Hacking UINavigationBar / Apple approval

Here is a screenshot from Evernote. It appears to have (but i might be wrong) a custom UINavigationBar as well as a custom UITabBar.

A quick glance 开发者_高级运维at the apps on my phone shows i could use a screenshot of Instagram, Path, DailyBooth, ...

From the docs:-

Because managing the navigation bar is the responsibility of the navigation controller, direct modification of the navigation bar itself is considered off limits for the most part.

Does Apple regard this kind of thing as grounds for AppStore refusal?

There's a distinction between "custom" navigation bars and using private methods.

Apple prevent you from directly modifying the navigation bar by make a lot of the required methods private or properties read-only. If you were to modify a read-only property or use a private undocumented method your application would be rejected (Apple automatically analyse code upon submission to detect for this sort of thing).

However, there's nothing to stop you from implementing your own UINavigationBar equivalent, or customising it using publicly available SDK methods. The issue then becomes whether your application strays too far from the Human Interface Guidelines: although to be honest, Apple are generally fairly flexible on that.

Whilst I wouldn't necessarily recommend this, I've worked on one app where we rolled our own navigation controller because we had some animation and transition requirements that we couldn't achieve with Apple's own class. As long as you're not calling anything untoward or drastically going against the HIGs, you're generally fine.