title: Flutter: sliverAppBar resize issue on list scroll
body: <p>I want to make sliverAppBar resized while scrolling list below it.</p>
  
  <p>Now there are two issues:</p>
  
  <p>1) sliverAppBar doesn't resize while I am scrolling list (<a href="https://ibb.co/xJcr2wr" rel="nofollow noreferrer">screenshot</a>)</p>
  
  <p>2) I can't find example/solution how to resize child content of sliverAppBar when it change height (<a href="https://ibb.co/Ph8GCsD" rel="nofollow noreferrer">screenshot</a>)</p>
  
  <pre><code>@override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      body: CustomScrollView(
        slivers: &lt;Widget&gt;[
          SliverAppBar( // &lt;-- how to resize on scrolling ListView?
            expandedHeight: 200.0,
            floating: false,
            pinned: true,
            flexibleSpace: SafeArea(
              child: Column(
                children: [
                  Row( // &lt;-- how to make it flexible/resizable?
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Image.asset(
                        'assets/images/user.png',
                        fit: BoxFit.cover,
                        width: 120,
                      )
                    ],
                  ),
                ],
              ),
            )
          ),
          SliverFillRemaining(
            child: ListView.builder(
              shrinkWrap: false,
              itemCount: widget.europeanCountries.length,
              itemBuilder: (context, index) {
                return ListTile(
                  title: Text(widget.europeanCountries[index]),
                );
              },
            ),
          )
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
  </code></pre>