以编程方式将UILabel添加到UICollectionViewCell

class NTWaterfallViewCell :UICollectionViewCell, NTTansitionWaterfallGridViewProtocol{

    var photoName = ""
    var imageName : String?

    var imageViewContent : UIImageView = UIImageView()
    var label:UILabel = UILabel()

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = UIColor.lightGray
        contentView.addSubview(imageViewContent)
        contentView.addSubview(label)
    }
    override func layoutSubviews() {
        super.layoutSubviews()
        imageViewContent.frame = CGRect(x: 0, y: 0, width: frame.size.width, height: frame.size.height)
        imageViewContent.loadImageWithURL(imageName!)

        label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 21))
        label.center = CGPoint(x: 160, y: 285)
        label.textAlignment = .center
        label.text = photoName
    }