Is there a way for Flutter's Timer.periodic to wait for a function return plus a fixed duration before moving to the next cycle? - flutter

Question

I use Timer.periodic with a duration normally. This works perfectly for my current use case.
Duration fiveSecs = const Duration(seconds: 5);
new Timer.periodic(fiveSecs, checkChange);
void checkChange(Timer timer) async {
//do some network calls
}
In this particular case I make network calls that take no longer than 500ms, and doing them every 5 seconds is enough for whatever depends on what those calls return.
Now I want to check for new values as frequently as 2 seconds, however, based on what needs to be checked a network call could take anywhere from a few hundred milliseconds to even 10 seconds. I could give a large margin and use a frequency of like 20 seconds for the timer, but in this case I would even prefer a 1 second frequency if possible.
So is there a way the timer could wait for a function, and still have a fixed duration like 1 second. So the maximum time it would take would be 1 second + callback runtime? Or is there a better way this could be achieved, I'm open to suggestions. Thank you.

Answer 1

void startTimer() {
_timer = Timer.periodic(Duration(seconds: 1), (Timer t) async {
print("lets wait for 5 seconds");
_timer.cancel();
await Future.delayed(Duration(seconds: 5));
print("Job is done");
print(DateTime.now());
print("Do it again");
startTimer();
});
}

Answer 2

I have encountered the same situation lately,
what I did was (in my case inside a static class) to add a static boolean value and toggle it accoding to my situation needs, later checking it's value inside the Timer.Periodic callback.
Timer.periodic(ConstantValues.socketTimerOperationDelay, (Timer t) async{
if(_udpHandlerCompleted){
_udpHandlerCompleted = false;
if(!_shouldSendBroadcast || _shutDown)
t.cancel();
else
_writeAllToUdpSocket(_udpSocket, data, ConstantValues.udpMulticastGroup, ConstantValues.udpMulticastPort);
_udpHandlerCompleted = true;
}
});
As you can see in my situation, I had to wait for the callback to end before I move to the next one, I believe this is what you're looking for, but in case you need to await for a different method the solution would be similar,
simply toggle the boolean _udpHandlerCompleted (in my case) in the other function.
Edit:
If my soultion helped you, kindly mark it as the accepted answer. Good luck!

Answer 3

At the end checkChange add Future.delayed(const Duration(seconds: 5), checkChange) then call it once instead of running the timer. You can add/check a boolean flag if you need to kill it at any point.