self.navigationItem.title = @"my title"; //sets navigation bar title.

self.tabBarItem.title = @"my title"; //sets tab bar title.

self.title = @"my title"; //sets both of these.

参考:http://blog.csdn.net/huifeidexin_1/article/details/8078118

UITabBarItem title 和self.title设置不同的标题