momo/lib/provider/token.dart

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:shared_preferences/shared_preferences.dart';

class TokenNotifier extends Notifier<String> {
  @override
  String build() {
    return "";
  }

  setToken(String token) {
    state = token;
    SharedPreferences.getInstance().then((prefs) {
      prefs.setString("token", token);
    });
  }

  removeToken() {
    state = '';
    SharedPreferences.getInstance().then((prefs) {
      prefs.setString("token", "");
    });
  }
}

final tokenProvider =
    NotifierProvider<TokenNotifier, String>(() => TokenNotifier());