實現(xiàn)思路：通過遍歷tabBar的subviews拿到到點擊的view,然后再做動畫效果

在UITabBarController繼承類上對didSelectItem操作
indexFlag:全局變量：作用是防止重復點擊相同的bar觸發(fā)動畫效果
下面的代碼的動畫消果是:點擊縮小再恢復原樣

-(void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item{
    NSInteger index = [self.tabBar.items indexOfObject:item];
    if (self.indexFlag == index) {
        return;
    }
        NSMutableArray *btnArray = [NSMutableArray array];
        for (UIView *barView in self.tabBar.subviews) {
            if ([barView isKindOfClass:NSClassFromString(@"UITabBarButton")]) {
                [btnArray addObject:barView];
            }
        }
    UIView *btnView = [btnArray objectAtIndex:index];
    for (UIImageView *btnImageView in btnView.subviews) {
        if ([btnImageView isKindOfClass:[UIImageView class]]) {
            [UIView animateWithDuration:0.15 animations:^{
                btnImageView.transform = CGAffineTransformMakeScale(0.7, 0.7);
            } completion:^(BOOL finished) {
                [UIView animateWithDuration:0.15 animations:^{
                    btnImageView.transform = CGAffineTransformIdentity;
                }];
            }];
        }
    }
    self.indexFlag = index;
}