Periodic stream
- Flutter course
- Intermediate
- Lesson 29/99
- 4 min
Emit periodic values with Stream.periodic.
Stream.periodic
Stream.periodic creates a Stream that produces values at fixed intervals. The first parameter is a Duration, the second is a callback that produces each value.
Stream.periodic(Duration(seconds: 1), (count) => count);count starts at 0 and increments each period.
Duration and callback
Duration determines how often Stream.periodic produces values. The callback receives the counter value each period and produces a result.
Stream.periodic(
Duration(seconds: 2),
(count) => count * 10,
)The counter starts at 0 and increments each period.
Practice Produce a periodic stream with Stream.periodic
The sayiAkisi function should use Stream.periodic. It should produce twice the counter value every second. In main, call print('başladı').
Starter code
import 'package:flutter/material.dart';
// sayiAkisi: periyodik akış üret
void main() {
print('başladı');
}Sample solution
import 'package:flutter/material.dart';
Stream<int> sayiAkisi() {
return Stream.periodic(Duration(seconds: 1), (sayac) => sayac * 2);
}
void main() {
print('başladı');
}Expected output
başladı
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does Stream.periodic produce?
- A single Future
- A Widget
- A Stream producing values at fixed intervals Correct answer
- A List
Explanation: Stream.periodic creates a Stream that produces values at fixed Duration intervals; the callback is called each period.
2 Set Duration in seconds
Stream.periodic(
____(seconds: 1),
(sayac) => sayac,
)Stream.periodic(
Duration(seconds: 1),
(sayac) => sayac,
)Explanation: Stream.periodic's first parameter is Duration; it determines the production interval.
3 Stream.periodic parts
| Term | Meaning |
|---|---|
Stream.periodic |
Stream producing periodic values |
Duration |
Determines the period interval |
sayac |
Value incrementing each period |
callback |
Function producing each value |