开始滚动CollectionView时的Swift 4 Fade标签

Question

我有问题...开始滚动CollectionView时如何淡出标签“相册”？我试图检测何时滚动收藏集。

ios http://ipic.su/img/img7/fs/SimulatorScreenShot-iPhone7Plus-2019-01-09at12.1547030165.png http://ipic.su/img/img7/fs/SimulatorScreenShot-iPhone7Plus-2019-01-09at12.1547030165.png

func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        if scrollView == self.collectionViewA {
            // do something with collectionViewA
        } else if scrollView == self.collectionViewB {
            // do something with collectionViewB
        }
}