iOS 11 : Adapt cell size to content with UITableViewAutomaticDimension

Question

我希望 UITableView 的单元格在 iOS 10 和 11 中适应其内容的大小:

tableView.estimatedRowHeight = UITableViewAutomaticDimension // default in iOS 11
tableView.rowHeight = UITableViewAutomaticDimension

没有将 tableView.rowHeight 设置为明确的数值，这是 iOS 11 中的新默认值。

UIView 没有固有的内容大小，因此我为其高度 anchor 设置了布局约束。然而，该 anchor 在运行时中断。

UITableViewCell 中的哪些内部约束对于单元格适应其内容是必要的？

---

这仅适用于 iOS 11:

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        let tableView = UITableView()
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.estimatedRowHeight = UITableViewAutomaticDimension
        tableView.rowHeight = UITableViewAutomaticDimension
        tableView.delegate = self
        tableView.dataSource = self
        tableView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(tableView)

        NSLayoutConstraint.activate([
            tableView.topAnchor.constraint(equalTo: view.topAnchor),
            tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            tableView.leftAnchor.constraint(equalTo: view.leftAnchor),
            tableView.rightAnchor.constraint(equalTo: view.rightAnchor)
            ])
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = UITableViewCell(style: UITableViewCellStyle.subtitle, reuseIdentifier: "cell")

        let view = UIView()
        view.backgroundColor = .blue
        view.translatesAutoresizingMaskIntoConstraints = false
        cell.contentView.addSubview(view)

        NSLayoutConstraint.activate([
            view.topAnchor.constraint(equalTo: cell.contentView.topAnchor),
            view.bottomAnchor.constraint(equalTo: cell.contentView.bottomAnchor),
            view.leftAnchor.constraint(equalTo: cell.contentView.leftAnchor),
            view.rightAnchor.constraint(equalTo: cell.contentView.rightAnchor),
            view.heightAnchor.constraint(equalToConstant: 300)
            ])

        return cell
    }

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

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 1
    }
}

在 iOS 10 中它抛出这个运行时错误并且单元格大小不适应:

[LayoutConstraints] Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. ( "NSLayoutConstraint:0x17009c020 V:|-(0)-[test.MyView:0x11dd1acb0] (active, names: '|':UITableViewCellContentView:0x11dd15220 )", "NSLayoutConstraint:0x17009c160 test.MyView:0x11dd1acb0.bottom == UITableViewCellContentView:0x11dd15220.bottom (active)", "NSLayoutConstraint:0x17009c390 test.MyView:0x11dd1acb0.height == 300 (active)", "NSLayoutConstraint:0x17009be40 'UIView-Encapsulated-Layout-Height' UITableViewCellContentView:0x11dd15220.height == 43.6667 (active)" )

Will attempt to recover by breaking constraint NSLayoutConstraint:0x17009c390 test.MyView:0x11dd1acb0.height == 300 (active)

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in UIKit/UIView.h may also be helpful.

---

这在 iOS 10 和 11 中有效，但不使用新的 iOS 11 方法，因为 tableView.estimatedRowHeight 不是 UITableViewAutomaticDimension:

class ViewController_TableView: UIViewController, UITableViewDataSource, UITableViewDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        let tableView = UITableView()
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.estimatedRowHeight = 30
        tableView.rowHeight = UITableViewAutomaticDimension
        tableView.delegate = self
        tableView.dataSource = self
        tableView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(tableView)

        NSLayoutConstraint.activate([
            tableView.topAnchor.constraint(equalTo: view.topAnchor),
            tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            tableView.leftAnchor.constraint(equalTo: view.leftAnchor),
            tableView.rightAnchor.constraint(equalTo: view.rightAnchor)
            ])
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = UITableViewCell(style: UITableViewCellStyle.subtitle, reuseIdentifier: "cell")

        let view = MyView()
        view.backgroundColor = .blue
        view.translatesAutoresizingMaskIntoConstraints = false
        cell.contentView.addSubview(view)

        NSLayoutConstraint.activate([
            view.topAnchor.constraint(equalTo: cell.contentView.topAnchor),
            view.bottomAnchor.constraint(equalTo: cell.contentView.bottomAnchor),
            view.leftAnchor.constraint(equalTo: cell.contentView.leftAnchor),
            view.rightAnchor.constraint(equalTo: cell.contentView.rightAnchor)
            ])

        return cell
    }

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

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 1
    }
}

class MyView: UIView {

    override var intrinsicContentSize: CGSize {
        get {
            return CGSize(width: 300, height: 300)
        }
    }
}

Answer 1

您没有使委托(delegate)符合您的 Controller 。然后使用代码

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    let params : [String: Any] = ["q": "dd", "format": "json", "pretty": 1,"no_html": 1, "skip_disambig": 1]
    Alamofire.request("https://api.duckduckgo.com", method: .get, parameters: params).responseJSON { (responseData) in
        print(responseData)
    }

    let tableView = UITableView()
    tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
    tableView.estimatedRowHeight = 40
    tableView.delegate = self
    tableView.dataSource = self
    tableView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(tableView)

    NSLayoutConstraint.activate([
        tableView.topAnchor.constraint(equalTo: view.topAnchor),
        tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        tableView.leftAnchor.constraint(equalTo: view.leftAnchor),
        tableView.rightAnchor.constraint(equalTo: view.rightAnchor)
        ])

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = UITableViewCell(style: UITableViewCellStyle.subtitle, reuseIdentifier: "cell")

    let view = UIView()
    view.backgroundColor = .blue
    view.translatesAutoresizingMaskIntoConstraints = false
    cell.contentView.addSubview(view)

    NSLayoutConstraint.activate([
        view.topAnchor.constraint(equalTo: cell.contentView.topAnchor),
        view.bottomAnchor.constraint(equalTo: cell.contentView.bottomAnchor),
        view.leftAnchor.constraint(equalTo: cell.contentView.leftAnchor),
        view.rightAnchor.constraint(equalTo: cell.contentView.rightAnchor),
        view.heightAnchor.constraint(equalToConstant: 300) // this breaks on run time
        ])

    return cell
}

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

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return 1
}
// use this delegate 
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return UITableViewAutomaticDimension
}


}