如果在UINavigationController中显示UIViewController，则必须覆盖childViewControllerForHomeIndicatorAutoHidden()函数:

If you show your UIViewController in UINavigationController, you have to override childViewControllerForHomeIndicatorAutoHidden() function:

extension UINavigationController {
    open override func childViewControllerForHomeIndicatorAutoHidden() -> UIViewController? {
        return topViewController
    }
}

或者，如果像父视图控制器的子视图一样显示UIViewController，则还必须重写此功能并返回子视图控制器.

Or if you show your UIViewController like subview of parent view controller, you also have to override this function and return child view controller.