Compose Multiplatform and Jetpack Compose patterns for KMP projects — state management, navigation, theming, performance, and platform-specific UI.
Compose Multiplatform Patterns
Patterns for building shared UI across Android, iOS, Desktop, and Web using Compose Multiplatform and Jetpack Compose. Covers state management, navigation, theming, and performance.
When to Activate
Building Compose UI (Jetpack Compose or Compose Multiplatform)
Managing UI state with ViewModels and Compose state
Implementing navigation in KMP or Android projects
Designing reusable composables and design systems
Optimizing recomposition and rendering performance
State Management
ViewModel + Single State Object
Use a single data class for screen state. Expose it as StateFlow and collect in Compose:
data class ItemListState(
val items: List<Item> = emptyList(),
val isLoading: Boolean = false,
val error: String? = null,
val searchQuery: String = ""
)
class ItemListViewModel(
private val getItems: GetItemsUseCase
) : ViewModel() {
private val _state = MutableStateFlow(ItemListState())
val state: StateFlow<ItemListState> = _state.asStateFlow()
fun onSearch(query: String) {
_state.update { it.copy(searchQuery = query) }
loadItems(query)
}
private fun loadItems(query: String) {
viewModelScope.launch {
_state.update { it.copy(isLoading = true) }
getItems(query).fold(
onSuccess = { items -> _state.update { it.copy(items = items, isLoading = false) } },
onFailure = { e -> _state.update { it.copy(error = e.message, isLoading = false) } }
)
}
}
}
Collecting State in Compose
@Composable
fun ItemListScreen(viewModel: ItemListViewModel = koinViewModel()) {
val state by viewModel.state.collectAsStateWithLifecycle()
ItemListContent(
state = state,
onSearch = viewModel::onSearch
)
}
@Composable
private fun ItemListContent(
state: ItemListState,
onSearch: (String) -> Unit
) {
// Stateless composable — easy to preview and test
}
Event Sink Pattern
For complex screens, use a sealed interface for events instead of multiple callback lambdas:
sealed interface ItemListEvent {
data class Search(val query: String) : ItemListEvent
data class Delete(val itemId: String) : ItemListEvent
data object Refresh : ItemListEvent
}
// In ViewModel
fun onEvent(event: ItemListEvent) {
when (event) {
is ItemListEvent.Search -> onSearch(event.query)
is ItemListEvent.Delete -> deleteItem(event.itemId)
is ItemListEvent.Refresh -> loadItems(_state.value.searchQuery)
}
}
// In Composable — single lambda instead of many
ItemListContent(
state = state,
onEvent = viewModel::onEvent
)
Navigation
Type-Safe Navigation (Compose Navigation 2.8+)
Define routes as @Serializable objects:
@Serializable data object HomeRoute
@Serializable data class DetailRoute(val id: String)
@Serializable data object SettingsRoute
@Composable
fun AppNavHost(navController: NavHostController = rememberNavController()) {
NavHost(navController, startDestination = HomeRoute) {
composable<HomeRoute> {
HomeScreen(onNavigateToDetail = { id -> navController.navigate(DetailRoute(id)) })
}
composable<DetailRoute> { backStackEntry ->
val route = backStackEntry.toRoute<DetailRoute>()
DetailScreen(id = route.id)
}
composable<SettingsRoute> { SettingsScreen() }
}
}
Dialog and Bottom Sheet Navigation
Use dialog() and overlay patterns instead of imperative show/hide:
NavHost(navController, startDestination = HomeRoute) {
composable<HomeRoute> { /* ... */ }
dialog<ConfirmDeleteRoute> { backStackEntry ->
val route = backStackEntry.toRoute<ConfirmDeleteRoute>()
ConfirmDeleteDialog(
itemId = route.itemId,
onConfirm = { navController.popBackStack() },
onDismiss = { navController.popBackStack() }
)
}
}
Composable Design
Slot-Based APIs
Design composables with slot parameters for flexibility:
@Composable
fun AppCard(
modifier: Modifier = Modifier,
header: @Composable () -> Unit = {},
content: @Composable ColumnScope.() -> Unit,
actions: @Composable RowScope.() -> Unit = {}
) {
Card(modifier = modifier) {
Column {
header()
Column(content = content)
Row(horizontalArrangement = Arrangement.End, content = actions)
}
}
}
Modifier Ordering
Modifier order matters — apply in this sequence:
Text(
text = "Hello",
modifier = Modifier
.padding(16.dp) // 1. Layout (padding, size)
.clip(RoundedCornerShape(8.dp)) // 2. Shape
.background(Color.White) // 3. Drawing (background, border)
.clickable { } // 4. Interaction
)
KMP Platform-Specific UI
expect/actual for Platform Composables
// commonMain
@Composable
expect fun PlatformStatusBar(darkIcons: Boolean)
// androidMain
@Composable
actual fun PlatformStatusBar(darkIcons: Boolean) {
val systemUiController = rememberSystemUiController()
SideEffect { systemUiController.setStatusBarColor(Color.Transparent, darkIcons) }
}
// iosMain
@Composable
actual fun PlatformStatusBar(darkIcons: Boolean) {
// iOS handles this via UIKit interop or Info.plist
}
Performance
Stable Types for Skippable Recomposition
Mark classes as @Stable or @Immutable when all properties are stable:
@Immutable
data class ItemUiModel(
val id: String,
val title: String,
val description: String,
val progress: Float
)
Use key() and Lazy Lists Correctly
LazyColumn {
items(
items = items,
key = { it.id } // Stable keys enable item reuse and animations
) { item ->
ItemRow(item = item)
}
}
Defer Reads with derivedStateOf
val listState = rememberLazyListState()
val showScrollToTop by remember {
derivedStateOf { listState.firstVisibleItemIndex > 5 }
}
Avoid Allocations in Recomposition
// BAD — new lambda and list every recomposition
items.filter { it.isActive }.forEach { ActiveItem(it, onClick = { handle(it) }) }
// GOOD — key each item so callbacks stay attached to the right row
val activeItems = remember(items) { items.filter { it.isActive } }
activeItems.forEach { item ->
key(item.id) {
ActiveItem(item, onClick = { handle(item) })
}
}
Theming
Material 3 Dynamic Theming
@Composable
fun AppTheme(
darkTheme: Boolean = isSystemInDarkTheme(),
dynamicColor: Boolean = true,
content: @Composable () -> Unit
) {
val colorScheme = when {
dynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
if (darkTheme) dynamicDarkColorScheme(LocalContext.current)
else dynamicLightColorScheme(LocalContext.current)
}
darkTheme -> darkColorScheme()
else -> lightColorScheme()
}
MaterialTheme(colorScheme = colorScheme, content = content)
}
Anti-Patterns to Avoid
Using mutableStateOf in ViewModels when MutableStateFlow with collectAsStateWithLifecycle is safer for lifecycle
Passing NavController deep into composables — pass lambda callbacks instead
Heavy computation inside @Composable functions — move to ViewModel or remember {}
Using LaunchedEffect(Unit) as a substitute for ViewModel init — it re-runs on configuration change in some setups
Creating new object instances in composable parameters — causes unnecessary recomposition
References
See skill: android-clean-architecture for module structure and layering.
See skill: kotlin-coroutines-flows for coroutine and Flow patterns.don't have the plugin yet? install it then click "run inline in claude" again.