要实现单击item转场动画，只需实现UITabBarDelegate下面的这个方法- tabBar: didSelectItem:，先看效果：

该代理方法加入位置，为自定义的UITabBarController视图控制器中，如：

@interface BuyerTabbarCtrl : UITabBarController<UITabBarControllerDelegate>

- (void)viewDidLoad

{

     [super viewDidLoad];

     self.delegate = self;

}

- (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item

{

     CATransition *animation = [CATransition animation]; //创建CATransition对象

     animation.duration = 0.77f;  //设置运动时间

      animation.type = @"rippleEffect"; //设置运动type

       //    animation.type = kCATransitionPush;

       animation.subtype = kCATransitionFromLeft; //设置子类

       animation.timingFunction = UIViewAnimationOptionCurveEaseInOut; //设置运动速度

      [self.view.layer addAnimation:animation forKey:@"animation"];

}