Swift 5扩展

这可以作为一个扩展，并调用:UIApplication.topSafeAreaHeight

extension UIApplication {
    static var topSafeAreaHeight: CGFloat {
        var topSafeAreaHeight: CGFloat = 0
         if #available(iOS 11.0, *) {
               let window = UIApplication.shared.windows[0]
               let safeFrame = window.safeAreaLayoutGuide.layoutFrame
               topSafeAreaHeight = safeFrame.minY
             }
        return topSafeAreaHeight
    }
}

Extension of UIApplication是可选的，可以是UIView的扩展或者任何你喜欢的，或者更好的全局函数。

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
}

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
    }
}

在iOS 11中，有一个方法告诉安全区域什么时候发生了变化。

override func viewSafeAreaInsetsDidChange() {
    super.viewSafeAreaInsetsDidChange()
    let top = view.safeAreaInsets.top
    let bottom = view.safeAreaInsets.bottom
}

objective - c 当keyWindow等于nil时谁有问题。 把上面的代码放在viewDidAppear中(不是viewDidLoad中)