解决方案包括3个简单步骤:

启用动态单元格大小

flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize

设置来自collectionView(:cellForItemAt:)的containerview . widthachor .constraint来限制contentView的宽度为collectionView的宽度。

class ViewController: UIViewController, UICollectionViewDataSource {
    ...

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! MultiLineCell
        cell.textView.text = dummyTextMessages[indexPath.row]
        cell.maxWidth = collectionView.frame.width
        return cell
    }

    ...
}

class MultiLineCell: UICollectionViewCell{
    ....

    var maxWidth: CGFloat? {
        didSet {
            guard let maxWidth = maxWidth else {
                return
            }
            containerViewWidthAnchor.constant = maxWidth
            containerViewWidthAnchor.isActive = true
        }
    }

    ....
}

因为你想要启用UITextView的自调整大小，它有一个额外的步骤来;

3.计算和设置高度tanchor。常量的UITextView。

当contentView的宽度被设置时，我们会在didSet的maxWidth中调整UITextView的高度。

UICollectionViewCell Inside job:

var maxWidth: CGFloat? {
    didSet {
        guard let maxWidth = maxWidth else {
            return
        }
        containerViewWidthAnchor.constant = maxWidth
        containerViewWidthAnchor.isActive = true
        
        let sizeToFitIn = CGSize(width: maxWidth, height: CGFloat(MAXFLOAT))
        let newSize = self.textView.sizeThatFits(sizeToFitIn)
        self.textViewHeightContraint.constant = newSize.height
    }
}

这些步骤会让你得到想要的结果。

完整的可运行的要旨

参考:Vadim Bulavin博客文章-集合视图单元格自我调整:一步一步的教程

截图:

内容查看主播奥秘:

在一个奇怪的例子中

    contentView.translatesAutoresizingMaskIntoConstraints = false

不会起作用。在contentView中添加了四个显式的锚，它工作了。

class AnnoyingCell: UICollectionViewCell {
    
    @IBOutlet var word: UILabel!
    
    override init(frame: CGRect) {
        super.init(frame: frame); common() }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder); common() }
    
    private func common() {
        contentView.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            contentView.leftAnchor.constraint(equalTo: leftAnchor),
            contentView.rightAnchor.constraint(equalTo: rightAnchor),
            contentView.topAnchor.constraint(equalTo: topAnchor),
            contentView.bottomAnchor.constraint(equalTo: bottomAnchor)
        ])
    }
}

像往常一样

    estimatedItemSize = UICollectionViewFlowLayout.automaticSize

在你的布局:UICollectionViewFlowLayout

谁知道呢?也许能帮到别人。

信贷

https://www.vadimbulavin.com/collection-view-cells-self-sizing/

无意中发现了这个技巧——在其他1000篇文章中从未见过。

更新更多信息:

If you use flowLayout.estimatedItemSize, suggest use iOS8.3 later version. Before iOS8.3, it will crash [super layoutAttributesForElementsInRect:rect];. The error message is *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil' Second, in iOS8.x version, flowLayout.estimatedItemSize will cause different section inset setting did not work. i.e. function: (UIEdgeInsets)collectionView:layout:insetForSectionAtIndex:.

如果你实现uicollectionviewdelegatflowlayout方法:

- (CGSize)collectionView:(UICollectionView*)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath*)indexPath

当你调用collectionview performBatchUpdates:completion:时，size height将使用sizeForItemAtIndexPath代替 preferredLayoutAttributesFittingAttributes。

performBatchUpdates:completion的呈现过程将通过preferredLayoutAttributesFittingAttributes方法，但它会忽略您的更改。

我尝试使用estimatedItemSize，但在插入和删除单元格时，如果estimatedItemSize不完全等于单元格的高度，则有一堆错误。我停止设置estimatedItemSize，并通过使用原型单元格实现动态单元格。这是如何做到的:

创建这个协议:

protocol SizeableCollectionViewCell {
    func fittedSize(forConstrainedSize size: CGSize)->CGSize
}

在你的自定义UICollectionViewCell中实现这个协议:

class YourCustomCollectionViewCell: UICollectionViewCell, SizeableCollectionViewCell {

    @IBOutlet private var mTitle: UILabel!
    @IBOutlet private var mDescription: UILabel!
    @IBOutlet private var mContentView: UIView!
    @IBOutlet private var mTitleTopConstraint: NSLayoutConstraint!
    @IBOutlet private var mDesciptionBottomConstraint: NSLayoutConstraint!

    func fittedSize(forConstrainedSize size: CGSize)->CGSize {

        let fittedSize: CGSize!

        //if height is greatest value, then it's dynamic, so it must be calculated
        if size.height == CGFLoat.greatestFiniteMagnitude {

            var height: CGFloat = 0

            /*now here's where you want to add all the heights up of your views.
              apple provides a method called sizeThatFits(size:), but it's not 
              implemented by default; except for some concrete subclasses such 
              as UILabel, UIButton, etc. search to see if the classes you use implement 
              it. here's how it would be used:
            */
            height += mTitle.sizeThatFits(size).height
            height += mDescription.sizeThatFits(size).height
            height += mCustomView.sizeThatFits(size).height    //you'll have to implement this in your custom view

            //anything that takes up height in the cell has to be included, including top/bottom margin constraints
            height += mTitleTopConstraint.constant
            height += mDescriptionBottomConstraint.constant

            fittedSize = CGSize(width: size.width, height: height)
        }
        //else width is greatest value, if not, you did something wrong
        else {
            //do the same thing that's done for height but with width, remember to include leading/trailing margins in calculations
        }

        return fittedSize
    }
}

现在让你的控制器符合UICollectionViewDelegateFlowLayout，在它里面，有这个字段:

class YourViewController: UIViewController, UICollectionViewDelegateFlowLayout {
    private var mCustomCellPrototype = UINib(nibName: <name of the nib file for your custom collectionviewcell>, bundle: nil).instantiate(withOwner: nil, options: nil).first as! SizeableCollectionViewCell
}

它将被用作一个原型单元格来绑定数据，然后确定该数据如何影响您想要动态的维度

最后，必须实现uicollectionviewdelegatflowlayout的collectionView(:layout:sizeForItemAt:):

class YourViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {

    private var mDataSource: [CustomModel]

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath)->CGSize {

        //bind the prototype cell with the data that corresponds to this index path
        mCustomCellPrototype.bind(model: mDataSource[indexPath.row])    //this is the same method you would use to reconfigure the cells that you dequeue in collectionView(:cellForItemAt:). i'm calling it bind

        //define the dimension you want constrained
        let width = UIScreen.main.bounds.size.width - 20    //the width you want your cells to be
        let height = CGFloat.greatestFiniteMagnitude    //height has the greatest finite magnitude, so in this code, that means it will be dynamic
        let constrainedSize = CGSize(width: width, height: height)

        //determine the size the cell will be given this data and return it
        return mCustomCellPrototype.fittedSize(forConstrainedSize: constrainedSize)
    }
}

就是这样。在collectionView(:layout:sizeForItemAt:)中返回单元格的大小，以这种方式防止我不得不使用estimatedItemSize，并且插入和删除单元格工作得很好。

在iOS 10+中，这是一个非常简单的2步过程。

Ensure that all your cell contents are placed within a single UIView (or inside a descendant of UIView like UIStackView which simplifies autolayout a lot). Just like with dynamically resizing UITableViewCells, the whole view hierarchy needs to have constraints configured, from the outermost container to the innermost view. That includes constraints between the UICollectionViewCell and the immediate childview Instruct the flowlayout of your UICollectionView to size automatically yourFlowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize