StreamController callbacks example

stream_controller_callbacks.dart

import 'dart:async';

void main() async {
   final subscription = numberStreamWithController(8)
      .listen((event) => print("received $event"));

  await Future.delayed(Duration(seconds: 3));

  print("idling for 2 seconds");
  subscription.pause();

  await Future.delayed(Duration(seconds: 2));

  subscription.resume();
  await Future.delayed(Duration(seconds: 4));

  subscription.cancel();
}

Stream<int> numberStreamWithController(int countTo) {
  var controller = null;
  Timer timer = null;
  var counter = 0;

  void count(_) {
      controller.add(counter);
      if (counter == countTo) {
        timer.cancel();
      }
      counter++;
  }

  void start() {
    print("starting the Stream");
    timer = Timer.periodic(Duration(milliseconds: 1000), count);
    timer.tick;
  }
  void pause() {
    print("pausing the Stream");
    timer.cancel();
  }

  void resume() {
    print("resuming the Stream");
    timer = Timer.periodic(Duration(milliseconds: 1000), count);
    timer.tick;
  }

  void stop() {
    print("stopping the Stream");
    timer.cancel();
  }

  controller = StreamController<int>(
      onListen: start,
      onPause: pause,
      onResume: resume,
      onCancel: stop);

  return controller.stream;
}