新的Flatter Cloud Firestore[副本]

Question

我又开始学习颤振（前一段时间开始，但停止了）。您可以在下面找到我的代码。如果我在智能手机上运行应用程序，则会出现错误：[核心/无应用程序]未创建Firebase应用程序['DEFAULT'}-调用Firebase.initializeApp（）。我阅读了文档，但由于我使用的是最新版本的firebase\u core：^0.5.0、firebase\u auth：^0.18.0 1、cloud\u firestore：^0.14.0 2，因此文档似乎还没有完成，或者我没有得到它。我需要在哪里初始化那个？为什么这还不够：CollectionReference users=FirebaseFirestore。例子集合（“用户”）；

时间线。dart（代码主要来自颤振入门）：

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:example/widgets/header.dart';
import 'package:example/widgets/progress.dart';

class Timeline extends StatefulWidget {
  @override
  _TimelineState createState() => _TimelineState();
}

class _TimelineState extends State<Timeline> {
  @override
  void initState() {
    // getUserById();
    super.initState();
  }
   
  @override
  Widget build(BuildContext context) {
    CollectionReference users = FirebaseFirestore.instance.collection('users');
    return StreamBuilder<QuerySnapshot>(
      stream: users.snapshots(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (snapshot.hasError) {
          return Text('Something went wrong');
        }

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

        return new ListView(
          children: snapshot.data.documents.map((DocumentSnapshot document) {
            return new ListTile(
              title: new Text(document.data()['username']),
              subtitle: new Text(document.data()['posts_count']),
            );
          }).toList(),
        );
      },
    );
  }
}

这是我的main代码。飞奔

    import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'pages/home.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Example',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.red,
        accentColor: Colors.blue,
      ),
      home: Home(),
    );
  }
}

提前非常感谢！

Answer 1

您可以像这样修改MyApp小部件，使其正常工作。

class MyApp extends StatelessWidget {
      // This widget is the root of your application.
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          home: FutureBuilder(
            future: Firebase.initializeApp(),
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                if (snapshot.hasError) {
                  print(snapshot.error.toString());
                  return Center(child: Text('Error'));
                } else {
                  // ! RETURN THE SCREEN YOU WANT HERE
                  return Timeline();
                }
            },
          ),
        );
      }
    }

Answer 2

在main.dart中，添加以下内容

dart prettyprint-override">void main() async {
  WidgetsFlutterBinding.ensureInitialized(); //add this
  await Firebase.initializeApp(); //initialize here
  runApp(MyApp());
}

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