title: Null check operator used on a null value, The relevant error-causing widget was, StreamBuilder<ArticleResponse>
body: <p>ive been facing this problem for quite time now and im new to flutter and the output display Null check operator used on a null.</p>
  <p>The following _CastError was thrown building StreamBuilder(dirty, state: _StreamBuilderBaseState&lt;ArticleResponse, AsyncSnapshot&gt;#39173):
  Null check operator used on a null value</p>
  <pre><code>  import 'package:carousel_slider/carousel_slider.dart';
  import 'package:firstapp/bloc/get_top_headlines_bloc.dart';
  import 'package:firstapp/elements/error_element.dart';
  import 'package:firstapp/elements/loader_element.dart';
  import 'package:firstapp/model/article.dart';
  import 'package:firstapp/model/article_response.dart';
  import 'package:flutter/material.dart';
  import 'package:timeago/timeago.dart' as timeago;
  
  class HeadlineSliderWidget extends StatefulWidget {
    const HeadlineSliderWidget({Key? key}) : super(key: key);
  
    @override
    _HeadlineSliderWidgetState createState() =&gt; _HeadlineSliderWidgetState();
  }
  
  class _HeadlineSliderWidgetState extends State&lt;HeadlineSliderWidget&gt; {
    @override
    void initState() {
      super.initState();
      getTopHeadlinesBloc..getHeadlines();
    }
  
    @override
    Widget build(BuildContext context) {
      return StreamBuilder&lt;ArticleResponse&gt;(
        stream: getTopHeadlinesBloc.subject.stream,
        builder: (context, AsyncSnapshot&lt;ArticleResponse&gt; snapshot) {
          if (snapshot.hasData) {
            if (snapshot.data?.error != null &amp;&amp; snapshot.data!.error.length &gt; 0) {
              return buildErrorWidget(snapshot.data!.error);
            }
            return _buildHeadlineSliderWidget(snapshot.data!);
          }else if (snapshot.hasError){
            return buildErrorWidget(snapshot.data!.error);
          } else {
            return buildLoadingWidget();
          }
          // if (snapshot.hasData) {
          //  return _buildHeadlineSliderWidget(snapshot.data!);
          // } else if (!snapshot.hasError) {
          //   return buildErrorWidget(snapshot.data!.error);
          // } else {
          //   return buildLoadingWidget();
          // }
        },
      );
    }
    //   ignore: unrelated_type_equality_checks
    //   if (snapshot.hasError !=  snapshot.data!.error.length &gt; 0) {
    //     return buildErrorWidget(snapshot.data!.error);
    //   }
    //   var data = snapshot.data!;
    //   return _buildHeadlineSliderWidget(data);
    // } else if (snapshot.hasError) {
    //   return buildErrorWidget(snapshot.data!.error);
    // } else {
    //   return buildLoadingWidget();
  
    Widget _buildHeadlineSliderWidget(ArticleResponse data) {
      List&lt;ArticleModel&gt; articles = data.articles;
      return Container(
        child: CarouselSlider(
          options: CarouselOptions(
              enlargeCenterPage: false, height: 200.0, viewportFraction: 0.9),
          items: getExpenseSliders(articles),
        ),
      );
    }
  
    getExpenseSliders(List&lt;ArticleModel&gt; articles) {
      return articles
          .map(
            (article) =&gt; GestureDetector(
              onTap: () {},
              child: Container(
                padding: const EdgeInsets.only(
                    left: 5.0, right: 5.0, top: 10.0, bottom: 10.0),
                child: Stack(
                  children: &lt;Widget&gt;[
                    Container(
                      decoration: new BoxDecoration(
                        borderRadius: BorderRadius.all(Radius.circular(8.0)),
                        shape: BoxShape.rectangle,
                        image: new DecorationImage(
                            fit: BoxFit.cover,
                            // ignore: unrelated_type_equality_checks
                            image: article.img != String
                                ? NetworkImage(article.img!)
                                : AssetImage(&quot;assets/img/placeholder.jpg&quot;)
                                    as ImageProvider),
                      ),
                    ),
                    Container(
                      decoration: BoxDecoration(
                        borderRadius: BorderRadius.all(Radius.circular(8.0)),
                        gradient: LinearGradient(
                            begin: Alignment.bottomCenter,
                            end: Alignment.topCenter,
                            stops: [
                              0.1,
                              0.9
                            ],
                            colors: [
                              Colors.black.withOpacity(0.9),
                              Colors.white.withOpacity(0.0)
                            ]),
                      ),
                    ),
                    Positioned(
                        bottom: 30.0,
                        child: Container(
                          padding: EdgeInsets.only(left: 10.0, right: 10.0),
                          width: 250.0,
                          child: Column(
                            children: &lt;Widget&gt;[
                              Text(
                                article.title!,
                                style: TextStyle(
                                    height: 1.5,
                                    color: Colors.white,
                                    fontWeight: FontWeight.bold,
                                    fontSize: 12.0),
                              ),
                            ],
                          ),
                        )),
                    Positioned(
                        bottom: 10.0,
                        left: 10.0,
                        child: Text(
                          article.source.name!,
                          style: TextStyle(color: Colors.white54, fontSize: 9.0),
                        )),
                    Positioned(
                        bottom: 10.0,
                        right: 10.0,
                        child: Text(
                          timeAgo(DateTime.parse(article.date!)),
                          style: TextStyle(color: Colors.white54, fontSize: 9.0),
                        )),
                  ],
                ),
              ),
            ),
          )
          .toList();
    }
  
    String timeAgo(DateTime date) {
      return timeago.format(date, allowFromNow: true, locale: 'en');
    }
  }
  
  </code></pre>