在swift中使用UICollectionView粘性标头 [英] UICollectionView sticky header in swift

问题描述

我正在尝试创建一个粘性补充标头，它始终保持在顶部并且不会响应滚动事件。到目前为止我发现的解决方案仍然对bounch滚动做出反应并使用自定义flowlayout进行修复，这可能也是我的问题的解决方案。

I'm trying to create a sticky supplementary header, which stays in top all the time and wont response to scrolling events. The solutions I found so far still react on bounch scrolling and are fixed using a custom flowlayout, which will probably be the fix for mine issue as well.

我想要的原因这样，标题是在其他地方使用，应该是可重用的。我希望这可以通过这种方式解决，我不必创建一个单独的视图。

The reason I want it this way, is that the header is used on other places and should be reusable. I'm hoping this could be solved this way and I don't have to create a separated view.

正如我在Swift中这样做的，它会很棒在Swift中有一个例子。

As I'm doing this in Swift, it would be great to have an example in Swift.

推荐答案

我找到的最终解决方案：

使用此自定义流布局可以修复此粘性标题：

Using this custom flow layout it was possible to fix this sticky header:

class StickyHeaderCollectionViewFlowLayout: UICollectionViewFlowLayout {

    override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]? {

        var superAttributes: [UICollectionViewLayoutAttributes]? = super.layoutAttributesForElementsInRect(rect) as? [UICollectionViewLayoutAttributes]

        if superAttributes == nil {
            // If superAttributes couldn't cast, return
            return super.layoutAttributesForElementsInRect(rect)
        }

        let contentOffset = collectionView!.contentOffset
        var missingSections = NSMutableIndexSet()

        for layoutAttributes in superAttributes! {
            if (layoutAttributes.representedElementCategory == .Cell) {
                if let indexPath = layoutAttributes.indexPath {
                    missingSections.addIndex(layoutAttributes.indexPath.section)
                }
            }
        }

        for layoutAttributes in superAttributes! {
            if let representedElementKind = layoutAttributes.representedElementKind {
                if representedElementKind == UICollectionElementKindSectionHeader {
                    if let indexPath = layoutAttributes.indexPath {
                        missingSections.removeIndex(indexPath.section)
                    }
                }
            }
        }

        missingSections.enumerateIndexesUsingBlock { idx, stop in
            let indexPath = NSIndexPath(forItem: 0, inSection: idx)
            if let layoutAttributes = self.layoutAttributesForSupplementaryViewOfKind(UICollectionElementKindSectionHeader, atIndexPath: indexPath) {
                superAttributes!.append(layoutAttributes)
            }
        }

        for layoutAttributes in superAttributes! {
            if let representedElementKind = layoutAttributes.representedElementKind {
                if representedElementKind == UICollectionElementKindSectionHeader {
                    let section = layoutAttributes.indexPath!.section
                    let numberOfItemsInSection = collectionView!.numberOfItemsInSection(section)

                    let firstCellIndexPath = NSIndexPath(forItem: 0, inSection: section)!
                    let lastCellIndexPath = NSIndexPath(forItem: max(0, (numberOfItemsInSection - 1)), inSection: section)!


                    let (firstCellAttributes: UICollectionViewLayoutAttributes, lastCellAttributes: UICollectionViewLayoutAttributes) = {
                        if (self.collectionView!.numberOfItemsInSection(section) > 0) {
                            return (
                                self.layoutAttributesForItemAtIndexPath(firstCellIndexPath),
                                self.layoutAttributesForItemAtIndexPath(lastCellIndexPath))
                        } else {
                            return (
                                self.layoutAttributesForSupplementaryViewOfKind(UICollectionElementKindSectionHeader, atIndexPath: firstCellIndexPath),
                                self.layoutAttributesForSupplementaryViewOfKind(UICollectionElementKindSectionFooter, atIndexPath: lastCellIndexPath))
                        }
                        }()

                    let headerHeight = CGRectGetHeight(layoutAttributes.frame)
                    var origin = layoutAttributes.frame.origin

                    origin.y = min(contentOffset.y, (CGRectGetMaxY(lastCellAttributes.frame) - headerHeight))
                    // Uncomment this line for normal behaviour:
                    // origin.y = min(max(contentOffset.y, (CGRectGetMinY(firstCellAttributes.frame) - headerHeight)), (CGRectGetMaxY(lastCellAttributes.frame) - headerHeight))

                    layoutAttributes.zIndex = 1024
                    layoutAttributes.frame = CGRect(origin: origin, size: layoutAttributes.frame.size)
                }
            }
        }

        return superAttributes
    }

    override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
        return true
    }

}

要像传统一样创建标题粘贴的布局，请更改此行：

To create a layout where the headers are sticky like traditional, change this line:

origin.y = min(contentOffset.y, (CGRectGetMaxY(lastCellAttrs.frame) - headerHeight))

到此行：

origin.y = min(max(contentOffset.y, (CGRectGetMinY(firstCellAttrs.frame) - headerHeight)), (CGRectGetMaxY(lastCellAttrs.frame) - headerHeight))

希望这对其他人有用！

更新

更新以修复崩溃（感谢Robert Atkins！）和Swift 1.2的一些更新

Updated to fix a crash (thanks to Robert Atkins!) and some updates to Swift 1.2

tvOS& iOS 9

tvOS和iOS 9引入了属性 sectionHeadersPinToVisibleBounds 可以使用

tvOS and iOS 9 introduced the property sectionHeadersPinToVisibleBounds which can be used

这篇关于在swift中使用UICollectionView粘性标头的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！