👀 Views: 59 💬 Answers: 1 📅 Created: 2025-07-03

ios uicollectionview performance swift

I just started working with I need help solving I'm relatively new to this, so bear with me. After trying multiple solutions online, I still can't figure this out... I'm experiencing significant performance issues when scrolling a UICollectionView that uses a custom layout in iOS 17. The collection view is displaying a grid of images, and I have implemented a custom layout to adjust the size of the cells based on their position in the grid. However, when I scroll, the frames of the cells stutter, and I notice a drop in the frame rate, especially when a large number of items are being loaded. I've tried implementing `prepareLayout()` and `layoutAttributesForElements(in:)`, but the scrolling remains jittery. Here’s a simplified version of my layout code: ```swift class CustomLayout: UICollectionViewLayout { private var cache: [UICollectionViewLayoutAttributes] = [] private var contentWidth: CGFloat = 0 private var contentHeight: CGFloat = 0 override func prepare() { guard cache.isEmpty else { return } let itemWidth: CGFloat = collectionView!.bounds.width / 2 let itemHeight: CGFloat = itemWidth var xOffset: CGFloat = 0 var yOffset: CGFloat = 0 for item in 0..<collectionView!.numberOfItems(inSection: 0) { if item % 2 == 0 && item != 0 { xOffset = 0 yOffset += itemHeight } let frame = CGRect(x: xOffset, y: yOffset, width: itemWidth, height: itemHeight) let attributes = UICollectionViewLayoutAttributes(forCellWith: IndexPath(item: item, section: 0)) attributes.frame = frame cache.append(attributes) xOffset += itemWidth } contentWidth = collectionView!.bounds.width contentHeight = yOffset + itemHeight } override var collectionViewContentSize: CGSize { return CGSize(width: contentWidth, height: contentHeight) } override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? { return cache.filter { $0.frame.intersects(rect) } } } ``` I've also confirmed that the images are being cached properly using `NSCache`, but when I run the app with Instruments, I see a lot of time being spent in layout calculations when scrolling. I’m currently running this on an iPhone 13 with iOS 17. Any suggestions on optimizing this custom layout or alternative approaches would be greatly appreciated. I've tried disabling layout invalidation and adjusting my caching strategy, but nothing seems to help. My development environment is Ubuntu. Has anyone else encountered this? My development environment is Linux. Thanks in advance! Is there a better approach? I'm working with Swift in a Docker container on Windows 10. For reference, this is a production CLI tool.