UICollectionView self-sizing-cell on iOS 8 will crash with UIDynamic flowLayout and repeating call to _updateVisibleCellsNow

Question

I am trying to use the so called "self sizing cell" which means:

• set estimatedItemSize on flowLayout
• overide preferredLayoutAttributesFittingAttributes in cell class

Such as this: UICollectionView Self Sizing Cells with Auto Layout

And I need dynamic effect like this:http://www.teehanlax.com/blog/implementing-a-bouncy-uicollectionviewlayout-with-uikit-dynamics/

It works fine without UIDynamic, but I need UIDynamic. As what I see, it will call the prepareLayout and layoutAttributesForElementsInRect until die, there will be too many _updateVisibleCellsNow waiting in line.

I have no idea how to solve that, please help me in case u see. Or, if I am using those technologies in wrong way, please let me know.

Answer 1

If any size or frame position changed, it will trigger all cells' preferredLayoutAttributesFittingAttributes until all cells' frames did not change.

The behavior flow is as the following:

1. Before self-sizing cell

2. Validated self-sizing cell again after other cells recalculated.

3. Did changed self-sizing cell

If second steps can't get stable all cells' position and size, it will become infinite loop.

Please reference my post here: UICollectionView Self Sizing Cells with Auto Layout

Answer 2

Two things worked for me:

• Make sure your collection view itself has layout constraints defined for placement within its superview.
• I got this crash when the estimated size was larger than the final size. If I set the estimated size to a smaller value the crash stopped.