我尝试通过使用以下代码bu将管理员用户导航到特殊页面,它给出了NoSuchMethodError
这是代码
class Home extends StatelessWidget {
@override
Widget build(BuildContext context) {
final user = Provider.of<User>(context);
return StreamBuilder<DocumentSnapshot>(
stream: Firestore.instance.collection('users').document(user.uid).snapshots(),
builder: (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot){
if(snapshot.hasError){
return Text('Error: ${snapshot.error}');
}
switch(snapshot.connectionState){
case ConnectionState.waiting: return Loading();
default:
return checkRole(snapshot.data);
}
},
);
}
Widget checkRole(DocumentSnapshot snapshot){
if(snapshot.data['category']=='admin'){
return AproveNotice();
}else{
return HomePage();
}
}
}
这是我的错误
The method '[]' was called on null. Receiver: null Tried calling: []("category")
答案 0 :(得分:0)
更改此:
case ConnectionState.waiting: return Loading();
default:
return checkRole(snapshot.data);
}
对此:
case ConnectionState.waiting: return Loading();
case ConnectionState.done: return checkRole(snapshot.data);
}
答案 1 :(得分:0)
您的snapshot.data
对象在此处null
:
if(snapshot.data['category']=='admin'){
那是因为如果对象不存在,快照数据将为null。 Google建议先exists
检查一下:
https://firebase.google.com/docs/reference/android/com/google/firebase/firestore/DocumentSnapshot
如果DocumentSnapshot指向不存在的文档,则getData()及其对应的方法将返回null。您始终可以通过调用exist()显式检查文档是否存在。