ios - Swift Collection View自定义布局更改单元格侧的单元格宽度

Question

你好，我有工作的 collectionview 自定义布局代码，但我需要从 json 动态更改单元格端的单元格宽度。

我的 CustomCollectionViewLayout

import UIKit

public var CELL_HEIGHT = 22.0
public var CELL_WIDTH = 40.0 // HERE WIDTH SOME CELLS MUST BE 80

class CustomCollectionViewLayout: UICollectionViewLayout {

    // Used for calculating each cells CGRect on screen.
    // CGRect will define the Origin and Size of the cell.

    let STATUS_BAR = UIApplication.sharedApplication().statusBarFrame.height

    // Dictionary to hold the UICollectionViewLayoutAttributes for
    // each cell. The layout attribtues will define the cell's size 
    // and position (x, y, and z index). I have found this process
    // to be one of the heavier parts of the layout. I recommend
    // holding onto this data after it has been calculated in either 
    // a dictionary or data store of some kind for a smooth performance.
    var cellAttrsDictionary = Dictionary<NSIndexPath, UICollectionViewLayoutAttributes>()

    // Defines the size of the area the user can move around in
    // within the collection view.
    var contentSize = CGSize.zero

    // Used to determine if a data source update has occured.
    // Note: The data source would be responsible for updating
    // this value if an update was performed.
    var dataSourceDidUpdate = true

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

    override func prepareLayout() {

        // Only update header cells.
        if !dataSourceDidUpdate {

            // Determine current content offsets.
            let xOffset = collectionView!.contentOffset.x
            let yOffset = collectionView!.contentOffset.y

            if collectionView?.numberOfSections() > 0 {
                for section in 0...collectionView!.numberOfSections()-1 {

                    // Confirm the section has items.
                    if collectionView?.numberOfItemsInSection(section) > 0 {

                        // Update all items in the first row.
                        if section == 0 {
                            for item in 0...collectionView!.numberOfItemsInSection(section)-1 {

                                // Build indexPath to get attributes from dictionary.
                                let indexPath = NSIndexPath(forItem: item, inSection: section)

                                // Update y-position to follow user.
                                if let attrs = cellAttrsDictionary[indexPath] {
                                    var frame = attrs.frame

                                    // Also update x-position for corner cell.
                                    if item == 0 {
                                        frame.origin.x = xOffset
                                    }

                                    frame.origin.y = yOffset
                                    attrs.frame = frame
                                }

                            }

                            // For all other sections, we only need to update
                            // the x-position for the fist item.
                        } else {

                            // Build indexPath to get attributes from dictionary.
                            let indexPath = NSIndexPath(forItem: 0, inSection: section)

                            // Update y-position to follow user.
                            if let attrs = cellAttrsDictionary[indexPath] {
                                var frame = attrs.frame
                                frame.origin.x = xOffset
                                attrs.frame = frame
                            }

                        }
                    }
                }
            }


            // Do not run attribute generation code
            // unless data source has been updated.
            return
        }

        // Acknowledge data source change, and disable for next time.
        dataSourceDidUpdate = false

        var maxItemInASection: Int?

        // Cycle through each section of the data source.
        if collectionView?.numberOfSections() > 0 {
            for section in 0...collectionView!.numberOfSections()-1 {

                // Cycle through each item in the section.
                if collectionView?.numberOfItemsInSection(section) > 0 {
                    for item in 0...collectionView!.numberOfItemsInSection(section)-1 {

                        // Build the UICollectionVieLayoutAttributes for the cell.
                        let cellIndex = NSIndexPath(forItem: item, inSection: section)
                        let xPos = Double(item) * CELL_WIDTH
                        let yPos = Double(section) * CELL_HEIGHT

                        let cellAttributes = UICollectionViewLayoutAttributes(forCellWithIndexPath: cellIndex)
                        cellAttributes.frame = CGRect(x: xPos, y: yPos, width: CELL_WIDTH, height: CELL_HEIGHT)

                        // Determine zIndex based on cell type.
                        if section == 0 && item == 0 {
                            cellAttributes.zIndex = 4
                        } else if section == 0 {
                            cellAttributes.zIndex = 3
                        } else if item == 0 {
                            cellAttributes.zIndex = 2
                        } else {
                            cellAttributes.zIndex = 1
                        }

                        // Save the attributes.
                        cellAttrsDictionary[cellIndex] = cellAttributes

                        if maxItemInASection < item {
                            maxItemInASection = item
                        }

                    }
                }

            }
        }

        // Update content size.
        let contentWidth = Double(maxItemInASection ?? 0) * CELL_WIDTH
        let contentHeight = Double(collectionView!.numberOfSections()) * CELL_HEIGHT
        self.contentSize = CGSize(width: contentWidth, height: contentHeight)

    }

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

        // Create an array to hold all elements found in our current view.
        var attributesInRect = [UICollectionViewLayoutAttributes]()

        // Check each element to see if it should be returned.
        for cellAttributes in cellAttrsDictionary.values.elements {
            if CGRectIntersectsRect(rect, cellAttributes.frame) {
                attributesInRect.append(cellAttributes)
            }
        }

        // Return list of elements.
        return attributesInRect
    }

    override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
        return cellAttrsDictionary[indexPath]!
    }

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

}

这是我的手机代码。

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("customCell", forIndexPath: indexPath) as! CustomCollectionViewCell

     if items[indexPath.section].base == 2 {

              cell.label.text = items[indexPath.section].base


             cell.frame.size.width = 80
             cell.layer.frame.size.width = 80

             CELL_WIDTH = 80.0 // HERE I CHANGED SOME CELLS WIDTH 80 BUT DONT CHANGE THEM !!

}else{

   cell.label.text = items[indexPath.section].base



}

你可以看到顶部

CELL_WIDTH = 80.0 // HERE I CHANGED SOME CELLS WIDTH 80 BUT DONT CHANGE THEM !!

Answer 1

您可以实现 collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) 而不是继承 UICollectionViewLayout - 除非您有其他理由这样做。

它会有点像:

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {

    if indexPath.item % 3 == 0 { // <-- your condition here
        return CGSize(width: 40, height: 22) 
    }
    return CGSize(width: 80, height: 22)

}

顺便说一下，不要忘记设置 collectionView 的委托(delegate)以便调用此方法。 😁

已更新

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    if items[indexPath.section].base == 2 {
        return CGSize(width: 80, height: 22)
    } else {
        return CGSize(width: 44, height: 22)
    }
}

我认为您的方法应该是这样的。在您的 cellForItem 中，您只需要担心设置标签，让上面的代码处理单元格的大小。