flutter run function every x amount of seconds

Solution 1:

build() can and usually will be called more than once and every time a new Timer.periodic is created.

You need to move that code out of build() like

Timer? timer;

@override
void initState() {
  super.initState();
  timer = Timer.periodic(Duration(seconds: 15), (Timer t) => checkForNewSharedLists());
}

@override
void dispose() {
  timer?.cancel();
  super.dispose();
}

Even better would be to move out such code from widgets entirely in an API layer or similar and use a StreamBuilder to have the view updated in case of updated data.

Solution 2:

Use Cron lib which will be run periodically, but there is a difference between Timer and Cron,

Timer: It's running a task on given specific time intervals whether it is seconds, minutes, or hours.

Cron: It's used for more complex time intervals, eg: if a task needs to be run on a specific time of an hour. let's see the diagram

The above diagram has an asterisk that represents a number that appears in a specific position.

import 'package:cron/cron.dart';

main() {
  var cron = new Cron();
  cron.schedule(new Schedule.parse('*/3 * * * *'), () async {
    print('every three minutes');
  });
  cron.schedule(new Schedule.parse('8-11 * * * *'), () async {
    print('between every 8 and 11 minutes');
  });
}

The above examples are taken from the repository which pretty well explains that the first '*' represents minutes, similar for the hour and so on as shown in the diagram.

Another example of the hour would be Schedule.parse(* 1,2,3,4 * * *), This schedule will run every minute every day during the hours of 1 AM, 2 AM, 3 AM, and 4 AM.

for more reference https://code.tutsplus.com/tutorials/scheduling-tasks-with-cron-jobs--net-8800

Solution 3:

Timer.periodic(Duration(seconds: 10), (timer) {
  // do something or call a function 
});