将UICollectionView滚动到节标题视图

Question

下面的代码滚动到右边的单元格UICollectionView,但UINavigationBar在我的情况下隐藏了部分标题视图.我相信我应该使用scrollRectToVisible而我的问题是,CGRect当numberOfRows给定section的变量时,计算(y位置)的正确方法是什么.

- (void)scrollToPricing:(NSUInteger)row {

    [self.collectionView scrollToItemAtIndexPath:
      [NSIndexPath indexPathForItem:0 
                          inSection:row] 
                   atScrollPosition:UICollectionViewScrollPositionTop 
                           animated:YES];
}

Answer 1

似乎所有答案都过于复杂.这对我有用:

let attributes = self.collectionView.collectionViewLayout.layoutAttributesForSupplementaryViewOfKind(UICollectionElementKindSectionHeader, atIndexPath: NSIndexPath(forItem: 0, inSection: section))

self.collectionView.setContentOffset(CGPointMake(0, attributes!.frame.origin.y - self.collectionView.contentInset.top), animated: true)

斯威夫特3:

if let attributes = collectionView.collectionViewLayout.layoutAttributesForSupplementaryView(ofKind: UICollectionElementKindSectionHeader, at: IndexPath(item: 0, section: section)) {
    collectionView.setContentOffset(CGPoint(x: 0, y: attributes.frame.origin.y - collectionView.contentInset.top), animated: true)
}

Answer 2

我想这可能会对你有所帮助

UICollectionViewLayoutAttributes *attributes = [self.collectionView layoutAttributesForItemAtIndexPath:indexPath];

然后你可以通过访问该位置 attributes.frame

Answer 3

首先,获取节中标题的框架:

- (CGRect)frameForHeaderForSection:(NSInteger)section {
    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:1 inSection:section];
    UICollectionViewLayoutAttributes *attributes = [self.collectionView layoutAttributesForItemAtIndexPath:indexPath];
    CGRect frameForFirstCell = attributes.frame;
    CGFloat headerHeight = [self collectionView:_collectionView layout:_layout referenceSizeForHeaderInSection:section].height;
    return CGRectOffset(frameForFirstCell, 0, -headerHeight);
}

注:我只是把值1的indexPath.item.您可能需要将其更改为适合您的实现的内容.

然后,滚动UIScrollView到标题顶部的点:

- (void)scrollToTopOfSection:(NSInteger)section animated:(BOOL)animated {
    CGRect headerRect = [self frameForHeaderForSection:section];
    CGPoint topOfHeader = CGPointMake(0, headerRect.origin.y - _collectionView.contentInset.top);
    [_collectionView setContentOffset:topOfHeader animated:animated];
}

注意:您必须减去contentInset,否则它将被丢弃,您的滚动视图将滚动状态栏和/或导航栏后面.

Answer 4

根据@pixelfreak答案

Swift 4.2+ iOS 11 Safe Area支持（适用于iPhone X及更高版本）

if let attributes = collectionView.layoutAttributesForSupplementaryElement(ofKind: UICollectionView.elementKindSectionHeader, at: IndexPath(item: 0, section: section)) {
    var offsetY = attributes.frame.origin.y - collectionView.contentInset.top
    if #available(iOS 11.0, *) {
        offsetY -= collectionView.safeAreaInsets.top
    }
    collectionView.setContentOffset(CGPoint(x: 0, y: offsetY), animated: true) // or animated: false
}

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