设置纯色背景图

[self.tabBarsetBackgroundImage:[LocalImageHelperimageWithColor:[UIColorwhiteColor]]];
[self.tabBarsetShadowImage:[LocalImageHelper imageWithColor:[UIColor clearColor]]];

系统阴影

self.tabBar.layer.shadowOpacity=0.5;
self.tabBar.layer.shadowColor= [UIColorgrayColor].CGColor;
self.tabBar.layer.shadowRadius=3;
self.tabBar.layer.shadowOffset=CGSizeMake(1,1);