Question

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。

我想这样做的原因是标头在其他地方使用并且应该是可重复使用的。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。

正如我在Swift中所做的那样，在Swift中有一个例子会很棒。

Answer 1

最简单的iOS 9 +解决方案，因为它不需要编写UICollectionViewFlowLayout的子类。

在带有collectionView的viewController的viewDidLoad中使用以下代码：

let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout // casting is required because UICollectionViewLayout doesn't offer header pin. Its feature of UICollectionViewFlowLayout
layout?.sectionHeadersPinToVisibleBounds = true

@Antoine也暗示了它。

Answer 2

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：

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
    }

}

要创建标题粘贴的布局，请更改此行：

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

到这一行：

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

希望这对其他人有用！

<强>更新

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

tvOS＆amp; iOS 9

tvOS和iOS 9引入了可以使用的属性sectionHeadersPinToVisibleBounds

Answer 3

使用swift 2.0

为我工作

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

    var superAttributes:NSMutableArray = NSMutableArray(array: super.layoutAttributesForElementsInRect(rect)!) as NSMutableArray

    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)
        let layoutAttributes = self.layoutAttributesForSupplementaryViewOfKind(UICollectionElementKindSectionHeader, atIndexPath: indexPath)
        superAttributes.addObject(layoutAttributes!)
    }

    for la in superAttributes {

        let layoutAttributes = la as! UICollectionViewLayoutAttributes;

        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)                    

                var firstCellAttributes:UICollectionViewLayoutAttributes
                var lastCellAttributes:UICollectionViewLayoutAttributes

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

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

                 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 NSArray(array: superAttributes) as? [UICollectionViewLayoutAttributes]
}

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

Answer 4

我通过测试this gist中建议的空白部分测试来修复崩溃。我还为额外的Swift风格点添加了几个if let s ;-)。这对我有用：

class StickyHeaderCollectionViewFlowLayout: UICollectionViewFlowLayout {

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

        var answer: [UICollectionViewLayoutAttributes] = super.layoutAttributesForElementsInRect(rect)! as [UICollectionViewLayoutAttributes]
        let contentOffset = collectionView!.contentOffset

        var missingSections = NSMutableIndexSet()

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

        for layoutAttributes in answer {
            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) {
                answer.append(layoutAttributes)
            }
        }

        for layoutAttributes in answer {
            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(max(contentOffset.y, (CGRectGetMinY(firstCellAttributes.frame) - headerHeight)), (CGRectGetMaxY(lastCellAttributes.frame) - headerHeight))

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

        return answer
    }

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

}

Answer 5

根据GregP的答案测试了Swift 2.2版本。 Greg的代码在 lastCellIndexPath 上抛出了一个解包可选错误，因为section的数量最初为零。所以我移动了 numberOfItemsInSection＆gt; 0 检查。

$type = filter_input(INPUT_GET, "type");


$target_dir_header = $includesDir . "dashboard/resources/header_pic/";
$dataHeader = $_FILES['input7'];
$dataHeader_ext = explode('/', $dataHeader['type']);
$imageFileType_header = $dataHeader_ext[1];
$target_file_header = $target_dir_header . basename("header" . $imageFileType_header);


echo $type . " - " . $imageFileType_header;

Answer 6

如果您只有一个部分，这是一个简单的解决方案。

class StickyHeaderLayout: UICollectionViewFlowLayout {

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

  override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]? {
    var attributes = super.layoutAttributesForElementsInRect(rect)! as! [UICollectionViewLayoutAttributes]

      let offset          = collectionView?.contentOffset


      for attrs in attributes {
        if attrs.representedElementKind == nil {
          let indexPath        = NSIndexPath(forItem: 0, inSection: attrs.indexPath.section)
          let layoutAttributes = self.layoutAttributesForSupplementaryViewOfKind(UICollectionElementKindSectionHeader, atIndexPath: indexPath)

          attributes.append(layoutAttributes)
        }
      }

      for attrs in attributes {
        if attrs.representedElementKind == nil {
          continue
        }

        if attrs.representedElementKind == UICollectionElementKindSectionHeader {

          var headerRect = attrs.frame
          headerRect.size.height = headerHeight
          headerRect.origin.y = offset!.y
          attrs.frame = headerRect
          attrs.zIndex = 1024
          break
        }
      }

    return attributes
  }
}

Answer 7

Cleaner Swift 2.3测试了Irina的答案

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

    guard var superAttributes = super.layoutAttributesForElementsInRect(rect) else {
        return super.layoutAttributesForElementsInRect(rect)
    }

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

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

        if let representedElementKind = layoutAttributes.representedElementKind {
            if representedElementKind == UICollectionElementKindSectionHeader {
                missingSections.removeIndex(layoutAttributes.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)

                var firstCellAttributes:UICollectionViewLayoutAttributes
                var lastCellAttributes:UICollectionViewLayoutAttributes

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

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

                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
}

Answer 8

Swift 3版本试图避免！＆＃39; s它在哪里有意义。

class StickyHeaderCollectionViewFlowLayout: UICollectionViewFlowLayout {

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard var superAttributes = super.layoutAttributesForElements(in: rect), let collectionView = collectionView else {
            return super.layoutAttributesForElements(in: rect)
        }

        let collectionViewTopY = collectionView.contentOffset.y + collectionView.contentInset.top
        let contentOffset = CGPoint(x: 0, y: collectionViewTopY)
        let missingSections = NSMutableIndexSet()

        superAttributes.forEach { layoutAttributes in
            if layoutAttributes.representedElementCategory == .cell && layoutAttributes.representedElementKind != UICollectionElementKindSectionHeader {
                missingSections.add(layoutAttributes.indexPath.section)
            }
        }

        missingSections.enumerate(using: { idx, stop in
            let indexPath = IndexPath(item: 0, section: idx)
            if let layoutAttributes = self.layoutAttributesForSupplementaryView(ofKind: UICollectionElementKindSectionHeader, at: indexPath) {
                superAttributes.append(layoutAttributes)
            }
        })

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

                    let firstCellIndexPath = IndexPath(item: 0, section: section)
                    let lastCellIndexPath = IndexPath(item: max(0, (numberOfItemsInSection - 1)), section: section)                   

                    let cellAttributes:(first: UICollectionViewLayoutAttributes, last: UICollectionViewLayoutAttributes) = {
                        if (collectionView.numberOfItems(inSection: section) > 0) {
                            return (
                                self.layoutAttributesForItem(at: firstCellIndexPath)!,
                                self.layoutAttributesForItem(at: lastCellIndexPath)!)
                        } else {
                            return (
                                self.layoutAttributesForSupplementaryView(ofKind: UICollectionElementKindSectionHeader, at: firstCellIndexPath)!,
                                self.layoutAttributesForSupplementaryView(ofKind: UICollectionElementKindSectionFooter, at: lastCellIndexPath)!)
                        }
                    }()

                    let headerHeight = layoutAttributes.frame.height
                    var origin = layoutAttributes.frame.origin
                    // This line makes only one header visible fixed at the top
//                    origin.y = min(contentOffset.y, cellAttributes.last.frame.maxY - headerHeight)
                    // Uncomment this line for normal behaviour:
                    origin.y = min(max(contentOffset.y, cellAttributes.first.frame.minY - headerHeight), cellAttributes.last.frame.maxY - headerHeight)

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

        return superAttributes
    }

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

Answer 9

我在我的项目中使用它。希望它有所帮助。

    func collectionView(collectionView: UICollectionView,
    layout collectionViewLayout: UICollectionViewLayout,
    referenceSizeForHeaderInSection section: Int) -> CGSize
{
    return CGSizeMake(UIScreen.mainScreen().bounds.width, 40)
}

当然。你可以返回任何你想要的尺寸。

在swift中使用UICollectionView粘贴头

9 个答案: