flutter_stopwatch

main.dart

import 'dart:async';
import "package:intl/intl.dart";
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Timer App',
      theme: ThemeData(
        primarySwatch: Colors.blueGrey
      ),

      home: DefaultTabController(
        length: 2,
        child: Scaffold(
          appBar: AppBar(
            bottom: TabBar(
              tabs: [
                Tab(text: '時計'),
                Tab(text: 'ストップウォッチ'),
              ],
            ),
            title: Text('時間アプリ'),
          ),
          body: TabBarView(
            children: [
              ClockPage(),
              StopwatchPage(),
            ],
          ),
        ),
      ),
    );
  }
}


class ClockPage extends StatefulWidget {
  @override
  _ClockPageState createState() => _ClockPageState();
}

class StopwatchPage extends StatefulWidget {
  @override
  _StopwatchPageState createState() => _StopwatchPageState();
}


class _ClockPageState extends State<ClockPage> {
  Timer _timer;
  final _formatter = DateFormat('y/MM/dd HH:mm:ss');

  @override
  void initState() {
    super.initState();
    _timer = Timer.periodic(
      Duration(seconds: 1),
      (_t) => setState(() {}),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              '現在時間',
              style: TextStyle(fontSize: 25),
              ),
            Text(
              '${_formatter.format(DateTime.now())}',
              style: TextStyle(fontSize: 30),
            )
          ],
        )
      )
    );
  }
}


class _StopwatchPageState extends State<StopwatchPage> {
  Timer _timer;
  final _formatter = DateFormat('HH:mm:ss.S');

  var StartTime = 0;
  var NowTime = 0;
  var RunState = 0; // 0:stop, 1:run

  @override
  void initState() {
    super.initState();
    _timer = Timer.periodic(
      Duration(milliseconds: 123), // 数値小->高速に時間刻む
      (_t) => setState(() {}),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    if (RunState==1){
      NowTime = DateTime.now().millisecondsSinceEpoch.toInt();
    }

    void _StartButton(){
      if (RunState == 0){
        StartTime = DateTime.now().millisecondsSinceEpoch.toInt();
        NowTime = DateTime.now().millisecondsSinceEpoch.toInt();
        RunState = 1;
      }
    }

    void _StopButton(){
      if (RunState == 1){
        RunState = 0;
      }
      else{
        StartTime = 0;
        NowTime = 0;
      }
    }

    var DiffTime = DateTime.fromMillisecondsSinceEpoch(NowTime - StartTime).toUtc();

    var ButtonWidget = Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        IconButton(
          icon: Icon(Icons.play_circle_filled),
          iconSize: 50,
          onPressed: _StartButton,
          color: Colors.green,
        ),
        
        IconButton(
          icon: Icon(Icons.stop),
          iconSize: 50,
          onPressed: _StopButton,
          color: Colors.red,
        ),
      ],
    );

    var DiffWidget = Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        Column(
        mainAxisAlignment: MainAxisAlignment.center,
          children:[
            Text(
              '時間差',
              style: TextStyle(fontSize: 25),
            ),
            Text(
              '${_formatter.format(DiffTime)}',
              style: TextStyle(fontSize: 30),
            ),
          ],
        ),
      ],
    );

    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        DiffWidget,
        ButtonWidget,
      ],
    );
  }
}