Flutter：从查询快照构建列表

Question

我正在尝试根据谷歌的这个示例构建一个列表。 https://codelabs.developers.google.com/codelabs/flutter-firebase#8

不知何故，这行有错误

return _buildList(context, snapshot.data.documents);

带有错误消息：未为“QuerySnapshot”类定义 getter“documents”

这个例子曾经可以工作，但可能有升级，现在这不起作用。任何帮助将不胜感激。

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Baby Names',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() {
    return _MyHomePageState();
  }
}

class _MyHomePageState extends State<MyHomePage> {
  final databaseReference = FirebaseFirestore.instance;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Baby Name Votes')),
      body: _buildBody(context),
    );
  }

  Widget _buildBody(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: FirebaseFirestore.instance.collection('baby').snapshots(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) return LinearProgressIndicator();

        return _buildList(context, snapshot.data.documents);
      },
    );
  }

  Widget _buildList(BuildContext context, List<DocumentSnapshot> snapshot) {
    return ListView(
      padding: const EdgeInsets.only(top: 20.0),
      children: snapshot.map((data) => _buildListItem(context, data)).toList(),
    );
  }

  Widget _buildListItem(BuildContext context, DocumentSnapshot data) {
    final record = Record.fromSnapshot(data);

    return Padding(
      key: ValueKey(record.name),
      padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
      child: Container(
        decoration: BoxDecoration(
          border: Border.all(color: Colors.grey),
          borderRadius: BorderRadius.circular(5.0),
        ),
        child: ListTile(
          title: Text(record.name),
          trailing: Text(record.votes.toString()),
          onTap: () => print(record),
        ),
      ),
    );
  }
}

class Record {
  final String name;
  final int votes;
  final DocumentReference reference;

  Record.fromMap(Map<String, dynamic> map, {this.reference})
      : assert(map['name'] != null),
        assert(map['votes'] != null),
        name = map['name'],
        votes = map['votes'];

  Record.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data(), reference: snapshot.reference);

  @override
  String toString() => "Record<$name:$votes>";
}

Answer 1

替换已弃用的代码

根据 Flutter 的最新 Firebase Firestore 文档，您必须使用 getter docs 而不是 documents。

QuerySnapshot query = ...
List<DocumentSnapshot> docs = query.docs;

documents 已被弃用，将在即将到来的更新中删除。 More info

修复错误

Widget _buildBody(BuildContext context) {
  return StreamBuilder<QuerySnapshot>(
    stream: FirebaseFirestore.instance.collection('baby').snapshots(),
    builder: (context, snapshot) {
print('State: ${snapshot.connectionState}, Has Data: ${snapshot.hasData}'); // Only for debugging
      if (snapshot.connectionState == ConnectionState.done && snapshot.hasData) {
        return _buildList(context, snapshot.data.documents);
      }
      else return LinearProgressIndicator();
    },
  );
}