Flutter – 实现日历

Flutter是一种UI工具包，可用于构建高效的、美观的移动应用程序。在Flutter中，您可以使用现成的小部件轻松创建日历，例如滚动列表、容器、文本输入字段等。

实现步骤

1.创建项目

要开始使用Flutter构建应用程序，您需要首先创建一个新的Flutter项目。您可以使用Flutter CLI命令创建新项目，或者使用集成开发环境（IDE）中的“新项目”向导。

2.导入日历库

在Flutter应用程序中实现日历的最简单方法是使用第三方库。 Flutter社区中有许多完整的日历小部件包可供选择。您可以在pub.dev网站上找到这些包的列表并选择最适合您应用程序需求的库。

3.创建日历小部件

创建日历小部件的方法取决于您选择的日历库。大多数库都提供了封装好的小部件，可以轻松地在应用程序中使用。

4.集成日历小部件

一旦创建了日历小部件，您需要将其集成到应用程序的UI中。通常，您需要在应用程序的主视图中使用“小组件槽”，并将日历小部件放置在该槽中。若要让小部件与其他UI元素一起工作，您需要将其与状态管理器集成。

示例代码

在下面的代码片段中，我们将使用第三方库表格日历，以创建一个基本的Flutter应用程序。此程序将显示当前日期以及本月的日历。

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Table Calendar Example',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Table Calendar Example'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
  Map<DateTime, List<dynamic>> _events;
  List<dynamic> _selectedEvents;
  AnimationController _animationController;
  CalendarController _calendarController;

  @override
  void initState() {
    super.initState();
    final _selectedDay = DateTime.now();

    _events = {
      _selectedDay.subtract(Duration(days: 30)): ['Event A0', 'Event B0', 'Event C0'],
      _selectedDay.subtract(Duration(days: 27)): ['Event A1'],
      _selectedDay.subtract(Duration(days: 20)): ['Event A2', 'Event B2', 'Event C2', 'Event D2'],
      _selectedDay.subtract(Duration(days: 16)): ['Event A3', 'Event B3'],
      _selectedDay.subtract(Duration(days: 10)): ['Event A4', 'Event B4', 'Event C4'],
      _selectedDay.subtract(Duration(days: 4)): ['Event A5', 'Event B5', 'Event C5'],
      _selectedDay.subtract(Duration(days: 2)): ['Event A6', 'Event B6'],
      _selectedDay: ['Event A7', 'Event B7', 'Event C7', 'Event D7'],
      _selectedDay.add(Duration(days: 1)): ['Event A8', 'Event B8', 'Event C8', 'Event D8'],
      _selectedDay.add(Duration(days: 3)): Set.from(['Event A9', 'Event A9', 'Event B9']).toList(),
      _selectedDay.add(Duration(days: 7)): ['Event A10', 'Event B10', 'Event C10'],
      _selectedDay.add(Duration(days: 11)): ['Event A11', 'Event B11'],
      _selectedDay.add(Duration(days: 17)): ['Event A12', 'Event B12', 'Event C12', 'Event D12'],
      _selectedDay.add(Duration(days: 22)): ['Event A13', 'Event B13'],
      _selectedDay.add(Duration(days: 26)): ['Event A14', 'Event B14', 'Event C14'],
    };

    _selectedEvents = _events[_selectedDay] ?? [];
    _calendarController = CalendarController();
    _animationController = AnimationController(
        vsync: this,
        duration: const Duration(milliseconds: 400)
    );

    _animationController.forward();
  }

  @override
  void dispose() {
    _animationController.dispose();
    _calendarController.dispose();
    super.dispose();
  }

  void _onDaySelected(DateTime day, List<dynamic> events) {
    print('CALLBACK: _onDaySelected');
    setState(() {
      _selectedEvents = events;
    });
  }

  void _onVisibleDaysChanged(DateTime first, DateTime last, CalendarFormat format) {
    print('CALLBACK: _onVisibleDaysChanged');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Column(
        mainAxisSize: MainAxisSize.max,
        children: <Widget>[
          _buildTableCalendar(),
          const SizedBox(height: 8.0),
          _buildEventList(),
        ],
      ),
    );
  }

  // Simple TableCalendar configuration (using Styles)
  Widget _buildTableCalendar() {
    return TableCalendar(
      calendarController: _calendarController,
      events: _events,
      holidays: _holidays,
      startingDayOfWeek: StartingDayOfWeek.monday,
      calendarStyle: CalendarStyle(
        selectedColor: Colors.deepOrange[400],
        todayColor: Colors.deepOrange[200],
        markersColor: Colors.brown[700],
        outsideDaysVisible: false,
      ),
      headerStyle: HeaderStyle(
        formatButtonTextStyle:
        TextStyle().copyWith(color: Colors.white, fontSize: 15.0),
        formatButtonDecoration: BoxDecoration(
          color: Colors.deepOrange[400],
          borderRadius: BorderRadius.circular(16.0),
        ),
      ),
      onDaySelected: _onDaySelected,
      onVisibleDaysChanged: _onVisibleDaysChanged,
    );
  }

  Widget _buildEventList() {
    return Expanded(
      child: SingleChildScrollView(
        child: Column(
          children: _selectedEvents
              .map((event) => Container(
            decoration: BoxDecoration(
              border: Border.all(width: 0.8),
              borderRadius: BorderRadius.circular(12.0),
            ),
            margin: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 4.0),
            child: ListTile(
              title: Text(event.toString()),
              onTap: () => print('$event tapped!'),
            ),
          ))
              .toList(),
        ),
      ),
    );
  }

  final Map<DateTime, List> _holidays = {
    DateTime(2020, 1, 1): ['New Year\'s Day'],
    DateTime(2020, 1, 6): ['Epiphany'],
    DateTime(2020, 2, 14): ['Valentine\'s Day'],
    DateTime(2020, 4, 21): ['Easter Sunday'],
    DateTime(2020, 4, 22): ['Easter Monday'],
  };
}

总结

Flutter是一种出色的工具包，它可以使开发者轻松构建美观、高效的移动应用程序。实现日历应用程序可以有许多方法，其中包括使用现成的第三方日历库。无论您选择哪种方法，都应始终遵循最佳实践，并开发出用户友好且易于维护的应用程序。