Tried to get location before initializing timezone database - flutter

Question

I am trying to schedule a notification:but I got this error:
Unhandled Exception: Tried to get location before initializing timezone database
Although I initialized the Timezone in the init function:
tz.initializeTimeZones();
schedule code:
Future<void> scheduleNotifications(String title,int yy,int mm,int dd,int hh,int ii) async {
final loc_egypt = tz.getLocation('Africa/Cairo');
final tz.TZDateTime now = tz.TZDateTime.now(loc_egypt);
var schedule_30before=tz.TZDateTime(loc_egypt,yy,mm,dd,hh,ii).subtract(Duration(minutes: 30));
await flutterLocalNotificationsPlugin.zonedSchedule(
0,
title,
"The Webinar will start after 30 minutes",
schedule_30before,
NotificationDetails(android: _androidNotificationDetails),
androidAllowWhileIdle: true,
uiLocalNotificationDateInterpretation:
UILocalNotificationDateInterpretation.absoluteTime);
}

Answer 1

In my case the problem was with invalid assets. I am working on a Flutter Web project, so I was doing:
import 'package:timezone/browser.dart' as tz;
void main() async {
await tz.initializeTimeZone();
// other stuff
}
After digging into the source code of timezone package, I discovered that it is initialising using a *.tzf file, which I wasn't including in my project's assets (rookie's mistake). So I edited my pubspec.yaml like this:
flutter:
assets:
- packages/timezone/data/latest.tzf
# - packages/timezone/data/latest_all.tzf <- for all the db variants
# - packages/timezone/data/latest_10y.tzf <- for 10y db variant
But there was still one more thing to do. As it turns out tz.initializeTimeZone() assumes that a default path is packages/timezone/data/latest.tzf BUT my Flutter Web project was putting all the assets in assets catalogue, so the actual path was assets/packages/timezone/data/latest.tzf and I just had to pass it as an argument to tz.initializeTimeZone('assets/packages/timezone/data/$dbVariant'). Of course you need to replace $dbVariant with the variant of your choice, the one that you included in your assets.
TL;DR
Include a timezone database in assets:
flutter:
assets:
- packages/timezone/data/latest.tzf
Initialise timezone with a full path to assets:
import 'package:timezone/browser.dart' as tz;
void main() async {
await tz.initializeTimeZone('assets/packages/timezone/data/latest.tzf');
// other stuff
}

Answer 2

You need to import the following packages:
import 'package:timezone/data/latest.dart' as tzl;
import 'package:timezone/standalone.dart' as tz;
Then, you can call for example something like:
ElevatedButton(
onPressed: ()async {
await scheduleNotifications("title", 2022, 9, 1, 1, 47);
},
child: Text("Notify Me!"))
Given you put tzl.initializeTimeZones(); in your initState().
Your issue is in using initializeTimeZones() of a package different than "package:timezone/data/latest.dart"

Answer 3

In the main() method of your app, verify your imports and call the init method
//Pick one of the three following imports :
//If you just want the latest
import 'package:timezone/data/latest.dart' as tz;
//If you use the 10y db variant
import 'package:timezone/data/latest_10y.dart' as tz;
//If you want to import all the db variants
import 'package:timezone/data/latest_all.dart' as tz;
void main() {
tz.initializeTimeZones();
}

Answer 4

In my case I created a future method and initialized it in the main() function of the main.dart file. This is my code:
import 'package:timezone/browser.dart' as tz;
Future<void> main() async {
initTimeZone();
// add other setup here
}
void initTimeZone(){
tz.initializeTimeZones();
}
Hope this helps!