title: Flutter SliverAppBar, Collapse background to fill the leading space
body: <p>I want to use create a sliver list view with a <code>SliverAppBar</code> such that when I scroll up the list, the icon inside the body shrinks to take place in the <code>leading</code> space of appBar. </p>
  
  <p>The images here show something that I want to achieve. When I scroll up, the chart should move up and slide beside the title. (Something similar to Hero widget)</p>
  
  <p>Till now, I tried <code>SliverAppBar</code>, but was not able to succeed. I am happy to use some other widget to achieve this. Thank you.</p>
  
  <p><a href="https://i.stack.imgur.com/8n0c3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8n0c3.png" alt="enter image description here"></a></p>