title: Flutter: How to create a reverse ListView that initially fills empty space at the bottom
body: <p>I have a reverse ListView.builder that grows downward but initially has only a single widget in it.</p>
  
  <p>See repo: <a href="https://github.com/gmlewis/reverse_listview" rel="noreferrer">https://github.com/gmlewis/reverse_listview</a></p>
  
  <p>It puts all the empty space above the first widget in the list due to the <code>reverse: true</code>, and it looks like: <a href="https://github.com/gmlewis/reverse_listview/raw/master/assets/images/UndesiredListView.png" rel="noreferrer">https://github.com/gmlewis/reverse_listview/raw/master/assets/images/UndesiredListView.png</a></p>
  
  <p>As more widgets are added, it looks like: <a href="https://github.com/gmlewis/reverse_listview/raw/master/assets/images/PopulatedListView.png" rel="noreferrer">https://github.com/gmlewis/reverse_listview/raw/master/assets/images/PopulatedListView.png</a></p>
  
  <p>I would like it to fill all empty space at the bottom instead of at the top, and look like: <a href="https://github.com/gmlewis/reverse_listview/raw/master/assets/images/DesiredListView.png" rel="noreferrer">https://github.com/gmlewis/reverse_listview/raw/master/assets/images/DesiredListView.png</a>
  Obviously, when the content starts getting long enough to fill the screen, the initial widget scrolls off the top as you would expect.</p>
  
  <p>I dug into the <code>ScrollView</code> and <code>Viewport</code> classes and found the <code>anchor</code> and <code>center</code> settings but could not make it do what I want.</p>
  
  <p>It seems like my only remaining option might be to move the first widget to the bottom of the <code>AppBar</code> but I was hoping to not go that route.</p>
  
  <p>Any ideas?</p>