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| // | |
| // SectionBackgroundFlowLayout.swift | |
| // | |
| // Created by Samuel's on 2020/7/29. | |
| import UIKit | |
| @objc protocol SectionBackgroundFlowLayoutDelegate: NSObjectProtocol { | |
| func sectionsNeedBackgroundColor(in collectionView: UICollectionView, layout: UICollectionViewFlowLayout) -> [Int] | |
| func classForBackgroundViewAttributes() -> UICollectionViewLayoutAttributes.Type | |
| func classForBackgroundView() -> UICollectionReusableView.Type | |
| func configSectionBackgroundViewAttributes(_ attributes: UICollectionViewLayoutAttributes, | |
| layout: UICollectionViewFlowLayout, | |
| at section: Int) | |
| @objc optional func sectionBackgroundViewInset(at section: Int) -> UIEdgeInsets | |
| } | |
| class SectionBackgroundColorLayoutAttributes: UICollectionViewLayoutAttributes { | |
| var color: UIColor? | |
| override func copy(with zone: NSZone? = nil) -> Any { | |
| let new = super.copy(with: zone) | |
| (new as? SectionBackgroundColorLayoutAttributes)?.color = color | |
| return new | |
| } | |
| } | |
| class SectionBackgroundReusableView: UICollectionReusableView { | |
| override func apply(_ layoutAttributes: UICollectionViewLayoutAttributes) { | |
| super.apply(layoutAttributes) | |
| let scLayoutAttributes = layoutAttributes as! SectionBackgroundColorLayoutAttributes | |
| backgroundColor = scLayoutAttributes.color | |
| } | |
| } | |
| class SectionBackgroundFlowLayout: UICollectionViewFlowLayout { | |
| private static let sectionBackgroundColorElement = "sectionBackgroundColorElement" | |
| private var sectionMaxYPairs: [Int: CGFloat] = [:] | |
| private var sectionInsetPairs: [Int: UIEdgeInsets] = [:] | |
| private var sectionLineSpacing: [Int: CGFloat] = [:] | |
| private var sectionBackgroundAttributesPairs: [Int: UICollectionViewLayoutAttributes] = [:] | |
| weak var sectionBackgroundDelegate: SectionBackgroundFlowLayoutDelegate? | |
| // MARK: prepareLayout | |
| override func prepare() { | |
| super.prepare() | |
| guard let delegate = sectionBackgroundDelegate else { | |
| // assertionFailure("SET sectionBackgroundDelegate FIRST!") | |
| return | |
| } | |
| register(delegate.classForBackgroundView(), forDecorationViewOfKind: SectionBackgroundFlowLayout.sectionBackgroundColorElement) | |
| prepareSectionInsetPairs() | |
| prepareSectionLineSpacing() | |
| prepareIndices() | |
| prepareSectionBackgroundAttributes() | |
| } | |
| private func prepareSectionInsetPairs() { | |
| sectionInsetPairs.removeAll() | |
| guard let collectionView = collectionView else { | |
| return | |
| } | |
| for section in 0 ..< collectionView.numberOfSections { | |
| let inset = (collectionView.delegate as? UICollectionViewDelegateFlowLayout)? | |
| .collectionView?(collectionView, layout: self, insetForSectionAt: section) ?? sectionInset | |
| sectionInsetPairs[section] = inset | |
| } | |
| } | |
| private func prepareSectionLineSpacing() { | |
| sectionLineSpacing.removeAll() | |
| guard let collectionView = collectionView else { return } | |
| for section in 0 ..< collectionView.numberOfSections { | |
| let spacing = (collectionView.delegate as? UICollectionViewDelegateFlowLayout)? | |
| .collectionView?(collectionView, layout: self, minimumLineSpacingForSectionAt: section) ?? minimumLineSpacing | |
| sectionLineSpacing[section] = spacing | |
| } | |
| } | |
| private func prepareIndices() { | |
| sectionInsetPairs.removeAll() | |
| sectionMaxYPairs.removeAll() | |
| guard let collectionView = collectionView else { return } | |
| prepareSectionInsetPairs() | |
| let numberOfSections = collectionView.numberOfSections | |
| var currentSectionMaxY: CGFloat = 0 | |
| for section in 0 ..< numberOfSections { | |
| let numberOfItems = collectionView.numberOfItems(inSection: section) | |
| guard numberOfItems > 0 else { | |
| // remove may exists decorate | |
| sectionBackgroundAttributesPairs[section] = nil | |
| continue | |
| } | |
| let interitemSpacing = (collectionView.delegate as? UICollectionViewDelegateFlowLayout)? | |
| .collectionView?(collectionView, layout: self, minimumInteritemSpacingForSectionAt: section) ?? minimumInteritemSpacing | |
| let currentSectionInset = sectionInsetPairs[section]! | |
| let sizeArray = (0 ..< numberOfItems) | |
| .map { item in | |
| (collectionView.delegate as? UICollectionViewDelegateFlowLayout)? | |
| .collectionView?(collectionView, layout: self, sizeForItemAt: IndexPath(item: item, section: section)) ?? itemSize | |
| } | |
| let sectionWidth = collectionViewContentSize.width - currentSectionInset.left - currentSectionInset.right | |
| currentSectionMaxY = currentSectionMaxY | |
| + ((collectionView.delegate as? UICollectionViewDelegateFlowLayout)?.collectionView?(collectionView, layout: self, referenceSizeForHeaderInSection: section).height ?? 0) | |
| + currentSectionInset.top | |
| var lineWidth: CGFloat = 0 | |
| var lineHeight: CGFloat = 0 | |
| let widthArray = sizeArray.map { $0.width } | |
| for itemIndex in 0 ..< widthArray.count { | |
| assert(widthArray[itemIndex] <= sectionWidth, "Only Vertical Support!! itemWidth Should <= sectionWidth") | |
| lineHeight = max(sizeArray[itemIndex].height, lineHeight) | |
| let hasNext = widthArray.indices ~= itemIndex + 1 | |
| let isLineEnd: Bool = { | |
| if hasNext { | |
| let currentLineWidth = lineWidth + widthArray[itemIndex] | |
| return currentLineWidth + interitemSpacing + widthArray[itemIndex + 1] >= sectionWidth | |
| } else { | |
| return true | |
| } | |
| }() | |
| let lineSpacing = sectionLineSpacing[section]! | |
| switch (hasNext, isLineEnd) { | |
| case (true, true): | |
| // current row is over | |
| currentSectionMaxY = currentSectionMaxY + lineHeight + lineSpacing | |
| lineWidth = 0 | |
| lineHeight = 0 | |
| case (true, false): | |
| // continue current row | |
| lineWidth = lineWidth + widthArray[itemIndex] + interitemSpacing | |
| case (false, _): | |
| // current row is over | |
| let sectionFooterH = ((collectionView.delegate as? UICollectionViewDelegateFlowLayout)?.collectionView?(collectionView, layout: self, referenceSizeForFooterInSection: section).height ?? 0) | |
| currentSectionMaxY = currentSectionMaxY | |
| + lineHeight | |
| + currentSectionInset.bottom | |
| + sectionFooterH | |
| lineWidth = 0 | |
| lineHeight = 0 | |
| } | |
| } | |
| sectionMaxYPairs[section] = currentSectionMaxY | |
| } | |
| } | |
| private func prepareSectionBackgroundAttributes() { | |
| sectionBackgroundAttributesPairs.removeAll() | |
| guard let collectionView = collectionView, | |
| let sectionBackgroundDelegate = sectionBackgroundDelegate | |
| else { return } | |
| let sections = sectionBackgroundDelegate | |
| .sectionsNeedBackgroundColor(in: collectionView, layout: self) | |
| .filter { $0 < collectionView.numberOfSections } | |
| sections.forEach { section in | |
| // let inset = sectionInsetPairs[section]! | |
| // ignore inset | |
| let x: CGFloat = 0 | |
| let y = sectionMaxYPairs[section - 1] ?? 0 | |
| guard let maxY = sectionMaxYPairs[section], | |
| maxY - y > 0 | |
| else { return } | |
| let w = collectionView.bounds.width | |
| let h = maxY - y | |
| let attClass = sectionBackgroundDelegate.classForBackgroundViewAttributes() | |
| let att = attClass.init(forDecorationViewOfKind: SectionBackgroundFlowLayout.sectionBackgroundColorElement, with: IndexPath(row: 0, section: section)) | |
| let rawframe = CGRect(x: x, y: y, width: w, height: h) | |
| let insets = sectionBackgroundDelegate.sectionBackgroundViewInset?(at: section) ?? .zero | |
| att.frame = rawframe.inset(by: insets) | |
| att.zIndex = -100 // may not ok | |
| sectionBackgroundDelegate.configSectionBackgroundViewAttributes(att, layout: self, at: section) | |
| sectionBackgroundAttributesPairs[section] = att | |
| } | |
| } | |
| // MARK: layoutAttributesForElementsInRect | |
| override func layoutAttributesForDecorationView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? { | |
| guard elementKind == SectionBackgroundFlowLayout.sectionBackgroundColorElement | |
| else { return nil } | |
| if let collectionView = collectionView, | |
| let sectionBackgroundDelegate = sectionBackgroundDelegate, | |
| collectionView.numberOfItems(inSection: indexPath.section) == 0 { | |
| // 如果section.numberOfItems 由 > 0 => 0，会call 这个方法，若返回nil会导致assert fail | |
| // 所以返回 att.frame = .zero 的att | |
| let attClass = sectionBackgroundDelegate.classForBackgroundViewAttributes() | |
| let att = attClass.init(forDecorationViewOfKind: SectionBackgroundFlowLayout.sectionBackgroundColorElement, with: IndexPath(row: 0, section: indexPath.section)) | |
| att.frame = .zero | |
| return att | |
| } | |
| return sectionBackgroundAttributesPairs[indexPath.section] | |
| } | |
| override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? { | |
| var attributes = super.layoutAttributesForElements(in: rect) | |
| let intersects: [UICollectionViewLayoutAttributes] = sectionBackgroundAttributesPairs.compactMap { pair in | |
| if pair.value.frame.intersects(rect) { | |
| return pair.value | |
| } | |
| return nil | |
| } | |
| attributes?.append(contentsOf: intersects) | |
| return attributes | |
| } | |
| } |
计算Section的背景 高度 有点问题。https://github.com/ericchapman/ios_decoration_view/blob/master/ECDecorationView/ViewController.m
计算就是正确的
修复了高度问题。这是生产的代码。
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计算Section的背景 高度 有点问题。https://github.com/ericchapman/ios_decoration_view/blob/master/ECDecorationView/ViewController.m
计算就是正确的