[英]How to set drop shadow around a section for UITableView in iOS Swift 4?
使用UICollectionView
輕松實現這UICollectionView
,
通過子類UICollectionViewFlowLayout
和DecorationView
將UITableViewCell
變成UICollectionViewCell
,
使用裝飾視圖實現剖面部分的陰影
class DecorationFlow: UICollectionViewFlowLayout {
private var cache = [IndexPath: UICollectionViewLayoutAttributes]()
override func prepare() {
super.prepare()
register(HistoDecorationV.self, forDecorationViewOfKind: HistoDecorationV.id)
let originX: CGFloat = 15
let widH: CGFloat = UI.std.width - originX * 2
guard let collect = collectionView else{
return
}
let sections = collect.numberOfSections
var originY: CGFloat = 0
for sect in 0..<sections{
let sectionFirst = IndexPath(item: 0, section: sect)
let attributes = UICollectionViewLayoutAttributes(forDecorationViewOfKind: HistoDecorationV.id, with: sectionFirst)
let itemCount = collect.numberOfItems(inSection: sect)
originY = originY + 80
let h: CGFloat = 50 * CGFloat(itemCount)
attributes.frame = CGRect(x: originX, y: originY, width: widH, height: h)
originY = originY + h + 15
cache[sectionFirst] = attributes
}
}
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
return true
}
private func prepareCache() {
cache.removeAll(keepingCapacity: true)
cache = [IndexPath: UICollectionViewLayoutAttributes]()
}
override func layoutAttributesForDecorationView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return cache[indexPath]
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var array = super.layoutAttributesForElements(in: rect)
guard let collection = collectionView, collection.numberOfSections > 0 else{
return array
}
var z = 0
array?.forEach({
$0.zIndex = z + 100
z += 1
})
z = 0
for (_, attributes) in cache {
if attributes.frame.intersects(rect){
attributes.zIndex = z + 10
array?.append(attributes)
}
z += 1
}
return array
}
}
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