如何使用自定义布局跳转到UICollectionView中的任何单元格？

Question

我的水平UICollectionView中有40个单元格和一个按钮.

当我点击按钮时,我可以从5号单元格跳转到10号单元格.

但是一旦我想要进一步的细胞(例如从5到25),

它不起作用,而是变为0.

码:

func setValue(value: Int, animated: Bool) {
   self.value = value
   if let row = find(values, value) {
   let indexPath = NSIndexPath(forRow: row, inSection: 0)
   selectedCell = collectionView.cellForItemAtIndexPath(indexPath) as? StepperCell
   collectionView.scrollToItemAtIndexPath(indexPath, atScrollPosition: .CenteredHorizontally, animated: animated)
  }
 }

override func prepareLayout() {
   let start = Int(collectionView!.bounds.size.width * 0.5) - statics.width / 2
   let length = collectionView!.numberOfItemsInSection(0)

if cache.isEmpty && length > 0 {
   for item in 0..<length {
     let indexPath = NSIndexPath(forItem: item, inSection: 0)
     let attributes = UICollectionViewLayoutAttributes(forCellWithIndexPath: indexPath)
     attributes.frame = CGRect(
      x: start + (statics.width + statics.padding) * indexPath.item,
      y: 0,
      width: statics.width,
      height: statics.height
    )
    cache.append(attributes)
  }
  contentWidth = CGRectGetMaxX(cache.last!.frame) + CGFloat(start)
   }
 }

 override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]? {
   var layoutAttributes = [UICollectionViewLayoutAttributes]()
   for attributes in cache {
      if CGRectIntersectsRect(attributes.frame, rect) {
        layoutAttributes.append(attributes)
    }
  }
  return layoutAttributes
  }
 }

Answer 1

我认为你可以省去行逻辑.毕竟 - 你只是使用传递Int.如果您的if let子句失败,则不会滚动.

此外,将呼叫放到cellForItemAtIndexPath- 您不需要它(您也没有使用它).

我想也许你应该使用NSIndexPath(forItem, inSection)而不是NSIndexPath(forRow, inSection).(表视图使用row,collectionView使用item.)

collectionView.scrollToItemAtIndexPath(
      NSIndexPath(forItem: value, inSection: 0), 
      atScrollPosition: .CenteredHorizontally, animated: true)