swift--纯代码获取安全区frame

public func safeAreaFrame(_ viewController:UIViewController) -> CGRect {
    let isIphoneX = UIScreen.main.bounds.height >= 812 ? true : false
    
    var navigationBarHeight:CGFloat = isIphoneX ? 44 : 20
    var tabBarHeight:CGFloat = isIphoneX ? 34 : 0
    
    //标志导航视图控制器是否存在 默认不存在
    //为什么需要这个？
    //这里有个坑，当没有导航栏时，如果是iPhoneX等设备，tabBar.frame.height = 49 会不包含底部返回条的高度（34）, 存在导航栏时 tabBar.frame.height = 83
    var noNavigationExists = true
    
    if let navigation = viewController.navigationController {
        noNavigationExists = false
        navigationBarHeight = navigationBarHeight + CGFloat(navigation.navigationBar.frame.height)
    }
    if let tabBarController = viewController.tabBarController {
        tabBarHeight = noNavigationExists ? tabBarHeight : 0
        tabBarHeight = tabBarHeight + CGFloat(tabBarController.tabBar.frame.height)
    }

    let frame = CGRect(x: 0, y: navigationBarHeight, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height - tabBarHeight - navigationBarHeight)

    return frame
}

使用

    override func viewDidLoad() {
        super.viewDidLoad()

        let view = UIView(frame: safeAreaFrame(self))
        view.backgroundColor = UIColor.red
        self.view.addSubview(view)
    }

效果：