Flutter tab bar error after upgraded flutter "The getter 'key' was called on null"

Question

The following NoSuchMethodError was thrown building MediaQuery(MediaQueryData(size: Size(360.0, 640.0), devicePixelRatio: 3.0, textScaleFactor: 1.0, platformBrightness: Brightness.light, padding: EdgeInsets.zero, viewPadding: EdgeInsets.zero, viewInsets: EdgeInsets.zero, physicalDepth: 1.7976931348623157e+308, alwaysUse24HourFormat: false, accessibleNavigation: false, disableAnimations: false, invertColors: false, boldText: false)): The getter 'key' was called on null. Receiver: null Tried calling: key

User-created ancestor of the error-causing widget was: Scaffold file:///home/midhilajm/Downloads/al-qasier-flutter-solving_issue_20/lib/orderDetails/OrderDetails.dart:27:16 When the exception was thrown, this was the stack:

0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)

1 new KeyedSubtree.wrap (package:flutter/src/widgets/basic.dart:6605:27)

2 KeyedSubtree.ensureUniqueKeysForList (package:flutter/src/widgets/basic.dart:6623:44)

3 _TabBarViewState._updateChildren (package:flutter/src/material/tabs.dart:1237:37)

4 _TabBarViewState.initState (package:flutter/src/material/tabs.dart:1206:5) ...

════════════════════════════════════════════════════════════════════════════════════════════════════

import 'package:alqaiser/cart/MyCart.dart'; import 'package:alqaiser/orderHistory/OrderHistoryModule.dart'; import 'package:alqaiser/orderHistory/OrderItem.dart'; import 'package:alqaiser/toolbar/MyToolBar.dart'; import 'package:alqaiser/utlity/Milla.dart'; import 'package:flutter/material.dart';

class OrderDetails extends StatefulWidget {
  OrderItem order;
  OrderDetails({this.order}) {}
  @override
  _OrderDetailsState createState() => _OrderDetailsState(order: order);
}

class _OrderDetailsState extends State<OrderDetails> {
  OrderItem order;
  _OrderDetailsState({this.order}) {

  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: MyToolBar().getAppBar(context),
      body: DefaultTabController(
        length: 2,
        child: Scaffold(
          appBar: AppBar(
            title: TabBar(
              tabs: [
                Tab(
                  text: "Work followup",
                ),
                Tab(
                  text: "Payment ",
                ),
              ],
            ),
          ),
          body: TabBarView(children: [getWorkStatus(), getPaymentStatus()]),
        ),
      ),
    );
  }

  Widget getPaymentStatus() {
    if (this.order.paymentS != null)
      return ListView.builder(
          itemCount: this.order.paymentS.length,
          itemBuilder: (BuildContext context, int index) {
            return Bubble(message: this.order.paymentS[index]);
          });
  }

  Widget getWorkStatus() {
    if (this.order.statues != null)
      return ListView.builder(
          itemCount: this.order.statues.length,
          itemBuilder: (BuildContext context, int index) {
            return Bubble(message: this.order.statues[index]);
          });
  }
}

class Bubble extends StatelessWidget {
  Color bg =Colors.blueGrey ;
  String message1="",message2="";
  Bubble(
      {this.message,
      this.time = "12",
      this.delivered = false,
      this.isMe = false});

  final String message, time;
  final delivered, isMe;
  List<String> messageSplit = [];
  @override
  Widget build(BuildContext context) {
    messageSplit = message.split(":");
    if(messageSplit.length>=1?messageSplit[0]!=null?true:false:false)
  message1=messageSplit[0];
    if(messageSplit.length>=3?
  messageSplit[2]!=null?true:false:false)
    message2=messageSplit[2];
    if(messageSplit.length>=2?
    messageSplit[1]!=null?true:false:false)
    bg=isMe ? Colors.white :HexColor(messageSplit[1]);
    final align = isMe ? CrossAxisAlignment.start : CrossAxisAlignment.end;
    final icon = delivered ? Icons.done_all : Icons.done;
    final radius = isMe
        ? BorderRadius.only(
            topRight: Radius.circular(5.0),
            bottomLeft: Radius.circular(10.0),
            bottomRight: Radius.circular(5.0),
          )
        : BorderRadius.only(
            topLeft: Radius.circular(5.0),
            bottomLeft: Radius.circular(5.0),
            bottomRight: Radius.circular(10.0),
          );
    return Column(
      crossAxisAlignment: align,
      children: <Widget>[
        Container(
          margin: const EdgeInsets.all(3.0),
          padding: const EdgeInsets.all(8.0),
          decoration: BoxDecoration(
            boxShadow: [
              BoxShadow(
                  blurRadius: .5,
                  spreadRadius: 1.0,
                  color: Colors.black.withOpacity(.12))
            ],
            color: bg,
            borderRadius: radius,
          ),
          child:Column(
            children: <Widget>[
              Container(

              child:    Text(message1,textAlign: TextAlign.right,style: TextStyle(color: Colors.white),),
          )
          ,
              Text(message2,textAlign: TextAlign.right,
                  style: TextStyle(
                    color: Colors.white70,
                    fontSize: 10.0,
                  )),
            ],
          ),
        )
      ],
    );
  }
}

Answer 1

You can't have methods that might not return any value. What will be returned when payments == null?

Widget getPaymentStatus() {
if (this.order.paymentS != null)
  return ListView.builder(
      itemCount: this.order.paymentS.length,
      itemBuilder: (BuildContext context, int index) {
        return Bubble(message: this.order.paymentS[index]);
      });
}

You shoud handle all conditions, for example:

Widget getPaymentStatus() {
 if (this.order.paymentS != null){
   return ListView.builder(
      itemCount: this.order.paymentS.length,
      itemBuilder: (BuildContext context, int index) {
        return Bubble(message: this.order.paymentS[index]);
      });
 }
 else{
  return Container()
 }
}