为什么 scrollViewWillEndDragging 会影响 UICollectionView 和 UITableView？

Question

我在同一个视图控制器上使用 UITableView 和 UICollectionView。

我想改变 UICollectionView 的滚动方式，所以我在扩展中添加了 scrollViewWillBeginDragging 和 scrollViewWillEndDragging 函数。

然而，scrollViewWillBeginDragging 和 scrollViewWillEndDragging也影响 UITableView，尽管它们不在同一个扩展中。

我该如何解决这个问题？有没有办法只选择 UICollectionView？

这是我的代码的简短版本：

extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    // This is where I put all of the UICollectionView code, including `scrollViewWillBeginDragging` and a `scrollViewWillEndDragging`

    func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        // Why is the code in here affecting the UITableView?

    }

    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        // Same as with `scrollViewWillBeginDragging`

    }

}

extension ViewController: UITableViewDelegate, UITableViewDataSource {
    // This is where I put all of the UITableView code, it's separate from the UICollectionView so why are `scrollViewWillBeginDragging` and `scrollViewWillEndDragging` affecting it?

}

Answer 1

这是因为

UITableViewDelegate 和 UICollectionViewDelegate 都继承自 UIScrollViewDelegate

所以你能做的就是

extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    // This is where I put all of the UICollectionView code, including `scrollViewWillBeginDragging` and a `scrollViewWillEndDragging`

    func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {

        if scrollView is UICollectionView {
          // Add code here for collectionView
        }
    }

    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {

        if scrollView is UICollectionView {
          // Add code here for collectionView
        }
    }

}