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Reimplemented StretchingOverscrollIndicator with SpringSimulation. #173849

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Reimplemented StretchingOverscrollIndicator with SpringSimulation. #173849

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MTtankkeo
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Fixed an issue #169659

This PR improves the StretchingOverscrollIndicator to better match native Android behavior.

  • Previously, the stretch effect worked well only for slow dragging, and during fast flings it was absent or felt clipped.
  • Implemented a SpringSimulation-based animation that responds naturally to both slow drags and high-velocity flings.
  • The result closely resembles the native Android overscroll behavior while maintaining Flutter's performance characteristics.

This change ensures that momentum-based gestures produce a more natural and intuitive overscroll experience, especially for users accustomed to native Android scroll views.

Fling

3.mp4

Pull And Reduce

Also, a very similar animation is implemented when pulling as well.

3.mp4

Pre-launch Checklist

  • I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
  • I read the [Tree Hygiene] wiki page, which explains my responsibilities.
  • I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
  • I signed the [CLA].
  • I listed at least one issue that this PR fixes in the description above.
  • I updated/added relevant documentation (doc comments with ///).
  • I added new tests to check the change I am making, or this PR is [test-exempt].
  • I followed the [breaking change policy] and added [Data Driven Fixes] where supported.
  • All existing and new tests are passing.

@github-actions github-actions bot added framework flutter/packages/flutter repository. See also f: labels. f: scrolling Viewports, list views, slivers, etc. labels Aug 15, 2025
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Code Review

This pull request is a great improvement to the StretchingOverscrollIndicator, replacing the previous animation logic with a more physically realistic SpringSimulation. This results in a much more natural feel, especially for high-velocity flings, aligning it better with native Android behavior. The code is well-structured, and the addition of a regression test is appreciated.

I've found a critical issue related to animation controller lifecycle management that could lead to race conditions. I've also identified a couple of medium-severity issues related to code clarity and maintainability. Addressing these will make the implementation more robust and easier to understand.

Overall, this is a high-quality contribution.

@justinmc justinmc requested a review from dkwingsmt August 19, 2025 22:11
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@dkwingsmt dkwingsmt Awaiting requested review from dkwingsmt

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