Overlay card widget over NestedScrollView

Question

In my screen I am already using NestedScrollView() along with headerSliverBuilder and SliverAppBar(). I tried to add a Stack widget to the body of headerSliverBuilder but it never came in between the blue and white part as expected (expected result in the screenshot). It stays on the white portion only. I followed this answer but failed as mentioned above. Here is the expected result:

Answer 1

call the Stack from your Scaffold body instead, not the headerSliverBuilder