timer_builder 1.2.2

A widget that rebuilds itself on scheduled, periodic, or dynamically generated time events.

example/lib/example.dart

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

void main() {
  runApp(SampleApp());
}

class SampleApp extends StatefulWidget {

  @override
  State<StatefulWidget> createState() {
    return SampleAppState();
  }

}

class SampleAppState extends State<SampleApp> {

  DateTime alert;

  @override
  void initState() {
    super.initState();
    alert = DateTime.now().add(Duration(seconds: 10));
  }

  @override
  Widget build(BuildContext context) {

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Sample App'),
        ),
        body:

        TimerBuilder.scheduled([alert],
          builder: (context) {
            // This function will be called once the alert time is reached
            var now = DateTime.now();
            var reached = now.compareTo(alert) >= 0;
            final textStyle = Theme.of(context).textTheme.title;
            return Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: <Widget>[
                  Icon(
                    reached ? Icons.alarm_on: Icons.alarm,
                    color: reached ? Colors.red: Colors.green,
                    size: 48,
                  ),
                  !reached ?
                    TimerBuilder.periodic(
                        Duration(seconds: 1),
                        alignment: Duration.zero,
                        builder: (context) {
                          // This function will be called every second until the alert time
                          var now = DateTime.now();
                          var remaining = alert.difference(now);
                          return Text(formatDuration(remaining), style: textStyle,);
                        }
                    )
                    :
                    Text("Alert", style: textStyle),
                  RaisedButton(
                    child: Text("Reset"),
                    onPressed: () {
                      setState(() {
                        alert = DateTime.now().add(Duration(seconds: 10));
                      });
                    },
                  ),
                ],
              ),
            );
          }
        ),
      ),
      theme: ThemeData(
        backgroundColor: Colors.white
      ),
    );
  }
}

String formatDuration(Duration d) {
  String f(int n) {
    return n.toString().padLeft(2, '0');
  }
  // We want to round up the remaining time to the nearest second
  d += Duration(microseconds: 999999);
  return "${f(d.inMinutes)}:${f(d.inSeconds%60)}";
}