iOS UISplitViewController -如何在从紧凑布局更改为常规布局时恢复导航状态

func splitViewController(_ splitViewController: UISplitViewController, 
                         willChangeTo displayMode: UISplitViewController.DisplayMode) {
    if displayMode == .primaryHidden || displayMode == .primaryOverlay {
        // 切换为常规布局
        if let navigationController = splitViewController.viewControllers.first as? UINavigationController {
            // 获取当前主视图控制器的堆栈顶部视图控制器
            if let topViewController = navigationController.topViewController {
                // 获取需要显示的细节视图控制器
                let detailViewController = // 根据业务逻辑获取细节视图控制器
                splitViewController.showDetailViewController(detailViewController, sender: nil)
            }
        }
    }
}