如何使用Kotlin协程实现计时器

问题描述

我想使用Kotlin协程实现计时器，类似于使用RxJava实现的计时器:

I want to implement timer using Kotlin coroutines, something similar to this implemented with RxJava:

       Flowable.interval(0, 5, TimeUnit.SECONDS)
                    .observeOn(AndroidSchedulers.mainThread())
                    .map { LocalDateTime.now() }
                    .distinctUntilChanged { old, new ->
                        old.minute == new.minute
                    }
                    .subscribe {
                        setDateTime(it)
                    }

它将每隔一分钟发出LocalDateTime.

It will emit LocalDateTime every new minute.

推荐答案

我认为它仍处于试验阶段，但是您可以使用 TickerChannel 会每X毫秒产生一个值:

I believe it is still experimental, but you may use a TickerChannel to produce values every X millis:

val tickerChannel = ticker(delayMillis = 60_000, initialDelayMillis = 0)

repeat(10) {
    tickerChannel.receive()
    val currentTime = LocalDateTime.now()
    println(currentTime)
}

如果您需要在订阅"为每个滴答"做某事时继续进行工作，则可以launch从该频道读取并执行您想要做的事的背景协程:

If you need to carry on doing your work while your "subscribe" does something for each "tick", you may launch a background coroutine that will read from this channel and do the thing you want:

val tickerChannel = ticker(delayMillis = 60_000, initialDelayMillis = 0)

launch {
    for (event in tickerChannel) {
        // the 'event' variable is of type Unit, so we don't really care about it
        val currentTime = LocalDateTime.now()
        println(currentTime)
    }
}

delay(1000)

// when you're done with the ticker and don't want more events
tickerChannel.cancel()

如果您想从循环内部停止，可以简单地中断循环，然后取消频道:

If you want to stop from inside the loop, you can simply break out of it, and then cancel the channel:

val ticker = ticker(500, 0)

var count = 0

for (event in ticker) {
    count++
    if (count == 4) {
        break
    } else {
        println(count)
    }
}

ticker.cancel()

这篇关于如何使用Kotlin协程实现计时器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！