UICollectionView点击空白处，将点击事件传递到su

在加载scrollView的类中添加如下代码

override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
    guard self.point(inside: point, with: event) else {
        return super.hitTest(point, with: event)
    }
    let newPoint = convert(point, to: collectionView)
    if collectionView.point(inside: newPoint, with: event) {
        for subView in collectionView.visibleCells {
            let subViewPoint = convert(point, to: subView)
            if subView.point(inside: subViewPoint, with: event) {
                return subView
            }
        }
    }
    return self
}