无法从云firestore中检索Flutter中的多个集合

import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Firestore Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Firestore Demo'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
              child: Text('Retrieve Collection 1'),
              onPressed: () {
                retrieveCollection1();
              },
            ),
            RaisedButton(
              child: Text('Retrieve Collection 2'),
              onPressed: () {
                retrieveCollection2();
              },
            ),
          ],
        ),
      ),
    );
  }

  void retrieveCollection1() async {
    QuerySnapshot snapshot = await Firestore.instance.collection('collection1').getDocuments();
    List<DocumentSnapshot> documents = snapshot.documents;
    
    // 处理集合1的数据
    for (var document in documents) {
      Map<String, dynamic> data = document.data;
      // 处理数据逻辑
    }
  }

  void retrieveCollection2() async {
    QuerySnapshot snapshot = await Firestore.instance.collection('collection2').getDocuments();
    List<DocumentSnapshot> documents = snapshot.documents;
    
    // 处理集合2的数据
    for (var document in documents) {
      Map<String, dynamic> data = document.data;
      // 处理数据逻辑
    }
  }
}