[Material3] TabBar indicator stretch effect behaving weirdly with long tabs #149662
Description
Steps to reproduce
Create a TabBar with some text tabs in different lengths, even with some that are truncated. TabBar can be scrollable or not (but issue is more prominent with scrollable).
Expected results
The TabBar indicator should animate smoothly even with tabs with longer text, without expanding in opposite direction of slide animation.
Actual results
Indicator first expands to the left (if navigating to the right) while extending width of indicator. This expanding to the left does not seem to happen on shorter tabs and causes the animation to look glitchy. Also if swiping quickly between screens/tabs this becomes very jarring.
The new _applyStretchEffect method used in tabs.dart seems to be making the indicator behave weirdly when tabs with longer text is used. I tried setting final double stretchSize = rect.width; to half or a quarter, which seems to help with the expanding width animation a bit, but it's not perfect.
The best solution (for the project I'm working on at least) would be to have _applyStretchEffect as an optional parameter, as disabling it works best for the scrolling use case (according to me). But this might not go in line with the material spec?
Code sample
Code sample
import 'package:flutter/material.dart';
void main() {
runApp(const MainApp());
}
class MainApp extends StatelessWidget {
const MainApp({super.key});
@override
Widget build(BuildContext context) {
return const MaterialApp(
home: DefaultTabController(
length: 8,
child: SafeArea(
child: Scaffold(
appBar: TabBar(
isScrollable: true,
tabAlignment: TabAlignment.center,
tabs: [
Tab(text: 'Home'),
Tab(text: 'Search'),
Tab(text: 'Add'),
Tab(text: 'Favorite'),
Tab(text: 'The longest text...'),
Tab(text: 'Short'),
Tab(text: 'Longer text...'),
Tab(text: 'Profile'),
],
),
body: TabBarView(
children: <Widget>[
Center(child: Text("Page")),
Center(child: Text("Page")),
Center(child: Text("Page")),
Center(child: Text("Page")),
Center(child: Text("Page")),
Center(child: Text("Page")),
Center(child: Text("Page")),
Center(child: Text("Page")),
],
),
),
),
),
);
}
}
Screenshots or Video
Screenshots / Video demonstration
Example of jarring animation:
RPReplay_Final1717514051.MP4
RPReplay_Final1717514442.MP4
With final double stretchSize = rect.width / 2;
RPReplay_Final1717514092.MP4
Logs
Logs
[Paste your logs here]Flutter Doctor output
Doctor output
[✓] Flutter (Channel stable, 3.22.1, on macOS 14.5 23F79 darwin-arm64, locale en-SE)
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• Framework revision a14f74ff3a (13 days ago), 2024-05-22 11:08:21 -0500
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• Dart version 3.4.1
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