swift - 如果 Collection View 为空，则删除 Collection View 标题

Question

如果 Collection View 为空，如何删除 Collection View 标题？如果 Collection View 文件中的 Collection View 为空，我能够以编程方式添加标签，但我似乎无法找到如何删除标题。

 let messageLabel = UILabel(frame: CGRect(x: 20.0, y: 10, width: self.collectionViews!.bounds.size.width - 40.0, height: (self.collectionViews?.bounds.size.height)!))
 messageLabel.text = "No info yet"
 messageLabel.font = messageLabel.font.withSize(20)
 messageLabel.font = UIFont.boldSystemFont(ofSize: messageLabel.font.pointSize)
 messageLabel.textColor = UIColor.white
 messageLabel.numberOfLines = 0
 messageLabel.textAlignment = NSTextAlignment.center
 messageLabel.sizeToFit()

self.collectionViews?.backgroundColor = blue
self.collectionViews?.backgroundView = messageLabel

Answer 1

我认为你可以这样实现:

extension ViewController: UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {

        if collectionView.numberOfItems(inSection: section) == 0 {
            return CGSize.zero
        } else {
            let headerView = self.view.subviews[0].subviews[0] as! UICollectionReusableView
            let existingSize = headerView.frame.size

            return existingSize
        }
    }
}