我认为你不能改变导航栏的高度。除非您添加提示消息...但这不是您想要的。

I don't think you can change the height of a navigation bar. Except when you add a prompt message... But that's not what you want.

框架是视图的可见区域。界限是内部区域。通常它的原点为（0,0），并且与帧一样宽和高。但是，当内容超出可见区域时（如使用UIScrollView），边界可能更大（原点不同）。你很少看到小于它们各自帧的边界。

Frame is the visible area of a view. Bounds is the internal area. Usually this has an origin of (0, 0) and is as wide and high as the frame. However, when the content exceeds the visible area (like with a UIScrollView) the bounds can be larger (and the origin different). You rarely see bounds that are smaller than their respective frames.

编辑：看看你的代码，[UINavigationController new]是什么？你应该做[[UINavigationController alloc] init]，不是吗？

Looking at your code, what is [UINavigationController new] about? You should do [[UINavigationController alloc] init], shouldn't you?

另外，你所做的并不是真正的子类化......

Also, what you are doing is not really subclassing...