Null check operator error when all variables have values? - flutter

Question

I have this Table_Calendar that I am trying to add events to. For some reason, a null check error is thrown (all variables have values) and no data is added to my Map.
I added the line // ### THIS IS WHERE IT FAILS to show where the error pops (inside the _loadMeetupsForMonth function).
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:bark/helpers.dart' as helpers;
import 'package:loading_overlay/loading_overlay.dart';
import 'package:table_calendar/table_calendar.dart';
import 'package:line_icons/line_icons.dart';
import 'package:bark/addMeetup.dart';
class Meetups extends StatefulWidget {
Meetups({Key? key}) : super(key: key);
#override
_MeetupsState createState() => _MeetupsState();
}
class _MeetupsState extends State<Meetups> {
FirebaseFirestore _firestore = FirebaseFirestore.instance;
Map<DateTime, List<CalendarEvent>> eventsForMonth =
new Map<DateTime, List<CalendarEvent>>();
bool _isLoading = false;
List<Widget> _meetups = [];
// ### ADD NEW MEETUP
_addMeetup() async {
var _user = FirebaseAuth.instance.currentUser;
if (_user != null) {
var doRefresh = await Navigator.of(context)
.push(new MaterialPageRoute(builder: (context) => AddMeetup()));
if (doRefresh == true || doRefresh == null) {
// Refresh calendar
}
} else {
// Not logged in. Show login popup.
helpers.showLoginCreateForm(context);
}
}
_loadMeetupsForMonth(DateTime _date) async {
DateTime _start = DateTime(_date.year, _date.month, 1);
DateTime _end = DateTime(_date.month < 12 ? _date.year : _date.year + 1,
_date.month < 12 ? _date.month + 1 : 1, 0);
print(_start);
print(_end);
print("Loading data START");
// Get all for month
QuerySnapshot querySnapshot = await _firestore
.collection('Meetups')
.where("is_deleted", isEqualTo: false)
.where("meetup_time", isGreaterThanOrEqualTo: _start)
.where("meetup_time", isLessThanOrEqualTo: _end)
.orderBy("meetup_time", descending: true)
.get();
if (querySnapshot.docs.isEmpty) {
print("No meetups for the month");
} else {
for (final doc in querySnapshot.docs) {
Timestamp _meetupTime = doc['meetup_time'] ?? DateTime.now();
CalendarEvent _event = new CalendarEvent(
title: doc["meetup_title"], postedBy: doc["poster_name"]);
// ### THIS IS WHERE IT FAILS
eventsForMonth[_meetupTime.toDate()]!.add(_event);
}
}
print(
"Loading data END: Event count = " + eventsForMonth.length.toString());
}
List<CalendarEvent> _getEventsForDay(DateTime day) {
print("Getting for day " + day.toString());
return eventsForMonth[day] ?? [];
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
leading: IconButton(
icon: Icon(
LineIcons.chevronLeft,
color: Colors.black,
),
onPressed: () {
Navigator.of(context).pop();
},
),
actions: [
IconButton(
icon: Icon(
LineIcons.plus,
color: Colors.black,
),
onPressed: () => _addMeetup()),
],
elevation: 1,
title: Text(
"Meetups",
style: TextStyle(color: Colors.black),
),
backgroundColor: helpers.appBarColor,
foregroundColor: Colors.black,
),
body: Column(
children: [
TableCalendar(
onPageChanged: (focusedDay) => {_loadMeetupsForMonth(focusedDay)},
firstDay: DateTime.now(),
lastDay: DateTime.utc(2050, 12, 31),
focusedDay: DateTime.now(),
onDaySelected: (selectedDay, focusedDay) {
print(selectedDay);
},
eventLoader: (day) {
return _getEventsForDay(day);
},
),
],
),
);
}
#override
initState() {
eventsForMonth = new Map<DateTime, List<CalendarEvent>>();
_loadMeetupsForMonth(DateTime.now());
super.initState();
}
}
class CalendarEvent {
final String title;
final String postedBy;
CalendarEvent({required this.title, required this.postedBy});
}
The error is:
Unhandled Exception: Null check operator used on a null value
Anyone have a solution?

Answer 1

replacing eventsForMonth[_meetupTime.toDate()]!.add(_event); with
if(eventsForMonth[_meetupTime.toDate()]!=null)
eventsForMonth[_meetupTime.toDate()]!.add(_event);
else print("got null");
let me know if it solves