Save and Retrieve notification with shared preferences list flutter - flutter

Question

I have implemented Firebase Cloud Messaging in my flutter application. Everything works well but I want to store all list of messages locally with shared preferences and retrieve them in another screen. All my logic does not work well as I can't save the messages when the onMessage function is called.
PushNotificationService
class PushNotificationService {
final FirebaseMessaging _fcm = FirebaseMessaging();
List<String> titles;
List<String> msgs;
Future initialise() async {
notiList = List<NotiMessage>();
if (Platform.isIOS) {
// request permissions if we're on android
_fcm.requestNotificationPermissions(IosNotificationSettings());
_fcm.configure();
// For testing purposes print the Firebase Messaging token
String token = await _fcm.getToken();
print("FirebaseMessaging token: $token");
} else{
String token = await _fcm.getToken();
print("FirebaseMessaging token: $token");
}
_fcm.configure(
// Called when the app is in the foreground and we receive a push notification
onMessage: (Map<String, dynamic> message) async {
print('onMessage: $message');
//add list of messages to shared preferences
_setMessage(message);
},
// Called when the app has been closed comlpetely and it's opened
// from the push notification.
onLaunch: (Map<String, dynamic> message) async {
print('onLaunch: $message');
_serialiseAndNavigate(message);
//add list of messages to shared preferences
_setMessage(message);
},
// Called when the app is in the background and it's opened
// from the push notification.
onResume: (Map<String, dynamic> message) async {
print('onResume: $message');
_serialiseAndNavigate(message);
//add list of messages to shared preferences
_setMessage(message);
},
);
}
void _serialiseAndNavigate(Map<String, dynamic> message) {
var notificationData = message['data'];
var view = notificationData['view'];
if (view != null) {
// Navigate to desired page
if (view == 'create_post') {
}
}
}
_setMessage(Map<String, dynamic> message) {
//add list of messages to shared preferences
final notification = message['notification'];
final data = message['data'];
final String title = notification['title'];
final String body = notification['body'];
String mMessage = data['message'];
//add to list
titles.add(title);
msgs.add(mMessage);
//save to shared preferences (does not work)
storeTitles(titles);
storeMsgs(msgs);
print("Title: $title, body: $body, message: $mMessage");
}
void storeTitles(List<String> list) async{
SharedPreferences prefs = await SharedPreferences.getInstance();
await prefs.setStringList("notiTitles", list);
//list returns null
}
void storeMsgs(List<String> list) async{
SharedPreferences prefs = await SharedPreferences.getInstance();
await prefs.setStringList("notiMsgs", list);
}
Future<List<String>> getTitles(List<String> list) async{
SharedPreferences prefs = await SharedPreferences.getInstance();
list = prefs.getStringList("notiTitles");
return prefs.getStringList("notiTitles");
}
Future<List<String>> getMsgs(List<String> list) async{
SharedPreferences prefs = await SharedPreferences.getInstance();
list = prefs.getStringList("notiMsgs");
return prefs.getStringList("notiMsgs");
}
}
Whats the best way to achieve this. I want to save the messages persistently and call them in another screen. Please help me.

Answer 1

The code on saving the List on shared_preferences seems to be ok. The issue might be on how the data is fetched. If you're storing critical data, I suggest to better use something like provider instead. The shared_preferences plugin is unable to guarantee that writes will be persisted to disk after returning as mentioned in its docs.