Fix: Flicker when reorderable list doesn't change its position #151026

rkishan516 · 2024-06-29T06:22:44Z

Fix: Flicker when no update in index of dragged item

This PR ensures that even if we move dragged item anywhere in list and comeback to initial position, we smoothly adjust to that position.

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.

flutter-dashboard · 2024-06-29T06:22:47Z

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact "@test-exemption-reviewer" in the #hackers channel in Chat (don't just cc them here, they won't see it! Use Discord!).

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.

goderbauer · 2024-07-02T22:04:44Z

@rkishan516 Thank you for the contribution. It looks like it is failing some checks. Can you please take a look? Also, as per the bot message above: Can you add a test for this so we never regress this in the future? Thank you.

rkishan516 · 2024-07-03T04:09:17Z

@goderbauer Sure, I will check failing checks and add tests.

rkishan516 · 2024-07-06T05:40:50Z

@goderbauer I have added regression test for this PR, but need some help with other failing test.

goderbauer · 2024-07-09T22:10:02Z

Here are some resources that may be of help: https://github.com/flutter/flutter/blob/master/docs/contributing/testing/Running-and-writing-tests.md

rkishan516 · 2024-07-19T13:51:32Z

@goderbauer I have fixed the tests, But I might have messed up in code quality. Can you please review ?

chunhtai · 2024-07-23T22:24:21Z

Hi @Piinks Can you take a look at this pr? feel free to reassign if not.

packages/flutter/lib/src/widgets/reorderable_list.dart

Piinks · 2024-08-28T17:31:42Z

packages/flutter/test/widgets/reorderable_list_test.dart

    expect(tester.getTopLeft(find.text('item 0')), const Offset(0, 500));
  });

+  testWidgets('SliverReorderableList - properly animates the drop at starting position', (WidgetTester tester) async {


Can you add a similar test where reverse: true?

@Piinks I have pushed the required test.

Piinks · 2024-08-28T17:32:02Z

packages/flutter/lib/src/widgets/reorderable_list.dart

    int newIndex = _insertIndex!;
    for (final _ReorderableItemState item in _items.values) {
-      if (item.index == _dragIndex! || !item.mounted) {
+      if ((_reverse && item.index == _dragIndex!) || !item.mounted) {


We should add a test in reverse as well to cover this case.

Piinks

@rkishan516 this looks just about ready to land, can you check the changes in the dropdown menu file? Maybe they were pulled in accidentally from a merge.

Piinks · 2024-09-11T17:50:58Z

packages/flutter/lib/src/material/dropdown_menu.dart

-  int? search(List<DropdownMenuEntry<T>> entries, TextEditingController textEditingController) {
-    final String searchText = textEditingController.value.text.toLowerCase();
+  int? search(List<DropdownMenuEntry<T>> entries) {
+    final String searchText = _localTextEditingController!.value.text.toLowerCase();


@rkishan516 should these changes be here? They appear unrelated.

Sorry, I don't know, How I messed it up today. I have fixed and pushed.

Piinks

LGTM, thank you!

QuncCccccc

LGTM with nits:) Thanks for the contribution!

QuncCccccc · 2024-09-11T21:43:23Z

packages/flutter/lib/src/widgets/reorderable_list.dart

      } else {
-        if (itemStart <= proxyItemStart && proxyItemStart <= itemMiddle) {
+        if (item.index == _dragIndex!) {
+          // If end of the proxy is in not in ending half of item


Typo?

Suggested change

// If end of the proxy is in not in ending half of item

// If end of the proxy is not in ending half of item,

QuncCccccc · 2024-09-11T21:48:35Z

packages/flutter/lib/src/widgets/reorderable_list.dart

-        if (itemStart <= proxyItemStart && proxyItemStart <= itemMiddle) {
+        if (item.index == _dragIndex!) {
+          // If end of the proxy is in not in ending half of item
+          // We don't process, because its drag item index


Suggested change

// We don't process, because its drag item index

// we don't process, because its drag item index.

This comment looks a little bit confusing, could you help double check? "because it's the original dragged item"?

@QuncCccccc I have pushed the required changes.

flutter/flutter#151026)

flutter/flutter@303f222...2d30fe4 2024-09-13 [email protected] Roll Packages from 91caa7a to 330581f (4 revisions) (flutter/flutter#155171) 2024-09-13 [email protected] Fix: Flicker when reorderable list doesn't change its position (flutter/flutter#151026) 2024-09-13 [email protected] Stop reading .packages from flutter_tools. (flutter/flutter#154912) 2024-09-13 [email protected] Roll Flutter Engine from 70109e3b40c0 to bef48e87f438 (1 revision) (flutter/flutter#155156) 2024-09-13 [email protected] Roll Flutter Engine from d917a15823f3 to 70109e3b40c0 (1 revision) (flutter/flutter#155151) 2024-09-13 [email protected] Roll Flutter Engine from 94696ed75dea to d917a15823f3 (1 revision) (flutter/flutter#155147) 2024-09-13 [email protected] Fix TextField content should be selected on desktop when gaining focus (flutter/flutter#154916) 2024-09-13 [email protected] Roll Flutter Engine from 04802b779045 to 94696ed75dea (1 revision) (flutter/flutter#155144) 2024-09-13 [email protected] Roll Flutter Engine from 3d8163f47919 to 04802b779045 (2 revisions) (flutter/flutter#155138) 2024-09-13 [email protected] Roll Flutter Engine from 4d5fea97e933 to 3d8163f47919 (1 revision) (flutter/flutter#155136) 2024-09-13 [email protected] Mark `_LayoutBuilderElement` as always clean (flutter/flutter#154694) 2024-09-13 [email protected] Roll Flutter Engine from 8609af642725 to 4d5fea97e933 (7 revisions) (flutter/flutter#155134) 2024-09-12 [email protected] Disable fuchsia in flutter_tools (flutter/flutter#155111) 2024-09-12 [email protected] Address frame policy benchmark flakes (flutter/flutter#155130) 2024-09-12 [email protected] Roll Flutter Engine from 48ddaf578fb0 to 8609af642725 (11 revisions) (flutter/flutter#155128) 2024-09-12 49699333+dependabot[bot]@users.noreply.github.com Bump peter-evans/create-pull-request from 7.0.1 to 7.0.2 (flutter/flutter#155126) 2024-09-12 [email protected] Prevent the keyboard from reshowing on iOS (flutter/flutter#154584) 2024-09-12 [email protected] fix(Linux): specify application id (flutter/flutter#154522) 2024-09-12 [email protected] update changelog on master (flutter/flutter#155109) 2024-09-12 [email protected] iOS: update provisioning profile for 2024-2025 cert (flutter/flutter#155101) 2024-09-12 [email protected] Roll Packages from 4c18648 to 91caa7a (2 revisions) (flutter/flutter#155103) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected],[email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

flutter/flutter#151026)

@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

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fix: Flicker when reorderable list doesn't change its position

f3a82d7

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Roll Flutter from 303f222e17e3 to bbc17fae3a1e (20 revisions) flutter/packages#7644

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bbc17fa Fix: Flicker when reorderable list doesn't change its position (

9cc6a79

flutter/flutter#151026)

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Roll Flutter from 303f222e17e3 to 2d30fe448cd4 (21 revisions) flutter/packages#7646

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bbc17fa Fix: Flicker when reorderable list doesn't change its position (

347c9aa

flutter/flutter#151026)

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Flutter Framework Team: Notable Commits #121415

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bbc17fa Fix: Flicker when reorderable list doesn't change its position (

99e0904

flutter/flutter#151026)

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bbc17fa Fix: Flicker when reorderable list doesn't change its position (

b200c90

flutter/flutter#151026)

lukemmtt mentioned this pull request Jul 24, 2025

Fix ReorderableList proxy animation for partial drag-back #172380

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rkishan516 deleted the reorderable-list-flicker branch July 26, 2025 05:46

	// If end of the proxy is in not in ending half of item
	// If end of the proxy is not in ending half of item,

	// We don't process, because its drag item index
	// we don't process, because its drag item index.

Fix: Flicker when reorderable list doesn't change its position #151026

Fix: Flicker when reorderable list doesn't change its position #151026

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rkishan516 commented Jul 6, 2024 •

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