Tried to get location before initializing timezone database

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

1. Include a timezone database in assets:

flutter:
  assets:
    - packages/timezone/data/latest.tzf

2. 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
}