Flutter -从Firestore获取数据，并在应用程序启动时保存到提供商

import 'package:firebase_core/firebase_core.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

CollectionReference users = FirebaseFirestore.instance.collection('users');
DocumentSnapshot snapshot = await users.doc('user1').get();
Map<String, dynamic> data = snapshot.data();

class DataProvider extends ChangeNotifier {
  Map<String, dynamic> _data;

  Map<String, dynamic> get data => _data;

  void setData(Map<String, dynamic> newData) {
    _data = newData;
    notifyListeners();
  }
}

void main() async {
  // ...

  DocumentSnapshot snapshot = await users.doc('user1').get();
  Map<String, dynamic> data = snapshot.data();

  DataProvider dataProvider = DataProvider();
  dataProvider.setData(data);

  // ...
}