IOS 7修改UITabbar背景图片、UITabBarItem图片以及UITabBarItem的文字颜色.

IOS7中常常会遇到这样的总是UITabbar的颜色和整体设计风格不搭调，默认的灰色常常让人抓狂!

[[UITabBarItems appearance] setTitleTextAttributes:[NSDictionary
dictionaryWithObjectsAndKeys: [UIColor whiteColor],NSForegroundColorAttributeName, nil]
forState:UIControlStateNormal];

修改背景图片
[self.tabBar setBackgroundImage:[UIImage imageNamed:@"home_bg"]];

默认情况下，Tabbar中的icon无论初始是什么颜色，都会变强制成灰色,这需要我们用另一种方法载入

NSArray *items = self.tabBar.items;
UITabBarItem *homeItem = items[0];
homeItem.image = [[UIImage imageNamed:@"home"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
homeItem.selectedImage = [[UIImage imageNamed:@"home"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];