title: Flutter, StreamController is not working on fetching image from network
body: <p>I'm practicing Stream and implemented simple app which fetches image and show to the screen.</p>
  
  <p>Here is my code, but it doesn't show anything why??</p>
  
  <p>I'm studying StreamController and it's usage, so I don't want to use Future or other Widget. This logic worked on simple counter app.</p>
  
  <pre><code>class MyAppPageState extends State&lt;MyAppPage&gt; {
  
    StreamController&lt;List&lt;String&gt;&gt; _controller = StreamController&lt;List&lt;String&gt;&gt;();
  
    @override
      Widget build(BuildContext context) {
        return Scaffold(
          appBar: AppBar(backgroundColor: Colors.orange),
          body: Center(
            child: StreamBuilder(
                stream: _controller.stream,
                builder: (BuildContext context, AsyncSnapshot snapshot) =&gt; 
                  Image.network(snapshot.data[0])
            )
          ),
          floatingActionButton: FloatingActionButton(
            onPressed: () =&gt; _addDataToStream()
          ),
        );
      }
  
      void _addDataToStream() {
        http.get('https://comic.naver.com/webtoon/weekdayList.nhn?week=mon')
          .then((response){
            dom.Document document = parser.parse(response.body);
            final e = document.querySelectorAll('.img_list .thumb');
            List&lt;String&gt; url = e.map((element){
              return element.getElementsByTagName('img')[0]
                .attributes['src'];
            }).toList();
            _controller.sink.add(url);
        });
      }
  
      @override
        void dispose() {
          _controller.close();
          super.dispose();
        }
  }
  </code></pre>