【发布时间】：2019-05-28 00:45:55
【问题描述】：
我在 Flutter 上使用 Firebase 制作了一个简单的婴儿名字项目， 成功完成本教程后，应用程序出现此错误：“package:firebase_demo/main.dart': Failed assertion: line 86 pos 16: 'map['votes] != null': is not true.”
同样的帮助。
我的密码 -:
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：
正在执行热重启... 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。 我/颤振（2257）：══╡小部件库发现异常╞═════════════════════════════════════════════ ═════════════════════════ I/flutter（2257）：在构建 StreamBuilder（脏，状态： 我/颤振（2257）：_StreamBuilderBaseState>#94c3a）： I/flutter（2257）：'package:firebase_demo/main.dart'：断言失败：第 86 行 pos 16：'map['votes']！= null'：不是 我/颤动（2257）：是的。 我/颤动（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)：在任何一种情况下，请通过在 GitHub 上提交错误来报告此断言： 我/颤振（2257）：https://github.com/flutter/flutter/issues/new?template=BUG.md 我/颤动（2257）： I/flutter (2257)：当异常被抛出时，这是堆栈： I/flutter (2257): #2 new Record.fromMap (package:firebase_demo/main.dart:86:16) I/flutter（2257）：#3 新 Record.fromSnapshot（包：firebase_demo/main.dart:91:14） 我/颤振（2257）：#4 _MyHomePageState._buildListItem（包：firebase_demo/main.dart:59:27） 我/颤振（2257）：#5 _MyHomePageState._buildList。 （包：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) 我/颤振（2257）：#8 _MyHomePageState._buildList（包：firebase_demo/main.dart:54:71） 我/颤振（2257）：#9 _MyHomePageState._buildBody。 （包：firebase_demo/main.dart:46:16） I/flutter（2257）：#10 StreamBuilder.build（包：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 (package:flutter/src/widgets/framework.dart:3721:15) I/flutter (2257): #14 Element.rebuild (package: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&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:676:20) I/flutter (2257): #17 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._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:990:15) 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 _AssertionError 类中省略了 2 帧） 我/颤振（2257）：══════════════════════════════════════════════════════ ══════════════════════════════════════════════════ ═══════ I/1.gpu (2257): type=1400 audit(0.0:191179):avc: denied {ioctl} for path="/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)：等待阻塞的 GC ProfileSaver I/an.firebasedem(2257)：WaitForGcToComplete 在 ProfileSaver 上阻止 ProfileSaver 30.771 毫秒
【问题讨论】：
-
第二个断言失败，这意味着 firestore 中的一条记录有名称但没有投票字段。您手动检查了所有记录吗？
标签： firebase flutter assertion