NoSuchMethodError：方法“ []”在null上被调用
我遇到以下错误：
在构建StreamBuilder时引发了以下NoSuchMethodError（脏，状态：_StreamBuilderBaseState>＃12214）： 方法'[]'在null上被调用。 接收者：null 尝试致电：
由用户创建的导致错误的小部件的祖先是： 消费者
出于某种原因，这是在实现提供者和使用者之后发生的，但是我认为我的实现没有问题。 （应用程序在没有提供者和使用者的情况下运行良好）。我的Firestore数据库看起来像这样
我张贴了我的main.dart代码的图片，有没有提供者和消费者。 （无需调用它们，代码即可正常运行。）
带有消费者/提供者的Main.dart：
void main() {
runApp(
ChangeNotifierProvider(
builder: (context) => UserModel(),
child: MyApp(),
),
);
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Profile Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Profile'),
);
}
}
class User {
final int name;
final DocumentReference reference;
User.fromMap(Map<String, dynamic> map, {this.reference})
: name = map['name'];
User.fromSnapshot(DocumentSnapshot snapshot)
: this.fromMap(snapshot.data, reference: snapshot.reference);
}
class Photo {
final int photourl;
final DocumentReference reference;
Photo.fromMap(Map<String, dynamic> map, {this.reference})
: photourl = map['photourl'];
Photo.fromSnapshot(DocumentSnapshot snapshot)
: this.fromMap(snapshot.data, reference: snapshot.reference);
}
class Questions {
final int totalquestions;
final DocumentReference reference;
Questions.fromMap(Map<String, dynamic> map, {this.reference})
: totalquestions = map['totalquestions'];
Questions.fromSnapshot(DocumentSnapshot snapshot)
: this.fromMap(snapshot.data, reference: snapshot.reference);
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
Widget build(BuildContext context) {
final _width = MediaQuery
.of(context)
.size
.width;
final _height = MediaQuery
.of(context)
.size
.height;
return Consumer<UserModel>(
builder: (context, userModel, child) {
return StreamBuilder<DocumentSnapshot>(
stream: Firestore.instance.collection(userModel.uid)
.document(userModel.uid).snapshots(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return Stack(
children: <Widget>[
new Container(
color: Colors.blue,
),
new Image.network(
snapshot.data['photourl'].toString(),
fit: BoxFit.fill,
),
new BackdropFilter(
filter: new ui.ImageFilter.blur(
sigmaX: 6.0,
sigmaY: 6.0,
),
child: new Container(
decoration: BoxDecoration(
color: Colors.blue.withOpacity(0.9),
borderRadius: BorderRadius.all(Radius.circular(50.0)),
),
)),
new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
centerTitle: false,
elevation: 0.0,
backgroundColor: Colors.transparent,
),
drawer: new Drawer(
child: new Container(),
),
backgroundColor: Colors.transparent,
body: new Center(
child: new Column(
children: <Widget>[
new SizedBox(
height: _height / 12,
),
new CircleAvatar(
radius: _width < _height ? _width / 4 : _height /
4,
backgroundImage: NetworkImage(snapshot
.data['photourl']),
),
new SizedBox(
height: _height / 25.0,
),
new Text(
snapshot.data['name'],
style: new TextStyle(
fontWeight: FontWeight.bold,
fontSize: _width / 15,
color: Colors.white),
),
new Padding(
padding: new EdgeInsets.only(
top: _height / 30,
left: _width / 8,
right: _width / 8),
),
new Divider(
height: _height / 15,
color: Colors.white,
),
new Row(
children: <Widget>[
rowCell(
snapshot.data['totalquestions'], 'Answers'),
rowCell(
'£ ${int.parse(
snapshot.data['totalquestions']) * 2}',
'Earned'),
],
),
new Divider(
height: _height / 15, color: Colors.white),
],
),
),
),
],
);
} else {
return CircularProgressIndicator();
}
});
});
}
Widget rowCell(String count, String type) => new Expanded(
child: new Column(
children: <Widget>[
new Text(
'$count',
style: new TextStyle(color: Colors.white),
),
new Text(type,
style: new TextStyle(
color: Colors.white, fontWeight: FontWeight.normal))
],
));
}
没有使用者/提供者的main.dart：
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Profile Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Profile'),
);
}
}
class User {
final int name;
final DocumentReference reference;
User.fromMap(Map<String, dynamic> map, {this.reference})
: name = map['name'];
User.fromSnapshot(DocumentSnapshot snapshot)
: this.fromMap(snapshot.data, reference: snapshot.reference);
}
class Photo {
final int photourl;
final DocumentReference reference;
Photo.fromMap(Map<String, dynamic> map, {this.reference})
: photourl = map['photourl'];
Photo.fromSnapshot(DocumentSnapshot snapshot)
: this.fromMap(snapshot.data, reference: snapshot.reference);
}
class Questions {
final int totalquestions;
final DocumentReference reference;
Questions.fromMap(Map<String, dynamic> map, {this.reference})
: totalquestions = map['totalquestions'];
Questions.fromSnapshot(DocumentSnapshot snapshot)
: this.fromMap(snapshot.data, reference: snapshot.reference);
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
Widget build(BuildContext context) {
final _width = MediaQuery.of(context).size.width;
final _height = MediaQuery.of(context).size.height;
// final String imgUrl =
// 'https://pixel.nymag.com/imgs/daily/selectall/2017/12/26/26-eric-schmidt.w700.h700.jpg';
// final String userId;
return StreamBuilder<DocumentSnapshot>(
stream: Firestore.instance
.collection('users')
.document('testuser')
.snapshots(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return Stack(
children: <Widget>[
new Container(
color: Colors.blue,
),
new Image.network(
snapshot.data['photourl'].toString(),
fit: BoxFit.fill,
),
new BackdropFilter(
filter: new ui.ImageFilter.blur(
sigmaX: 6.0,
sigmaY: 6.0,
),
child: new Container(
decoration: BoxDecoration(
color: Colors.blue.withOpacity(0.9),
borderRadius: BorderRadius.all(Radius.circular(50.0)),
),
)),
new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
centerTitle: false,
elevation: 0.0,
backgroundColor: Colors.transparent,
),
drawer: new Drawer(
child: new Container(),
),
backgroundColor: Colors.transparent,
body: new Center(
child: new Column(
children: <Widget>[
new SizedBox(
height: _height / 12,
),
new CircleAvatar(
radius: _width < _height ? _width / 4 : _height / 4,
backgroundImage: NetworkImage(snapshot.data['photourl']),
),
new SizedBox(
height: _height / 25.0,
),
new Text(
snapshot.data['name'],
style: new TextStyle(
fontWeight: FontWeight.bold,
fontSize: _width / 15,
color: Colors.white),
),
new Padding(
padding: new EdgeInsets.only(
top: _height / 30,
left: _width / 8,
right: _width / 8),
),
new Divider(
height: _height / 15,
color: Colors.white,
),
new Row(
children: <Widget>[
rowCell(
snapshot.data['totalquestions'], 'Answers'),
rowCell(
'£ ${int.parse(snapshot.data['totalquestions']) * 2}', 'Earned'),
],
),
new Divider(
height: _height / 15, color: Colors.white),
],
),
))
],
);
} else {
return CircularProgressIndicator();
}
});
}
Widget rowCell(String count, String type) => new Expanded(
child: new Column(
children: <Widget>[
new Text(
'$count',
style: new TextStyle(color: Colors.white),
),
new Text(type,
style: new TextStyle(
color: Colors.white, fontWeight: FontWeight.normal))
],
));
}
user_model.dart类：
class UserModel extends ChangeNotifier {
String uid = 'testuser';
}
0 个答案:
没有答案
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