ios - Swift imageView 动画不起作用

Question

我有创建动画的代码:

var imageView: UIImageView!

override func viewDidLoad() {
    super.viewDidLoad()

    imageView = UIImageView(frame:CGRect(x: 10, y: 10, width: 10, height: 10))
    imageView.image = UIImage(named:"2.png")

    UIView.animate(withDuration: 5) {

        self.imageView = UIImageView(frame:CGRect(x: 10, y: 10, width: 500, height: 500))

        self.view.addSubview(self.imageView)
        self.view.layoutIfNeeded()

        }
    }

但是动画不行。并且 imageView 没有显示。

Answer 1

您应该在动画 block 之前设置约束的常量，并在内部调用 layoutIfNeeded

self.imageViewWidth.constant = 500
self.imageViewHeight.constant = 500

UIView.animate(withDuration: 10) {
    self.layoutIfNeeded()
}