'firebase/main.dart'：断言失败

Question

我在 flutter 上使用 firebase 做了一个简单的婴儿名字项目，在成功完成本教程后，应用程序给出了这个错误：“ package:firebase_demo/main.dart': Failed assertion: line 86 pos 16: 'map['votes] : = null'. 不是真的。”

帮助相同。

我的代码-：

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

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

final dummySnapshot = [
  {"name": "Filip", "votes": 15},
  {"name": "Abraham", "votes": 14},
  {"name": "Richard", "votes": 11},
  {"name": "Ike", "votes": 10},
  {"name": "Justin", "votes": 1},
];

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> {
  @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: Firestore.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>";
}

输出：

执行热重启...正在将文件同步到设备 Redmi Note 4...在 1,994 毫秒内重新启动应用程序。 I/flutter ( 2257 ): ══╡ 小部件库异常 ╞═════════════════════════════════════ ═════════════════════════ I/flutter ( 2257 ): 以下断言被抛出构建 StreamBuilder( 脏，状态： I/flutter ( 2257 ) : _StreamBuilderBaseState>#94c3a): I/flutter ( 2257): 'package:firebase_demo/main.dart': Failed assertion: line 86 pos 16: 'map['votes']:= null': is not I/flutter ( 2257). true: I/flutter ( 2257): I/flutter ( 2257), 要么断言表明框架本身有错误：要么我们应该提供实质性的 I/flutter ( 2257)。 此错误消息中的更多信息可帮助您确定和修复根本原因：I/flutter ( 2257)，无论哪种情况：请通过在 GitHub 上提交错误来报告此断言：I/flutter ( 2257)： https://github .com/flutter/flutter/issues/new?template=BUG.md I/flutter ( 2257): I/flutter ( 2257): 当抛出异常时，这是堆栈： I/flutter ( 2257): #2新 Record.fromMap (package:firebase_demo/main.dart:86:16) I/flutter ( 2257): #3 新 Record.fromSnapshot (package:firebase_demo/main.dart:91:14) I/flutter ( 2257): #4 _MyHomePageState._buildListItem (package:firebase_demo/main.dart:59:27) I/flutter ( 2257): #5 _MyHomePageState._buildList。 (package:firebase_demo/main.dart:54:40) I/flutter ( 2257): #6 MappedListIterable.elementAt (dart:_internal/iterable.dart:414:29) I/flutter ( 2257): #7 ListIterable.toList (dart:_internal/iterable.dart:219:19) I/flutter (2257): #8 _MyHomePageState._buildList (package:firebase_demo/main.dart:54:71) I/flutter (2257): #9 _MyHomePageState._buildBody . (package:firebase_demo/main.dart:46:16) I/flutter (2257):#10 StreamBuilder.build (package:flutter/src/widgets/async.dart:423:74) I/flutter (2257):# 11 _StreamBuilderBaseState.build (package:flutter/src/widgets/async.dart:125:48) I/flutter (2257):#12 StatefulElement.build (package:flutter/src/widgets/framework.dart:3809:27) I/flutter（2257）：#13 ComponentElement.performRebuild（包：flutter/src/widgets/framework.dart:3721:15） I/flutter（2257）：#14 Element.rebuild（包：flutter/src/widgets/ framework.dart:3547:5) I/flutter ( 2257): #15 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2286:33) I/flutter ( 2257): #16 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&BindingWidgetingsInding&Rmantics (包:flutter/src/widgets/framework.dart:2286:33) ＃16 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&BindingWendersBinding&Rmantics包：flutter/src/widgets/binding.dart:676:20) I/flutter ( 2257): #17 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&Rend ererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:219:5) I/flutter (2257): #18 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990) I /flutter ( 2257): #19 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9) I/flutter ( 2257): #20 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding .dart:842:5) I/flutter (2257): #21 _invoke (dart:ui/hooks.dart:154:13) I/flutter (2257): #22 _drawFrame (dart:ui/hooks.dart:143 :3) I/flutter ( 2257): (从类 _AssertionError 中删除 2 帧) I/flutter ( 2257): ═════════════════════════ ══════════════════════════════════════════════════ ═════════════════════════ I/1.gpu (2257): type=1400 audit(0.0:191179): avc: denied { ioctl }对于路径 ="/dev/kgsl-3d0" dev="tmpfs" ino=15394 ioctlcmd=945 scontext=u:r:untrusted_app_27:s0:c512,c768 tcontext=u:object_r:device:s0 tclass=chr_file permissive=1 I/ 1.gpu (2257): type=1400 audit(0.0:191180): avc: denied { read write } for path="/dev/kgsl-3d0" dev="tmpfs" ino=15394 scontext=u:r:untrusted_app_27 :s0:c512,c768 tcontext=u:object_r:device:s0 tclass=chr_file permissive=1 I/an.firebasedem( 2257): 等待阻塞 GC ProfileSaver I/an.firebasedem( 2257): WaitForGcToComplete 在 ProfileSaver 上阻塞 ProfileSaver 30.771 毫秒

Answer 1

也许你可以先在 firebase 中检查你的集合名称。

stream: Firestore.instance.collection('your_collection_name_here').snapshots(),

Answer 2

确保您在 Firebase 中的字段与 Record 的属性相匹配。

例如：名称匹配数据库中的名称字段投票匹配数据库中的投票字段