如何自定义UITabBarController的标签栏？

I have an iPad project using UITabBarController. I want to customize tab bar which shows up in the bottom. I want to create tabs of equal length, which is not a default case. If you create 3 tabs, the middle one is given a little space and the other two taking up lot of space. How to make these three tabs of equal length?I have an iPad project using UITabBarController