动画UIScrollView contentInset会导致跳转卡顿 [英] Animating UIScrollView contentInset causes jump stutter

问题描述

我实现了自定义刷新控件（我自己的类，而不是子类），并且由于某些原因，因为移动到iOS 8，设置滚动视图的contentInset（特别是UICollectionView）以启动刷新动画会导致奇怪的跳转/口吃。这是我的代码：

I implemeted a custom refresh control (my own class, not a subclass), and for some reason since moving to iOS 8, setting the contentInset of the scroll view (specifically, UICollectionView) to start the refresh animation causes a weird jump/stutter. Here is my code:

- (void)containingScrollViewDidScroll:(UIScrollView *)scrollView
{
    CGFloat scrollPosition = scrollView.contentOffset.y + scrollView.contentInset.top;

    if( scrollPosition > 0 || self.isRefreshing )
    {
        return;
    }

    CGFloat percentWidth = fabs( scrollPosition ) / self.frame.size.height / 2;

    CGRect maskFrame = self.maskLayer.frame;

    maskFrame.size.width = self.imageLayer.frame.size.width * percentWidth;

    [CATransaction begin];
    [CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];
    self.maskLayer.frame = maskFrame;
    [CATransaction commit];
}

- (void)containingScrollViewDidEndDragging:(UIScrollView *)scrollView
{
    if( ( self.maskLayer.frame.size.width >= self.imageLayer.frame.size.width ) && !self.isRefreshing )
    {
        self.isRefreshing = YES;
        [self setLoadingScrollViewInsets:scrollView];
        [self startAnimation];
        [self sendActionsForControlEvents:UIControlEventValueChanged];
    }
}

- (void)setLoadingScrollViewInsets:(UIScrollView *)scrollView
{
    UIEdgeInsets loadingInset = scrollView.contentInset;
    loadingInset.top += self.frame.size.height;

    UIViewAnimationOptions options = UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionBeginFromCurrentState;

    [UIView animateWithDuration:0.2 delay:0 options:options animations:^
    {
        scrollView.contentInset = loadingInset;
    }
    completion:nil];
}

基本上，一旦用户发布刷新，我将contentInset设置为动画的高度刷新控制。我认为动画会减少口吃/跳跃，这是在iOS 7中完成的。但是在iOS 8中，当scrollView从拖动中释放出来，而不是仅仅动画到contentInset时，滚动视图内容从发布点开始跳跃快速，然后顺利动画。我不确定这是iOS 8中的错误还是什么。我也试过添加：

Basically once the user releases to refresh, I animate the contentInset to the height of the refresh control. I figure the animation would reduce stuttering/jumpiness, which it did in iOS 7. But in iOS 8, when the scrollView is released from dragging, instead of just animating to the contentInset, the scroll view content jumps down from the point of release really quickly, and then animates up smoothly. I'm not sure if this is a bug in iOS 8 or what. I've also tried adding:

scrollView.contentOffset = CGPointZero;

动画块中的

，没有任何改变。

in the animation block, which didn't change anything.

有没有人有任何想法？任何帮助将受到高度赞赏。谢谢！

Does anyone have any ideas? Any help would be highly appreciated. Thanks!

推荐答案

我用动画块改变了方法：

I changed the method with my animation block to:

- (void)setLoadingScrollViewInsets:(UIScrollView *)scrollView
{
    UIEdgeInsets loadingInset = scrollView.contentInset;
    loadingInset.top += self.view.frame.size.height;

    CGPoint contentOffset = scrollView.contentOffset;

    [UIView animateWithDuration:0.2 animations:^
    {
        scrollView.contentInset = loadingInset;
        scrollView.contentOffset = contentOffset;
    }];
}

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