设置集合视图单元格的动态宽度时出现问题

Question

我正在尝试动态设置集合视图单元格的宽度。最初它没有按预期呈现。但是当我点击单元格时，它会根据需要进行调整。这是我写的代码：

代码

import UIKit

class ViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDataSource {

    @IBOutlet weak var collView: UICollectionView!


    var tasksArray = ["To Do", "SHOPPING","WORK"]
    var selectedIndex = Int()

    override func viewDidLoad() {
        super.viewDidLoad()
        let layout = collView?.collectionViewLayout as! UICollectionViewFlowLayout
        layout.itemSize = UICollectionViewFlowLayout.automaticSize
        layout.estimatedItemSize = CGSize(width: 93, height: 40)
        // Do any additional setup after loading the view, typically from a nib.
    }
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return tasksArray.count
    }
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CollectionViewCell
        cell.lblName.text = tasksArray[indexPath.row]
        if selectedIndex == indexPath.row
        {
            cell.backgroundColor = UIColor.lightGray
        }
        else
        {
            cell.backgroundColor = UIColor.white
        }
        cell.layer.borderWidth = 1
        cell.layer.cornerRadius = cell.frame.height / 2
        return cell
    }
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        selectedIndex = indexPath.row
        self.collView.reloadData()
    }
}

这里我附上两张点击前和点击后的图片，方便大家理解

[![这是我点击前的图像

on cell]2]2

所以请告诉我我的代码有什么问题

Answer 1

我找到了 swift 4.2

的小技巧

对于动态宽度和固定高度：

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let label = UILabel(frame: CGRect.zero)
    label.text = textArray[indexPath.item]
    label.sizeToFit()
    return CGSize(width: label.frame.width, height: 32)
}

Answer 2

在您的 CollectionViewCell 覆盖 preferredLayoutAttributesFitting 函数中，单元格可以在此处指示其首选属性，包括我们使用自动布局计算的大小。

 override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
    setNeedsLayout()
    layoutIfNeeded()
    let size = contentView.systemLayoutSizeFitting(layoutAttributes.size)
    var frame = layoutAttributes.frame
    frame.size.width = ceil(size.width)
    layoutAttributes.frame = frame
    return layoutAttributes
}

Answer 3

很明显，您必须使用 sizeForItemAt 流布局委托才能传递动态宽度。但棘手的部分是根据文本计算单元格的宽度。如果你有字体，你实际上可以计算文本的宽度。

让我们介绍几个扩展，这将在整个过程中帮助我们

StringExtensions.swift

extension String {

    public func width(withConstrainedHeight height: CGFloat, font: UIFont) -> CGFloat {
        let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)
        let boundingBox = self.boundingRect(with: constraintRect,
                                        options: .usesLineFragmentOrigin,
                                        attributes: [.font: font], context: nil)

        return ceil(boundingBox.width)
    }
}

这个方法让我们知道字符串的宽度，如果我给它提供高度和字体的话。然后在sizeForItem里面使用如下

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let height = 40
    let text = YOUR_TEXT
    let width = text.width(withConstrainedHeight: height, font: Font.regular.withSize(.extraSmall)) + EXTRA_SPACES_FOR_LEFT_RIGHT_PADDING
    return CGSize(width: width, height: height)
}

设置集合视图单元格的动态宽度时出现问题

issue while set dynamic width of collection view cell

ios

swift

uicollectionview

uicollectionviewdelegateflowlayout