scrollRectToVisible

.m

    CGRect menuScrollViewRect = CGRectMake(
                                           menuRect.origin.x - (tabMenuRect.size.width - menuRect.size.width) / 2,
                                           menuRect.origin.y,
                                           tabMenuRect.size.width,
                                           tabMenuRect.size.height
                                           );
    [menuScrollView scrollRectToVisible:menuScrollViewRect animated:YES];