如何从Firestore中获取数据并自动刷新状态，而无需单击扑动

Question

我正在使用日历轮播小部件，并且正在尝试从Cloud Firestore添加事件。 我成功地从firebase获取了日期，问题是只有在单击任何日期后才能看到该日期，因此，当用户第一次查找日历时，服务器端没有有关事件的信息。 如果我返回到父级并返回日历，屏幕也会刷新。 如何刷新日历上的数据？我在网上浏览时，仅发现使用ListViews的示例。

仅当我单击按钮时，才会显示Firebase数据。 （或者返回父级并返回时），如gif所示。

import 'package:flutter/material.dart';
import 'package:father_home_flutter/model/constants.dart';
import 'package:flutter_calendar_carousel/classes/event.dart';
import 'package:flutter_calendar_carousel/classes/event_list.dart';
import 'package:flutter_calendar_carousel/flutter_calendar_carousel.dart'
    show CalendarCarousel;
import 'package:cloud_firestore/cloud_firestore.dart';

class ScreenCalendar extends StatefulWidget {
  @override
  _ScreenCalendarState createState() => new _ScreenCalendarState();
}

class _ScreenCalendarState extends State<ScreenCalendar> {
  static String noEventText = "Событий нет";
  String tabBarTitle = "Calendar";
  String calendarText = noEventText;
  DateTime _currentDate = DateTime.now();
  Color _colorButtonColor = Colors.indigo;
  Color _colorTextButtonColor = Colors.black;
  Color _colorTextTodayButton = Colors.white;

  static const String _calendarRussian = "calendarRussian";
  static const String _eventTitle = "eventTitle";

  static const String _eventDay = "eventDay";
  static const String _eventMonth = "eventMonth";
  static const String _eventYear = "eventYear";

  void getCalendarEventList() {
    Firestore.instance.collection(_calendarRussian).snapshots().listen((data) =>
        data.documents.forEach((doc) => _markedDateMap.add(
                new DateTime(int.parse(doc[_eventYear]),
                    int.parse(doc[_eventMonth]), int.parse(doc[_eventDay])),
                new Event(
                    date: new DateTime(int.parse(doc[_eventYear]),
                        int.parse(doc[_eventMonth]), int.parse(doc[_eventDay])),
                    title: doc[_eventTitle],
                    icon: _eventIcon))
//            context.setState(() => refresh(DateTime.now()))}
            ));
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(
            tabBarTitle,
            style: Constants.myTextStyleAppBar,
          ),
          iconTheme: Constants.myIconThemeDataAppBar,
          elevation: Constants.myElevationAppBar,
          backgroundColor: Constants.myAppBarColor,
        ),
        body: SingleChildScrollView(
            child: Column(children: <Widget>[
          Card(
              child: CalendarCarousel(
            weekendTextStyle: TextStyle(
              color: Colors.red,
            ),
            weekFormat: false,
            selectedDateTime: _currentDate,
            markedDatesMap: _markedDateMap,
            selectedDayBorderColor: Colors.transparent,
            selectedDayButtonColor: Colors.indigo[300],
            todayTextStyle:
                TextStyle(color: Colors.black, fontWeight: FontWeight.bold),
            selectedDayTextStyle: TextStyle(color: _colorTextButtonColor),
            todayBorderColor: Colors.indigo,
            weekdayTextStyle: TextStyle(color: Colors.black),
            height: 420.0,
            daysHaveCircularBorder: true,
            todayButtonColor: Colors.transparent,
            locale: 'RUS',
            onDayPressed: (DateTime date, List<Event> events) {
              this.setState(() => refresh(date));
            },
          )),
          Card(
              child: Container(
                  child: Padding(
                      padding: EdgeInsets.fromLTRB(16.0, 16.0, 16.0, 16.0),
                      child: Center(
                          child: Text(
                        calendarText,
                        style: Constants.textStyleCommonText,
                      )))))
        ])));
  }

  void refresh(DateTime date) {
    _currentDate = date;
    print('selected date ' +
        date.day.toString() +
        date.month.toString() +
        date.year.toString() +
        ' ' +
        date.toString());
    if (_markedDateMap
        .getEvents(new DateTime(date.year, date.month, date.day))
        .isNotEmpty) {
      calendarText = _markedDateMap
          .getEvents(new DateTime(date.year, date.month, date.day))[0]
          .title;
    } else {
      calendarText = noEventText;
    }
    if (date == _currentDate) {
      _colorButtonColor = Colors.indigo;
      _colorTextButtonColor = Colors.white;
      _colorTextTodayButton = Colors.white;
    } else {
      _colorTextButtonColor = Colors.indigo;
      _colorTextTodayButton = Colors.black;
    }
  }
}

EventList<Event> _markedDateMap = new EventList<Event>(events: {
  new DateTime(2019, 1, 24): [
    new Event(
      date: new DateTime(2019, 1, 24),
      title: 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, '
          'sed eiusmod tempor incidunt ut labore et dolore magna aliqua.'
          ' \n\nUt enim ad minim veniam,'
          ' quis nostrud exercitation ullamco laboris nisi ut aliquid ex ea commodi consequat.'
          ' \n\nQuis aute iure reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. '
          'Excepteur sint obcaecat cupiditat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.',
      icon: _eventIcon,
    )
  ]
});

Widget _eventIcon = new Container(
  decoration: new BoxDecoration(
      color: Colors.white,
      borderRadius: BorderRadius.all(Radius.circular(1000)),
      border: Border.all(color: Colors.blue, width: 2.0)),
  child: new Icon(
    Icons.person,
    color: Colors.amber,
  ),
);

Answer 1

好吧，我找到了一种使用async和await来解决它的方法，这是我更改的代码的一部分。

  Future<void> getCalendarEventList() async {
    await Firestore.instance.collection(_calendarRussian).snapshots().listen(
        (data) => data.documents.forEach((doc) => _markedDateMap.add(
            new DateTime(int.parse(doc[_eventYear]),
                int.parse(doc[_eventMonth]), int.parse(doc[_eventDay])),
            new Event(
                date: new DateTime(int.parse(doc[_eventYear]),
                    int.parse(doc[_eventMonth]), int.parse(doc[_eventDay])),
                title: doc[_eventTitle],
                icon: _eventIcon))));
    setState(() {});
  }

为避免重复日历事件，我决定清理marketDataMap：

  @override
  void dispose(){
    _markedDateMap.clear();
    super.dispose();
  }