//title上移
// [vc.tabBarItem setTitlePositionAdjustment:UIOffsetMake(0,y)];
//image上移
viewController.tabBarItem.imageInsets=UIEdgeInsetsMake(-15,0,15,0);
//这里y为0时即系统title位置，y小于0时title上移，image上移时x小于0，x与w为相反数，image位置才会显示在中间。
文字设置富文本
UITabBarItem *item = [UITabBarItem appearanceWhenContainedIn:self, nil];
NSMutableDictionary *dic = [NSMutableDictionary dictionary];
dic[NSForegroundColorAttributeName] = [UIColor whiteColor];
dic[NSFontAttributeName] = [UIFont systemFontOfSize:12];
[item setTitleTextAttributes:dic forState:UIControlStateSelected];
