如何正确获取 tableViewCell 的 contentView 绑定大小？

Question

资源：

我已经阅读了来自 Using Auto Layout in UITableView for dynamic cell layouts & variable row heights

的多个答案

并遵循了他们的建议，但没有用。

重现设置：

如果您 copy/paste MyTableViewCell 和 ViewController 片段：那么您可以重现该问题。

我已将 MyTableViewCell 子类化并添加了我自己的标签。

    import UIKit

    class MyTableViewCell: UITableViewCell {

        lazy var customLabel : UILabel = {
            let lbl = UILabel()
            lbl.translatesAutoresizingMaskIntoConstraints = false
            lbl.numberOfLines = 0
            return lbl
        }()

        override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
            super.init(style: style, reuseIdentifier: reuseIdentifier)
            setupLayout()
        }
        private func setupLayout(){
            contentView.addSubview(customLabel)

            let top = customLabel.topAnchor.constraint(equalTo: contentView.topAnchor)
            let bottom = customLabel.bottomAnchor.constraint(equalTo: contentView.bottomAnchor)
            let leadingFromImage = customLabel.leadingAnchor.constraint(equalTo: imageView!.trailingAnchor, constant: 5)
            let trailing = customLabel.trailingAnchor.constraint(equalTo: contentView.trailingAnchor)

            NSLayoutConstraint.activate([top, bottom, leadingFromImage, trailing])
        }

        required init?(coder aDecoder: NSCoder) {
            fatalError()
        }
    }

以下 ViewController 包含我的表格视图：

import UIKit

class ViewController: UIViewController {

    var datasource = ["It would have been a great day had Manchester United Lost its \n game. Anyhow I hope tomorrow Arsenal will win the game"]

    lazy var tableView : UITableView = {
        let table = UITableView()
        table.delegate = self
        table.dataSource = self
        table.translatesAutoresizingMaskIntoConstraints = false
        table.estimatedRowHeight = 100
        table.rowHeight = UITableViewAutomaticDimension
        return table
    }()
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(tableView)
        tableView.pinToAllEdges(of: view)
        tableView.register(MyTableViewCell.self, forCellReuseIdentifier: "id")
    }
}

extension ViewController: UITableViewDelegate, UITableViewDataSource {

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return datasource.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "id", for: indexPath) as! MyTableViewCell

        cell.customLabel.text = datasource[indexPath.row]
        logInfo(of: cell)

        cell.accessoryType = .detailDisclosureButton
        cell.imageView?.image = UIImage(named: "honey")
        cell.layoutSubviews()
        cell.customLabel.preferredMaxLayoutWidth = tableView.bounds.width
        logInfo(of: cell)
        print("---------")

        return cell
    }

    private func logInfo(of cell: MyTableViewCell){
        print("boundsWidth: \(cell.contentView.bounds.width) | maxLayoutWidth: \(cell.contentView.bounds.width - 44 - 15 - 5) | systemLayoutSizeFitting : \(cell.customLabel.systemLayoutSizeFitting(UILayoutFittingCompressedSize))")
    }    
}

extension UIView{

    func pinToAllEdges(of view: UIView){
        let leading = leadingAnchor.constraint(equalTo: view.leadingAnchor)
        let top = topAnchor.constraint(equalTo: view.topAnchor)
        let trailing = trailingAnchor.constraint(equalTo: view.trailingAnchor)
        let bottom = bottomAnchor.constraint(equalTo: view.bottomAnchor)        

        NSLayoutConstraint.activate([leading, top, trailing, bottom])
    }
}

Link for honey image 我用过。我已将其大小设置为 44 * 44

主要问题

我的主要问题在里面 cellForRowAtIndex:

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "id", for: indexPath) as! MyTableViewCell

    cell.customLabel.text = datasource[indexPath.row]
    logInfo(of: cell)

    cell.accessoryType = .detailDisclosureButton
    cell.imageView?.image = UIImage(named: "honey")
    cell.layoutSubviews()
    cell.customLabel.preferredMaxLayoutWidth = cell.contentView.bounds.width
    logInfo(of: cell)
    print("---------")

    return cell
}

问题：

无论出于何种原因赋值给：

cell.customLabel.preferredMaxLayoutWidth

好像不太对。

Q1:这是为什么？

Q2: 我在调用 cell.layoutSubviews 之前和之后记录了 contentView 的绑定，它从 320 切换到 260 但是然后最终在 viewDebugger 中显示为 308!!!

为什么contenView的边界又变了？！

_{我从问题中删除了一些其他屏幕截图。它们大多杂乱无章，但也许值得一看。大家可以看看修改历史}

Answer 1

我认为问题与使用默认单元格的 imageView.

有关

图像视图本身在其 .image 属性设置之前不存在，因此在您的单元格初始化中，您将自定义标签限制为图像视图 0,0， 0,0

然后，在 cellForRowAt 中，您设置 .image 属性，它出现那个动作也设置contentView的高度。我找不到关于它的任何文档，并且在调试中挖掘我找不到任何冲突的约束，所以我不完全确定为什么会这样。

两个选项：

1 - 不创建和添加自定义标签，而是将默认 .textLabel 上的 .numberOfLines 设置为 0。应该就够了。

2 - 如果您需要自定义标签，还添加自定义图像视图。

选项 2 在这里：

class MyTableViewCell: UITableViewCell {

    lazy var customLabel : UILabel = {
        let lbl = UILabel()
        lbl.translatesAutoresizingMaskIntoConstraints = false
        lbl.numberOfLines = 0
        lbl.setContentCompressionResistancePriority(.required, for: .vertical)
        return lbl
    }()

    lazy var customImageView: UIImageView = {
        let v = UIImageView()
        v.translatesAutoresizingMaskIntoConstraints = false
        return v
    }()

    override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        setupLayout()
    }

    private func setupLayout(){
        contentView.addSubview(customLabel)

        contentView.addSubview(customImageView)

        // constrain leading of imageView to be 15-pts from the leading of the contentView
        let imgViewLeading = customImageView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 15)

        // constrain width of imageView to 42-pts
        let imgViewWidth = customImageView.widthAnchor.constraint(equalToConstant: 42)

        // constrain height of imageView to be equal to width of imageView
        let imgViewHeight = customImageView.heightAnchor.constraint(equalTo: customImageView.widthAnchor, multiplier: 1.0)

        // center imageView vertically
        let imgViewCenterY = customImageView.centerYAnchor.constraint(equalTo: contentView.centerYAnchor, constant: 0.0)

        // top and bottom constraints for the imageView also need to be set,
        // otherwise the image will exceed the height of the cell when there
        // is not enough text to wrap and expand the height of the label

        // constrain top of imageView to be *at least* 4-pts from the top of the cell
        let imgViewTop = customImageView.topAnchor.constraint(greaterThanOrEqualTo: contentView.topAnchor, constant: 4)

        // constrain bottom of imageView to be *at least* 4-pts from the bottom of the cell
        let imgViewBottom = customImageView.topAnchor.constraint(lessThanOrEqualTo: contentView.bottomAnchor, constant: -4)

        // constrain top of the label to be *at least* 4-pts from the top of the cell
        let top = customLabel.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 4)

        // if you want the text in the label vertically centered in the cell
        // constrain bottom of the label to be *exactly* 4-pts from the bottom of the cell
        let bottom = customLabel.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -4)

        // if you want the text in the label top-aligned in the cell
        // constrain bottom of the label to be *at least* 4-pts from the bottom of the cell
        // let bottom = customLabel.bottomAnchor.constraint(lessThanOrEqualTo: contentView.bottomAnchor, constant: -4)

        // constrain leading of the label to be 5-pts from the trailing of the image
        let leadingFromImage = customLabel.leadingAnchor.constraint(equalTo: customImageView.trailingAnchor, constant: 5)

        // constrain the trailing of the label to the trailing of the contentView
        let trailing = customLabel.trailingAnchor.constraint(equalTo: contentView.trailingAnchor)

        NSLayoutConstraint.activate([
            top, bottom, leadingFromImage, trailing,
            imgViewLeading, imgViewCenterY, imgViewWidth, imgViewHeight,
            imgViewTop, imgViewBottom
            ])

    }

    required init?(coder aDecoder: NSCoder) {
        fatalError()
    }
}

class HoneyViewController: UIViewController {

    var datasource = [
        "It would have been a great day had Manchester United Lost its game. Anyhow I hope tomorrow Arsenal will win the game",
        "One line.",
        "Two\nLines.",
    ]

    lazy var tableView : UITableView = {
        let table = UITableView()
        table.delegate = self
        table.dataSource = self
        table.translatesAutoresizingMaskIntoConstraints = false
        table.estimatedRowHeight = 100
        table.rowHeight = UITableViewAutomaticDimension
        return table
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(tableView)
        tableView.pinToAllEdges(of: view)
        tableView.register(MyTableViewCell.self, forCellReuseIdentifier: "id")
    }
}

extension HoneyViewController: UITableViewDelegate, UITableViewDataSource {

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return datasource.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "id", for: indexPath) as! MyTableViewCell

        cell.customLabel.text = datasource[indexPath.row]
        logInfo(of: cell)

        cell.accessoryType = .detailDisclosureButton
        cell.customImageView.image = UIImage(named: "Honey")
        logInfo(of: cell)
        print("---------")

        return cell
    }

    private func logInfo(of cell: MyTableViewCell){
        print("boundsWidth: \(cell.contentView.bounds.width) | maxLayoutWidth: \(cell.contentView.bounds.width - 44 - 15 - 5) | systemLayoutSizeFitting : \(cell.customLabel.systemLayoutSizeFitting(UILayoutFittingCompressedSize))")
    }
}

extension UIView{

    func pinToAllEdges(of view: UIView){
        let leading = leadingAnchor.constraint(equalTo: view.leadingAnchor)
        let top = topAnchor.constraint(equalTo: view.topAnchor)
        let trailing = trailingAnchor.constraint(equalTo: view.trailingAnchor)
        let bottom = bottomAnchor.constraint(equalTo: view.bottomAnchor)

        NSLayoutConstraint.activate([leading, top, trailing, bottom])
    }
}

编辑：

还需要一些约束。如果单元格只有一行的文本（没有换行），imageView 高度将超过单元格的高度：

因此，我们向 imageView 添加顶部和底部约束以适应至少单元格的顶部和底部：

而且，加上一些填充可能看起来会好一些，所以我们将 imageView 的顶部和底部限制为距顶部和底部至少 4 磅单元格的：

如果需要，我们还可以 "top-align" 标签中的文本，方法是将其底部限制为距底部至少 4 磅，而不是正好从底部算起 4 分：

我编辑的代码中的注释应该解释每一个差异。

如何正确获取 tableViewCell 的 contentView 绑定大小？

How to correctly get tableViewCell's contentView bound size?

uitableview

ios

contentsize

autolayout

swift

资源：

重现设置：

主要问题