Add a flexibleSpace widget that fills the available
expandedHeight.

Tip:
  Play around with the
  various properties you can pass to the SliverAppBar widget,
  and use hot reload to see the results. For example, use an Image
  widget for the flexibleSpace property to create a background image that
  shrinks in size as it’s scrolled offscreen.

3. Add a list of items using a SliverList

Now that you have the app bar in place, add a list of items to the
CustomScrollView. You have two options: a SliverList
or a SliverGrid.  If you need to display a list of items one after the other,
use the SliverList widget.
If you need to display a grid list, use the SliverGrid widget.

SliverChildDelegate, which provides a list
of widgets to

SliverChildBuilderDelegate
allows you to create a list of items that are built lazily as you scroll,
just like the