Question

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：

- (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，我就会将contentInset设置为刷新控件的高度。我认为动画会减少口吃/跳跃，这是在iOS 7中做的。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真实地跳下来快速，然后顺利动画。我不确定这是iOS 8中的错误还是什么。我也尝试过添加：

scrollView.contentOffset = CGPointZero;

在动画块中，没有改变任何东西。

有没有人有任何想法？任何帮助将受到高度赞赏。谢谢！

Answer 1

我用动画块将方法更改为：

- (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;
    }];
}

Answer 2

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
    CGPoint point = scrollView.contentOffset;

    static CGFloat refreshViewHeight = 200.0f;

    if (scrollView.contentInset.top == refreshViewHeight) {
        //openning
        if (point.y>-refreshViewHeight) {
            //will close
            //必须套两层animation才能避免闪动!
            [UIView animateWithDuration:0 animations:NULL completion:^(BOOL finished) {
                [UIView animateWithDuration:0.25 animations:^{
                    scrollView.contentOffset = CGPointMake(0.0f, 0.0f);
                    scrollView.contentInset = UIEdgeInsetsMake(0.0f, 0.0f, 0.0f, 0.0f);
                } completion:NULL];
            }];

        }
    }
    else{
        //closing
        static CGFloat openCriticalY = 40.0f;//会执行打开的临界值
        if(point.y<-openCriticalY){
            //will open
            [UIView animateWithDuration:0 animations:NULL completion:^(BOOL finished) {
                [UIView animateWithDuration:0.25 animations:^{
                    scrollView.contentInset = UIEdgeInsetsMake(refreshViewHeight, 0.0f, 0.0f, 0.0f);
                    scrollView.contentOffset = CGPointMake(0.0f, -refreshViewHeight);
                } completion:NULL];
            }];
        }
    }
}

你可以尝试这个，关键是使用两个动画。

Answer 3

为了消除跳跃，ryanthon的答案将成功。在我的iOS9.0应用程序中，甚至不需要动画块来移除跳转，只需在设置contentInset后重置contentOffset即可。

如果你想在隐藏刷新视图时控制tableView的滚动速度，那么在user3044484的回答中的双动画块技巧将会起到魔力，一个动画块是不够的。

if (self.tableView.contentInset.top == 0)
{
    UIEdgeInsets tableViewInset = self.tableView.contentInset;
    tableViewInset.top = -1.*kTableHeaderHeight;
    [UIView animateWithDuration: 0 animations: ^(void){} completion:^(BOOL finished) {
        [UIView animateWithDuration: 0.5 animations:^{
        //no need to set contentOffset, setting contentInset will change contentOffset accordingly.
            self.tableView.contentInset = tableViewInset;  
        }];
    }];
}

Answer 4

我遇到了同样的问题，并将我的动画块移到了......

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView

委托方法代替。不完美，但我还不能确定问题。看起来像在iOS8下更频繁地调用scrollView的-layoutSubviews方法，导致跳动动画。

Answer 5

两种解决方案：

开始加载时禁用退回，并在加载完成后启用退回
在开始加载时设置内容插入后，请将内容偏移设置为常量值

Answer 6

我已经解决了： -

将ContentInset更新为contentOffsetY时禁用Bounce。

跟踪contentOffset并更新到tableView ContentInset。

 var contentOffsetY:CGFloat = 100
    func tracScrollContent(location: UIScrollView) {
        if(location.contentOffset.y  == -contentOffsetY ) {
            tblView.isScrollEnabled = true
            tblView.bounces = false
            tblView.contentInset = UIEdgeInsets(top: contentOffsetY, left: 0, bottom: 0, right: 0)
        }else if(location.contentOffset.y >= 0 ){
            tblView.bounces = true
            tblView.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
        }
    }

Github Demo Swift-3

Answer 7

不幸的是，- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView中的动画对我来说不起作用。无论如何，滚动视图都会反弹。

根据Bounds automatically changes on UIScrollView with content insets，这对我来说似乎是一个iOS8错误......

动画UIScrollView contentInset会导致跳转卡顿

7 个答案: