Flow 和 LiveData 之操作符：throttleFirst、 throttleLast 、throttleLatest、debounce

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Flow 和 LiveData 之操作符：throttleFirst、 throttleLast 、throttleLatest、debounce

前言

因为使用kotlin 和协程后准备移除RxJava，其中大部分功能，可以使用Flow进行替代，但是出现了部分操作符功能缺少，所有进行改进。

这是一遍没有检验的文章，部分操作操作符只是按逻辑写的，没有测试。有几个只是按自己的需求写的，可能和RxJava的存在差异

一、Flow 之操作符扩展

1. ThrottleFirst

fun <T> Flow<T>.throttleFirst(duration: Long = 1000L) = this.throttleFirstImpl(duration)

fun <T> Flow<T>.throttleFirstImpl(periodMillis: Long): Flow<T> {return flow {var lastTime = 0Lcollect { value ->val currentTime = System.currentTimeMillis()if (currentTime - lastTime >= periodMillis) {lastTime = currentTimeemit(value)}}}
}

2. ThrottleLast

fun <T> Flow<T>.throttleLast(duration: Long = 1000L) = this.sample(duration)

3. ThrottleLatest

fun <T> Flow<T>.throttleLatest(duration: Long = 1000L) = this.throttleLatestImpl(duration)

internal fun <T> Flow<T>.throttleLatestImpl(periodMillis: Long): Flow<T> {return channelFlow {var lastValue: T?var timer: Timer? = nullonCompletion { timer?.cancel() }collect { value ->lastValue = valueif (timer == null) {timer = Timer()timer?.scheduleAtFixedRate(object : TimerTask() {override fun run() {val value = lastValuelastValue = nullif (value != null) {launch {send(value as T)}} else {timer?.cancel()timer = null}}},0,periodMillis)}}}
}

4. Debounce (Flow自带)

flow {emit(1)delay(90.milliseconds)emit(2)delay(90.milliseconds)emit(3)delay(1010.milliseconds)emit(4)delay(1010.milliseconds)emit(5)
}.debounce(1000.milliseconds)

一、LiveData 之操作符扩展

1. ThrottleFirst

/*** @Author stj* * @Date 2021/10/8-18:38* * @Email 375105540@qq.com* * 间隔固定时间内，取第一个的值*/
fun <T> LiveData<T>.throttleFirst(duration: Long = 1000L) = MediatorLiveData<T>().also { mld ->val source = thisval handler = Handler(Looper.getMainLooper())val isUpdate = AtomicBoolean(true)val runnable = Runnable {isUpdate.set(true)}mld.addSource(source) {if (isUpdate.compareAndSet(true,false)){mld.value = source.valuehandler.postDelayed(runnable, duration)}}
}

2. ThrottleLast

fun <T> LiveData<T>.throttleLast(duration: Long = 1000L) = MediatorLiveData<T>().also { mld ->val source = thisval handler = Handler(Looper.getMainLooper())val isUpdate = AtomicBoolean(true)val runnable = Runnable {if (isUpdate.compareAndSet(false,true)){mld.value = source.value}}mld.addSource(source) {if (isUpdate.compareAndSet(true,false)) {handler.postDelayed(runnable, duration)}}
}

3. ThrottleLatest

fun <T> LiveData<T>.throttleLatest(duration: Long = 1000L) = MediatorLiveData<T>().also { mld ->val source = thisval isFirst = AtomicBoolean(true)val handler =  HandlerCompat.createAsync(Looper.getMainLooper())val isUpdate = AtomicBoolean(true)val runnable = Runnable {if (isUpdate.compareAndSet(false,true)){mld.value = source.value}}mld.addSource(source) {if (isFirst.compareAndSet(true,false)){mld.value = source.value}if (isUpdate.compareAndSet(true,false)) {handler.postDelayed(runnable, duration)}}
}

4. Debounce

fun <T> LiveData<T>.debounce(duration: Long = 1000L) = MediatorLiveData<T>().also { mld ->val source = thisval handler = HandlerCompat.createAsync(Looper.getMainLooper())val runnable = Runnable {mld.value = source.value}mld.addSource(source) {handler.removeCallbacks(runnable)handler.postDelayed(runnable, duration)}
}

Tip

有几个没有测试过，因为需求需要了，所有改了几个，其他结果是按逻辑写的，可能会有问题

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