从 Swift 中的 nib 自定义 UITableViewCell [英] Custom UITableViewCell from nib in Swift

问题描述

I'm trying to create a custom table view cell from a nib. I'm referring to this article here. I'm facing two issues.

I created a .xib file with a UITableViewCell object dragged on to it. I created a subclass of UITableViewCell and set it as the cell's class and Cell as the reusable identifier.

import UIKit

class CustomOneCell: UITableViewCell {

    @IBOutlet weak var middleLabel: UILabel!
    @IBOutlet weak var leftLabel: UILabel!
    @IBOutlet weak var rightLabel: UILabel!

    required init(coder aDecoder: NSCoder!) {
        super.init(coder: aDecoder)
    }

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

    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }

}

In the UITableViewController I have this code,

import UIKit

class ViewController: UITableViewController, UITableViewDataSource, UITableViewDelegate {

    var items = ["Item 1", "Item2", "Item3", "Item4"]

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

    // MARK: - UITableViewDataSource
    override func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int {
        return items.count
    }

    override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! {
        let identifier = "Cell"
        var cell: CustomOneCell! = tableView.dequeueReusableCellWithIdentifier(identifier) as? CustomOneCell
        if cell == nil {
            tableView.registerNib(UINib(nibName: "CustomCellOne", bundle: nil), forCellReuseIdentifier: identifier)
            cell = tableView.dequeueReusableCellWithIdentifier(identifier) as? CustomOneCell
        }

        return cell
    }
}

This code complies with no errors but when I run it in the simulator, it looks like this.

In the UITableViewController in the storyboard I haven't done anything to the cell. Blank identifier and no subclass. I tried adding the Cell identifier to the prototype cell and ran it again but I get the same result.

Another error I faced is, when I tried to implement the following method in the UITableViewController.

override func tableView(tableView: UITableView!, willDisplayCell cell: CustomOneCell!, forRowAtIndexPath indexPath: NSIndexPath!) {

    cell.middleLabel.text = items[indexPath.row]
    cell.leftLabel.text = items[indexPath.row]
    cell.rightLabel.text = items[indexPath.row]
}

As shown in the article I mentioned I changed the cell parameter's type form UITableViewCell to CustomOneCell which is my subclass of UITableViewCell. But I get the following error,

Overriding method with selector 'tableView:willDisplayCell:forRowAtIndexPath:' has incompatible type '(UITableView!, CustomOneCell!, NSIndexPath!) -> ()'

Anyone have any idea how to resolve these errors? These seemed to work fine in Objective-C.

Thank you.

EDIT: I just noticed if I change the simulator's orientation to landscape and turn it back to portrait, the cells appear! I still couldn't figure out what's going on. I uploaded an Xcode project here demonstrating the problem if you have time for a quick look.

解决方案

With Swift 5 and iOS 12.2, you should try the following code in order to solve your problem:

CustomCell.swift

import UIKit

class CustomCell: UITableViewCell {

    // Link those IBOutlets with the UILabels in your .XIB file
    @IBOutlet weak var middleLabel: UILabel!
    @IBOutlet weak var leftLabel: UILabel!
    @IBOutlet weak var rightLabel: UILabel!

}

TableViewController.swift

import UIKit

class TableViewController: UITableViewController {

    let items = ["Item 1", "Item2", "Item3", "Item4"]

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.register(UINib(nibName: "CustomCell", bundle: nil), forCellReuseIdentifier: "CustomCell")
    }

    // MARK: - UITableViewDataSource

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

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

        cell.middleLabel.text = items[indexPath.row]
        cell.leftLabel.text = items[indexPath.row]
        cell.rightLabel.text = items[indexPath.row]

        return cell
    }

}

---

The image below shows a set of constraints that work with the provided code without any constraints ambiguity message from Xcode:

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