ios - 将可视格式的约束转换为 NSLayoutAnchor API

Question

我从 this SO question a few months ago 获得了以下扩展名，我想将其转换为 NSLayoutAnchor(或更详细的布局 API)，原因很简单，即视觉格式不支持指定安全区域布局指南。

链接中的扩展是这个:

extension UIView {

    /// Adds constraints to this `UIView` instances `superview` object to make sure this always has the same size as the superview.
    /// Please note that this has no effect if its `superview` is `nil` – add this `UIView` instance as a subview before calling this.
    func bindFrameToSuperviewBounds() {
        guard let superview = self.superview else {
            print("Error! `superview` was nil – call `addSubview(view: UIView)` before calling `bindFrameToSuperviewBounds()` to fix this.")
            return
        }

        self.translatesAutoresizingMaskIntoConstraints = false
        superview.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-0-[subview]-0-|", options: .directionLeadingToTrailing, metrics: nil, views: ["subview": self]))
        superview.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-0-[subview]-0-|", options: .directionLeadingToTrailing, metrics: nil, views: ["subview": self]))
    }
}

我的 View 层次结构是:

UINavigationController -> Root View Controller :UIPageViewController -> 第一页:UIViewController -> UIScrollView -> UIImageView

当我调用 bindFrameToSuperviewBounds() 时，结果如下:

这看起来大部分都很好。问题是 ImageView 位于导航栏下方，这是我不想要的。所以为了解决这个问题，我尝试重写 bindFrameToSuperviewBounds() 如下:

guard let superview = self.superview else {
            fatalError("Attempting to bound to a non-existing superview.")
        }

translatesAutoresizingMaskIntoConstraints = false
self.topAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.topAnchor).isActive = true
self.leadingAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.leadingAnchor).isActive = true
self.bottomAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.bottomAnchor).isActive = true
self.trailingAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.trailingAnchor).isActive = true

结果是这样的:

这次它正确地没有进入导航栏下方，但是......你可以看到它被拉长了，这是我不想要的。

将视觉布局 API 转换为可以考虑安全区域布局指南的东西的正确方法是什么？

为了完成，设置 ScrollView 和 ImageView 的代码如下:

override func viewDidLoad() {
    super.viewDidLoad()
    imageScrollView.addSubview(imageView)
    imageScrollView.layoutIfNeeded()
    imageView.bindFrameToSuperviewBounds()
    view.addSubview(imageScrollView)
    imageView.layoutIfNeeded()
    imageScrollView.backgroundColor = .white
    imageScrollView.bindFrameToSuperviewBounds()
    imageScrollView.delegate = self
}

Answer 1

通过 Fattie 提供的代码，我得到了这个解决方案:

guard let superview = self.superview else {
    fatalError("Attempting to bound to a non-existing superview.")
}

translatesAutoresizingMaskIntoConstraints = false
self.topAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.topAnchor).isActive = true
self.leadingAnchor.constraint(equalTo: superview.leadingAnchor).isActive = true
self.bottomAnchor.constraint(equalTo: superview.bottomAnchor).isActive = true
self.trailingAnchor.constraint(equalTo: superview.trailingAnchor).isActive = true

(现在我只是将顶部锚定到安全布局是指南。这是否会给 iPhone X 带来问题还有待观察)。

这给出了我期望的结果: