flutter中如何使用台历创建活动

Question

I have copied this code from table calender repo on github table calender and i am getting this errors: Undefined name 'kEvents',kFirstDay, kLastDay and the method 'daysInRange' isn't defined for the type '_TableEventsExampleState'. How do i solve it. Here is my code, you can also check out the code on the link.

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

class TableEventsExample extends StatefulWidget {
  @override
  _TableEventsExampleState createState() => _TableEventsExampleState();
}

class _TableEventsExampleState extends State<TableEventsExample> {
  late final ValueNotifier<List<Event>> _selectedEvents;
  CalendarFormat _calendarFormat = CalendarFormat.month;
  RangeSelectionMode _rangeSelectionMode = RangeSelectionMode
      .toggledOff; // Can be toggled on/off by longpressing a date
  DateTime _focusedDay = DateTime.now();
  DateTime? _selectedDay;
  DateTime? _rangeStart;
  DateTime? _rangeEnd;

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

    _selectedDay = _focusedDay;
    _selectedEvents = ValueNotifier(_getEventsForDay(_selectedDay!));
  }

  @override
  void dispose() {
    _selectedEvents.dispose();
    super.dispose();
  }

  List<Event> _getEventsForDay(DateTime day) {
    // Implementation example
    return kEvents[day] ?? [];
  }

  List<Event> _getEventsForRange(DateTime start, DateTime end) {
    // Implementation example
    final days = daysInRange(start, end);

    return [
      for (final d in days) ..._getEventsForDay(d),
    ];
  }

  void _onDaySelected(DateTime selectedDay, DateTime focusedDay) {
    if (!isSameDay(_selectedDay, selectedDay)) {
      setState(() {
        _selectedDay = selectedDay;
        _focusedDay = focusedDay;
        _rangeStart = null; // Important to clean those
        _rangeEnd = null;
        _rangeSelectionMode = RangeSelectionMode.toggledOff;
      });

      _selectedEvents.value = _getEventsForDay(selectedDay);
    }
  }

  void _onRangeSelected(DateTime? start, DateTime? end, DateTime focusedDay) {
    setState(() {
      _selectedDay = null;
      _focusedDay = focusedDay;
      _rangeStart = start;
      _rangeEnd = end;
      _rangeSelectionMode = RangeSelectionMode.toggledOn;
    });

    // `start` or `end` could be null
    if (start != null && end != null) {
      _selectedEvents.value = _getEventsForRange(start, end);
    } else if (start != null) {
      _selectedEvents.value = _getEventsForDay(start);
    } else if (end != null) {
      _selectedEvents.value = _getEventsForDay(end);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('TableCalendar - Events'),
      ),
      body: Column(
        children: [
          TableCalendar<Event>(
            firstDay: kFirstDay,
            lastDay: kLastDay,
            focusedDay: _focusedDay,
            selectedDayPredicate: (day) => isSameDay(_selectedDay, day),
            rangeStartDay: _rangeStart,
            rangeEndDay: _rangeEnd,
            calendarFormat: _calendarFormat,
            rangeSelectionMode: _rangeSelectionMode,
            eventLoader: _getEventsForDay,
            startingDayOfWeek: StartingDayOfWeek.monday,
            calendarStyle: CalendarStyle(
              // Use `CalendarStyle` to customize the UI
              outsideDaysVisible: false,
            ),
            onDaySelected: _onDaySelected,
            onRangeSelected: _onRangeSelected,
            onFormatChanged: (format) {
              if (_calendarFormat != format) {
                setState(() {
                  _calendarFormat = format;
                });
              }
            },
            onPageChanged: (focusedDay) {
              _focusedDay = focusedDay;
            },
          ),
          const SizedBox(height: 8.0),
          Expanded(
            child: ValueListenableBuilder<List<Event>>(
              valueListenable: _selectedEvents,
              builder: (context, value, _) {
                return ListView.builder(
                  itemCount: value.length,
                  itemBuilder: (context, index) {
                    return Container(
                      margin: const EdgeInsets.symmetric(
                        horizontal: 12.0,
                        vertical: 4.0,
                      ),
                      decoration: BoxDecoration(
                        border: Border.all(),
                        borderRadius: BorderRadius.circular(12.0),
                      ),
                      child: ListTile(
                        onTap: () => print('${value[index]}'),
                        title: Text('${value[index]}'),
                      ),
                    );
                  },
                );
              },
            ),
          ),
        ],
      ),
    );
  }
}

Answer 1

With the code that you have provided, you don't seem to have defined any of the variables you mention or the method. You try to access the variables down in the widget creation but flutter doesn't know where they point to. You need to first define the variables and the method and then use them.