iOS UIRefreshControl基本用法

- (void) loadRefreshView
{
    // 下拉刷新
    _refreshControl = [[UIRefreshControl alloc] init];
    _refreshControl.attributedTitle = [[NSAttributedString alloc] initWithString:@"下拉刷新"];
    [_refreshControl addTarget:self action:@selector(loadData) forControlEvents:UIControlEventValueChanged];
    [self.securityCollectionView addSubview:_refreshControl];
    [self.securityCollectionView sendSubviewToBack:_refreshControl];
}

// 设置刷新状态
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    decelerate = YES;
    if (scrollView.contentOffset.y < HEIGHT_REFRESH) {
        dispatch_async(dispatch_get_main_queue(), ^{
            _refreshControl.attributedTitle = [[NSAttributedString alloc] initWithString:@"正在刷新"];
        });
        [_refreshControl beginRefreshing];
        [self loadData];
    }
}

// 设置刷新状态
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    if (scrollView.contentOffset.y >= HEIGHT_REFRESH) {
        _refreshControl.attributedTitle = [[NSAttributedString alloc] initWithString:@"下拉刷新"];
    }
    else if (!scrollView.decelerating) {
        _refreshControl.attributedTitle = [[NSAttributedString alloc] initWithString:@"松开刷新"];
    }
}

// 结束刷新
- (void) endRefreshControl
{
    [_refreshControl endRefreshing];
}

// 刷新的回调方法
- (void) loadData
{
    [self endRefreshControl];
   // [self performSelector:@selector(endRefreshControl) withObject:nil afterDelay:2];
}

//设置如果collection的内容没有占满整个collectionView，
//这个就不能下拉滑动，没法实现下拉；但是设置下面这个就可以实现下拉了
self.rootView.collectionView.alwaysBounceVertical = YES;