sizeForItemAt方法在使用自定义布局时未调用

Question

我正在为我的集合视图使用自定义布局，但如果我使用自定义布局sizeForItemAt方法未调用。

我的自定义布局：

public class HorizontalCollectionViewLayout : UICollectionViewLayout { 
    var itemSize = CGSize(width: 0, height: 0) { 
     didSet { 
      invalidateLayout() 
     } 
    } 
    private var cellCount = 0 
    private var boundsSize = CGSize(width: 0, height: 0) 

    public override func prepare() { 
     cellCount = self.collectionView!.numberOfItems(inSection: 0) 
     boundsSize = self.collectionView!.bounds.size 
    } 
    public override var collectionViewContentSize: CGSize { 
     let verticalItemsCount = Int(floor(boundsSize.height/itemSize.height)) 
     let horizontalItemsCount = Int(floor(boundsSize.width/itemSize.width)) 

     let itemsPerPage = verticalItemsCount * horizontalItemsCount 
     let numberOfItems = cellCount 
     let numberOfPages = Int(ceil(Double(numberOfItems)/Double(itemsPerPage))) 

     var size = boundsSize 
     size.width = CGFloat(numberOfPages) * boundsSize.width 
     return size 
    } 

    public override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? { 
     var allAttributes = [UICollectionViewLayoutAttributes]() 
     if cellCount > 0 { 
     for i in 0...(cellCount-1) { 
      let indexPath = IndexPath(row: i, section: 0) 
      let attr = self.computeLayoutAttributesForCellAt(indexPath: indexPath) 
      allAttributes.append(attr) 
     } 
     } 
     return allAttributes 
    } 

    public override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? { 
     return computeLayoutAttributesForCellAt(indexPath: indexPath) 
    } 

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

    private func computeLayoutAttributesForCellAt(indexPath:IndexPath) 
     -> UICollectionViewLayoutAttributes { 
      let row = indexPath.row 
      let bounds = self.collectionView!.bounds 

      let verticalItemsCount = Int(floor(boundsSize.height/itemSize.height)) 
      let horizontalItemsCount = Int(floor(boundsSize.width/itemSize.width)) 
      let itemsPerPage = verticalItemsCount * horizontalItemsCount 

      let columnPosition = row % horizontalItemsCount 
      let rowPosition = (row/horizontalItemsCount)%verticalItemsCount 
      let itemPage = Int(floor(Double(row)/Double(itemsPerPage))) 

      let attr = UICollectionViewLayoutAttributes(forCellWith: indexPath) 

      var frame = CGRect(x: 0,y: 0,width: 0,height: 0) 
      frame.origin.x = CGFloat(itemPage) * bounds.size.width + CGFloat(columnPosition) * itemSize.width 
      frame.origin.y = CGFloat(rowPosition) * itemSize.height 
      frame.size = itemSize 
      attr.frame = frame 

      return attr 
    } 
} 

，我在viewDidLoad方法设置此布局：

let itemWidth = 100 
let itemHeight = 100 
let horizontalCV = HorizontalCollectionViewLayout(); 
horizontalCV.itemSize = CGSize(width: itemWidth, height: itemHeight) 

instagramCollection.collectionViewLayout = horizontalCV 
self.instagramCollection.delegate=self 
self.instagramCollection.dataSource=self 

其他collection视图方法工作正常像numberOfItemsInSection或cellForItemAt等，但我不能为我的收藏视图设置插图或单元格间距。

我试过下面的代码，下面的方法没有调用。

func collectionView(_ collectionView: UICollectionView, 
        layout collectionViewLayout: UICollectionViewLayout, 
        sizeForItemAt indexPath: IndexPath) -> CGSize { 
    return CGSize.init(width: (instagramCollection.frame.width/3.0), height: instagramCollection.frame.height/2.0) 
} 


func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets { 
    return UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10) 
} 
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat { 
    return 10.0 
} 
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat { 
    return 10.0 
} 

我也试图设置从故事板instets和间距也没有奏效。

我的集合视图现在使用零的所有插入和间距。

如何解决这个问题？

Answer 1

您应该在您的控制器布局委托实现中添加。 （你添加了这些方法，但他们不叫）

所以，不仅UICollectionViewDelegate，UICollectionViewDataSource，而且还有UICollectionViewDelegateFlowLayout。例如，像扩展一样，

。

extension YourController: UICollectionViewDelegateFlowLayout { 
func collectionView(_ collectionView: UICollectionView, 
        layout collectionViewLayout: UICollectionViewLayout, 
        sizeForItemAt indexPath: IndexPath) -> CGSize { 
    return CGSize.init(width: (instagramCollection.frame.width/3.0), height: instagramCollection.frame.height/2.0) 
} 


func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets { 
    return UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10) 
} 
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat { 
    return 10.0 
} 
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat { 
    return 10.0 
} 
}