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

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
}

斯威夫特4

if let window = UIApplication.shared.windows.first {
    
    let topPadding = window.safeAreaInsets.top
    let bottomPadding = window.safeAreaInsets.bottom
    
}

从课堂使用

class fitToTopInsetConstraint: NSLayoutConstraint {
    
    override func awakeFromNib() {
        
        if let window = UIApplication.shared.windows.first {
            
            let topPadding = window.safeAreaInsets.top
            
            self.constant += topPadding
            
        }
        
    }
}

class fitToBottomInsetConstraint: NSLayoutConstraint {
    
    override func awakeFromNib() {
        
        if let window = UIApplication.shared.windows.first {
            
            let bottomPadding = window.safeAreaInsets.bottom
            
            self.constant += bottomPadding
            
        }
        
    }
}

在构建应用程序时，您将看到安全区域填充。

extension UIViewController {
    var topbarHeight: CGFloat {
        return
            (view.window?.safeAreaInsets.top ?? 0) +
            (view.window?.windowScene?.statusBarManager?.statusBarFrame.height ?? 0.0) +
            (self.navigationController?.navigationBar.frame.height ?? 0.0)
    }
}

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
        }
}

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