commit c652b538194cc8dce5d826cc7a806908e43f9a9e
author Luke Memet <1598289+lukemmtt@users.noreply.github.com> Tue Nov 04 20:20:33 2025 -0400
committer GitHub <noreply@github.com> Wed Nov 05 00:20:33 2025 +0000
tree 987e4701c1bb0184f91aae4af2f129585c903f46
parent 3667ffd1821dacdf1e4ca647756ef05e4ca01cab

Fix `ReorderableList` items jumping when drag direction reverses mid-animation (#173241)

When rapidly dragging items in a ReorderableList before animations
complete, items would jump to their expected positions rather than
smoothly transitioning.

## Problem

<p align="center">
<img
src="https://github.com/user-attachments/assets/0efb250c-2960-4942-959f-59eccc20cefb"
alt="demo2" width="250">
</p>

The issue occurs when a reorder animation is interrupted by starting a
new drag operation. The interrupted animation would reset to the
starting position of the original animation rather than capturing the
current animated position, causing a visual jump.

## Solution

This PR fixes the issue by:
1. Storing the previous target offset before updating to a new target
2. When an animation is interrupted, calculating the actual current
position based on the animation's progress
3. Using this calculated position as the new starting point for the next
animation

<p align="center">
<img
src="https://github.com/user-attachments/assets/c24e4834-1c6b-41c1-8f44-17b4c79e0993"
alt="demo2" width="250">
</p>

This PR is part of a series of `ReorderableList` enhancements I've
developed for [TimeFinder](https://timefinder.app):
- #172740
- #172380
- #172739
- #172738

Fixes #173243

## Code Changes

```dart
// Before
_startOffset = offset;

// After  
final double currentAnimValue = Curves.easeInOut.transform(_offsetAnimation\!.value);
final Offset currentPosition = Offset.lerp(_startOffset, previousTarget, currentAnimValue)\!;
_startOffset = currentPosition;
```

This ensures smooth transitions without visual jumping, making rapid
reordering gestures feel more responsive and natural.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [migration
guide] as needed.
- [x] All existing and new tests are passing.
- [x] The analyzer (`flutter analyze --flutter-repo`) does not report
any problems on my PR.
- [x] I am willing to follow-up on review comments in a timely manner.

[Contributor Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[test-exempt]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[migration guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#create-a-migration-guide