UINavigationBar *navigationBar = self.navigationController.navigationBar;
// white.png图片自己下载个纯白色的色块,或者自己ps做一个
[navigationBar setBackgroundImage:[UIImage imageNamed:@"nav2"]
forBarPosition:UIBarPositionAny
barMetrics:UIBarMetricsDefault];
[navigationBar setShadowImage:[UIImage new]];
原文:http://www.cnblogs.com/yangxiaolong/p/5196966.html