Kotlin TickerModes之间的区别

Posted 2021-05-05

我无法理解Kotlin股票频道TickerMode.FIXED_DELAY and TickerMode.FIXED_PERIOD之间的区别。我和两个人一起玩过，但我无法从他们的行为中得出推论。我也读过docs中的例子。我将感激更清楚的解释，并举例说明。

答案

正如你在coroutines sources中所发现的那样，不同之处在于FIXED_PERIOD更复杂，并且考虑到接收器无法跟上并在下次调用send之前调整延迟的事实。尽管如此，这可能很棘手，因为你需要测量接收器等待下一个滴答的时间。

附：请注意，此功能被标记为过时，即“相应声明的设计具有严重的已知缺陷，并且将来会重新设计。”在这种情况下，原因是它没有与结构化并发集成。

fun main() = runBlocking {
    println("
FIXED_PERIOD")
    val tickerPeriodMode = ticker(100, 0, mode = TickerMode.FIXED_PERIOD)
    consumer(tickerPeriodMode)

    println("
FIXED_DELAY")
    val tickerDelayMode = ticker(100, 0, mode = TickerMode.FIXED_DELAY)
    consumer(tickerDelayMode)
}

private suspend fun CoroutineScope.consumer(ticker: ReceiveChannel<Unit>) {
    val job = launch {
        var i = 0
        while (isActive) {
            val waitTime = measureTimeMillis {
                ticker.receive()
            }
            print("[%4d ms]".format(waitTime))

            if (i++ == 1) {
                delay(150)
                println(" adding extra 150ms delay")
            } else
                println(" going ahead")
        }
    }
    delay(1_000L)
    job.cancel()
    ticker.cancel() // indicate that no more elements are needed
}

产量

FIXED_PERIOD
[   1 ms] going ahead
[  91 ms] adding extra 150ms delay
[   0 ms] going ahead
[  46 ms] going ahead
[ 100 ms] going ahead
[ 102 ms] going ahead
[  98 ms] going ahead
[ 100 ms] going ahead
[  99 ms] going ahead
[ 100 ms] going ahead
[ 100 ms] going ahead

FIXED_DELAY
[   0 ms] going ahead
[ 105 ms] adding extra 150ms delay
[   0 ms] going ahead
[ 101 ms] going ahead
[ 100 ms] going ahead
[ 103 ms] going ahead
[ 103 ms] going ahead
[ 101 ms] going ahead
[ 101 ms] going ahead
[ 105 ms] going ahead