如何在flutter中从firebase中的子集合中获取数据？

import 'package:firebase_core/firebase_core.dart';

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

import 'package:cloud_firestore/cloud_firestore.dart';

final FirebaseFirestore firestore = FirebaseFirestore.instance;

Stream<QuerySnapshot> getDataFromSubcollection() {
  return firestore
      .collection('users')
      .doc('user_id')
      .collection('subcollection')
      .snapshots();
}

StreamBuilder<QuerySnapshot>(
  stream: getDataFromSubcollection(),
  builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
    if (snapshot.hasError) {
      return Text('Error: ${snapshot.error}');
    }

    if (snapshot.connectionState == ConnectionState.waiting) {
      return Text('Loading...');
    }

    return ListView.builder(
      itemCount: snapshot.data.docs.length,
      itemBuilder: (BuildContext context, int index) {
        DocumentSnapshot document = snapshot.data.docs[index];
        return ListTile(
          title: Text(document['field']),
        );
      },
    );
  },
);