Using an Isolate in Flutter

isolate_flutter.dart

import 'dart:async';
import 'dart:isolate';

class CountdownTimer {
  final receivePort = ReceivePort();
  late Isolate _isolate;

  void stop() {
    receivePort.close();
    _isolate.kill(priority: Isolate.immediate);
  }

  Future<void> start(Duration initialDuration) async {
    Map map = {
      'port': receivePort.sendPort,
      'initial_duration': initialDuration,
    };
    _isolate = await Isolate.spawn(_entryPoint, map);
    receivePort.sendPort.send(initialDuration);
  }

  static void _entryPoint(Map map) async {
    Duration initialTime = map['initial_duration'];
    SendPort port = map['port'];

    Timer.periodic(
      Duration(seconds: 1),
      (timer) {
        if (timer.tick == initialTime.inSeconds) {
          timer.cancel();
          port.send(timer.tick);
          port.send('Timer finished');
        } else {
          port.send(timer.tick);
        }
      },
    );
  }
}

void main() {
  final countdownTimer = CountdownTimer();
  countdownTimer.start(Duration(seconds: 10));

  countdownTimer.receivePort.listen((dynamic data) {
    if (data is int) {
      print('Timer tick: $data seconds');
    } else if (data is String) {
      print('Timer completed: $data');
      countdownTimer.stop();
    }
  });
}