SliverAppBar without fading in the AppBar - flutter

Question

I really love using Slivers, but really have a Problem with SliverAppBar:
usually, I use the SliverAppBar Widget for creating a AppBar that has a Background Image with the Parallax effect. So all I use is the flexible space, which unfortunately gets blocked by the AppBar Portion whenever you scroll down.
I tried making the AppBar portion transparent by setting the color value to transparent, but all it does is make the whole thing, including the flexiblespace, transparent..
Is there a way to use only the flexiblespace of a SliverAppBar without fading in the AppBar portion when scrolling down?
here is the code I use:
SliverAppBar(
expandedHeight: 220,
pinned: false,
forceElevated: true,
backgroundColor: Colors.transparent,
stretch: true,
leading: Container(),
flexibleSpace: FlexibleSpaceBar(
collapseMode: CollapseMode.pin,
background:Stack(
children: <Widget>[
Image(
fit: BoxFit.cover,
width: MediaQuery.of(context).size.width,
image: AssetImage('assets/images/image2.png'),
),
Positioned(
bottom: 0,
child: Container(
height: 110,
width: MediaQuery.of(context).size.width,
color: Colors.grey,
),
),
Positioned(
bottom: 10,
left: 10,
child: CircleAvatar(
radius: 45,
backgroundImage: AssetImage('assets/images/image.png'),
),
),
Positioned(
bottom: 77,
left: 110,
child: Container(
width: MediaQuery.of(context).size.width -110 -60,
child: Text(
'Name...',
overflow: TextOverflow.ellipsis,
maxLines: 1,
style: TextStyle(
fontSize: 20,
color: Colors.white
),
),
),
),
Positioned(
bottom: 63,
left: 110,
child: Container(
width: MediaQuery.of(context).size.width -110 -60,
child: Text(
'description...',
overflow: TextOverflow.ellipsis,
maxLines: 1,
style: TextStyle(
fontSize: 14,
color: Colors.white70
),
),
),
),
Positioned(
bottom: 5,
left: 110,
child: Container(
width: MediaQuery.of(context).size.width-110,
child: Row(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
],
),
),
),
],
),
),
),
Hope these Images help explain my problem:
The flexiblespace looks as follows:Image 1
but once you scroll down, the flexible space fades away as seen in this picture:Image 2
I don't want to flexiblespace to fade away.

Answer 1

You've propably found the answer allready but I thought if someone like me encounter your question this might be a the answer you are looking for.
FlexibleSpaceBar include fade out animation and only way to exclude it is to write your own LayoutBuilder that will handle the collapse.
Here is a code example how you can create the custom flexibleSpace Widget with LayoutBuilder.
NestedScrollView(
headerSliverBuilder: (context, innerBoxIsScrolled) {
return [
SliverAppBar(
titleSpacing: 0,
pinned: false,
backgroundColor: Colors.transparent,
automaticallyImplyLeading: false,
elevation: 0.0,
actions: [
IconButton(
splashRadius: 20,
icon: Icon(
FontAwesomeIcons.cog,
color: Colors.grey[200],
),
onPressed: () {
},
),
],
toolbarHeight: kToolbarHeight,
expandedHeight: maxExtent,
flexibleSpace: LayoutBuilder(
builder: (context, constraints) {
double currentExtent = constraints.maxHeight;
final double deltaExtent = maxExtent - minExtent;
// 0.0 -> Expanded
// 1.0 -> Collapsed to toolbar
final double t =
(1.0 - (currentExtent - minExtent) / deltaExtent)
.clamp(0.0, 1.0) as double;
return Stack(
fit: StackFit.loose,
overflow: Overflow.clip,
children: [
Positioned(
top: _getCollapsePadding(t),
left: 0.0,
right: 0.0,
height: maxExtent,
child: Wrap(
crossAxisAlignment: WrapCrossAlignment.start,
children: [
//Insert Widgets add to your flexible space
],
),
),
],
);
},
),
),
];
},
body: Container()
),
double get maxExtent => 300;
double get minExtent => kToolbarHeight;
double _getCollapsePadding(double t) {
final double deltaExtent = maxExtent - minExtent;
return -Tween<double>(begin: 0.0, end: deltaExtent / 4).transform(t);
}