Firebase 从实时Firestore文档获取数据

我看到过类似的问题和答案在StreamBuilder小部件中得到解决

在我的例子中，当我实现它时，我的代码并不等待获取数据，而只是继续在我的例子中，应用程序跳转到下一页。因此，我是否需要build a StreamBuilder小部件，或者是否有一种简单的方法可以实时工作并获取数据

我注意到我没有在asterisc中使用async*，但是如果我这样做，那么身份验证就不起作用了

澄清：

代码未输入以下行：

if (!snapshot.hasData)
 return new Text('Loading...');
return new Text(
  snapshot.data.data['name']
 );

还有打印测试；语句打印以下内容：

StreamBuilder<DocumentSnapshot>

以下是在标准颤振项目中实施的StreamBuilder：

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

void main() => runApp(MyApp());

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

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final _auth = FirebaseAuth.instance;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              'Testing',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // DocumentReference documentReference = await Firestore.instance
          //     .collection('Employees')
          //     .document('8nss0gppzNfOBMuRz9H44dv7gSd2');
          // documentReference.snapshots().listen((datasnapshot) {
          //   if (datasnapshot.exists) {
          //     print(datasnapshot.data['name'].toString());
          //   } else {
          //     print('Error!');
          //   }
          // });
          StreamBuilder<DocumentSnapshot>(
            stream: Firestore.instance
                .collection('Employees')
                .document('8nss0gppzNfOBMuRz9H44dv7gSd2')
                .snapshots(),
            builder: (BuildContext context,
                AsyncSnapshot<DocumentSnapshot> snapshot) {
              if (snapshot.hasError)
                return new Text('Error: ${snapshot.error}');
              switch (snapshot.connectionState) {
                case ConnectionState.waiting:
                  return new Text('Loading...');
                default:
                  return new Text(snapshot.data.data['name']);
              }
            },
          );
        },
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

---

将代码更改为以下内容：

builder: : (BuildContext context,
              AsyncSnapshot<DocumentSnapshot> snapshot) {
            if (!snapshot.hasData){
              return new Text('Loading...');
          }
          else{
              print(snapshot);
              Navigator.pushReplacementNamed(
                   context, TabCreator.screenId);
           }

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  bool visible = false;
  final firestoreInstance = Firestore.instance;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
            Visibility(
              child: StreamBuilder<DocumentSnapshot>(
                stream: Firestore.instance
                    .collection('users')
                    .document('FIJbBBiplAGorYzdtUQF')
                    .snapshots(),
                builder: (BuildContext context,
                    AsyncSnapshot<DocumentSnapshot> snapshot) {
                  print(snapshot);
                  if (snapshot.hasError)
                    return new Text('Error: ${snapshot.error}');
                  else if (snapshot.hasData) {
                    print(snapshot.data.data);
                    return new Text(snapshot.data.data["age"].toString());
                  }
                  return new CircularProgressIndicator();
                },
              ),
              visible: visible,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            visible = true;
          });
        },
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

---

因此，这里我也使用可见性小部件来隐藏它，但是当单击FAB按钮时，firestore中的数据将出现。

问题出在哪里？这是Wait_auth.sign with email and password email:email，password:password；工作正常吗？@PeterHaddad是的，这部分工作正常。问题在于Widget test=Wait StreamBuilder。。。。代码不等待从流中获取数据，而是跳转到下一页。打印只返回以下StreamBuilder，当处于调试模式时，代码不会进入以if开头的代码中！快照。hasData…不，不是这个。代码甚至没有到达if-else部分。它只是跳过它。跳过它是什么意思，它在执行什么？调试时，Widget test=wait StreamBuilder然后返回onPressed:async{then back to Widget test=等待StreamBuilder，然后跳出StreamBuilder…我在if语句中有一个断点，但它只是忽略了它。随着您的更改，它永远不会跳转到下一页。它只是停留在登录页。检查此项以了解为什么需要使用if elsewhat is _firestore？这应该是一种方法

builder: : (BuildContext context,
              AsyncSnapshot<DocumentSnapshot> snapshot) {
            if (!snapshot.hasData){
              return new Text('Loading...');
          }
          else{
              print(snapshot);
              Navigator.pushReplacementNamed(
                   context, TabCreator.screenId);
           }

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  bool visible = false;
  final firestoreInstance = Firestore.instance;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
            Visibility(
              child: StreamBuilder<DocumentSnapshot>(
                stream: Firestore.instance
                    .collection('users')
                    .document('FIJbBBiplAGorYzdtUQF')
                    .snapshots(),
                builder: (BuildContext context,
                    AsyncSnapshot<DocumentSnapshot> snapshot) {
                  print(snapshot);
                  if (snapshot.hasError)
                    return new Text('Error: ${snapshot.error}');
                  else if (snapshot.hasData) {
                    print(snapshot.data.data);
                    return new Text(snapshot.data.data["age"].toString());
                  }
                  return new CircularProgressIndicator();
                },
              ),
              visible: visible,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            visible = true;
          });
        },
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}