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)

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
}

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

对于iPhone 14设备使用如下。

let app = UIApplication.shared
var statusBarHeight: CGFloat = 0.0
let window = app.windows.filter {$0.isKeyWindow}.first
statusBarHeight = window?.windowScene?.statusBarManager?.statusBarFrame.height ?? 0
let topPadding = window?.safeAreaInsets.top ?? 0.0
statusBarHeight = statusBarHeight >= topPadding ? statusBarHeight:topPadding

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。

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