reorderChildren method

void reorderChildren(TKey parentKey, List<TKey> orderedKeys)

Reorders the children of parentKey to match orderedKeys.

orderedKeys must contain exactly the current live (non-pending-deletion) children of parentKey. Expansion state, animation state, and measured extents are preserved.

Implementation

void reorderChildren(TKey parentKey, List<TKey> orderedKeys) {
  if (!_hasKey(parentKey)) {
    throw ArgumentError.value(parentKey, "parentKey", "not found");
  }
  final currentChildren = _childListOf(parentKey) ?? <TKey>[];

  final pendingChildren = <TKey>[];
  final liveChildSet = <TKey>{};
  for (final k in currentChildren) {
    if (_isPendingDeletion(k)) {
      pendingChildren.add(k);
    } else {
      liveChildSet.add(k);
    }
  }
  // Validate in all build modes — see reorderRoots for rationale.
  if (orderedKeys.length != liveChildSet.length ||
      orderedKeys.toSet().length != orderedKeys.length ||
      !liveChildSet.containsAll(orderedKeys)) {
    throw ArgumentError.value(
      orderedKeys,
      "orderedKeys",
      "must contain exactly the current live children of $parentKey with "
          "no duplicates",
    );
  }

  _setChildList(parentKey, [...orderedKeys, ...pendingChildren]);
  bool needsVisibleRebuild =
      _isExpandedKey(parentKey) && _ancestorsExpandedFast(parentKey);
  if (!needsVisibleRebuild) {
    // Even if the parent is not expanded, children may still be present
    // in _visibleOrder because they are mid-animation (collapse in
    // progress, pending-deletion exit). Those entries would otherwise
    // retain the old order until the animation completes.
    for (final child in _childListOf(parentKey)!) {
      if (_hasOperationGroup(child) ||
          _bulkAnimationGroup?.members.contains(child) == true ||
          _hasStandalone(child)) {
        needsVisibleRebuild = true;
        break;
      }
    }
  }
  if (needsVisibleRebuild) {
    _markVisibleOrderDirty();
  }
  // See reorderRoots: pure reorder — no builder output changes.
  _notifyStructural(affectedKeys: const {});
}