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)

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 SwiftUI：

Code

private struct SafeAreaInsetsKey: EnvironmentKey {
    static var defaultValue: EdgeInsets {
        UIApplication.shared.windows[0].safeAreaInsets.insets
    }
}

extension EnvironmentValues {
    
    var safeAreaInsets: EdgeInsets {
        self[SafeAreaInsetsKey.self]
    }
}

private extension UIEdgeInsets {
    
    var insets: EdgeInsets {
        EdgeInsets(top: top, leading: left, bottom: bottom, trailing: right)
    }
}

使用

struct MyView: View {
    
    @Environment(\.safeAreaInsets) private var safeAreaInsets
    
    var body: some View {
        Text("Ciao")
            .padding(safeAreaInsets)
    }
}

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
        }
}

对于iOS 13+/Swift 5，除了这个，没有其他方法适合我:

    if #available(iOS 13.0, *) {
        topPadding = UIApplication.shared.windows.first?.safeAreaInsets.top ?? 0
        bottomPadding = UIApplication.shared.windows.first?.safeAreaInsets.bottom ?? 0
    }

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