Hi,
I'm trying to create a UICollectionView where the cell high is automatic. Cells contains a UILabel with all anchors to the contentView of the cell.
It seems to work but I have a strange behavior with longer text, on reload data and on device rotation: Cells do not display the whole text or they change row, both randomly.
To create my collection view I first create the collection view with a custom flow layout setting the automatic size on viewWillAppear:
let collectionViewFlowLayout = CustomFlowLayout()
collectionViewFlowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
collectionView = UICollectionView(frame: .zero, collectionViewLayout: collectionViewFlowLayout)
and I have also overridden:
override func willAnimateRotation(to toInterfaceOrientation: UIInterfaceOrientation, duration: TimeInterval) {
collectionView.setNeedsLayout()
self.collectionView.layoutIfNeeded()
self.collectionView.collectionViewLayout.invalidateLayout()
//self.collectionView.reloadData()
}
Then, I created the custom layout as follow:
import UIKit
final class CustomFlowLayout: UICollectionViewFlowLayout {
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
let layoutAttributesObjects = super.layoutAttributesForElements(in: rect)?.map{ $0.copy() } as? [UICollectionViewLayoutAttributes]
layoutAttributesObjects?.forEach({ layoutAttributes in
if layoutAttributes.representedElementCategory == .cell {
if let newFrame = layoutAttributesForItem(at: layoutAttributes.indexPath)?.frame {
layoutAttributes.frame = newFrame
}
}
})
return layoutAttributesObjects
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
guard let collectionView = collectionView else {
fatalError()
}
guard let layoutAttributes = super.layoutAttributesForItem(at: indexPath)?.copy() as? UICollectionViewLayoutAttributes else {
return nil
}
layoutAttributes.frame.origin.x = sectionInset.left
if(indexPath.section == 0){
layoutAttributes.frame.size.width = collectionView.safeAreaLayoutGuide.layoutFrame.width - sectionInset.left - sectionInset.right
} else if (indexPath.section == collectionView.numberOfSections - 1){
let width = ScreenUtility.getCollectionCellWidthForElement(in: collectionView, sectionLeft: sectionInset.left, sectionRight: sectionInset.right, minimumInteritemSpacing: minimumInteritemSpacing, multiplier: 3)
layoutAttributes.frame.origin.x = ScreenUtility.getCollectionCellOriginForElement(in: collectionView, at: indexPath, forElementHavingWidth: width, sectionLeft: sectionInset.left, sectionRight: sectionInset.right, minimumInteritemSpacing: minimumInteritemSpacing, multiplier: 3)
layoutAttributes.frame.size.width = width
} else if (indexPath.section == collectionView.numberOfSections - 3) || (indexPath.section == collectionView.numberOfSections - 4){
let width = ScreenUtility.getCollectionCellWidthForElement(in: collectionView, sectionLeft: sectionInset.left, sectionRight: sectionInset.right, minimumInteritemSpacing: minimumInteritemSpacing)
layoutAttributes.frame.origin.x = ScreenUtility.getCollectionCellOriginForElement(in: collectionView, at: indexPath, forElementHavingWidth: width, sectionLeft: sectionInset.left, sectionRight: sectionInset.right, minimumInteritemSpacing: minimumInteritemSpacing)
layoutAttributes.frame.size.width = width
} else {
let width = ScreenUtility.getCollectionCellSizeForElementFullRow(in: collectionView, sectionLeft: sectionInset.left, sectionRight: sectionInset.right)
layoutAttributes.frame.origin.x = ScreenUtility.getCollectionCellOriginForElementFullRow(in: collectionView, sectionLeft: sectionInset.left, sectionRight: sectionInset.right)
layoutAttributes.frame.size.width = width
}
return layoutAttributes
}
}
And finally on collection view cells:
override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
setNeedsLayout()
layoutIfNeeded()
let targetSize = CGSize(width: layoutAttributes.frame.width, height: 0)
layoutAttributes.frame.size = contentView.systemLayoutSizeFitting(targetSize, withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel)
return layoutAttributes
}
override func prepareForReuse() {
self.nameLabel.text = ""
self.idLabel.text = ""
self.contentView.setNeedsLayout()
self.contentView.layoutIfNeeded()
}
Let me show you an example on the iPad that is the worst.
First Time I open the collection view I have cells on wrong rows and not sized properly
Then I rotate the device portrait and the cells are fine
On landscape again it changes behavior:
This is just an example, things happens apparently randomly, and also sometimes cells disappear (I think the height is set to 0).
I really do not understand why, cells width seems to be computed correctly, and cell label is set via setter:
open var step: String = "" {
didSet {
nameLabel.text = step
nameLabel.sizeToFit()
self.contentView.setNeedsLayout()
self.contentView.layoutIfNeeded()
}
}
matmacsystem
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