[Swift]UICollectionViewCellを上揃え
UICollectionViewCellを上揃え
import UIKit
class TopAlignedCollectionViewFlowLayout: UICollectionViewFlowLayout {
override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]? {
var sameYElements:[UICollectionViewLayoutAttributes] = []
var baseline:CGFloat = -2.0
var height:CGFloat = 0.0
var basey:CGFloat = 0.0
let attributesToReturn:[UICollectionViewLayoutAttributes] = super.layoutAttributesForElementsInRect(rect) as [UICollectionViewLayoutAttributes]
for attributes in attributesToReturn {
if attributes.representedElementCategory == UICollectionElementCategory.Cell {
let centerY:CGFloat = CGRectGetMidY(attributes.frame)
if 1.0 < fabs(centerY - baseline) {
baseline = centerY
self.__alignTopWithElements(sameYElements, basey:basey)
sameYElements.removeAll()
height = 0.0
basey = 0.0
}
sameYElements.append(attributes)
if height < attributes.frame.size.height {
height = attributes.frame.size.height
basey = attributes.frame.origin.y
}
}
}
self.__alignTopWithElements(sameYElements, basey:basey)
return attributesToReturn
}
private func __alignTopWithElements(elements:[UICollectionViewLayoutAttributes], basey:CGFloat) {
if elements.count < 1 {
return
}
for attributes in elements {
var rect:CGRect = attributes.frame
rect.origin.y = basey
attributes.frame = rect
}
}
}
