方式一 
代码实现 这种要写很多代码 ，每个控制器都要写 
 UIImage *image=[UIImage imageNamed:@"tabBar_friendTrends_click_icon"];
//    不让tabbar底部有渲染的关键代码
     image=[image imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    vc01.tabBarItem.selectedImage=image;
 
更改tabbar下方的文字样式，大小， 颜色
  NSMutableDictionary *atts=[NSMutableDictionary dictionary];
// 更改文字大小
    atts[NSFontAttributeName]=[UIFont systemFontOfSize:12];
// 更改文字颜色
    atts[NSForegroundColorAttributeName]=[UIColor darkGrayColor];
 
    NSMutableDictionary *selectedAtts=[NSMutableDictionary dictionary];
    selectedAtts[NSFontAttributeName]=[UIFont systemFontOfSize:12];
    selectedAtts[NSForegroundColorAttributeName]=[UIColor greenColor];
    [vc01.tabBarItem setTitleTextAttributes:selectedAtts forState:UIControlStateSelected];
 

方式二
在 Assets.xcassets文件夹中更改 改变之后不用代码 并且在所有的控制器里面都会被作用到
具体操作

818241-20160525090140084-966278469.png

appearance属性
//    通过appearance统一设置所有的UITabBarItem的文字属性
//    后面带有UI_APPEARANCE_SELECTOR的方法，都可以通过appearance同意设置
例如UITabBarItem的文字属性
案例； 

    NSMutableDictionary *atts=[NSMutableDictionary dictionary];
    atts[NSFontAttributeName]=[UIFont systemFontOfSize:12];
    atts[NSForegroundColorAttributeName]=[UIColor grayColor];
   
    NSMutableDictionary *selectedAtts=[NSMutableDictionary dictionary];
    selectedAtts[NSFontAttributeName]=atts[NSFontAttributeName];
    selectedAtts[NSForegroundColorAttributeName]=[UIColor darkGrayColor];
// 在这里 只要更改，所有的文字都改
 
    UITabBarItem *item=[UITabBarItem appearance];
    [item setTitleTextAttributes:atts forState:UIControlStateNormal];
    [item setTitleTextAttributes:selectedAtts forState:UIControlStateSelected];
   
    //    添加子控制器
    UIViewController *vc01=[[UIViewController alloc]init];
    vc01.view.backgroundColor=[UIColor redColor];
    vc01.tabBarItem.title=@"精华";
    vc01.tabBarItem.image=[UIImage imageNamed:@"tabBar_essence_icon"];
    UIImage *image=[UIImage imageNamed:@"tabBar_friendTrends_click_icon"];
//    不让tabbar底部有渲染的关键代码
     image=[image imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    vc01.tabBarItem.selectedImage=image;
// 把控制器 添加到 UITabBarController里面去
    [self addChildViewController:vc01];
   
    UIViewController *vc02=[[UIViewController alloc]init];
    vc02.tabBarItem.title=@"新帖";
    vc02.tabBarItem.image=[UIImage imageNamed:@"tabBar_new_click_icon"];
    vc02.tabBarItem.selectedImage=[UIImage imageNamed:@"tabBar_new_click_icon"];
    vc02.view.backgroundColor=[UIColor cyanColor];
    [self addChildViewController:vc02];
   
    UIViewController *vc03=[[UIViewController alloc]init];
    vc03.view.backgroundColor=[UIColor blueColor];
    vc03.tabBarItem.title=@"关注";
    vc03.tabBarItem.image=[UIImage imageNamed:@"tabBar_friendTrends_icon"];
    vc03.tabBarItem.selectedImage=[UIImage imageNamed:@"tabBar_friendTrends_click_icon"];
    [self addChildViewController:vc03];
   
    UIViewController *vc04=[[UIViewController alloc]init];
    vc04.tabBarItem.title=@"我";
    vc04.tabBarItem.image=[UIImage imageNamed:@"tabBar_me_icon"];
    vc04.tabBarItem.selectedImage=[UIImage imageNamed:@"tabBar_me_click_icon"];
    vc04.view.backgroundColor=[UIColor yellowColor];
    [self addChildViewController:vc04];