I am trying to save the notification title and body using shared preference but i am unable to

Issue

#I am trying to save the notification title and body locally and fetch the title and body inside my app to show all the sent notification in a listview but i am unable to

#this is the code i am running this code in my main.dart inside initstate and that detail.add is my list which i created manually but i am getting error saying 102:45: Error: This expression has type ‘void’ and can’t be used.prefs.setString(‘notificationData’, setData); when i try to setString this is the error i get

List<String?> detail = [];
FirebaseMessaging.onMessage.listen((message) async{
      if(message.notification!=null){
        // print(message.notification!.body);
        // print(message.notification!.title);
        final title = message.notification?.title;
        final body = message.notification?.body;
         SharedPreferences prefs = await SharedPreferences.getInstance();
         final String notificationData = json.encode({"title":title,"body":body});
         final setData =  detail.add(notificationData);
        prefs.setString('notificationData', setData);
        print(notificationData);
        print(setData);
      }

Solution

The detail.add(notificationData) function returns nothing (void) and only adds to the existing array, so your setData variable is empty but you can use the original updated detail array like so:

FirebaseMessaging.onMessage.listen((message) async{
  if(message.notification!=null){
    // print(message.notification!.body);
    // print(message.notification!.title);
    final title = message.notification?.title;
    final body = message.notification?.body;
    SharedPreferences prefs = await SharedPreferences.getInstance();
    final String notificationData = json.encode({"title":title,"body":body});
    detail.add(notificationData);
    prefs.setString('notificationData', detail.toString());
    print(notificationData);
    print(detail);
  }
//...
});

Answered By – Roaa

Answer Checked By – Robin (FlutterFixes Admin)