iOS11 SafeArea 对应swift 片段

在开发过程中遇到tableView内容下移20pt或下移64pt的问题，对当tableView超出安全区域时系统自动调整了SafeAreaInsets值，进而影响adjustedContentInset值，在iOS 11中决定tableView的内容与边缘距离的是adjustedContentInset属性，而不是contentInset。
adjustedContentInset = safeAreaInset + contentInset

在 UIViewContoller 实现 viewSafeAreaInsetsDidChange 方法

    override func viewSafeAreaInsetsDidChange() {
        if #available(iOS 11.0, *) {
            super.viewSafeAreaInsetsDidChange()
            NSLog("viewSafeAreaInsetsDidChange-%@",NSStringFromUIEdgeInsets(self.view.safeAreaInsets))
        } else {
            // Fallback on earlier versions
        }
        self.updateOrientation()
    }

对应的 updateOrientation() 方法内容为

    /**
     更新屏幕safearea frame
     */
    func updateOrientation()
    {
        if #available(iOS 11.0, *) {
            var frame = self.customView.frame
            frame.origin.x = self.view.safeAreaInsets.left
            frame.size.width  = self.view.frame.size.width - self.view.safeAreaInsets.left - self.view.safeAreaInsets.right
            frame.size.height = self.view.frame.size.height - self.view.safeAreaInsets.bottom
            self.customView.frame = frame
        }

    }