Does the nested `launch` block around `taskDao.inc...

# coroutines

[Florian]

Does the nested launch block around taskDao.increaseMillisCompletedToday (which is a database operation) look dangerous? I use this to measure time but without the nested launch, I think the length of the database operation itself is causing imprecision. The tick interval is every 1s.

fun startTimer() {
    timerJob?.cancel()
    timerJob = applicationScope.launch {
        val selectedTask = selectedTask.first()
        if (selectedTask != null) {
            taskDao.updateLastActiveTimestamp(selectedTask.id, System.currentTimeMillis())
            startTimerService()
            timerRunningFlow.value = true
            while (true) {
                val timeBefore = SystemClock.elapsedRealtime()
                delay(TICK_DELAY)
                val timeAfter = SystemClock.elapsedRealtime()
                val elapsedTime = timeAfter - timeBefore
                launch {
                    taskDao.increaseMillisCompletedToday(selectedTask.id, elapsedTime)
                }
            }
        }
    }
}

[groostav]

Right I think you hit the nail on the head. In old java terms Delay works as ScheduledExecutorService.scheduleWithFixedDelay where Im guessing what you want is ScheduledExecutorService.scheduleAtFixedRate

[groostav]

I'm not sure what the best way to do that is but I think the answer really depends on how you want to handle backpressure

[Florian]

@groostav Thank you for your answer. Is there something in Java or Kotlin world that gives me a fixed delay that is not affected by the time in the device's settings?

[Florian]

because Timer is affected by it

[Nick Allen]

If fixed delay is ok, but you just want the reported time to be accurate, then you could track the total time instead of just the delay.
Something like:

val startTime = SystemClock.elapsedRealtime()
var lastReportedTime = 0
while(true) {
    delay(TICK_DELAY)
    val totalElapsedTime = SystemClock.elapsedRealtime() - startTime
    taskDao.increaseMillisCompletedToday(selectedTask.id, totalElapsedTime - lastReportedTime)
    lastReportedTime = totalElapsedTime
}

[Florian]

@Nick Allen that's a great idea!

[Florian]

Thanks I'll use that