UIRefreshControl加到UIScrollView上下拉刷新，出现跳跃

一个UIViewController 的- (void)viewDidLoad中初始化了一个UIScrollView在它上面加一个UIRefreshControl，实现下拉刷新。下拉刷新的过程中ScrollView会出现跳跃。谁知道这是为什么？（请回答中不要告诉我可以采用其他方法如EGO，我就是想知道为什么，谢谢大神）
下面是viewDidLoad的代码。

 - (void)viewDidLoad
      {
       [super viewDidLoad];
       UIScrollView *scrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
    [scrollView setBackgroundColor:[UIColor whiteColor]];
    [scrollView setContentSize:CGSizeMake([UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
    scrollView.alwaysBounceVertical = YES;
    [self.view addSubview:scrollView];
    UIView *topView = [[UIView alloc] initWithFrame:CGRectMake(0, -200, scrollView.bounds.size.width, 200)];
    [topView setBackgroundColor:[UIColor brownColor]];
    [scrollView addSubview:topView];
    UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
    [refreshControl addTarget:self action:@selector(testRefresh:) forControlEvents:UIControlEventValueChanged];

    [scrollView addSubview:refreshControl];
    [self.view addSubview:scrollView];
    }

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这个问题解决了吗？

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是因为contentOffset改变导致的，再设置一下contentOffset应该就行了

dispatch_async(dispatch_get_main_queue(), ^{
            [UIView animateWithDuration:kAnimationDuration animations:^{
                self.scrollView.contentInset = inset;
                [self.scrollView setContentOffset:CGPointMake(0, -inset.top) animated:NO];
            } completion:^(BOOL finished) {
            }];
        });

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Because the refresh control is specifically designed for use in a table view that's managed by a table view controller, using it in a different context can result in undefined behavior.

我没有试过你这样来用UIRefreshControl。同时，苹果文档已经指出，UIRefreshControl是为了tableView而设计的。所以，会有一些不明确的行为就如上所说。
如果是我，我的解决办法是将UIScrollView改称一个static的UITableView with one cell only, 然后那个cell的高度和你屏幕的高度一样。

多查查文档