要获得布局参考线之间的高度，只需这样做

let guide = view.safeAreaLayoutGuide
let height = guide.layoutFrame.size.height

所以全帧高度= 812.0，安全区高度= 734.0

下面的例子中，绿色视图的框架为guide.layoutFrame

Swift 5, Xcode 11.4

`UIApplication.shared.keyWindow` 

它将给出弃用警告。" keyWindow "在iOS 13.0中已弃用:不应该用于支持多场景的应用程序，因为它会在所有连接的场景中返回一个键窗口。我用这种方法。

extension UIView {

    var safeAreaBottom: CGFloat {
         if #available(iOS 11, *) {
            if let window = UIApplication.shared.keyWindowInConnectedScenes {
                return window.safeAreaInsets.bottom
            }
         }
         return 0
    }

    var safeAreaTop: CGFloat {
         if #available(iOS 11, *) {
            if let window = UIApplication.shared.keyWindowInConnectedScenes {
                return window.safeAreaInsets.top
            }
         }
         return 0
    }
}

extension UIApplication {
    var keyWindowInConnectedScenes: UIWindow? {
        return windows.first(where: { $0.isKeyWindow })
    }
}

更全面的方法

  import SnapKit

  let containerView = UIView()
  containerView.backgroundColor = .red
  self.view.addSubview(containerView)
  containerView.snp.remakeConstraints { (make) -> Void in
        make.width.top.equalToSuperView()
        make.top.equalTo(self.view.safeArea.top)
        make.bottom.equalTo(self.view.safeArea.bottom)
  }




extension UIView {
    var safeArea: ConstraintBasicAttributesDSL {
        if #available(iOS 11.0, *) {
            return self.safeAreaLayoutGuide.snp
        }
        return self.snp
    }


    var isIphoneX: Bool {

        if #available(iOS 11.0, *) {
            if topSafeAreaInset > CGFloat(0) {
                return true
            } else {
                return false
            }
        } else {
            return false
        }

    }

    var topSafeAreaInset: CGFloat {
        let window = UIApplication.shared.keyWindow
        var topPadding: CGFloat = 0
        if #available(iOS 11.0, *) {
            topPadding = window?.safeAreaInsets.top ?? 0
        }

        return topPadding
    }

    var bottomSafeAreaInset: CGFloat {
        let window = UIApplication.shared.keyWindow
        var bottomPadding: CGFloat = 0
        if #available(iOS 11.0, *) {
            bottomPadding = window?.safeAreaInsets.bottom ?? 0
        }

        return bottomPadding
    }
}

safeAreaLayoutGuide 当视图在屏幕上可见时，该指南反映了未被导航栏、选项卡栏、工具栏和其他祖先视图覆盖的视图部分。(在tvOS中，安全区域反映未覆盖屏幕边框的区域。)如果视图当前没有安装在视图层次结构中，或者在屏幕上还不可见，布局指南边等于视图的边。

然后在截图中获得红色箭头的高度:

self.safeAreaLayoutGuide.layoutFrame.size.height

对于那些切换到横向模式的人，你必须确保在旋转后使用viewSafeAreaInsetsDidChange来获得最新的值:

private var safeAreaInsets = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)

override func viewSafeAreaInsetsDidChange() {
        if #available(iOS 11.0, *) {
            safeAreaInsets = UIApplication.shared.keyWindow!.safeAreaInsets
        }
}

试试这个:

在Objective C中

if (@available(iOS 11.0, *)) {
    UIWindow *window = UIApplication.sharedApplication.windows.firstObject;
    CGFloat topPadding = window.safeAreaInsets.top;
    CGFloat bottomPadding = window.safeAreaInsets.bottom;
}

在斯威夫特

if #available(iOS 11.0, *) {
    let window = UIApplication.shared.keyWindow
    let topPadding = window?.safeAreaInsets.top
    let bottomPadding = window?.safeAreaInsets.bottom
}

在Swift - iOS 13.0及以上

//使用windows数组中的第一个元素，KeyWindow已弃用

if #available(iOS 13.0, *) {
    let window = UIApplication.shared.windows.first
    let topPadding = window.safeAreaInsets.top
    let bottomPadding = window.safeAreaInsets.bottom
}