代码如下：

//设置滑动的判定范围- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset{    // 上滑动隐藏TabBar，上滑值越来越小，下滑动越来越大    if (self.historyY+20
     
      y)    {        [self setTabBarHidden:YES];    }    else if(self.historyY-20>targetContentOffset->y)    {                [self setTabBarHidden:NO];    }    self.historyY=targetContentOffset->y;} //隐藏显示tabbar- (void)setTabBarHidden:(BOOL)hidden{    UIView *tab = self.tabBarController.view;    CGRect  tabRect=self.tabBarController.tabBar.frame;    if ([tab.subviews count] < 2) {        return;    }        UIView *view;    if ([[tab.subviews objectAtIndex:0] isKindOfClass:[UITabBar class]]) {        view = [tab.subviews objectAtIndex:1];    } else {        view = [tab.subviews objectAtIndex:0];    }        if (hidden) {        view.frame = tab.bounds;        tabRect.origin.y=[[UIScreen mainScreen]bounds].size.height+self.tabBarController.tabBar.frame.size.height;    } else {        view.frame = CGRectMake(tab.bounds.origin.x, tab.bounds.origin.y, tab.bounds.size.width, tab.bounds.size.height);        tabRect.origin.y=[[UIScreen mainScreen] bounds].size.height-self.tabBarController.tabBar.frame.size.height;    }        [UIView animateWithDuration:0.5f animations:^{        self.tabBarController.tabBar.frame=tabRect;    }completion:^(BOOL finished) {            }];}