问题
Is there a way to force the navigation bar of a UINavigationController to be laid out as if the status bar is showing even when the status bar is hidden? My motivation is to prevent the navigation bar for shifting when a navigation controller presents a view controller that returns YES for prefersStatusBarHidden. An example of this is when you look at an attached image in an email in the Gmail app.
来源：https://stackoverflow.com/questions/22586361/ios-7-how-to-force-navigation-bar-of-uinavigationcontroller-to-be-laid-out-as-i