Execute a function repeatedly in Flutter

Running a task once a while is a common task in most features.

Timer

Timer is a count-down timer that can be configured to fire once or repeatedly.

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:jiffy/jiffy.dart';

class TimerPage extends StatefulWidget {
  final String? title;

  TimerPage({Key? key, this.title}) : super(key: key);

  @override
  _TimerPageState createState() => _TimerPageState();
}

class _TimerPageState extends State<TimerPage> {
  late Timer timer;
  String time = '';

  void __displayTime() {
    setState(() {
      time = '${Jiffy().yMMMMEEEEd}\n${Jiffy().hour}:${Jiffy().minute}:${Jiffy().second}';
    });
  }

  @override
  void initState() {
    super.initState();

    __displayTime();
    timer = Timer.periodic(Duration(seconds: 1), (_) => __displayTime());
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title!),
      ),
      body: Center(child: Text(time, style: TextStyle(color: Colors.blue, fontSize: 24.0))),


      floatingActionButton: FloatingActionButton(
        onPressed: __displayTime,
        tooltip: 'Show',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

cron

cron is not a real package to create cron job, but it is a cron-like time-based job scheduler for Dart. It can run tasks periodically at fixed times or intervals defined with a cron time string.

This package allows developer to handle specific running time better. For example, you can make a function to be executed at an exact period such as 12:00 at noon, every 6 past 15.

final cron = Cron();
cron.schedule(Schedule.parse('* * * * *'), () async {
	print('execute every minute');
});
cron.schedule(Schedule.parse('3-7 * * * *'), () async {
	print('between every 3 and 7 minutes');
});