UIScrollView下拉刷新加载数据

首先为UIScrollView添加加载提示View

    UILabel *refresh = [[UILabel alloc] initWithFrame:CGRectMake(0, -50, 320, 50)];
    refresh.text  = @"下拉刷新";
    self.refresh = refresh;
    refresh.tag = 0;
    [scrollV addSubview:refresh];

实现UIScrollViewDelegate

//offset发生改变

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    if (scrollView.contentOffset.y <= -50) {
        if (self.refresh.tag == 0) {
            self.refresh.text = @"松开刷新";
        }
        self.refresh.tag = 1;
    }else{
       //防止用户在下拉到contentOffset.y <= -50后不松手，然后又往回滑动，需要将值设为默认状态
        self.refresh.tag = 0;
        self.refresh.text = @"下拉刷新";
    }
}

//即将结束拖拽
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint*)targetContentOffset{
    if (self.refresh.tag == 1) {
        [UIView animateWithDuration:.3 animations:^{
            self.refresh.text = @"加载中";
            scrollView.contentInset = UIEdgeInsetsMake(50.0f, 0.0f, 0.0f, 0.0f);
        }];
        //数据加载成功后执行；这里为了模拟加载效果，一秒后执行恢复原状代码
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
            [UIView animateWithDuration:.3 animations:^{
                self.refresh.tag = 0;
                self.refresh.text = @"下拉刷新";
                scrollView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0);
            }];
        });
    }
}