with one click
kotlin-coroutines-flows
// Kotlin协程与Flow在Android和KMP中的模式——结构化并发、Flow操作符、StateFlow、错误处理和测试。
// Kotlin协程与Flow在Android和KMP中的模式——结构化并发、Flow操作符、StateFlow、错误处理和测试。
React 18/19 patterns including hooks discipline, server/client component boundaries, Suspense + error boundaries, form actions, data fetching, state management decision trees, and accessibility-first composition. Use when writing or reviewing React components.
React and Next.js performance optimization patterns adapted from Vercel Engineering's React Best Practices (https://github.com/vercel-labs/agent-skills). Organizes 70+ rules across 8 priority categories — waterfalls, bundle size, server-side, client fetching, re-render, rendering, JS micro-perf, advanced. Use when writing, reviewing, or refactoring React/Next.js code for performance.
React component testing with React Testing Library, Vitest/Jest, MSW for network mocking, accessibility assertions with axe, and the decision boundary between component tests and Playwright/Cypress end-to-end runs. Use when writing or fixing tests for React components, hooks, or pages.
Agent-driven scheduling and publishing of social media posts across 13 platforms via SocialClaw. Use when the user wants to publish to X, LinkedIn, Instagram, Facebook Pages, TikTok, Discord, Telegram, YouTube, Reddit, WordPress, or Pinterest — or when managing campaigns, uploading media, or monitoring post delivery status.
End-to-end marketing campaign planning and execution. Covers audience research, positioning, campaign angle definition, landing page copy, email sequences, social posts, ad copy, short-form video scripts, and content calendars. Use as the orchestration layer for multi-channel product launches.
Accessibility patterns for React and Next.js — semantic HTML, ARIA attributes, form labeling, keyboard navigation, focus management, and screen reader support. Use when building any interactive UI component or form.
| name | kotlin-coroutines-flows |
| description | Kotlin协程与Flow在Android和KMP中的模式——结构化并发、Flow操作符、StateFlow、错误处理和测试。 |
| origin | ECC |
适用于 Android 和 Kotlin 多平台项目的结构化并发模式、基于 Flow 的响应式流以及协程测试。
Application
└── viewModelScope (ViewModel)
└── coroutineScope { } (结构化子作用域)
├── async { } (并发任务)
└── async { } (并发任务)
始终使用结构化并发——绝不使用 GlobalScope:
// BAD
GlobalScope.launch { fetchData() }
// GOOD — scoped to ViewModel lifecycle
viewModelScope.launch { fetchData() }
// GOOD — scoped to composable lifecycle
LaunchedEffect(key) { fetchData() }
使用 coroutineScope + async 处理并行工作:
suspend fun loadDashboard(): Dashboard = coroutineScope {
val items = async { itemRepository.getRecent() }
val stats = async { statsRepository.getToday() }
val profile = async { userRepository.getCurrent() }
Dashboard(
items = items.await(),
stats = stats.await(),
profile = profile.await()
)
}
当子协程失败不应取消同级协程时,使用 supervisorScope:
suspend fun syncAll() = supervisorScope {
launch { syncItems() } // failure here won't cancel syncStats
launch { syncStats() }
launch { syncSettings() }
}
fun observeItems(): Flow<List<Item>> = flow {
// Re-emits whenever the database changes
itemDao.observeAll()
.map { entities -> entities.map { it.toDomain() } }
.collect { emit(it) }
}
class DashboardViewModel(
observeProgress: ObserveUserProgressUseCase
) : ViewModel() {
val progress: StateFlow<UserProgress> = observeProgress()
.stateIn(
scope = viewModelScope,
started = SharingStarted.WhileSubscribed(5_000),
initialValue = UserProgress.EMPTY
)
}
WhileSubscribed(5_000) 会在最后一个订阅者离开后,保持上游活动 5 秒——可在配置更改时存活而无需重启。
val uiState: StateFlow<HomeState> = combine(
itemRepository.observeItems(),
settingsRepository.observeTheme(),
userRepository.observeProfile()
) { items, theme, profile ->
HomeState(items = items, theme = theme, profile = profile)
}.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), HomeState())
// Debounce search input
searchQuery
.debounce(300)
.distinctUntilChanged()
.flatMapLatest { query -> repository.search(query) }
.catch { emit(emptyList()) }
.collect { results -> _state.update { it.copy(results = results) } }
// Retry with exponential backoff
fun fetchWithRetry(): Flow<Data> = flow { emit(api.fetch()) }
.retryWhen { cause, attempt ->
if (cause is IOException && attempt < 3) {
delay(1000L * (1 shl attempt.toInt()))
true
} else {
false
}
}
class ItemListViewModel : ViewModel() {
private val _effects = MutableSharedFlow<Effect>()
val effects: SharedFlow<Effect> = _effects.asSharedFlow()
sealed interface Effect {
data class ShowSnackbar(val message: String) : Effect
data class NavigateTo(val route: String) : Effect
}
private fun deleteItem(id: String) {
viewModelScope.launch {
repository.delete(id)
_effects.emit(Effect.ShowSnackbar("Item deleted"))
}
}
}
// Collect in Composable
LaunchedEffect(Unit) {
viewModel.effects.collect { effect ->
when (effect) {
is Effect.ShowSnackbar -> snackbarHostState.showSnackbar(effect.message)
is Effect.NavigateTo -> navController.navigate(effect.route)
}
}
}
// CPU-intensive work
withContext(Dispatchers.Default) { parseJson(largePayload) }
// IO-bound work
withContext(Dispatchers.IO) { database.query() }
// Main thread (UI) — default in viewModelScope
withContext(Dispatchers.Main) { updateUi() }
在 KMP 中,使用 Dispatchers.Default 和 Dispatchers.Main(在所有平台上可用)。Dispatchers.IO 仅适用于 JVM/Android——在其他平台上使用 Dispatchers.Default 或通过依赖注入提供。
长时间运行的循环必须检查取消状态:
suspend fun processItems(items: List<Item>) = coroutineScope {
for (item in items) {
ensureActive() // throws CancellationException if cancelled
process(item)
}
}
viewModelScope.launch {
try {
_state.update { it.copy(isLoading = true) }
val data = repository.fetch()
_state.update { it.copy(data = data) }
} finally {
_state.update { it.copy(isLoading = false) } // always runs, even on cancellation
}
}
@Test
fun `search updates item list`() = runTest {
val fakeRepository = FakeItemRepository().apply { emit(testItems) }
val viewModel = ItemListViewModel(GetItemsUseCase(fakeRepository))
viewModel.state.test {
assertEquals(ItemListState(), awaitItem()) // initial
viewModel.onSearch("query")
val loading = awaitItem()
assertTrue(loading.isLoading)
val loaded = awaitItem()
assertFalse(loaded.isLoading)
assertEquals(1, loaded.items.size)
}
}
@Test
fun `parallel load completes correctly`() = runTest {
val viewModel = DashboardViewModel(
itemRepo = FakeItemRepo(),
statsRepo = FakeStatsRepo()
)
viewModel.load()
advanceUntilIdle()
val state = viewModel.state.value
assertNotNull(state.items)
assertNotNull(state.stats)
}
class FakeItemRepository : ItemRepository {
private val _items = MutableStateFlow<List<Item>>(emptyList())
override fun observeItems(): Flow<List<Item>> = _items
fun emit(items: List<Item>) { _items.value = items }
override suspend fun getItemsByCategory(category: String): Result<List<Item>> {
return Result.success(_items.value.filter { it.category == category })
}
}
GlobalScope——会导致协程泄漏,且无法结构化取消init {} 中收集 Flow——应使用 viewModelScope.launchMutableStateFlow 与可变集合一起使用——始终使用不可变副本:_state.update { it.copy(list = it.list + newItem) }CancellationException——应让其传播以实现正确的取消flowOn(Dispatchers.Main) 进行收集——收集调度器是调用方的调度器@Composable 中创建 Flow 而不使用 remember——每次重组都会重新创建 Flow关于 Flow 在 UI 层的消费,请参阅技能:compose-multiplatform-patterns。
关于协程在各层中的适用位置,请参阅技能:android-clean-architecture。