Implementing `shouldBeginMultipleSelectionInteractionAt` irreversibly turns on single-finger band selection on UICollectionView

Number:rdar://FB9833896 Date Originated:05/01/2022
Status:Open Resolved:
Product:iOS - UIKit Product Version:15.0+
Classification: Reproducible:Yes
Implementing `collectionView(_:shouldBeginMultipleSelectionInteractionAt:)` irreversibly turns on single-finger band/multi selection which works on phones as well. This seems to be handled by `UIMultiSelectInteraction` (not `UIBandSelectionInteraction`, which doesn't work on phones).

Note that this is different than the two-finger band selection gesture discussed in your documentation (which should be able to be disabled by returning `false` in `shouldBeginMultipleSelectionInteractionAt`) -- this works by just dragging a single finger across a collection view with multiple selection enabled. Removing the implementation of the delegate method removes this behavior.

Please either make this follow the value returned by `shouldBeginMultipleSelectionInteractionAt` or add a separate flag to disable it. Thanks.


Steps to reproduce:

  • Have a collection view with allowsSelection and allowsMultipleSelection set to YES.
  • Implement a dummy collectionView(_:shouldBeginMultipleSelectionInteractionAt:) delegate method which always returns NO.
  • Drag your finger across collection view elements. Notice how they are all selected as you drag along.

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