Prevent content from scrolling beneath SliverAppBar - user-interface

Question

I have a Sliver layout with a SliverAppBar on the top that collapses when scrolling down.
The problem is the following:
The content of my Sliver layout scrolls under the SliverAppBar: (undesired)
Instead I want to forbid scrolling further as soon as my SliverAppBar is collapsed.
This should be the maximum state you could scroll down:
Code:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
var scrollController = ScrollController();
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Home());
}
}
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: DefaultTabController(
length: 2,
child: NestedScrollView(
headerSliverBuilder:
(BuildContext context, bool innerBoxIsScrolled) {
return [
SliverAppBar(
expandedHeight: 200.0,
floating: false,
pinned: true,
flexibleSpace: FlexibleSpaceBar(
centerTitle: true,
title: Text("Collapsing Toolbar",
style: TextStyle(
color: Colors.white,
fontSize: 16.0,
)),
background: Image.network(
"https://images.pexels.com/photos/396547/pexels-photo-396547.jpeg?auto=compress&cs=tinysrgb&h=350",
fit: BoxFit.cover,
)),
),
SliverPadding(
padding: new EdgeInsets.all(16.0),
sliver: new SliverList(
delegate: new SliverChildListDelegate([
TabBar(
labelColor: Colors.black87,
unselectedLabelColor: Colors.grey,
tabs: [
new Tab(icon: new Icon(Icons.info), text: "Tab 1"),
new Tab(
icon: new Icon(Icons.lightbulb_outline),
text: "Tab 2"),
],
),
]),
),
),
];
},
body: Center(
child: Text("Sample text"),
),
),
));
}
}

Answer 1

You need SliverPersistentHeader and _SliverAppBarDelegate see full code below
You can copy paste run full code
detail please reference this https://medium.com/#diegoveloper/flutter-collapsing-toolbar-sliver-app-bar-14b858e87abe
code snippet
SliverPersistentHeader(
delegate: _SliverAppBarDelegate(
TabBar(
labelColor: Colors.black87,
unselectedLabelColor: Colors.grey,
tabs: [
Tab(icon: Icon(Icons.info), text: "Tab 1"),
Tab(icon: Icon(Icons.lightbulb_outline), text: "Tab 2"),
],
),
),
pinned: true,
),
working demo
full code
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
var scrollController = ScrollController();
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Home());
}
}
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: DefaultTabController(
length: 2,
child: NestedScrollView(
headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
return [
SliverAppBar(
expandedHeight: 200.0,
floating: false,
pinned: true,
snap: false,
flexibleSpace: FlexibleSpaceBar(
centerTitle: true,
title: Text("Collapsing Toolbar",
style: TextStyle(
color: Colors.white,
fontSize: 16.0,
)),
background: Image.network(
"https://images.pexels.com/photos/396547/pexels-photo-396547.jpeg?auto=compress&cs=tinysrgb&h=350",
fit: BoxFit.cover,
)),
),
SliverPersistentHeader(
delegate: _SliverAppBarDelegate(
TabBar(
labelColor: Colors.black87,
unselectedLabelColor: Colors.grey,
tabs: [
Tab(icon: Icon(Icons.info), text: "Tab 1"),
Tab(icon: Icon(Icons.lightbulb_outline), text: "Tab 2"),
],
),
),
pinned: true,
),
];
},
body: Center(
child: Text("Sample text"),
),
),
));
}
}
class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
_SliverAppBarDelegate(this._tabBar);
final TabBar _tabBar;
#override
double get minExtent => _tabBar.preferredSize.height;
#override
double get maxExtent => _tabBar.preferredSize.height;
#override
Widget build(
BuildContext context, double shrinkOffset, bool overlapsContent) {
return new Container(
child: _tabBar,
);
}
#override
bool shouldRebuild(_SliverAppBarDelegate oldDelegate) {
return false;
}
}