iOS 11 navigation bar height customizing
Now in iOS 11, the sizeThatFits method is not called from UINavigationBar subclasses. Changing the frame of UINavigationBar causes glitches and wrong insets.
So, any ideas how to customize navbar height now?
Answer
According to Apple developers (look here, here and here), changing navigation bar height in iOS 11 is not supported. Here they suggest to do workarounds like having a view under the navigation bar (but outside of it) and then remove the nav bar border. As a result, you will have this in storyboard:
look like this on the device:
Now you can do a workaround that was suggested in the other answers: create a custom subclass of UINavigationBar, add your custom large subview to it, override sizeThatFits and layoutSubviews, then set additionalSafeAreaInsets.top for the navigation's top controller to the difference customHeight - 44px, but the bar view will still be the default 44px, even though visually everything will look perfect. I didn't try overriding setFrame, maybe it works, however, as Apple developer wrote in one of the links above: "...and neither is [supported] changing the frame of a navigation bar that is owned by a UINavigationController (the navigation controller will happily stomp on your frame changes whenever it deems fit to do so)."
In my case the above workaround made views to look like this (debug view to show borders):
As you can see, the visual appearance is quite good, the additionalSafeAreaInsets correctly pushed the content down, the big navigation bar is visible, however I have a custom button in this bar and only the area that goes under the standard 44 pixel nav bar is clickable (green area in the image). Touches below the standard navigation bar height doesn't reach my custom subview, so I need the navigation bar itself to be resized, which the Apple developers say is not supported.