Kotlin流操作符简介

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lifecycleScope.launch {    flow.collect { value ->         // 处理值    }}

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flow.onEach { updateUI(it) }    .launchIn(viewModelScope)

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flow.stateIn(    scope = viewModelScope,    started = SharingStarted.WhileSubscribed(5000), // 5秒保活    initialValue = null)

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flow.shareIn(    scope = coroutineScope,    started = SharingStarted.WhileSubscribed,    replay = 1 // 新订阅者接收最近1个值)

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val result = flow.first() // 对空流抛出NoSuchElementException

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val result = flow.firstOrNull() // 对空流安全

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val sum = flow.fold(0) { acc, value -> acc + value }

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val sum = flowOf(1, 2, 3, 4).reduce { accumulator, value ->    accumulator + value // 累积求和 (结果为10)}

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flowOf(1, 2).transform { emit(it * 2); emit(it + 1) } // 输出：2, 3, 4, 5

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flowOf(1, 2).flatMapMerge { flowOf(it, it * 2) }

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flowOf(1, 2).flatMapLatest { flowOf(it, it * 2) }

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flow1.combine(flow2) { a, b -> "a-b" }

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flow { emit(1); delay(100); emit(2) }.debounce(200)

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flow { while(true) emit("弹幕") }.sample(1000)

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.retryWhen { cause, attempt -> attempt < 3 && cause is IOException }

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flow { ... }.cancellable()

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// implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.6.0")

flow.flowWithLifecycle(lifecycle, Lifecycle.State.STARTED)
    .collect { ... }

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lifecycleScope.launch {    repeatOnLifecycle(Lifecycle.State.STARTED) {        viewModel.uiState.collect { ... }    }}