How to implement timer with Kotlin coroutines

Question

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)
                    }

It will emit LocalDateTime every new minute.

Answer 1

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)
}

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

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