How to fade in/out a widget from SliverAppBar while scrolling?

[Jorge Andrés Pérez Montás]

I want to 'fade in' and 'fade out' a widget from SliverAppBar when user scrolls on the screen. This is an example of what I want to do (look at the circle avatar fading effect when scrolling):

Here is my code without 'fading':

https://gist.github.com/nesscx/721cd823350848e3d594ba95df68a7fa

So... How can I achieve this effect?

Thanks in advance.

[Dennis Riungu]

Check out this doc: https://flutter.io/cookbook/animation/opacity-animation/

Then try playing with some code I dropped in your gist.

Basically, it uses the AnimatedOpacity opacity property which is managed by the scroll controller of the enclosing CustomScrollView widget.