ios - UIViewPropertyAnimator 未按预期工作

Question

当用户点击 UIView 时，我尝试为 UIView 和 imageView 制作动画。这是我的代码:

// When the user taps on the featured story image view
@objc func feturedStoryTapped() {

    /*featuredStoryView.layer.zPosition = 1

    // Hide the necessary elements
    self.featuredTitle.isHidden = true
    self.bookTitle.isHidden = true
    self.authorName.isHidden = true

    // Unhide the necessary elements
    self.exitButton.isHidden = false*/

    let animator = UIViewPropertyAnimator(duration: 0.9, dampingRatio: 0.4, animations: {

        self.featuredStoryView.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height)
        self.bookCover.frame = CGRect(x: 100, y: 75, width: 250, height: 280)

    })

    animator.startAnimation()

}

预期行为: 当我点击 UIView 一次时， View 应该占据整个屏幕，而 imageView 应该缩小一点。

问题 问题是，当我点击一次 View 时， View 占据整个屏幕，但 imageView 不会缩小，只有当我第二次点击时它才会缩小。

我希望当我点击 View 一次时执行这两个任务。我将添加一个 GIF 来帮助理解。

Answer 1

修复它，只需在属性动画器内的两行代码之间添加 view.layoutIfNeeded() 即可。

// When the user taps on the featured story image view
    @objc func feturedStoryTapped() {

    /*featuredStoryView.layer.zPosition = 1

    // Hide the necessary elements
    self.featuredTitle.isHidden = true
    self.bookTitle.isHidden = true
    self.authorName.isHidden = true

    // Unhide the necessary elements
    self.exitButton.isHidden = false*/

    let animator = UIViewPropertyAnimator(duration: 0.9, dampingRatio: 0.4, animations: {

        self.featuredStoryView.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height)
        Self.view.layoutIfNeeded()

        self.bookCover.frame = CGRect(x: 100, y: 75, width: 250, height: 280)

    })

    animator.startAnimation()

}