I'd like to run a function over and over, with a delay in between. How can I do this with Dart?
Execute Periodically in Flutterperiodic(Duration(seconds: 1), (timer) { setState(() { greeting = "After Some time ${DateTime. now(). second}"; }); }); This will set the value to the greeting variable in every 1 second.
You can use the Timer
class to schedule one-shot and repeating functions.
Here is how you run a repeating function:
import 'dart:async'; main() { const oneSec = Duration(seconds:1); Timer.periodic(oneSec, (Timer t) => print('hi!')); }
The Timer takes two arguments, a duration and a function to run. The duration must be an instance of Duration
. The callback must take a single parameter, the timer itself.
Use timer.cancel()
to cancel a repeating timer. This is one reason why timer is passed to the callback run from a repeating timer.
To schedule a one-shot function after a delay (execute once, some time in the future):
import 'dart:async'; main() { const twentyMillis = Duration(milliseconds:20); Timer(twentyMillis, () => print('hi!')); }
Notice the callback for a one-shot timer does not take a parameter.
You can also request that a function is run as soon as possible, at least one event-loop tick in the future.
import 'dart:async'; main() { Timer.run(() => print('hi!')); }
Timers even work in HTML. In fact, window.setTimeout
was removed, so Timer is the only way to run a function in the future.
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