Show Snackbars After State Updates in Jetpack Compose

Jetpack Compose has revolutionized Android UI development, enabling developers to build dynamic, reactive user interfaces using declarative programming. One common UI pattern in modern apps is displaying feedback to the user—and Snackbars remain a popular choice for this purpose. In this blog post, we’ll explore how to effectively show Snackbars in response to state updates in Jetpack Compose, diving into best practices and advanced techniques to ensure a seamless user experience.

Why Snackbars Are Essential for User Feedback

Snackbars provide lightweight feedback about an operation performed by the user or the app. They are non-intrusive yet noticeable, appearing at the bottom of the screen and automatically dismissing after a few seconds. Key use cases include:

  • Confirming the success of an operation (e.g., "Item saved successfully").

  • Informing the user of an error (e.g., "Unable to connect to the server").

  • Providing undo functionality for reversible actions (e.g., "Message deleted. UNDO").

In Jetpack Compose, managing the display of Snackbars based on state updates can be tricky but is manageable with a well-structured approach.

Setting Up a Basic Snackbar in Jetpack Compose

Jetpack Compose provides the SnackbarHost and Snackbar components to display Snackbars. Let’s start with a simple setup:

@Composable
fun BasicSnackbarDemo() {
    val snackbarHostState = remember { SnackbarHostState() }
    val coroutineScope = rememberCoroutineScope()

    Column(
        modifier = Modifier.fillMaxSize(),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        Button(onClick = {
            coroutineScope.launch {
                snackbarHostState.showSnackbar(
                    message = "Hello, Snackbar!",
                    actionLabel = "Dismiss",
                    duration = SnackbarDuration.Short
                )
            }
        }) {
            Text("Show Snackbar")
        }

        SnackbarHost(hostState = snackbarHostState)
    }
}

In this example:

  • SnackbarHostState manages the state of the Snackbar.

  • showSnackbar is used to display the Snackbar.

  • A coroutine is launched to trigger the Snackbar display asynchronously.

Linking Snackbars with State Updates

Displaying Snackbars in response to state changes requires a reactive approach. Consider a scenario where a network request updates the UI state, and a Snackbar needs to notify the user of the outcome.

Step 1: Define Your State

Start with a state variable to track the operation's outcome. For example:

data class UiState(
    val message: String? = null,
    val isError: Boolean = false
)

@Composable
fun rememberUiState(): MutableState<UiState> {
    return remember { mutableStateOf(UiState()) }
}

Step 2: Observe and React to State Changes

Use LaunchedEffect to react to state updates and show the Snackbar.

@Composable
fun SnackbarWithState(uiState: MutableState<UiState>) {
    val snackbarHostState = remember { SnackbarHostState() }

    // React to state changes
    LaunchedEffect(uiState.value.message) {
        uiState.value.message?.let { message ->
            snackbarHostState.showSnackbar(
                message = message,
                duration = if (uiState.value.isError) SnackbarDuration.Long else SnackbarDuration.Short
            )

            // Reset the message after showing the Snackbar
            uiState.value = uiState.value.copy(message = null)
        }
    }

    Scaffold(
        snackbarHost = { SnackbarHost(hostState = snackbarHostState) }
    ) { padding ->
        // Content goes here
    }
}

Key Points:

  • LaunchedEffect listens for changes in uiState.value.message. When it changes, the Snackbar is triggered.

  • After displaying the Snackbar, reset the message to prevent repeated triggers.

Advanced Use Cases for Snackbars

1. Queueing Multiple Snackbars

When multiple events need Snackbars, ensure each message is shown sequentially. Use SnackbarHostState's built-in queueing mechanism:

val events = remember { mutableStateListOf<String>() }
val snackbarHostState = remember { SnackbarHostState() }
val coroutineScope = rememberCoroutineScope()

LaunchedEffect(events) {
    events.forEach { event ->
        snackbarHostState.showSnackbar(event)
    }
    events.clear()
}

Button(onClick = {
    events.add("New event occurred")
}) {
    Text("Trigger Event")
}

2. Snackbar Actions

Add actionable items like "Retry" or "Undo" to the Snackbar for enhanced user interaction.

snackbarHostState.showSnackbar(
    message = "Action failed",
    actionLabel = "Retry",
    duration = SnackbarDuration.Long
)

// Check user action
if (result == SnackbarResult.ActionPerformed) {
    // Retry the operation
}

3. Styling Snackbars

Customize the appearance of Snackbars by overriding the default styles:

Snackbar(
    modifier = Modifier.padding(16.dp),
    backgroundColor = Color.Red,
    contentColor = Color.White
) {
    Text(text = "Custom Styled Snackbar")
}

Best Practices for Managing Snackbars

  1. Debounce Triggering: Avoid overloading the user with multiple Snackbars in quick succession. Use a queue or debounce mechanism.

  2. Duration Management: Choose the duration (Short, Long, or Indefinite) based on the message’s importance and complexity.

  3. Testing: Test Snackbar behavior across different screen sizes and orientations to ensure consistency.

  4. State Reset: Always reset the state after showing a Snackbar to prevent unintended re-triggering.

  5. Accessibility: Use concise, meaningful messages and ensure Snackbars are accessible to users relying on screen readers.

Conclusion

Showing Snackbars after state updates in Jetpack Compose requires a combination of reactive programming and careful state management. By leveraging SnackbarHostState, LaunchedEffect, and advanced customization techniques, you can create responsive, user-friendly Snackbars that align with modern app design standards.

Implement these techniques in your next Compose project to elevate your app’s user experience. As always, keep experimenting and iterating to find the best approach for your specific use case. Happy coding!