秒表example

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
        // This makes the visual density adapt to the platform that you run
        // the app on. For desktop platforms, the controls will be smaller and
        // closer together (more dense) than on mobile platforms.
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
  ChangeNotifier _notifier = ChangeNotifier();

  DateTime start;

  List<Duration> durations = [];

  @override
  void initState() {
    super.initState();
    final ticker = createTicker((_) {
      _notifier
          .notifyListeners(); // ignore: invalid_use_of_protected_member,invalid_use_of_visible_for_testing_member
    });
    ticker.start();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            AnimatedBuilder(
              animation: _notifier,
              builder: (_, __) {
                return Column(
                  children: <Widget>[
                    Text('当前时间: ${DateTime.now()}'),
                  ],
                );
              },
            ),
            RaisedButton(
              onPressed: () {
                start = DateTime.now();
                durations.clear();
              },
              child: Text('开始计时'),
            ),
            RaisedButton(
              onPressed: () {
                if (start == null) {
                  return;
                }
                final currentDuration = DateTime.now().difference(start);
                durations.add(currentDuration);
              },
              child: Text('添加秒表项目'),
            ),
            AnimatedBuilder(
              animation: _notifier,
              builder: (_, __) {
                if (start == null) {
                  return Container();
                }
                final currentDuration = DateTime.now().difference(start);
                return Column(
                  children: <Widget>[
                    Text('已过时间: $currentDuration'),
                    Wrap(
                      children: <Widget>[
                        for (final d in durations)
                          Text('${d.inMilliseconds}ms'),
                      ],
                      runSpacing: 15,
                      spacing: 15,
                    ),
                  ],
                );
              },
            ),
          ],
        ),
      ),
    );
  }
}