如何在 UICollectionView 单元格中获取 UIImageView 的帧大小

Question

我正在尝试获取UICollectionViewCell内UIImageView的帧大小。我目前尝试使用thumbnailImageView.frame.size来实现这一点，但无论我从哪里调用此方法，这都会返回(0.0, 0.0)。

我想这样做的原因是在图像视图中对图像边缘进行圆角处理，但是由于我正在使用.scaleAspectFit我需要知道帧大小和图像大小才能正确圆角。

下面是单元格类：

class SomeCollectionViewCell: UICollectionViewCell {
override init(frame: CGRect) {
super.init(frame: frame)
setupViews()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
let thumbnailImageView: UIImageView = {
let imageView = UIImageView()
imageView.contentMode = .scaleAspectFit
return imageView
}()
private func setLabel(label: UILabel, textSize: CGFloat = 15.0, textColour: UIColor = UIColor.black) -> UILabel {
label.textColor = textColour
label.textAlignment = .center
label.font = label.font.withSize(textSize)
return label
}
var firstLabel: UILabel = UILabel()
var secondLabel: UILabel = UILabel()
var thirdLabel: UILabel = UILabel()
func setupViews() {
firstLabel = setLabel(label: firstLabel)
secondLabel = setLabel(label: secondLabel)
thirdLabel = setLabel(label: thirdLabel)
addSubview(thumbnailImageView)
addSubview(firstLabel)
addSubview(secondLabel)
addSubview(thirdLabel)
addConstraintWithFormat(format: "V:|-25-[v0(125)]-[v1(16)]-[v2(16)]-[v3(17)]-25-|", views: thumbnailImageView, firstLabel, secondLabel, thirdLabel)
addConstraintWithFormat(format: "H:|[v0]|", views: thumbnailImageView)
addConstraintWithFormat(format: "H:|[v0]|", views: firstLabel)
addConstraintWithFormat(format: "H:|[v0]|", views: secondLabel)
addConstraintWithFormat(format: "H:|[v0]|", views: thirdLabel)
}
}
extension UIView {
func addConstraintWithFormat(format: String, views: UIView...) -> Void {
var viewDictionary = [String : UIView]()
for (index, view) in views.enumerated() {
let key = "v(index)"
viewDictionary[key] = view
view.translatesAutoresizingMaskIntoConstraints = false
}
NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: format, options: NSLayoutFormatOptions(), metrics: nil, views: viewDictionary))
}
}

Answer 1

所以问题的解决方案是使用这种方法：

func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
}

此方法用于告知委托指定的单元格即将显示在集合视图中，此时，已为其指定边界。

Answer 2

另一种可能性 print(cell.frame.size(

Answer 3

也许这就是你想要的，试试吧：

print(cell.photo?.image.size)