Flutter StreamBuilder errors

Question

Implemented StreamBuilder to display items in shopping cart's updated prices. Everything works as expected when one or two items are in cart, but when add third item I get the third item correctly but first and second items in cart display following error: "Bad state: field does not exist within the DocumentSnapshotPlatform. The relevant error-causing widget was StreamBuilder<DocumentSnapshot<Map<String, dynamic>>>". I believe that is a timing error (async / await), or some sort of pause needed. This is my code:

class PriceUpdaterWidget extends StatelessWidget {
  const PriceUpdaterWidget({
    Key? key,
    required this.loginService,
    required this.code,
  }) : super(key: key);

  final LoginService loginService;
  final String? code;

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<DocumentSnapshot<Map<String, dynamic>>>(
        stream: FirebaseFirestore.instance
            .collection('shoppers')
            .doc(loginService.loggedInUserModel!.uid)
            .collection("cartItems")
            .doc(code)
            .snapshots(),
        builder: (BuildContext context,
            AsyncSnapshot<DocumentSnapshot<Map<String, dynamic>>> snapshot) {
          SellerNameService isSellerName =
              Provider.of<SellerNameService>(context, listen: false);

          var sellerName = isSellerName.isSellerName;

          final snapshotData = snapshot.data;

          if (snapshot.hasData) {
            return Text(
              snapshot.data![sellerName].toStringAsFixed(2),
              textAlign: TextAlign.center,
            );
          } else {
            return Text('No Datos');
          }
        });
  }
}

Edit: Items add to cart:

void add(BuildContext context, CartItem item) async {
    _items.add(item);
    int indexOfSeller = await getValue() ?? "";

    LoginService loginService =
        Provider.of<LoginService>(context, listen: false);

    Map<String, dynamic> cartMap = Map();
    var price = item.subCategory!.price as double;
    var isSelectedPrice = item.isSelectedPrice;
    var sellerName = item.subCategory!.parts[indexOfSeller].name;
    var codeTest = item.subCategory!.code!;
    var amount = item.subCategory!.amount;

    _items.forEach((CartItem item) {
      cartMap[item.subCategory!.code!] =
          (item.subCategory as SubCategory).amount;
      //
      cartMap[item.subCategory!.parts[indexOfSeller].name] =
          (item.subCategory!).parts[indexOfSeller].price;
    });

    _instance = FirebaseFirestore.instance;

    _instance!
        .collection('shoppers')
        .doc(loginService.loggedInUserModel!.uid)
        .collection("cartItems")
        .doc(codeTest)
        .set({codeTest: amount, sellerName: price},
            SetOptions(merge: false)).then((codeTest) {
      notifyListeners();
    });
  }

Answer 1

wrap your StreamBuilder in Expanded widget

Answer 2

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:new_app/custom/action_bar.dart';
import 'package:new_app/custom/constants.dart';
import 'package:new_app/custom/custom_btn.dart';
import 'package:new_app/users/HomePage.dart';

 class NewsView extends StatefulWidget {
   final String newsid;
  NewsView({required this.newsid});
 
   @override
   _NewsViewState createState() => _NewsViewState();
 }
 
 class _NewsViewState extends State<NewsView> {
    final CollectionReference _productsRef= 
 FirebaseFirestore.instance.collection("SportsNews");
   @override
   Widget build(BuildContext context) {
     return Scaffold(
      body: Stack(
        children: [
        FutureBuilder(
          future: _productsRef.doc(widget.newsid).get(),
          builder:(context, AsyncSnapshot<DocumentSnapshot> snapshot){
              if (snapshot.hasError) {
                return Scaffold(
                  body: Center(
                    child: Text("Error: ${snapshot.error}"),
                  ),
                );
              }
              // get data
              if(snapshot.connectionState==ConnectionState.done){
                  DocumentSnapshot<Object?> documentData = snapshot.data!;
                  // list
              
              
                  return Container(
                     
                    
                    child: ListView(
                      children: [
                        Container(
                        
                          // height:390,
                         
                          
                            child:
                            
                             Padding(
                               padding: const EdgeInsets.all(10.0),
                               child: Container(
                                 margin: EdgeInsets.only(top:50,bottom:5),
                                 height:260,
                                 
                                 child: PageView(
                                   children:[
                                    
                                     Container(
                                       
                                       child: ClipRRect(
                                          borderRadius: BorderRadius.circular(18.0),
                                         child: Image.network(
                                                                      (documentData['images']),
                                                                        fit:BoxFit.fill,
                                                                 ),
                                       ),
                                     ),
                                                            
                                                             
                                   ]
                                 ),
                               ),
                             ),
                          
                        ),
                       
                       Padding(
                          padding: const EdgeInsets.symmetric(
                            vertical: 0.8,
                            horizontal: 20.0
                          ),
                          child: Text("${documentData['Category']}",textAlign:TextAlign.right,style: Constants.smallText,),
                        ),
                        Padding(
                          padding: const EdgeInsets.symmetric(
                            vertical: 0.8,
                            horizontal: 20.0
                          ),
                          child: Text("${documentData['Heading']}",textAlign:TextAlign.justify,style: Constants.boldHeading,),
                        ),
                          Padding(
                          padding: const EdgeInsets.symmetric(
                            vertical:10.0,
                            horizontal: 20.0
                          ),
                          child: Text("${documentData['Subheading']}",textAlign:TextAlign.justify,style: Constants.regularHeading,),
                        ),
Padding(
                               padding: const EdgeInsets.all(10.0),
                               child: Container(
                                 margin: EdgeInsets.only(top:5,bottom:5),
                                 height:250,
child: ClipRRect(
  borderRadius: BorderRadius.circular(18.0),
  child:   Image.network(
  
   (documentData['images']),
  
   fit: BoxFit.fill,
  
  ),
),

                               ),),
                        Padding(
                          padding: const EdgeInsets.symmetric(
                            vertical: 0.10,
                            horizontal: 20.0
                          ),
                          child: Text("${documentData['desc']}",textAlign:TextAlign.justify,style: Constants.darkText,),
                        ),
                        Padding(
                               padding: const EdgeInsets.all(10.0),
                               child: Container(
                                 margin: EdgeInsets.only(top:5,bottom:5),
                                 height:250,
child: ClipRRect(
  borderRadius: BorderRadius.circular(18.0),
  child:   Image.network(
  
   (documentData['images']),
  
   fit: BoxFit.fill,
  
  ),
),

                               ),),
                         Padding(
                          padding: const EdgeInsets.symmetric(
                            vertical: 0.10,
                            horizontal: 20.0
                          ),
                          child: Text("${documentData['Subdesc']}",textAlign:TextAlign.justify,style: Constants.darkText,),
                        ),
                        
                         Custombtn(text: "Back",
                            outlinebtn: true, 
                            onPressed:(){
                             Navigator.push(context,MaterialPageRoute(builder: (context)=>HomePage()));
                           },
                            isLoading: false)
                      ],


                      
                    ),
                  );

              }

// loding is true
               return Scaffold(
                body: Center(
                  child: CircularProgressIndicator(),
                ),
              );
          }),
ActionBar(
  hasBackArrow: true,
   title: "", 
   hastitle:false, 
   hasBackGround:false,)
        ],
      )
    );
  }
}