Strange issue with updating UICollectionView size

Question

I have a UICollectionView, which initial height is 50. I want to update it when I know the size of the cell. For what I do:

func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
    let categoriesCount = 16
    let numberOfItemsInRow = 3
    let numberOfRows = ceil(CGFloat(categoriesCount) / CGFloat(numberOfItemsInRow))

    let newHeight = (numberOfRows * cell.frame.size.height)

    collectionHeight.constant = newHeight
    collectionView.collectionViewLayout.invalidateLayout()
}

But despite of calling invalidateLayout - the height of the collectionView stays the same - 50.

But when I switch screens it shows the correct height when I open that screen with UICollectionView for the second time.

What I am doing wrong and how can I update the height of my UICollectionView?

I even tried collectionView.updateConstraints() after the collectionView.collectionViewLayout.invalidateLayout but still no luck

UPDATE

I've tried also

collectionView.layoutIfNeeded()
self.superview?.layoutIfNeeded()

but no result.

score 0 · Answer 1 · answered Sep 12 '21 at 18:32

0

For this, you might have to call the self.view.layoutIfNeeded() method to force the view to update it's layout.

As per the documentation:

...this method lays out the view subtree starting at the root.

hence, updating your view

For more info, you can read this thread where you can pick bits and pieces to add to your solution.

answered Sep 12 '21 at 18:32

Visal Rajapakse

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unfortunately I've tried that also and it did not help me =/ – Apple John Sep 12 '21 at 18:57
Did you try wrapping the ui manipulations in a `dispatchQueue`? – Visal Rajapakse Sep 12 '21 at 19:03
I retried your code, and it works fine on my end without any supplementary code. Could you maybe append the rest of the code so we can get a better idea where things might have gone wrong? Also, are you using Storyboards? – Visal Rajapakse Sep 12 '21 at 19:22

score 0 · Answer 2 · answered Sep 12 '21 at 20:44

0

Instead of trying to update the collectionView later based on the size of the cell, can we not use estimated height adjustment of the cell.

answered Sep 12 '21 at 20:44

Maniac One

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score 0 · Answer 3 · answered Mar 03 '22 at 08:06

Change the Estimated size option in size inspector of collection view to "None" from "Automatic". See the Image Below for reference.

enter image description here

I tried many answers given in different threads, none worked in my case but this one.

Check https://stackoverflow.com/a/59783595/11806784 this thread for reference.

Strange issue with updating UICollectionView size

3 Answers3