ios - UICollectionView 滚动分页

Question

我的 UICollectionView 有以下 UICollectionViewLayout。

class CustomCollectionViewLayout: UICollectionViewLayout { 

var numberOfColumns = 8
var itemAttributes : NSMutableArray!
var itemsSize : NSMutableArray!
var contentSize : CGSize!

override func prepareLayout() {

    if self.collectionView?.numberOfSections() == 0 {
        return
    }

    if (self.itemAttributes != nil && self.itemAttributes.count > 0) {
        for section in 0..<self.collectionView!.numberOfSections() {
            var numberOfItems : Int = self.collectionView!.numberOfItemsInSection(section)
            for index in 0..<numberOfItems {
                if section != 0 && index != 0 {
                    continue
                }

                var attributes : UICollectionViewLayoutAttributes = self.layoutAttributesForItemAtIndexPath(NSIndexPath(forItem: index, inSection: section))
                if section == 0 {
                    var frame = attributes.frame
                    frame.origin.y = self.collectionView!.contentOffset.y
                    attributes.frame = frame
                }

                if index == 0 {
                    var frame = attributes.frame
                    frame.origin.x = self.collectionView!.contentOffset.x
                    attributes.frame = frame
                }
            }
        }
        return
    }

    if (self.itemsSize == nil || self.itemsSize.count != numberOfColumns) {
        self.calculateItemsSize()
    }

    var column = 0
    var xOffset : CGFloat = 0
    var yOffset : CGFloat = 0
    var contentWidth : CGFloat = 0
    var contentHeight : CGFloat = 0

    for section in 0..<self.collectionView!.numberOfSections() {
        var sectionAttributes = NSMutableArray()

        for index in 0..<numberOfColumns {
            var itemSize = self.itemsSize[index].CGSizeValue()
            var indexPath = NSIndexPath(forItem: index, inSection: section)
            var attributes = UICollectionViewLayoutAttributes(forCellWithIndexPath: indexPath)
            attributes.frame = CGRectIntegral(CGRectMake(xOffset, yOffset, itemSize.width, itemSize.height+20))

            if section == 0 && index == 0 {
                attributes.zIndex = 1024;
            } else  if section == 0 || index == 0 {
                attributes.zIndex = 1023
            }

            if section == 0 {
                var frame = attributes.frame
                frame.origin.y = self.collectionView!.contentOffset.y
                attributes.frame = frame
            }
            if index == 0 {
                var frame = attributes.frame
                frame.origin.x = self.collectionView!.contentOffset.x
                attributes.frame = frame
            }

            sectionAttributes.addObject(attributes)

            xOffset += itemSize.width
            column++

            if column == numberOfColumns {
                if xOffset > contentWidth {
                    contentWidth = xOffset
                }

                column = 0
                xOffset = 0
                yOffset += itemSize.height+20
            }
        }
        if (self.itemAttributes == nil) {
            self.itemAttributes = NSMutableArray(capacity: self.collectionView!.numberOfSections())
        }
        self.itemAttributes .addObject(sectionAttributes)
    }

    var attributes : UICollectionViewLayoutAttributes = self.itemAttributes.lastObject?.lastObject as! UICollectionViewLayoutAttributes
    contentHeight = attributes.frame.origin.y + attributes.frame.size.height
    self.contentSize = CGSizeMake(contentWidth+150, contentHeight)
}

override func collectionViewContentSize() -> CGSize {
    return self.contentSize
}

override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes! {

    let BondData:NSArray = self.itemAttributes[indexPath.section] as! NSArray

    return BondData[indexPath.row] as! UICollectionViewLayoutAttributes

}

override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
    var attributes = [UICollectionViewLayoutAttributes]()
    if self.itemAttributes != nil {
        for section in self.itemAttributes {

            let filteredArray  =  section.filteredArrayUsingPredicate(

                NSPredicate(block: { (evaluatedObject, bindings) -> Bool in
                    return CGRectIntersectsRect(rect, evaluatedObject!.frame)
                })
                ) as! [UICollectionViewLayoutAttributes]

            attributes.appendContentsOf(filteredArray)
        }
    }

    return attributes
}

override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
    return true
}

func sizeForItemWithColumnIndex(columnIndex: Int) -> CGSize {
    var text : String = ""
    switch (columnIndex) {
    case 0:
        text = "Col 0"
    case 1:
        text = "Col 1"
    case 2:
        text = "Col 2"
    case 3:
        text = "Col 3"
    case 4:
        text = "Col 4"
    case 5:
        text = "Col 5"
    case 6:
        text = "Col 6"
    case 7:
        text = "Col 7"        
    default:
        text = "Col 8"
    }

    let size : CGSize = (text as NSString).sizeWithAttributes([NSFontAttributeName: UIFont.systemFontOfSize(17.0)])
    let width : CGFloat = size.width + 80
    return CGSizeMake(width, 30)
}

func calculateItemsSize() {

    self.itemsSize = NSMutableArray(capacity: numberOfColumns)
    for index in 0..<numberOfColumns {
        self.itemsSize.addObject(NSValue(CGSize: self.sizeForItemWithColumnIndex(index)))
    }
}

我正在尝试使用以下代码在 UICollectionView 中实现滚动分页:

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {          
            let seconds = 7.0
            let delay = seconds * Double(NSEC_PER_SEC)
            let dispatchTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))

            dispatch_after(dispatchTime, dispatch_get_main_queue(), {

                self.loadMore()

                self.DataTableCollectionView.reloadData()                   

            })                

但是在使用上面的代码这样做时，我收到一个错误“由于未捕获的异常‘NSRangeException’而终止应用程序，原因:‘*** -[__NSArrayM objectAtIndex:]:索引 50 超出范围 [0 .. 49] '"

我正在使用以下代码使用 UICollectionView 创建表 https://github.com/brightec/CustomCollectionViewLayout

我怎样才能做到这一点？提前致谢!

Answer 1

1. 问题在于您试图访问超出其索引的数组。这与问题的标题并不相关。

2. 你应该在collectionView(_:cellForItemAt:)中提供和设置单元格的属性，而不是重新加载数据之类的。