Flutter - material design 2 semi transparent appbar - flutter

Question

I want to get effect like this - when scrolled up, appbar is transparent with listview visible below it:
And scrolled down, only white color - first item below appbar:
My window layout:
return Container(
color: AppTheme.nearlyWhite,
child: SafeArea(
top: false,
bottom: false,
child: Scaffold(
backgroundColor: AppTheme.nearlyWhite,
body: Stack(
children: <Widget>[
DrawerUserController(
screenIndex: _drawerIndex,
drawerWidth: MediaQuery.of(context).size.width * 0.75,
animationController: (AnimationController animationController) => _sliderAnimationController = animationController,
onDrawerCall: (DrawerIndex drawerIndexdata) => _onDrawerCall(drawerIndexdata, _forceRefresh),
onDrawerTap:(DrawerIndex drawerIndexdata) => _onDrawerTap(drawerIndexdata),
screenView: Column(
children: <Widget>[
Padding(
padding: EdgeInsets.fromLTRB(8, MediaQuery.of(context).padding.top + 8, 8, 8),
child: _createAppBar(),
),
Expanded(
child:
Container(
color: Colors.white,
child: _screenView,
)
),
],
),
),
new FabDialer(_fabMiniMenuItemList, Colors.blue, new Icon(Icons.add))
],
),
),
),
);
}
_screenView is simple Listview().builder() and it shows InkWell widget for each item. My appbar is custom, defined like this:
_createAppBar() {
return SizedBox(
height: AppBar().preferredSize.height,
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 8, left: 8),
child: Container(
width: AppBar().preferredSize.height - 8,
height: AppBar().preferredSize.height - 8,
),
),
Expanded(
child: Center(
child: Padding(
padding: const EdgeInsets.only(top: 4),
child: Column(
children: <Widget>[
Text(
_menuSelected,
style: TextStyle(
fontSize: 22,
color: AppTheme.darkText,
fontWeight: FontWeight.w400,
),
),
Text(
globals.cityName,
style: TextStyle(
fontSize: 15,
color: AppTheme.darkerText,
fontWeight: FontWeight.w400,
),
),
],
),
),
),
),
Padding(
padding: const EdgeInsets.only(top: 8, right: 8),
child: Container(
width: AppBar().preferredSize.height - 8,
height: AppBar().preferredSize.height - 8,
color: Colors.white,
child: Material(
color: Colors.transparent,
child: InkWell(
borderRadius:
BorderRadius.circular(AppBar().preferredSize.height),
child: Icon(Icons.refresh, color: AppTheme.dark_grey,),
onTap: () => setState(() => _forceRefresh = true),
),
),
),
),
],
),
);
}
That's how it looks now with first list item visible:
So, almost there, but when scrolled down, appbar won't be transparent:
I tried to mess around with setting my appbar backround to color with transparency, without success. Also I need to get my widgets actually overlapped (ListView needs to overlap my appbar) and it generates error messages from Flutter.
Any ideas how to do that properly?

Answer 1

set extendBodyBehindAppBar: true in Scaffold widget. Then use Opacity widget like this,
import 'package:flutter/material.dart';
void main() {
runApp(MaterialApp(home: Home()));
}
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
#override
Widget build(BuildContext context) {
return Scaffold(
extendBodyBehindAppBar: true,
appBar: PreferredSize(
preferredSize: const Size.fromHeight(kToolbarHeight),
child: Opacity( //Wrap your `AppBar`
opacity: 0.8,
child: AppBar(
title: Text("Demo"),
),
),
),
body: ListView.builder(
itemCount: 30,
itemBuilder: (context, index) {
return ListTile(
title: Text("Tile: $index"),
);
},
),
);
}
}

Answer 2

#override
Widget build(BuildContext context) {
return Container(
child: Stack(
children:[
Container(
color:Colors.white,
padding:EdgeInsets.all(10),
child:ListView.builder(
itemCount:25+1,
//length + 1 is beacause to show 1st item at the beginning
shrinkWrap:true,
itemBuilder:(con,ind){
return ind==0 ?
Container(height:70)
:ListTile(
title:Text('Item $ind',
style:TextStyle(color:Colors.black,))
);
}
)
),
Container(
height:70,
color:Colors.transparent,
child:Card(
color:Colors.white.withAlpha(80),
child: Row(
children:[
Expanded(
flex:1,
child: IconButton(
icon:Icon(Icons.list,color:Colors.black,size:25),
onPressed:(){
//todo
}
),
),
Expanded(
flex:3,
child: Text('Title',
style:TextStyle(color:Colors.black,)),
),
Expanded(
flex:1,
child: IconButton(
icon:Icon(Icons.search,color:Colors.black,size:25),
onPressed:(){
//todo
}
),
),
Expanded(
flex:1,
child: IconButton(
icon:Icon(Icons.more_vert,color:Colors.black,size:25),
onPressed:(){
//todo
}
),
)
]
),
)
)
]
)
);
}