Flutter CustomScrollView scrolls when there are not enough items - flutter

Question

Having an issue with scrolling when using slivers and a sliver appbar. How can I prevent the scrollview from scrolling when no scroll is needed like in the video. And if there are enough items for scrolling it should scroll (That works perfectly)
I followed this medium post. And you can see that he has the same problem.
https://medium.com/#diegoveloper/flutter-collapsing-toolbar-sliver-app-bar-14b858e87abe
https://youtu.be/l1EwM9GAfxw
class HomeScreen extends StatelessWidget{
#override
Widget build(BuildContext context) {
return Scaffold(
body: NestedScrollView(
headerSliverBuilder: (context, innerBoxIsScrolled) => [
SliverAppBar(
brightness: Brightness.dark,
backgroundColor: Colors.amber.withOpacity(0.5),
expandedHeight: 166,
flexibleSpace: FlexibleSpaceBar(
collapseMode: CollapseMode.pin,
background: SafeArea(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Container(
height: 80,
width: 80,
child: Placeholder(),
),
Row(
children: [
Text(
'sdalkf',
),
],
),
],
),
),
),
),
SliverPersistentHeader(
delegate: SliverAppBarDelegate(
MediaQuery.of(context).padding.top,
Container(
color: Colors.amber.withOpacity(0.5),
child: SafeArea(
bottom: false,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text('sdfaklladsjfkladslkf\nsadjflkasjklfs\nsdkjlfjlkadslfjk'),
],
),
),
),
),
pinned: true,
),
],
body: GridView.builder(
itemCount: 3,
padding: EdgeInsets.zero,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3, childAspectRatio: 0.68),
itemBuilder: (context, index) => Padding(
padding: const EdgeInsets.symmetric(horizontal: 8),
child: Container(
color: Colors.black54,
),
),
),
),
);
}
}
class SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
final Widget child;
final double topSafeArea;
_SliverAppBarDelegate(this.topSafeArea, this.child);
#override
double get minExtent => 105 + topSafeArea;
#override
double get maxExtent => 105 + topSafeArea;
#override
Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) {
return Container(
child: child,
);
}
#override
bool shouldRebuild(_SliverAppBarDelegate oldDelegate) {
return false;
}
}
Related to:
Flutter SliverAppBar with Tabs overlays content
The above link is not a sollution but a temp fix

Answer 1

Set physics behavior of ScrollView to AlwaysScrollableScrollPhysics
from documentation:
/// Scroll physics that always lets the user scroll.
///
/// This overrides the default behavior which is to disable scrolling
/// when there is no content to scroll. It does not override the
/// handling of overscrolling.