold(
snackbarHost = { SnackbarHost(hostState = snackbarHostState) }
) { paddingValues ->
// Your content here
}This approach ensures all Snackbar requests are handled sequentially, preventing overlap.
2. Prioritize Messages
Not all messages are of equal importance. Implement a priority mechanism to ensure critical messages are displayed first.
Modify the SnackbarManager to support priority:
data class SnackbarMessage(
val message: String,
val priority: Int = 0, // Higher value = higher priority
val actionLabel: String? = null,
val duration: SnackbarDuration = SnackbarDuration.Short
)
suspend fun SnackbarManager.showMessage(message: SnackbarMessage) {
_messages.emit(message)
}Sort messages by priority before displaying them:
LaunchedEffect(snackbarManager) {
snackbarManager.messages
.buffer() // Ensure proper ordering
.onEach { message ->
snackbarHostState.showSnackbar(
message = message.message,
actionLabel = message.actionLabel,
duration = message.duration
)
}
.collect()
}This ensures critical messages are not delayed or overshadowed by less important ones.
3. Handle Snackbar Cancellation
In some cases, a Snackbar might become irrelevant before it is shown. For instance, if the user resolves an error before the error message is displayed.
Enhance the SnackbarManager to support cancellation:
class SnackbarManager {
private val _messages = MutableSharedFlow<SnackbarMessage>(replay = 0)
private val activeMessages = mutableListOf<SnackbarMessage>()
suspend fun showMessage(message: SnackbarMessage) {
activeMessages.add(message)
_messages.emit(message)
}
fun cancelMessage(message: SnackbarMessage) {
activeMessages.remove(message)
}
}When emitting messages, check if they are still valid:
LaunchedEffect(snackbarManager) {
snackbarManager.messages
.filter { message -> snackbarManager.activeMessages.contains(message) }
.collect { message ->
snackbarHostState.showSnackbar(
message = message.message,
actionLabel = message.actionLabel,
duration = message.duration
)
}
}4. Leverage Dependency Injection
To make the SnackbarManager reusable across your app, integrate it with a dependency injection framework like Hilt:
@Module
@InstallIn(SingletonComponent::class)
object SnackbarModule {
@Provides
@Singleton
fun provideSnackbarManager(): SnackbarManager = SnackbarManager()
}Inject it into your ViewModel or Composable as needed:
@HiltViewModel
class MainViewModel @Inject constructor(
private val snackbarManager: SnackbarManager
) : ViewModel() {
fun triggerSnackbar() {
viewModelScope.launch {
snackbarManager.showMessage(SnackbarMessage("Example Snackbar"))
}
}
}Advanced Use Case: Multiple Hosts
In some applications, you might have multiple SnackbarHosts for different sections of your app. For instance, a main SnackbarHost for global messages and another for context-specific messages within a particular screen.
You can achieve this by creating scoped SnackbarManager instances and associating them with specific hosts.
Conclusion
Handling multiple Snackbars in Jetpack Compose requires a thoughtful approach to concurrency, prioritization, and state management. By using a centralized SnackbarManager, implementing prioritization, and integrating with dependency injection, you can create a robust system that enhances user experience.
For further reading, check out these resources:
By following these best practices, you’ll be well-equipped to handle even the most complex Snackbar requirements in your Compose applications.