安卓。 Kotlin Flow：如何取消倒数计时器？

Question

I have a kotlin flow timer. Here is my code:

class CountDownTimer {
    suspend fun startTimer(value: Int, onTick: OnTickCallback, onFinish: OnFinishCallback) {
onTick.invoke(0)
        (1..timerValue)
            .asSequence()
            .asFlow()
            .onEach {
                delay(DELAY)
                onTick.invoke(it)
            }
            .onCompletion {
                onFinish.invoke()
            }
            .cancellable()
            .collect()
}
}

Everything working well, but there are situations when I start a new timer, but the current one has not yet completed. So I want to cancel the timer if I start a new one. I know that for this I need to get a Job and call a cancel() on it. But I can't create job, because I haven't CoroutineScope . Yes, I could inject the scope in the constructor of my class CountDownTimer, but I need the timer to be attached to the viewModelScope.

Therefore, I start the timer in the view model in viewModelScope.

   viewModelScope.launch {
            countDownTimer.startTimer(
                60,
                onTick= { // some logic },
                onFinish= { // some logic }
            )
        }

Now I can get Job inside view model and before start timer cancel() job.

But it turns out I have to store the job object in the view model, will it be correct? Perhaps there is some more automated way to cancel a job. Or perhaps I'd better inject some other CoroutineScope into my CountDownTimer , then the question is what should the CoroutineScope be?

Please, help me.

Answer 1

viewModelScope.launch {} is a job. You can save it into a variable and cancel it anytime. It is ok to store it in a viewmodel .

val job = viewModelScope.launch { ... }

job.cancel()