swift - targetContentOffset(forProposedContentOffset :) in my CustomFlowLayout not called

Question

我正在编写一个自定义的 UICollectionViewFlowLayout，它覆盖了 targetContentOffset(forProposedContentOffset:)，以便在用户缩放时提供正确的 contentOffset，因为我遇到了这个问题(错误的 contentOffset)

Dynamically setting layout on UICollectionView causes inexplicable contentOffset change

class TimelineCollectionViewFlowLayout: UICollectionViewFlowLayout {
    
    // MARK: - Init
    
    override init() {
        super.init()
        self.minimumLineSpacing = 0
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    override func prepare() {
        if let collectionView = self.collectionView {
            collectionView.isPagingEnabled = false
            self.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
            self.scrollDirection = .horizontal
        }
    }
    
    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint {
        print("hello")
        return proposedContentOffset
    }
}

但不幸的是 targetContentOffset 没有被调用，你知道为什么吗？

谢谢!

蒂埃里

Answer 1

试试

override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint