Fix `ReorderableList` return-to-origin animation (refactoring approach) #172882

lukemmtt · 2025-07-28T21:05:50Z

This PR is an alternative to PR #172380, proposing a more substantial refactor to ReorderableList._dragEnd(...) to address the root cause, rather than adding more conditional logic.

Description

This PR fixes the proxy animation bug where dragging a ReorderableList item downward and then back to its original position causes it to animate to the wrong location (one position too low).

The Problem

When dragging a ReorderableList item downward and then back to its original position, the proxy widget briefly animates to the wrong location (one position too low) before snapping to the correct spot.

Reproduction: Drag any item down past at least one other item, then drag it back to where it started.

Root Cause

The bug stems from a fundamental mismatch: Flutter's onReorder callback receives an insertion index (calculated with the dragged item still in the list), but _dragEnd needs to animate to where the item will actually end up. This creates complex logic trying to work backwards from insertion point to final position, especially when dragging down where these indices differ by 1.

This complexity exists because of #24786: onReorder passes an insertion index rather than a final index.

Solution

Rather than adding another special case, this PR separates the concerns:

Extract index conversion: A new _insertionIndexToFinalIndex helper explicitly converts from insertion index to final position
Extract position calculation: A new _getProxyAnimationTarget method handles all position calculations using the final index
Simplify _dragEnd: Now just orchestrates by calling _getProxyAnimationTarget

This architectural change makes the correct behavior emerge naturally from the abstraction rather than from conditional patches.

Integration test running on patched code:

Before/After

Before: Mixed concerns with complex conditionals

void _dragEnd(_DragInfo item) {
  setState(() {
    if (_insertIndex == item.index) {
      _finalDropPosition = _itemOffsetAt(_insertIndex!);
    } else if (_reverse) {
      if (_insertIndex! >= _items.length) {
        _finalDropPosition = _itemOffsetAt(_items.length - 1) - _extentOffset(item.itemExtent, _scrollDirection);
      } else {
        _finalDropPosition = _itemOffsetAt(_insertIndex!) + _extentOffset(_itemExtentAt(_insertIndex!), _scrollDirection);
      }
    } else {
      if (_insertIndex! == 0) {
        _finalDropPosition = _itemOffsetAt(0) - _extentOffset(item.itemExtent, _scrollDirection);
      } else {
        final int atIndex = _insertIndex! - 1;
        _finalDropPosition = _itemOffsetAt(atIndex) + _extentOffset(_itemExtentAt(atIndex), _scrollDirection);
      }
    }
  });
  widget.onReorderEnd?.call(_insertIndex!);
}

After: Separated concerns with clear abstractions

// New helper: converts insertion index to final position
static int _insertionIndexToFinalIndex({
  required int insertionIndex,
  required int originalIndex,
}) {
  return insertionIndex > originalIndex ? insertionIndex - 1 : insertionIndex;
}

// New method: calculates position based on final index
Offset _getProxyAnimationTarget(int dragIndex, int insertIndex, double draggedItemExtent) {
  final int targetIndex = _insertionIndexToFinalIndex(
    insertionIndex: insertIndex,
    originalIndex: dragIndex,
  );
  
  if (targetIndex == dragIndex) {
    return _itemOffsetAt(dragIndex);
  }
  
  // Calculate gap position uniformly...
  // (contains the position calculation logic)
}

// Simplified _dragEnd
void _dragEnd(_DragInfo item) {
  setState(() {
    _finalDropPosition = _getProxyAnimationTarget(
      item.index, 
      _insertIndex!, 
      item.itemExtent
    );
  });
  widget.onReorderEnd?.call(_insertIndex!);
}

By separating index conversion from position calculation, the bug fix emerges naturally: we simply calculate where the item will actually be, rather than trying to patch the symptoms of working with the wrong index type.

Fixes #88331
Fixes #90856

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.

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flutter-dashboard · 2025-07-28T21:05:53Z

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

Revises proxy target calculation to convert to finalDropIndex-based coordinates before conditional logic, substantially clarifying the code and inherently resolving edge cases that previously required special-case fixes. Fixes flutter#88331 Fixes flutter#90856

Tests when dragging an item back 90% toward its original position, ensuring the proxy animates in the correct direction. Complements existing overshoot tests that test dragging back 110%.

Piinks · 2025-08-06T22:41:04Z

Self-ping to return to and compare notes over simplifying this logic. :)

@frankpape

_**Note:** Alongside this PR, I've also prepared [another PR](#172882) with an alternative solution involving a more substantial refactor that addresses the root cause, rather than adding more conditional logic._ ## Description This PR fixes the proxy animation bug where dragging a `ReorderableList` item downward and then back to its original position causes it to animate to the wrong location (one position too low). ## The Problem When dragging a `ReorderableList` item downward and then back to its original position, the proxy widget briefly animates to the wrong location (one position too low) before snapping to the correct spot. **Reproduction**: Drag any item down past at least one other item, then drag it back to where it started. <p align="center"> <img src="https://github.com/user-attachments/assets/d0931dff-5600-441c-8536-2c61789767d0" alt="demo2" width="250"> </p> ## Root Cause This bug is specific to dragging an item down and then bringing it back up to nearly (but not 100% of the way ) to its original position: 1. When the item approaches its original position **from below**, `_insertIndex` becomes `item.index + 1` - This happens because Flutter's `ReorderableList` calculates `_insertIndex` with the dragged item still present in the list (see #24786) 2. The proxy _should_ animate to the item's original position at `item.index` - _But the proxy actually animates one position too low._ - This happens because `_dragEnd` incorrectly calculates `_finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(...)` - The `_extentOffset(...)` addition, designed for items dropping _between other items_, shifts the position down by one item's height - The correct calculation for "returning home from below" should be just `_itemOffsetAt(_insertIndex! - 1)` Note that this only occurs when returning from below (`_insertIndex > item.index`). Dragging upward (in a vertical list for example) or doesn't trigger this bug. ## Existing Implementation The existing `_dragEnd` method in `reorderable_list.dart`: ```dart void _dragEnd(_DragInfo item) { setState(() { if (_insertIndex == item.index) { _finalDropPosition = _itemOffsetAt(_insertIndex!); } else if (_reverse) { if (_insertIndex! >= _items.length) { _finalDropPosition = _itemOffsetAt(_items.length - 1) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex!) + _extentOffset(_itemExtentAt(_insertIndex!), _scrollDirection); } } else { if (_insertIndex! == 0) { _finalDropPosition = _itemOffsetAt(0) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(_itemExtentAt(_insertIndex! - 1), _scrollDirection); } } }); } ``` When returning from below, the code falls through to the final else block, which incorrectly adds `_extentOffset`. ## Fix Detect when `_insertIndex - item.index == 1` (indicating a return to original position from below) and animate to the correct position. ```dart if (_insertIndex! - item.index == 1) { // Drop at the original position when item returns from below _finalDropPosition = _itemOffsetAt(_insertIndex! - 1); } ``` This fix was proposed by @frankpape in #90856 (comment); I've merely validated and researched the background of why the fix works, and supported it with tests. **_Demo of the fixed implementation:_** <p align="center"> <img src="https://github.com/user-attachments/assets/a53e8920-ebca-4326-abe9-3b43b34419e5" alt="fixed" width="250"> </p> Fixes #88331 Fixes #90856 Fixes #150843 ## A note about a previous PR: While investigating this issue, I found a PR addressing what seemed to be [the same exact issue](#150843): PR #151026; it turns out that that PR solved a _portion_ of the edge case: the case where an item is dragged down and back and slightly **overshoots** its original position when being dragged back & dropped—but that PR did not account for the presence of this bug when the dragged item slightly **undershoots** its original position on the return drag. This new PR effectively addresses the 'undershooting' case. With this, I've added a new pair of regression tests that are identical to the [previous PR's tests](https://github.com/flutter/flutter/blob/master/packages/flutter/test/widgets/reorderable_list_test.dart#L734), except for the fact that they simulate an undershoot on the return trip (90% of the way back instead of 110% like the original tests). This definitively captures the issue, failing in the master branch and passing in this PR's branch. Here is the specific case resolved by the [**old** PR](#151026): <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/b0ddc745-6e9e-4f12-97da-454e2e76b06d" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/03e181fa-f43b-4405-b0c0-16d3465ad990" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Here is the additional case resolved by **this** PR: <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/9b4bb591-aa2f-4cf0-88b8-a3ec32b0f0ac" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/31646e9c-78f4-4252-921f-53583193868f" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Two final observations worth noting: - The fix proposed in this PR seems to **supersede** the previous PR's solution; it addresses both cases (overshooting and undershooting) even in my tests with the [original PR's changes ](https://github.com/flutter/flutter/pull/151026/files#diff-23a4bb073009d89f09084bdf5f85232de135b8f11be625e6312bb85900a90e67) reverted. Probably best to keep the old PR's code anyway to be conservative, but noteworthy. - I also found it notable that neither this PR nor the older PR fix any issue with "reversed lists", which, in my tests, are simply not subject to this edge case as we've defined it. The regression tests added for the reverse case are thus purely precautionary. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [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 [Data Driven Fixes] where supported. - [x] All existing and new tests are passing.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

@frankpape

…172380) _**Note:** Alongside this PR, I've also prepared [another PR](flutter#172882) with an alternative solution involving a more substantial refactor that addresses the root cause, rather than adding more conditional logic._ ## Description This PR fixes the proxy animation bug where dragging a `ReorderableList` item downward and then back to its original position causes it to animate to the wrong location (one position too low). ## The Problem When dragging a `ReorderableList` item downward and then back to its original position, the proxy widget briefly animates to the wrong location (one position too low) before snapping to the correct spot. **Reproduction**: Drag any item down past at least one other item, then drag it back to where it started. <p align="center"> <img src="https://github.com/user-attachments/assets/d0931dff-5600-441c-8536-2c61789767d0" alt="demo2" width="250"> </p> ## Root Cause This bug is specific to dragging an item down and then bringing it back up to nearly (but not 100% of the way ) to its original position: 1. When the item approaches its original position **from below**, `_insertIndex` becomes `item.index + 1` - This happens because Flutter's `ReorderableList` calculates `_insertIndex` with the dragged item still present in the list (see flutter#24786) 2. The proxy _should_ animate to the item's original position at `item.index` - _But the proxy actually animates one position too low._ - This happens because `_dragEnd` incorrectly calculates `_finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(...)` - The `_extentOffset(...)` addition, designed for items dropping _between other items_, shifts the position down by one item's height - The correct calculation for "returning home from below" should be just `_itemOffsetAt(_insertIndex! - 1)` Note that this only occurs when returning from below (`_insertIndex > item.index`). Dragging upward (in a vertical list for example) or doesn't trigger this bug. ## Existing Implementation The existing `_dragEnd` method in `reorderable_list.dart`: ```dart void _dragEnd(_DragInfo item) { setState(() { if (_insertIndex == item.index) { _finalDropPosition = _itemOffsetAt(_insertIndex!); } else if (_reverse) { if (_insertIndex! >= _items.length) { _finalDropPosition = _itemOffsetAt(_items.length - 1) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex!) + _extentOffset(_itemExtentAt(_insertIndex!), _scrollDirection); } } else { if (_insertIndex! == 0) { _finalDropPosition = _itemOffsetAt(0) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(_itemExtentAt(_insertIndex! - 1), _scrollDirection); } } }); } ``` When returning from below, the code falls through to the final else block, which incorrectly adds `_extentOffset`. ## Fix Detect when `_insertIndex - item.index == 1` (indicating a return to original position from below) and animate to the correct position. ```dart if (_insertIndex! - item.index == 1) { // Drop at the original position when item returns from below _finalDropPosition = _itemOffsetAt(_insertIndex! - 1); } ``` This fix was proposed by @frankpape in flutter#90856 (comment); I've merely validated and researched the background of why the fix works, and supported it with tests. **_Demo of the fixed implementation:_** <p align="center"> <img src="https://github.com/user-attachments/assets/a53e8920-ebca-4326-abe9-3b43b34419e5" alt="fixed" width="250"> </p> Fixes flutter#88331 Fixes flutter#90856 Fixes flutter#150843 ## A note about a previous PR: While investigating this issue, I found a PR addressing what seemed to be [the same exact issue](flutter#150843): PR flutter#151026; it turns out that that PR solved a _portion_ of the edge case: the case where an item is dragged down and back and slightly **overshoots** its original position when being dragged back & dropped—but that PR did not account for the presence of this bug when the dragged item slightly **undershoots** its original position on the return drag. This new PR effectively addresses the 'undershooting' case. With this, I've added a new pair of regression tests that are identical to the [previous PR's tests](https://github.com/flutter/flutter/blob/master/packages/flutter/test/widgets/reorderable_list_test.dart#L734), except for the fact that they simulate an undershoot on the return trip (90% of the way back instead of 110% like the original tests). This definitively captures the issue, failing in the master branch and passing in this PR's branch. Here is the specific case resolved by the [**old** PR](flutter#151026): <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/b0ddc745-6e9e-4f12-97da-454e2e76b06d" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/03e181fa-f43b-4405-b0c0-16d3465ad990" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Here is the additional case resolved by **this** PR: <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/9b4bb591-aa2f-4cf0-88b8-a3ec32b0f0ac" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/31646e9c-78f4-4252-921f-53583193868f" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Two final observations worth noting: - The fix proposed in this PR seems to **supersede** the previous PR's solution; it addresses both cases (overshooting and undershooting) even in my tests with the [original PR's changes ](https://github.com/flutter/flutter/pull/151026/files#diff-23a4bb073009d89f09084bdf5f85232de135b8f11be625e6312bb85900a90e67) reverted. Probably best to keep the old PR's code anyway to be conservative, but noteworthy. - I also found it notable that neither this PR nor the older PR fix any issue with "reversed lists", which, in my tests, are simply not subject to this edge case as we've defined it. The regression tests added for the reverse case are thus purely precautionary. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [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 [Data Driven Fixes] where supported. - [x] All existing and new tests are passing.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

@frankpape

…172380) _**Note:** Alongside this PR, I've also prepared [another PR](flutter#172882) with an alternative solution involving a more substantial refactor that addresses the root cause, rather than adding more conditional logic._ ## Description This PR fixes the proxy animation bug where dragging a `ReorderableList` item downward and then back to its original position causes it to animate to the wrong location (one position too low). ## The Problem When dragging a `ReorderableList` item downward and then back to its original position, the proxy widget briefly animates to the wrong location (one position too low) before snapping to the correct spot. **Reproduction**: Drag any item down past at least one other item, then drag it back to where it started. <p align="center"> <img src="https://github.com/user-attachments/assets/d0931dff-5600-441c-8536-2c61789767d0" alt="demo2" width="250"> </p> ## Root Cause This bug is specific to dragging an item down and then bringing it back up to nearly (but not 100% of the way ) to its original position: 1. When the item approaches its original position **from below**, `_insertIndex` becomes `item.index + 1` - This happens because Flutter's `ReorderableList` calculates `_insertIndex` with the dragged item still present in the list (see flutter#24786) 2. The proxy _should_ animate to the item's original position at `item.index` - _But the proxy actually animates one position too low._ - This happens because `_dragEnd` incorrectly calculates `_finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(...)` - The `_extentOffset(...)` addition, designed for items dropping _between other items_, shifts the position down by one item's height - The correct calculation for "returning home from below" should be just `_itemOffsetAt(_insertIndex! - 1)` Note that this only occurs when returning from below (`_insertIndex > item.index`). Dragging upward (in a vertical list for example) or doesn't trigger this bug. ## Existing Implementation The existing `_dragEnd` method in `reorderable_list.dart`: ```dart void _dragEnd(_DragInfo item) { setState(() { if (_insertIndex == item.index) { _finalDropPosition = _itemOffsetAt(_insertIndex!); } else if (_reverse) { if (_insertIndex! >= _items.length) { _finalDropPosition = _itemOffsetAt(_items.length - 1) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex!) + _extentOffset(_itemExtentAt(_insertIndex!), _scrollDirection); } } else { if (_insertIndex! == 0) { _finalDropPosition = _itemOffsetAt(0) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(_itemExtentAt(_insertIndex! - 1), _scrollDirection); } } }); } ``` When returning from below, the code falls through to the final else block, which incorrectly adds `_extentOffset`. ## Fix Detect when `_insertIndex - item.index == 1` (indicating a return to original position from below) and animate to the correct position. ```dart if (_insertIndex! - item.index == 1) { // Drop at the original position when item returns from below _finalDropPosition = _itemOffsetAt(_insertIndex! - 1); } ``` This fix was proposed by @frankpape in flutter#90856 (comment); I've merely validated and researched the background of why the fix works, and supported it with tests. **_Demo of the fixed implementation:_** <p align="center"> <img src="https://github.com/user-attachments/assets/a53e8920-ebca-4326-abe9-3b43b34419e5" alt="fixed" width="250"> </p> Fixes flutter#88331 Fixes flutter#90856 Fixes flutter#150843 ## A note about a previous PR: While investigating this issue, I found a PR addressing what seemed to be [the same exact issue](flutter#150843): PR flutter#151026; it turns out that that PR solved a _portion_ of the edge case: the case where an item is dragged down and back and slightly **overshoots** its original position when being dragged back & dropped—but that PR did not account for the presence of this bug when the dragged item slightly **undershoots** its original position on the return drag. This new PR effectively addresses the 'undershooting' case. With this, I've added a new pair of regression tests that are identical to the [previous PR's tests](https://github.com/flutter/flutter/blob/master/packages/flutter/test/widgets/reorderable_list_test.dart#L734), except for the fact that they simulate an undershoot on the return trip (90% of the way back instead of 110% like the original tests). This definitively captures the issue, failing in the master branch and passing in this PR's branch. Here is the specific case resolved by the [**old** PR](flutter#151026): <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/b0ddc745-6e9e-4f12-97da-454e2e76b06d" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/03e181fa-f43b-4405-b0c0-16d3465ad990" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Here is the additional case resolved by **this** PR: <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/9b4bb591-aa2f-4cf0-88b8-a3ec32b0f0ac" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/31646e9c-78f4-4252-921f-53583193868f" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Two final observations worth noting: - The fix proposed in this PR seems to **supersede** the previous PR's solution; it addresses both cases (overshooting and undershooting) even in my tests with the [original PR's changes ](https://github.com/flutter/flutter/pull/151026/files#diff-23a4bb073009d89f09084bdf5f85232de135b8f11be625e6312bb85900a90e67) reverted. Probably best to keep the old PR's code anyway to be conservative, but noteworthy. - I also found it notable that neither this PR nor the older PR fix any issue with "reversed lists", which, in my tests, are simply not subject to this edge case as we've defined it. The regression tests added for the reverse case are thus purely precautionary. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [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 [Data Driven Fixes] where supported. - [x] All existing and new tests are passing.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

@frankpape

…172380) _**Note:** Alongside this PR, I've also prepared [another PR](flutter#172882) with an alternative solution involving a more substantial refactor that addresses the root cause, rather than adding more conditional logic._ ## Description This PR fixes the proxy animation bug where dragging a `ReorderableList` item downward and then back to its original position causes it to animate to the wrong location (one position too low). ## The Problem When dragging a `ReorderableList` item downward and then back to its original position, the proxy widget briefly animates to the wrong location (one position too low) before snapping to the correct spot. **Reproduction**: Drag any item down past at least one other item, then drag it back to where it started. <p align="center"> <img src="https://github.com/user-attachments/assets/d0931dff-5600-441c-8536-2c61789767d0" alt="demo2" width="250"> </p> ## Root Cause This bug is specific to dragging an item down and then bringing it back up to nearly (but not 100% of the way ) to its original position: 1. When the item approaches its original position **from below**, `_insertIndex` becomes `item.index + 1` - This happens because Flutter's `ReorderableList` calculates `_insertIndex` with the dragged item still present in the list (see flutter#24786) 2. The proxy _should_ animate to the item's original position at `item.index` - _But the proxy actually animates one position too low._ - This happens because `_dragEnd` incorrectly calculates `_finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(...)` - The `_extentOffset(...)` addition, designed for items dropping _between other items_, shifts the position down by one item's height - The correct calculation for "returning home from below" should be just `_itemOffsetAt(_insertIndex! - 1)` Note that this only occurs when returning from below (`_insertIndex > item.index`). Dragging upward (in a vertical list for example) or doesn't trigger this bug. ## Existing Implementation The existing `_dragEnd` method in `reorderable_list.dart`: ```dart void _dragEnd(_DragInfo item) { setState(() { if (_insertIndex == item.index) { _finalDropPosition = _itemOffsetAt(_insertIndex!); } else if (_reverse) { if (_insertIndex! >= _items.length) { _finalDropPosition = _itemOffsetAt(_items.length - 1) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex!) + _extentOffset(_itemExtentAt(_insertIndex!), _scrollDirection); } } else { if (_insertIndex! == 0) { _finalDropPosition = _itemOffsetAt(0) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(_itemExtentAt(_insertIndex! - 1), _scrollDirection); } } }); } ``` When returning from below, the code falls through to the final else block, which incorrectly adds `_extentOffset`. ## Fix Detect when `_insertIndex - item.index == 1` (indicating a return to original position from below) and animate to the correct position. ```dart if (_insertIndex! - item.index == 1) { // Drop at the original position when item returns from below _finalDropPosition = _itemOffsetAt(_insertIndex! - 1); } ``` This fix was proposed by @frankpape in flutter#90856 (comment); I've merely validated and researched the background of why the fix works, and supported it with tests. **_Demo of the fixed implementation:_** <p align="center"> <img src="https://github.com/user-attachments/assets/a53e8920-ebca-4326-abe9-3b43b34419e5" alt="fixed" width="250"> </p> Fixes flutter#88331 Fixes flutter#90856 Fixes flutter#150843 ## A note about a previous PR: While investigating this issue, I found a PR addressing what seemed to be [the same exact issue](flutter#150843): PR flutter#151026; it turns out that that PR solved a _portion_ of the edge case: the case where an item is dragged down and back and slightly **overshoots** its original position when being dragged back & dropped—but that PR did not account for the presence of this bug when the dragged item slightly **undershoots** its original position on the return drag. This new PR effectively addresses the 'undershooting' case. With this, I've added a new pair of regression tests that are identical to the [previous PR's tests](https://github.com/flutter/flutter/blob/master/packages/flutter/test/widgets/reorderable_list_test.dart#L734), except for the fact that they simulate an undershoot on the return trip (90% of the way back instead of 110% like the original tests). This definitively captures the issue, failing in the master branch and passing in this PR's branch. Here is the specific case resolved by the [**old** PR](flutter#151026): <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/b0ddc745-6e9e-4f12-97da-454e2e76b06d" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/03e181fa-f43b-4405-b0c0-16d3465ad990" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Here is the additional case resolved by **this** PR: <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/9b4bb591-aa2f-4cf0-88b8-a3ec32b0f0ac" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/31646e9c-78f4-4252-921f-53583193868f" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Two final observations worth noting: - The fix proposed in this PR seems to **supersede** the previous PR's solution; it addresses both cases (overshooting and undershooting) even in my tests with the [original PR's changes ](https://github.com/flutter/flutter/pull/151026/files#diff-23a4bb073009d89f09084bdf5f85232de135b8f11be625e6312bb85900a90e67) reverted. Probably best to keep the old PR's code anyway to be conservative, but noteworthy. - I also found it notable that neither this PR nor the older PR fix any issue with "reversed lists", which, in my tests, are simply not subject to this edge case as we've defined it. The regression tests added for the reverse case are thus purely precautionary. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [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 [Data Driven Fixes] where supported. - [x] All existing and new tests are passing.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

@frankpape

…172380) _**Note:** Alongside this PR, I've also prepared [another PR](flutter#172882) with an alternative solution involving a more substantial refactor that addresses the root cause, rather than adding more conditional logic._ ## Description This PR fixes the proxy animation bug where dragging a `ReorderableList` item downward and then back to its original position causes it to animate to the wrong location (one position too low). ## The Problem When dragging a `ReorderableList` item downward and then back to its original position, the proxy widget briefly animates to the wrong location (one position too low) before snapping to the correct spot. **Reproduction**: Drag any item down past at least one other item, then drag it back to where it started. <p align="center"> <img src="https://github.com/user-attachments/assets/d0931dff-5600-441c-8536-2c61789767d0" alt="demo2" width="250"> </p> ## Root Cause This bug is specific to dragging an item down and then bringing it back up to nearly (but not 100% of the way ) to its original position: 1. When the item approaches its original position **from below**, `_insertIndex` becomes `item.index + 1` - This happens because Flutter's `ReorderableList` calculates `_insertIndex` with the dragged item still present in the list (see flutter#24786) 2. The proxy _should_ animate to the item's original position at `item.index` - _But the proxy actually animates one position too low._ - This happens because `_dragEnd` incorrectly calculates `_finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(...)` - The `_extentOffset(...)` addition, designed for items dropping _between other items_, shifts the position down by one item's height - The correct calculation for "returning home from below" should be just `_itemOffsetAt(_insertIndex! - 1)` Note that this only occurs when returning from below (`_insertIndex > item.index`). Dragging upward (in a vertical list for example) or doesn't trigger this bug. ## Existing Implementation The existing `_dragEnd` method in `reorderable_list.dart`: ```dart void _dragEnd(_DragInfo item) { setState(() { if (_insertIndex == item.index) { _finalDropPosition = _itemOffsetAt(_insertIndex!); } else if (_reverse) { if (_insertIndex! >= _items.length) { _finalDropPosition = _itemOffsetAt(_items.length - 1) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex!) + _extentOffset(_itemExtentAt(_insertIndex!), _scrollDirection); } } else { if (_insertIndex! == 0) { _finalDropPosition = _itemOffsetAt(0) - _extentOffset(item.itemExtent, _scrollDirection); } else { _finalDropPosition = _itemOffsetAt(_insertIndex! - 1) + _extentOffset(_itemExtentAt(_insertIndex! - 1), _scrollDirection); } } }); } ``` When returning from below, the code falls through to the final else block, which incorrectly adds `_extentOffset`. ## Fix Detect when `_insertIndex - item.index == 1` (indicating a return to original position from below) and animate to the correct position. ```dart if (_insertIndex! - item.index == 1) { // Drop at the original position when item returns from below _finalDropPosition = _itemOffsetAt(_insertIndex! - 1); } ``` This fix was proposed by @frankpape in flutter#90856 (comment); I've merely validated and researched the background of why the fix works, and supported it with tests. **_Demo of the fixed implementation:_** <p align="center"> <img src="https://github.com/user-attachments/assets/a53e8920-ebca-4326-abe9-3b43b34419e5" alt="fixed" width="250"> </p> Fixes flutter#88331 Fixes flutter#90856 Fixes flutter#150843 ## A note about a previous PR: While investigating this issue, I found a PR addressing what seemed to be [the same exact issue](flutter#150843): PR flutter#151026; it turns out that that PR solved a _portion_ of the edge case: the case where an item is dragged down and back and slightly **overshoots** its original position when being dragged back & dropped—but that PR did not account for the presence of this bug when the dragged item slightly **undershoots** its original position on the return drag. This new PR effectively addresses the 'undershooting' case. With this, I've added a new pair of regression tests that are identical to the [previous PR's tests](https://github.com/flutter/flutter/blob/master/packages/flutter/test/widgets/reorderable_list_test.dart#L734), except for the fact that they simulate an undershoot on the return trip (90% of the way back instead of 110% like the original tests). This definitively captures the issue, failing in the master branch and passing in this PR's branch. Here is the specific case resolved by the [**old** PR](flutter#151026): <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/b0ddc745-6e9e-4f12-97da-454e2e76b06d" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/03e181fa-f43b-4405-b0c0-16d3465ad990" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Here is the additional case resolved by **this** PR: <table> <tr> <td align="center"> <img src="https://github.com/user-attachments/assets/9b4bb591-aa2f-4cf0-88b8-a3ec32b0f0ac" alt="Before" width="200"><br> <sub>Before</sub> </td> <td align="center"> <img src="https://github.com/user-attachments/assets/31646e9c-78f4-4252-921f-53583193868f" alt="After" width="200"><br> <sub>After</sub> </td> </tr> </table> Two final observations worth noting: - The fix proposed in this PR seems to **supersede** the previous PR's solution; it addresses both cases (overshooting and undershooting) even in my tests with the [original PR's changes ](https://github.com/flutter/flutter/pull/151026/files#diff-23a4bb073009d89f09084bdf5f85232de135b8f11be625e6312bb85900a90e67) reverted. Probably best to keep the old PR's code anyway to be conservative, but noteworthy. - I also found it notable that neither this PR nor the older PR fix any issue with "reversed lists", which, in my tests, are simply not subject to this edge case as we've defined it. The regression tests added for the reverse case are thus purely precautionary. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [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 [Data Driven Fixes] where supported. - [x] All existing and new tests are passing.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

github-actions bot added the framework flutter/packages/flutter repository. See also f: labels. label Jul 28, 2025

lukemmtt mentioned this pull request Jul 28, 2025

Fix ReorderableList proxy animation for partial drag-back #172380

Merged

9 tasks

lukemmtt changed the title ~~Fix ReorderableList return-to-origin animation via index abstraction~~ Fix ReorderableList return-to-origin animation (refactoring approach) Jul 28, 2025

lukemmtt force-pushed the fix-reorderable-proxy-abstraction branch 2 times, most recently from c8c2c2a to 6bb0730 Compare July 28, 2025 22:56

lukemmtt marked this pull request as draft July 28, 2025 23:16

lukemmtt force-pushed the fix-reorderable-proxy-abstraction branch 2 times, most recently from 0c54351 to cccddce Compare July 29, 2025 04:46

lukemmtt added 2 commits July 29, 2025 01:54

Add regression tests for SliverReorderableList undershoot drag animation

2907edd

Tests when dragging an item back 90% toward its original position, ensuring the proxy animates in the correct direction. Complements existing overshoot tests that test dragging back 110%.

lukemmtt force-pushed the fix-reorderable-proxy-abstraction branch from cccddce to 2907edd Compare July 29, 2025 05:54

lukemmtt mentioned this pull request Jul 29, 2025

ReorderableListView Weird Behaviour on reordering the second last child #90856

Closed

lukemmtt and others added 2 commits August 1, 2025 10:19

lint fixes

bf5b542

Merge branch 'master' into fix-reorderable-proxy-abstraction

c45609c

lukemmtt marked this pull request as ready for review August 6, 2025 22:39

lukemmtt closed this Aug 6, 2025

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Fix `ReorderableList` return-to-origin animation (refactoring approach) #172882

Fix `ReorderableList` return-to-origin animation (refactoring approach) #172882

lukemmtt commented Jul 28, 2025 •

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Piinks commented Aug 6, 2025

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Fix ReorderableList return-to-origin animation (refactoring approach) #172882

Fix ReorderableList return-to-origin animation (refactoring approach) #172882

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lukemmtt commented Jul 28, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Description

The Problem

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Solution

Before/After

Pre-launch Checklist

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flutter-dashboard bot commented Jul 28, 2025

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Piinks commented Aug 6, 2025

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Fix `ReorderableList` return-to-origin animation (refactoring approach) #172882

Fix `ReorderableList` return-to-origin animation (refactoring approach) #172882

lukemmtt commented Jul 28, 2025 •

edited

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