Question

我试图创建一个集合视图，单元格显示可变长度的字符串。

我使用此功能设置单元格布局：

 func collectionView(collectionView : UICollectionView,layout collectionViewLayout:UICollectionViewLayout,sizeForItemAtIndexPath indexPath:NSIndexPath) -> CGSize
    {
        var cellSize:CGSize = CGSizeMake(self.whyCollectionView.frame.width, 86)
        return cellSize
    }

我想要做的是根据cellSize.height长度操纵cell.labelString.utf16Count。基本逻辑将是sa

if((cell.labelString.text) > 70){
   cellSize.height = x
}
else{
   cellSize.height = y
}

但是，我无法设法检索始终返回nil的单元格标签字符串长度。（我认为它尚未加载......

为了更好地理解，这里是完整的代码：

// WhyCell section
    var whyData:NSMutableArray! = NSMutableArray()
    var textLength:Int!
    @IBOutlet weak var whyCollectionView: UICollectionView!

//Loading data
    @IBAction func loadData() {
        whyData.removeAllObjects()

        var findWhyData:PFQuery = PFQuery(className: "PlacesWhy")
        findWhyData.whereKey("placeName", equalTo: placeName)

        findWhyData.findObjectsInBackgroundWithBlock({
            (objects:[AnyObject]!,error:NSError!)->Void in

            if (error == nil) {
                for object in objects {
                    self.whyData.addObject(object)
                }

                let array:NSArray = self.whyData.reverseObjectEnumerator().allObjects
                self.whyData = array.mutableCopy() as NSMutableArray

                self.whyCollectionView.reloadData()
                println("loadData completed. datacount is \(self.whyData.count)")
            }
        })
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        self.loadData()


    }

    func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
        return 1
    }

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return whyData.count
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell:whyCollectionViewCell = whyCollectionView.dequeueReusableCellWithReuseIdentifier("whyCell", forIndexPath: indexPath) as whyCollectionViewCell

        // Loading content from NSMutableArray to cell
        let therew:PFObject = self.whyData.objectAtIndex(indexPath.row) as PFObject
        cell.userWhy.text = therew.objectForKey("why") as String!
        textLength = (therew.objectForKey("why") as String!).utf16Count
        self.whyCollectionView.layoutSubviews()

        // Displaying user information
        var whatUser:PFQuery = PFUser.query()
        whatUser.whereKey("objectId", equalTo: therew.objectForKey("reasonGivenBy").objectId)

        whatUser.findObjectsInBackgroundWithBlock({
            (objects: [AnyObject]!, error: NSError!)->Void in

            if !(error != nil) {
                if let user:PFUser = (objects as NSArray).lastObject as? PFUser {
                    cell.userName.text = user.username
                    // TODO Display avatar
                }

            }
        })

        return cell
    }

    func collectionView(collectionView : UICollectionView,layout collectionViewLayout:UICollectionViewLayout,sizeForItemAtIndexPath indexPath:NSIndexPath) -> CGSize
    {
        var cellSize:CGSize = CGSizeMake(self.whyCollectionView.frame.width, 86)
        return cellSize
    }

Answer 1

虽然上面的答案可以解决您的问题，但它建立了一种非常粗略的方式来分配每个单元格的高度。基于某些估计，您被迫对每个单元格高度进行硬编码。处理此问题的更好方法是在集合视图的sizeForItemAtIndexPath委托方法中设置每个单元格的高度。

我将向您介绍如何执行此操作的步骤。

第1步：让您的课程延长UICollectionViewDelegateFlowLayout

步骤2：创建一个函数来估计文本的大小：此方法将返回一个适合您的字符串的高度值！

private func estimateFrameForText(text: String) -> CGRect {
    //we make the height arbitrarily large so we don't undershoot height in calculation
    let height: CGFloat = <arbitrarilyLargeValue>

    let size = CGSize(width: yourDesiredWidth, height: height)
    let options = NSStringDrawingOptions.UsesFontLeading.union(.UsesLineFragmentOrigin)
    let attributes = [NSFontAttributeName: UIFont.systemFontOfSize(18, weight: UIFontWeightLight)]

    return NSString(string: text).boundingRectWithSize(size, options: options, attributes: attributes, context: nil)
}

步骤3：使用或覆盖下面的委托方法：

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    var height: CGFloat = <someArbitraryValue>

   //we are just measuring height so we add a padding constant to give the label some room to breathe! 
    var padding: CGFloat = <someArbitraryPaddingValue>

    //estimate each cell's height
    if let text = array?[indexPath.item].text {
         height = estimateFrameForText(text).height + padding
    }
    return CGSize(width: yourDesiredWidth, height: height)
}

Answer 2

您可以在cellForItemAtIndexPath函数中动态设置单元格的框架，因此如果忽略sizeForItemAtIndexPath函数，则可以根据标签自定义高度。通过自定义大小，您可能需要查看集合视图布局流程，但希望这可以指向正确的方向。它可能看起来像这样：

class CollectionViewController: UICollectionViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    var array = ["a","as","asd","asdf","asdfg","asdfgh","asdfghjk","asdfghjklas","asdfghjkl","asdghjklkjhgfdsa"]
    var heights = [10.0,20.0,30.0,40.0,50.0,60.0,70.0,80.0,90.0,100.0,110.0] as [CGFloat]

    override func viewDidLoad() {
        super.viewDidLoad()
    }


    override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
        return 1
    }

    override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return array.count
    }

    override func collectionView(collectionView: UICollectionView,
        cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

            let cell = collectionView.dequeueReusableCellWithReuseIdentifier("CellID", forIndexPath: indexPath) as Cell
            cell.textLabel.text = array[indexPath.row]
            cell.textLabel.sizeToFit()

            // Customize cell height
            cell.frame = CGRectMake(cell.frame.origin.x, cell.frame.origin.y, cell.frame.size.width, heights[indexPath.row])
            return cell
    }

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
        return CGSizeMake(64, 64)
    }
}

这给出了动态的高度 enter image description here

Answer 3

在Swift 3中，使用以下方法：

private func updateCollectionViewLayout(with size: CGSize) {
    var margin : CGFloat = 0;
    if isIPad {
        margin = 10
    }
    else{
        margin = 6
        /* if UIDevice.current.type == .iPhone6plus || UIDevice.current.type == .iPhone6Splus || UIDevice.current.type == .simulator{
         margin = 10

         }
         */
    }
    if let layout = menuCollectionView.collectionViewLayout as? UICollectionViewFlowLayout {
        layout.itemSize = CGSize(width:(self.view.frame.width/2)-margin, height:((self.view.frame.height-64)/4)-3)
        layout.invalidateLayout()
    }
}

CollectionView动态单元格高度快速

3 个答案: