How to add Scheduled notification in flutter

Issue

I have been trying to add a scheduled notification feature to my todo app but am unable to do so, when the notification is supposed to appear, it does not and the app crashes, I want the notification to be added when the add button in the todoScreen is clicked.
any help would be really appreciated.

todoScreen link: https://github.com/Rohith-JN/Reminders_App/blob/main/lib/Screens/TodoScreen.dart

notification link: https://github.com/Rohith-JN/Reminders_App/blob/main/lib/notification_service.dart

Solution

Okay pushing notification with flutter is pretty easy.
Add these dependencies to pubspec.yaml:

dependencies:
  flutter_local_notifications: ^1.4.2
  rxdart: ^0.23.1

Particular plugins: flutter_local_notifications and rxdart

then run this command in the terminal:

flutter pub get

Go to AndroidManifest.xml in /android/app/src/main/ and add these lines:

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />

Now, go to AppDelegate.swift in /ios/Runner/ Add:

if #available(iOS 10.0, *) {
UNUserNotificationCenter.current().delegate = self as ? 
UNUserNotificationCenterDelegate    
}

before these lines:

return super.application(application, didFinishLaunchingWithOptions: launchOptions)

Done?

Now, Create a notifications_helper.dart file and import the flutter_local_notifications and rxdart packages.
Then in that file add these:

class NotificationClass{
  final int id;
  final String title;
  final String body;
  final String payload;
NotificationClass({this.id, this.body, this.payload, this.title});
}

Also add these finals:

final rxSub.BehaviorSubject<NotificationClass> didReceiveLocalNotificationSubject =
    rxSub.BehaviorSubject<NotificationClass>();
final rxSub.BehaviorSubject<String> selectNotificationSubject =
    rxSub.BehaviorSubject<String>();

Now finally add the following method to helper file:

Future<void> initNotifications(
    notifs.FlutterLocalNotificationsPlugin
        notifsPlugin) async {
  var initializationSettingsAndroid =
      notifs.AndroidInitializationSettings('icon');
  var initializationSettingsIOS = notifs.IOSInitializationSettings(
      requestAlertPermission: false,
      requestBadgePermission: false,
      requestSoundPermission: false,
      onDidReceiveLocalNotification:
          (int id, String title, String body, String payload) async {
        didReceiveLocalNotificationSubject
            .add(NotificationClass(id: id, title: title, body: body, payload: payload));
      });
  var initializationSettings = notifs.InitializationSettings(
      initializationSettingsAndroid, initializationSettingsIOS);
  await notifsPlugin.initialize(initializationSettings,
      onSelectNotification: (String payload) async {
    if (payload != null) {
      print('notification payload: ' + payload);
    }
    selectNotificationSubject.add(payload);
  });
  print("Notifications initialised successfully");
}

For permission request method for iOS:

void requestIOSPermissions(
    notifs.FlutterLocalNotificationsPlugin notifsPlugin) {
  notifsPlugin.resolvePlatformSpecificImplementation<notifs.IOSFlutterLocalNotificationsPlugin>()
      ?.requestPermissions(
        alert: true,
        badge: true,
        sound: true,
      );
}

Done Up To This?

Now, scheduled notification, add these:

Future<void> scheduleNotification(
    {notifs.FlutterLocalNotificationsPlugin notifsPlugin,
    String id,
    String title,
    String body,
    DateTime scheduledTime}) async {
  var androidSpecifics = notifs.AndroidNotificationDetails(
    id, // This specifies the ID of the Notification
    'Scheduled notification', // This specifies the name of the notification channel
    'A scheduled notification', //This specifies the description of the channel
    icon: 'icon',
  );
  var iOSSpecifics = notifs.IOSNotificationDetails();
  var platformChannelSpecifics = notifs.NotificationDetails(
      androidSpecifics, iOSSpecifics);
  await notifsPlugin.schedule(0, title, "Scheduled notification",
      scheduledTime, platformChannelSpecifics); // This literally schedules the notification
}

Now modify the main.dart file:

NotificationAppLaunchDetails notifLaunch;
final FlutterLocalNotificationsPlugin notifsPlugin=    
FlutterLocalNotificationsPlugin();

Now within the main method, add

notifLaunch = await notifsPlugin.getNotificationAppLaunchDetails();
await initNotifications(notifsPlugin);
requestIOSPermissions(notifsPlugin);

NOW MAIN THING,
Triggering a scheduled Notification, Import your helper file and main.dart:

import '../helpers/notifications_helper.dart';
import '../main.dart';

Now call the scheduleNotification method:

scheduleNotification(
    notifsPlugin: notifsPlugin, //Or whatever you've named it in main.dart
    id: DateTime.now().toString(),
    body: "A scheduled Notification",
    scheduledTime: DateTime.now()); //Or whenever you actually want to trigger it

And My friend you are done!👍

Answered By – MNBWorld

Answer Checked By – Marilyn (FlutterFixes Volunteer)