Scheduling different notifications on each day Flutter

Question

I am a newbie on Flutter. I am developing an app with notifications where notifications will be shown in different parts of the day.

For instance: (3:25 AM, 12:24 PM, 17:22 PM, 19:52 PM, 21:02 PM).

These times will differ based on the day. Times are stored on DB with their corresponding days. These notifications should be displayed even if the app is terminated and not being used.

Problems:

1. Get new data on around midnight for the new day. (For example around 00:00 AM my app should reschedule all yesterdays' notifications with new times to inform the user with correct data)
2. I am using flutter_local_notifications to schedule notification. Sometimes it will not fire a notification (if the scheduled time difference is more than 2 hours). That's is why I am going to schedule the soonest notification (for example if notifications should appear 3:25 AM then I want to schedule notifications 30 minutes before). But I am not sure if it is possible.

What I tried.

1. background_fetch for syncing time with DB but I could not make it work

2. flutter_local_notifications for showing notifications

Please consider the case that I want to show the notifications even my app is not running or in the background as well as I want to support both Android and iOS

Any help or suggestions are welcome. Thanks in advance

Solution

For those who are facing the same issue, I managed to solve my problem by the following config

Future<void> initPlatformState() async {
    var config = BackgroundFetchConfig(
      minimumFetchInterval: 15,
      forceAlarmManager: true,
      stopOnTerminate: false,
      startOnBoot: true,
      enableHeadless: true,
      requiresBatteryNotLow: false,
      requiresCharging: false,
      requiresStorageNotLow: false,
      requiresDeviceIdle: false,
      requiredNetworkType: NetworkType.NONE,
    );
    BackgroundFetch.configure(config, _onBackgroundFetch);
  }

Github repo to see the working code. Do not forget to support, if the answer is helpful, upvoting the answer and give a star on github