My UITabBarController contains more than 16 view controllers. When I go in the "More" tab, I can see all the UITabBarItems. If I click the "Edit" button, I can see the 16 first icons, but there is not enough room to display more, so starting from the 17th item, the icons are only partially displayed. Starting from the 21st item, the icons are not displayed at all. And it is not possible to access the rest of the icons with a scroll bar.
By the way, this question gives a theoretical answer to my question, but does not address this practical corner case.
You need consider other modes of displaying view controllers if you have more than 5. For example the facebook app shows a revealing sidebar, maybe you need to figure out a way of displaying stuff in a similar manner.
来源：https://stackoverflow.com/questions/4867022/configuring-a-uitabbar-with-more-than-16-items