Description

TabBar sometimes jags when user interrupts ballistic scroll:

Almost at the end of the video, you can see a slight jagging. This happens because when user interrupts the ballistic scroll, ScrollEndNotification is called, but we don't update _controller.offset value as we do in ScrollUpdateNotification. This bug was found during another PR that I'd been working on: #60080 (comment)

cc. @chunhtai

void main() {
  runApp(Main());
}

class Main extends StatefulWidget {
  Main({Key key}) : super(key: key);

  @override
  _MainState createState() => _MainState();
}

class _MainState extends State<Main> with SingleTickerProviderStateMixin {
  final List<Tab> _tabs = <Tab>[
    Tab(text: 'Tab 1'),
    Tab(text: 'Tab 2'),
    Tab(text: 'Tab 3'),
  ];

  TabController _tabController;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(vsync: this, length: _tabs.length);
  }

  @override
  void dispose() {
    _tabController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          bottom: TabBar(
            controller: _tabController,
            tabs: _tabs,
            isScrollable: true,
            labelPadding: const EdgeInsets.symmetric(horizontal: 56),
          ),
        ),
        body: TabBarView(
          controller: _tabController,
          children: _tabs.map((Tab tab) {
            return Center(
              child: Text(tab.text),
            );
          }).toList(),
        ),
      ),
    );
  }
}

Related Issues

None

Tests

Added a test: TabController's animation value should be in sync with TabBarView's scroll value when user interrupts ballistic scroll

Checklist

Before you create this PR, confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I signed the CLA.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I updated/added relevant documentation (doc comments with ///).
• All existing and new tests are passing.
• The analyzer (flutter analyze --flutter-repo) does not report any problems on my PR.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Did any tests fail when you ran them? Please read Handling breaking changes.

• No, no existing tests failed, so this is not a breaking change.