Adding DraggableScrollableSheet to the bottom of a Sliver page - flutter

Question

I’m working on the concept that you can see on the screenshot below:
design concept
Note: the arrows are not the part of the UI, but were added to demonstrate the draggable functionality.
The screen has a SliverAppBar that displays location title, Sliver body that contains location description, and has a DraggableScrollableSheet (or a similar alternative).
When the location description is scrolled up, the title collapses.
When the DraggableScrollableSheet is scrolled up it expands to the full height of the screen.
I tried many times to put it together, but something is always off.
My last attempt was to add DraggableScrollableSheet as a ‘bottom sheet:’ in Scaffold. Since I have a BottomAppBar, it breaks the UI, and looks the following way:
current UI behavior
Scaffold
#override
Widget build(BuildContext context) {
return Scaffold(
body: body,
extendBody: true,
appBar: appBar,
bottomSheet: hasBottomSheet
? DraggableScrollableSheet(
builder:
(BuildContext context, ScrollController scrollController) {
return Container(
color: Colors.blue[100],
child: ListView.builder(
controller: scrollController,
itemCount: 25,
itemBuilder: (BuildContext context, int index) {
return ListTile(title: Text('Item $index'));
},
),
);
},
)
: null,
backgroundColor: Colors.white,
floatingActionButtonLocation: fab_position,
floatingActionButton: hasActionButton ? ScannerFAB() : null,
bottomNavigationBar: AppBarsNav(hasNavButtons: hasNavButtons));
}
Scaffold body
class LocationPage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return ScaffoldWithNav(
hasBottomSheet: true,
body: CustomScrollView(
slivers: <Widget>[
SliverBar(
title: "Location",
hasBackground: true,
backgroundImagePath: 'assets/testImage.jpg'),
SliverToBoxAdapter(
child: Text("very long text "),
),
SliverPadding(
padding: EdgeInsets.only(bottom: 70),
),
],
),
);
}
}
BottomAppBar FAB
class ScannerFAB extends StatelessWidget {
#override
Widget build(BuildContext context) {
return FloatingActionButton(
child: WebsafeSvg.asset('assets/qr-code.svg',
color: Colors.white, height: 24, width: 24),
);
}
}
The FAB jumps, the content is hidden.
When I set a fixed-sized container, the content comes back, but the FAB is still living its own life:)
current UI behavior2
If anyone has any idea how to solve this issue/those issues please share, I’ll be very grateful!

Answer 1

You can try to add another Scaffold on current body and put the DraggableScrollableSheet inside it. Then the DraggableScrollableSheet won't affect the FAB outside.
#override
Widget build(BuildContext context) {
return Scaffold(
body: Scaffold(
body: body,
bottomSheet: ... // move DraggableScrollableSheet to here
),
...
floatingActionButton: ... // keep FAB here
...
)

Answer 2

You can use Stack into Body, for example:
#override
Widget build(BuildContext context) {
return Scaffold(
body: Stack(
children. [
SingleChildScrollView(),
DraggableScrollableSheet(),
]
),
...
floatingActionButton: ... // keep FAB here
...
)