Flutter - Scroll with a fixed widget - flutter

Question

I would like to do a scroll that the map part fixed on top, once i scroll up those widget can be overlay on top of the map.
i tried to do the scroll effect.
i use a stack with one container(the map) and one SingleChildScroll.
but the map is not able to tap after i put the SingleChildScroll on top of the map.
So is there any ways to made this out?
Any suggestions that i can do this design?
Thanks a lot!
This is the normal view
after i scroll up little bit
here is the code
return Scaffold(
key: _scaffoldKey,
backgroundColor: ThemeColors.orangeYellow,
floatingActionButton: Padding(
padding: EdgeInsets.only(right: 30),
child: Row(
children: [
_profileButton,
],
),
),
floatingActionButtonLocation: FloatingActionButtonLocation.startTop,
body: Stack(
children: [
Positioned(
top: 0,
child: Stack(
alignment: Alignment.bottomCenter,
overflow: Overflow.visible,
children: <Widget>[
Container(),
_map,
_nearbyRestaurantBox,
_getCurrentLocationButton,
],
),
),
SingleChildScrollView(
physics: ClampingScrollPhysics(),
child: Column(
children: <Widget>[
Column(
// alignment: Alignment.bottomCenter,
// overflow: Overflow.visible,
children: <Widget>[
// Container(),
// _map,
Padding(
padding: EdgeInsets.only(top: _mapHeight - 70),
),
Stack(
children: [
Column(
children: [
SizedBox(
height: 70,
// child: Container(
// // color: Colors.green,
// ),
),
SizedBox(
height: 70,
child: Container(
color: Colors.amber,
),
)
],
),
// Padding(
// padding: EdgeInsets.only(top: 35),
// ),
Container(
alignment: Alignment.center,
child: Padding(
padding: EdgeInsets.only(top: 5),
child: _searchBox,
),
)
],
),
// Positioned(top: 0, child: _map),
// _searchBox,
// _nearbyRestaurantBox,
// _getCurrentLocationButton,
],
),
Container(
color: ThemeColors.orangeYellow,
child: Center(
child: Column(
children: <Widget>[
_categoryBox,
..._buildBanners(),
],
),
),
),
],
),
)
],
),
);