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Swift做图片可伸缩的UICollectionView

Swift做图片可伸缩的UICollectionView

作者: Funcy1Day | 来源:发表于2016-07-18 16:06 被阅读74次

    自定义一个继承自UICollectionViewLayout的layout文件:


    var delegate:StrechDelete?

    var currentOriginY:CGFloat= 215

    var headerReferenceSize:CGSize?

    var attributeArray:[UICollectionViewLayoutAttributes] = [UICollectionViewLayoutAttributes]()

    var insets:UIEdgeInsets=UIEdgeInsets(top: 15, left: 0, bottom: 0, right: 0)

    override funcprepareLayout() {

    super.prepareLayout()

    self.attributeArray.removeAll()

    let count =self.collectionView!.numberOfItemsInSection(0)

    for j in 0..<count{

    let attris =self.layoutAttributesForItemAtIndexPath(NSIndexPath(forRow: j, inSection: 0))

    self.attributeArray.append(attris)

    }

    headerReferenceSize=CGSizeMake(screenW,200)

    currentOriginY= (headerReferenceSize?.height)!+insets.top

    }

    override funcshouldInvalidateLayoutForBoundsChange(newBounds:CGRect) ->Bool{

    return true

    }

    override funclayoutAttributesForItemAtIndexPath(indexPath:NSIndexPath)->UICollectionViewLayoutAttributes{

    let width =screenW

    //代理计算传入每个cell的高度

    let height =self.delegate?.flowLayoutHeightForIndexPath(self, atIndexPath: indexPath)

    let x:CGFloat= 0

    let y =currentOriginY

    // 创建属性

    let attrs =UICollectionViewLayoutAttributes(forCellWithIndexPath:indexPath)

    attrs.frame=CGRectMake(x, y, width, height!)

    //通过代理获取从此cell开始是否有inset.top距离的cell间隔

    let flag:Bool= (self.delegate?.flowLayoutAfterIsSeparatedForIndexPath(self, atIndexPath: indexPath))!

    if flag {

    currentOriginY+= (height!+insets.top)

    }else{

    currentOriginY+= height!

    }

    return attrs;

    }

    //很重要的方法,当边界发生改变时,是否应该刷新布局。如果YES则在边界变化(一般是scroll到其

    //他地方)时,将重新计算需要的布局信息。

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

    var attributesArray = [UICollectionViewLayoutAttributes]()

    attributesArray.appendContentsOf(attributeArray)

    let index2 =self.collectionView!.indexOfAccessibilityElement(UICollectionElementKindSectionHeader)

    let attr2:UICollectionViewLayoutAttributes=self.collectionView!.layoutAttributesForSupplementaryElementOfKind(UICollectionElementKindSectionHeader, atIndexPath:NSIndexPath(forItem: index2, inSection: 0))!

    attributesArray.append(attr2)

    return attributesArray

    }

    override funclayoutAttributesForSupplementaryViewOfKind(elementKind:String, atIndexPath indexPath:NSIndexPath) ->UICollectionViewLayoutAttributes? {

    let attribute =UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: elementKind, withIndexPath: indexPath)

    if elementKind ==UICollectionElementKindSectionHeader{

    let width =self.collectionView!.frame.width

    attribute.frame=CGRect(x: 0,y: 0 ,width:width,height:headerReferenceSize!.height)

    let offset =self.collectionView?.contentOffset

    if offset?.y< 0 {//用户向下拉

    let deltay =fabs((offset?.y)!)

    //获取headView的frame

    var rect = attribute.frame

    //改变headView的高度,y值

    rect.size.height+= deltay

    rect.origin.y-= deltay

    attribute.frame= rect

    }

    return attribute

    }else{

    //由于个人需要,没有构建footerVIew,所以在layout文件中并没有实现footerView的attribute构建

    return nil

    }

    }

    override funccollectionViewContentSize() ->CGSize{

    returnCGSize(width: 0, height:screenH)

    }

    自定义的layout文件在uicollectionviewcontroller中实现delegate:StrechDelete的代理方法:

    funcflowLayoutHeightForIndexPath(layout:SuzeeStrechCollectionViewLayout, atIndexPath:NSIndexPath) ->CGFloat{

    return60

    }

    func flowLayoutAfterIsSeparatedForIndexPath(layout:SuzeeStrechCollectionViewLayout, atIndexPath:NSIndexPath) ->Bool{

    let row = atIndexPath.row

    switchrow {

    case0:

    return false

    case1:

    return true

    default:

    return true

    }

    }

    ,并重新定义collectionview的layout:

    let layoutNew =***CollectionViewLayout()

    //自定义layout创建delegate

    layoutNew.delegate=self

    self.collectionView!.collectionViewLayout= layoutNew

    并实现

    最终实现效果:

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