Your UI now renders itself differently depending on
whether it’s loading or loaded.
By temporarily commenting out the image URLs,
you can see the two ways your UI renders.

The next goal is to paint all of the colored areas
with a single gradient that looks like a shimmer.

Paint the shimmer gradient

The key to the effect achieved in this recipe is to use a widget 
called ShaderMask. The ShaderMask widget, as the name suggests,
applies a shader to its child, but only in the areas where
the child already painted something. For example,
you’ll apply a shader to only the black shapes that you 
configured earlier.

Define a chrome-colored, linear gradient that gets applied to the 
shimmer shapes.

Wrap your CircleListItem widgets with a ShimmerLoading widget.

Wrap your CardListItem widgets with a ShimmerLoading widget.