firebase - Firebase中基于角色的身份验证

我试图通过使用以下代码将管理员用户导航到特殊页面，但它给出了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")

最佳答案

您的snapshot.data对象在这里是null:if(snapshot.data['category']=='admin'){这是因为如果对象不存在，快照数据将为null。 Google建议先检查它是否为exists:
https://firebase.google.com/docs/reference/android/com/google/firebase/firestore/DocumentSnapshot

关于firebase - Firebase中基于角色的身份验证，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/62550128/