转自：http://blog.csdn.net/u013531246/article/details/44460115

为 Tabbar 添加 类别 ： HTBadge

.h文件

import <UIKit/UIKit.h>

@interface UITabBar (badge)

/显示小红点/

• (void)showBadgeOnItemIndex:(int)index;
  /隐藏小红点/
• (void)hideBadgeOnItemIndex:(int)index;

@end

.m文件

import "UITabBar+badge.h"

define TabbarItemNums 4.0 //tabbar的数量

@implementation UITabBar (badge)

• (void)showBadgeOnItemIndex:(int)index{

  //移除之前的小红点
  [self removeBadgeOnItemIndex:index];

  //新建小红点
  UIView *badgeView = [[UIView alloc]init];
  badgeView.tag = 888 + index;
  badgeView.layer.cornerRadius = 5;
  badgeView.backgroundColor = [UIColor redColor];
  CGRect tabFrame = self.frame;

  //确定小红点的位置
  float percentX = (index +0.6) / TabbarItemNums;
  CGFloat x = ceilf(percentX * tabFrame.size.width);
  CGFloat y = ceilf(0.1 * tabFrame.size.height);
  badgeView.frame = CGRectMake(x, y, 10, 10);
  [self addSubview:badgeView];

}

• (void)hideBadgeOnItemIndex:(int)index{

  //移除小红点
  [self removeBadgeOnItemIndex:index];

}

• (void)removeBadgeOnItemIndex:(int)index{

  //按照tag值进行移除
  for (UIView *subView in self.subviews) {

    if (subView.tag == 888+index) {
  
        [subView removeFromSuperview];
  
    }
  

  }
  }

@end

调用：
//显示
[self.tabBarController.tabBar showBadgeOnItemIndex:2];

//隐藏
[self.tabBarController.tabBar hideBadgeOnItemIndex:2]