將約束以可視格式轉換爲NSLayoutAnchor API

Question

我從this SO question a few months ago得到了以下擴展，並且我想將其轉換爲NSLayoutAnchor（或更詳細的佈局API），原因很簡單，原因是可視格式不支持指定安全區域佈局指南。

在鏈路的擴展是這一個：

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])) 
    } 
} 

我的視圖層次是：

的UINavigationController - >根視圖控制器：UIPageViewController - >第一頁：的UIViewController - >的UIScrollView - >的UIImageView

當我打電話bindFrameToSuperviewBounds()，結果如下：

看起來大多都很好。問題是圖像視圖在導航欄下，我不想要。因此，爲了解決這個問題，我試圖重寫bindFrameToSuperviewBounds()就象這樣：

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 

然後將結果是：

這一次，它正確地不會在導航欄下去，但是，好吧...你可以看到它被拉伸，我不想要。

將視覺佈局API轉換爲可以考慮安全區域佈局指南的東西的正確方法是什麼？

完成的緣故，建立滾動視圖和圖像視圖的代碼如下：

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

與Fattie提供的代碼，我能到達此解決方案：現在

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 

（即我只錨定的T適合安全的佈局是指導。這是否會給iPhone X帶來問題尚待觀察）。

其中給出的結果我想到：

Answer 2

老實說，我不會與離奇的「可視化」佈局的事情打擾，他們將很快消失。

這有幫助嗎？

extension UIView { 

    // put this view "inside" it's superview, simply stretched all four ways 
    // amazingly useful 

    func bindEdgesToSuperview() { 

     guard let s = superview else { 
      preconditionFailure("`superview` nil in bindEdgesToSuperview") 
     } 

     translatesAutoresizingMaskIntoConstraints = false 
     leadingAnchor.constraint(equalTo: s.leadingAnchor).isActive = true 
     trailingAnchor.constraint(equalTo: s.trailingAnchor).isActive = true 
     topAnchor.constraint(equalTo: s.topAnchor).isActive = true 
     bottomAnchor.constraint(equalTo: s.bottomAnchor).isActive = true 
    } 

} 

只要使用這樣的..

textOnTop = .. UILabel or whatever 
    userPhoto.addSubview(textOnTop) 
    textOnTop.bindEdgesToSuperview() 

容易！

（PS - 不要忘了，如果它是一個形象：你幾乎可以肯定要設置爲AspectFit，在所有情況下，所有的時間。）

安全佈局引導手柄就像.. 。

.safeAreaLayoutGuide