UIWindow *window = [[[UIApplication sharedApplication] delegate] window]; 
CGFloat fBottomPadding = window.safeAreaInsets.bottom;

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
    }
}

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
}

这适用于整个视图生命周期，在Swift中是一个简单的两行解决方案:

let top    = UIApplication.shared.windows[0].safeAreaInsets.top
let bottom = UIApplication.shared.windows[0].safeAreaInsets.bottom

我个人需要它在viewDidLoad和view中。safeAreaInsets还没有计算。

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 })
    }
}

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。