How to detect first and second scroll in flutter - flutter

Question

i want to detect my first and second scroll in flutter .when first scroll performed first list hide and category tab must show then on second scroll the appbar should be hide ,following code what i tried and its an example of collapsing toolbar and below image is the result what i want. iam a nube in flutter please help and sorry for my bad english
import 'dart:math';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: CustomSliverAppbar(),
);
}
}
class CustomSliverAppbar extends StatefulWidget {
#override
_CustomSliverAppbarState createState() => _CustomSliverAppbarState();
}
class _CustomSliverAppbarState extends State<CustomSliverAppbar>
with SingleTickerProviderStateMixin {
TabController _tabController;
#override
void initState() {
_tabController = TabController(
initialIndex: 0,
length: 2,
vsync: this,
);
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: NestedScrollView(
floatHeaderSlivers: true,
headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
return <Widget>[
SliverAppBar(
title: Text(
"WhatsApp type sliver appbar",
),
centerTitle: true,
pinned: true,
floating: true,
bottom: TabBar(
indicatorColor: Colors.black,
labelPadding: const EdgeInsets.only(
bottom: 16,
),
controller: _tabController,
tabs: [
Text("TAB A"),
Text("TAB B"),
]),
),
];
},
body: TabBarView(
controller: _tabController,
children: [
TabA(),
const Center(
child: Text('Display Tab 2',
style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold)),
),
],
),
),
);
}
#override
void dispose() {
_tabController.dispose();
super.dispose();
}
}
class TabA extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scrollbar(
child: ListView.separated(
separatorBuilder: (context, child) => Divider(
height: 1,
),
padding: EdgeInsets.all(0.0),
itemCount: 30,
itemBuilder: (context, i) {
return Container(
height: 100,
import 'dart:math';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: CustomSliverAppbar(),
);
}
}
class CustomSliverAppbar extends StatefulWidget {
#override
_CustomSliverAppbarState createState() => _CustomSliverAppbarState();
}
class _CustomSliverAppbarState extends State<CustomSliverAppbar>
with SingleTickerProviderStateMixin {
TabController _tabController;
#override
void initState() {
_tabController = TabController(
initialIndex: 0,
length: 2,
vsync: this,
);
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: NestedScrollView(
floatHeaderSlivers: true,
headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
return <Widget>[
SliverAppBar(
title: Text(
"WhatsApp type sliver appbar",
),
centerTitle: true,
pinned: true,
floating: true,
bottom: TabBar(
indicatorColor: Colors.black,
labelPadding: const EdgeInsets.only(
bottom: 16,
),
controller: _tabController,
tabs: [
Text("TAB A"),
Text("TAB B"),
]),
),
];
},
body: TabBarView(
controller: _tabController,
children: [
TabA(),
const Center(
child: Text('Display Tab 2',
style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold)),
),
],
),
),
);
}
#override
void dispose() {
_tabController.dispose();
super.dispose();
}
}
class TabA extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scrollbar(
child: ListView.separated(
separatorBuilder: (context, child) => Divider(
height: 1,
),
padding: EdgeInsets.all(0.0),
itemCount: 30,
itemBuilder: (context, i) {
return Container(
height: 100,
width: double.infinity,
color: Colors.primaries[Random().nextInt(Colors.primaries.length)],
);
},
),
);
}
} width: double.infinity,
color: Colors.primaries[Random().nextInt(Colors.primaries.length)],
);
},
),
);
}
}