UIIamgeView中的淡入/淡出图像没有持续时间

UIIamge 我在中以编程方式创建 viewDidLoad 的 DetailViewController .transitionCrossDissolve DetailViewCOntroller 显示开关立即发生,无论 duration

    let rect = CGRect(x: 0, y: UIApplication.shared.statusBarFrame.height, width: view.frame.size.width, height: view.frame.size.height / 3.0)
    let imageView = UIImageView(frame: rect)
    imageView.image = #imageLiteral(resourceName: "head1")
    imageView.contentMode = .scaleAspectFill
    imageView.clipsToBounds = true
    view.addSubview(imageView)
    UIView.transition(with: imageView,
                      duration: 16.0,
                      options: .transitionCrossDissolve,
                      animations: { imageView.image = #imageLiteral(resourceName: "head3") },
                      completion: nil)