How to get shuch effect of AppBar title in Flutter? - flutter

Question

How I can get such effect of AppBar title, sample:
The big title "Coffee shop" disappears when page scrolls and appears in appBar. Thanks.

Answer 1

probably you need SliverAppBar
You can also check this tutorial
An example based on the article:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'App',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MainCollapsingToolbar());
}
}
class MainCollapsingToolbar extends StatefulWidget {
#override
_MainCollapsingToolbarState createState() => _MainCollapsingToolbarState();
}
class _MainCollapsingToolbarState extends State<MainCollapsingToolbar> {
ScrollController _scrollController = ScrollController();
double offset = 0.0;
#override
void initState() {
super.initState();
_scrollController.addListener(() {
setState(() {
offset = _scrollController.offset;
});
});
}
#override
void dispose() {
_scrollController.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: DefaultTabController(
length: 2,
child: NestedScrollView(
controller: _scrollController,
headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
return <Widget>[
SliverAppBar(
expandedHeight: 200.0,
floating: false,
pinned: true,
flexibleSpace: FlexibleSpaceBar(
centerTitle: (offset == 0) ? false : true,
title: Text("Collapsing Toolbar",
style: TextStyle(
color: Colors.white,
fontSize: 16.0,
)),
),
),
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;
}
}