Unexpected behavior CustomScrollView with a short list, list jumps up and down with material 3 #118145
Description
Hi,
I found a unexpected behavior with CustomScrollView and material 3 when the list is very short (shorter than the viewport). If the view is overscrolled, the list starts to stretch as expected with M3. However if the direction is changed the opposite way even slightly, the view jumps back. This feels strange and unnatural, especially in combination with NestedScrollView.
Steps to Reproduce
- Scroll down and up (fling up and down), do not end the scroll.
- The list starts to jump up and down
Expected results:
I expect the same behavior with a list longer than the viewport. If the direction of the overscroll (short list) is the opposite of the initial overscroll then the stretch should be gradually disappear and not jump.
Actual results:
The list starts to jump up and down.
Code sample
import 'package:flutter/material.dart';
void main() => runApp(const AppBarApp());
class AppBarApp extends StatelessWidget {
const AppBarApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(useMaterial3: true),
home: const AppBarExample(),
);
}
}
class AppBarExample extends StatelessWidget {
const AppBarExample({super.key});
@override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
top: false,
bottom: false,
child: CustomScrollView(
slivers: <Widget>[
SliverPadding(
padding: const EdgeInsets.all(8.0),
sliver: SliverFixedExtentList(
itemExtent: 48.0,
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return ListTile(
title: Text('Item $index'),
);
},
childCount: 2,
),
),
),
],
)));
}
}
Logs
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.3.10, on openSUSE Tumbleweed 6.1.2-1-default, locale en_US.UTF-8)
[✓] Android toolchain - develop for Android devices (Android SDK version 32.1.0-rc1)
[✓] Chrome - develop for the web
[✓] Linux toolchain - develop for Linux desktop
[✓] Android Studio (version 2021.2)
[✓] VS Code (version 1.68.1)
[✓] Connected device (3 available)
[✓] HTTP Host Availability