ios - tabBarController.selectedViewController 的默认值？

Question

在我的 iOS 应用程序中，我有一个带有几个导航 Controller 的 tabBarController。在 applicationDidFinishLaunching tabBarController.selectedViewController 中为 null。这是在我将 navigationControllers 分配给 tabBar 的 tabBarItems 之后。

tabBarController.selectedViewController 的默认值是多少？

或许可以设置为第一个navigationController。可能需要小心从后台启动的应用程序(在这种情况下，用户可能没有在第一个 navigationController 处停止)。

Answer 1

来自 UITabBarController 的文档，在 selectedViewController 下:

This view controller is the one whose custom view is currently displayed by the tab bar interface. The specified view controller must be in the viewControllers array. Assigning a new view controller to this property changes the currently displayed view and also selects an appropriate tab in the tab bar. Changing the view controller also updates the selectedIndex property accordingly. The default value of this property is nil.