UITableViewCell 中的 Swift UICollectionView 无法正常工作

Question

我在 TableView 单元格中有一个 Collection View 。该模型是按愿望 list 名称分组的愿望 list 项目。可能有很多愿望 list 。当用户选择愿望 list 时，他们会得到一个平面数组的愿望 list ，但我想在单元格中显示愿望 list 的项目图像的预览。它们不可单独选择，单元格选择会转到所选愿望 list 的项目列表。同样，我将通过滑动删除 Action 删除整个愿望 list 。

我的问题是 collectionView 函数根本不触发。我正在测试的源数据有一个愿望 list 和 4 个项目。

这是我的 TableViewCell。

import Foundation
import UIKit
import Alamofire
import AlamofireImage

class WishListsCell: UITableViewCell {

var collectionView: UICollectionView!

let screenWidth = UIScreen.main.bounds.width

var alamofireRequest: Alamofire.Request?

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

    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    layout.itemSize = CGSize(width: screenWidth, height: ((screenWidth / 4) * Constants.IMAGE_ASPECT_RATIO))
    layout.minimumInteritemSpacing = 0
    layout.minimumLineSpacing = 0
    layout.estimatedItemSize.height = ((screenWidth / 4) * Constants.IMAGE_ASPECT_RATIO)
    layout.estimatedItemSize.width = screenWidth

    collectionView = UICollectionView(frame: contentView.frame, collectionViewLayout: layout)

    collectionView.delegate = self

    collectionView.dataSource = self   

    collectionView.register(WishListsCollectionViewCell.self, forCellWithReuseIdentifier: cellId)

    self.contentView.addSubview(collectionView)

}

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

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

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}
}


extension WishListsCell: UICollectionViewDelegate, UICollectionViewDataSource {


func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    debugPrint(wishListItems.count)

    return wishListItems.count

}


func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "WishListsCollectionViewCell", for: indexPath) as! WishListsCollectionViewCell

    if let imageUrl = wishListItems[indexPath.row]["image"] as? String {

        debugPrint(imageUrl)

        cell.imageView.image = nil

        if let image = ShoppingManager.sharedManager.photoCache.image(withIdentifier: imageUrl) {
            cell.imageView.image = image
        }
        else
        {                              
            cell.alamofireRequest?.cancel()

            cell.alamofireRequest = Alamofire.request(imageUrl)
                .responseImage { response in

                    let img = response.result.value

                    cell.imageView.image = img

                    cell.imageView.contentMode = UIViewContentMode.scaleAspectFit

                    let imageWidth:CGFloat = self.screenWidth/4

                    let imageHeight:CGFloat = imageWidth * Constants.IMAGE_ASPECT_RATIO

                    cell.imageView.frame.size.width = imageWidth

                    cell.imageView.frame.size.height = imageHeight

                    ShoppingManager.sharedManager.photoCache.add(img!, withIdentifier: imageUrl)               
            }
        }
    }
    return cell   
}   
}

这是我的 CollectionViewCell:

import Foundation
import UIKit
import Alamofire
import AlamofireImage

class WishListsCollectionViewCell: UICollectionViewCell {

    var alamofireRequest: Alamofire.Request?

    var imageView: UIImageView

    let screenWidth = UIScreen.main.bounds.width

    override init(frame: CGRect) {

        imageView = UIImageView()

        super.init(frame: frame)

        contentView.addSubview(imageView)

        imageView.translatesAutoresizingMaskIntoConstraints = false

        imageView.contentMode = .scaleAspectFit

        NSLayoutConstraint.activate([

           NSLayoutConstraint(item: imageView, attribute: .width, relatedBy: .equal,
                               toItem: nil, attribute: .width,
                               multiplier: 1.0, constant: screenWidth / 4),

            NSLayoutConstraint(item: imageView, attribute: .height, relatedBy: .equal,
                               toItem: nil, attribute: .height,
                               multiplier: 1.0, constant: (screenWidth / 4) * Constants.IMAGE_ASPECT_RATIO),

            ])
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }    
}

以下是我的 ViewController 代码的相关部分:

import UIKit
import Alamofire
import AlamofireImage
import MBProgressHUD
import DBAlertController

class WishListsViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

    var tableView: UITableView = UITableView()

    var screenSize: CGRect!
    var screenWidth: CGFloat!
    var screenHeight: CGFloat!

    var cellId = "WishListsCell"

    var didSelectItem:Bool = false

    override func viewDidLoad() {
        super.viewDidLoad()

        screenSize = UIScreen.main.bounds
        screenWidth = screenSize.width
        screenHeight = screenSize.height

        tableView.delegate      =   self

        tableView.dataSource    =   self

        tableView.backgroundColor = .white

        tableView.register(WishListsCell.self, forCellReuseIdentifier: cellId)

        self.view.addSubview(tableView)

        tableView.translatesAutoresizingMaskIntoConstraints = false

        tableView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        tableView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        tableView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true

        let customView = UIView(frame: CGRect(x:0, y:0, width:screenWidth, height:30))

        customView.backgroundColor = Constants.APP_BACKGROUND_COLOR

        let button = UIButton(frame: CGRect(x: 0, y: 0, width: screenWidth, height: 30))

        button.setTitle("Add New Wish List", for: .normal)

        button.setTitleColor(Constants.APP_TEXT_COLOR, for: .normal)

        button.titleLabel?.font = Constants.APP_HEADER_FONT

        button.addTarget(self, action: #selector(addButtonAction), for: .touchUpInside)

        customView.addSubview(button)

        tableView.tableHeaderView = customView        
    }

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

    func numberOfSections(in tableView: UITableView) -> Int {
        return wishLists.count
    }

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

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {

        return 120
    }

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

        let cell = tableView.dequeueReusableCell(withIdentifier: cellId, for: indexPath) as! WishListsCell

        let listId = wishLists[indexPath.section]["listid"] as! Int

        cell.alamofireRequest?.cancel()

        cell.alamofireRequest = Alamofire.request(myURL)
            .responseJSON(completionHandler: {
                response in  
                self.parseWishListItemData(JSONData: response.data!)             
            })
        return cell
    }

    func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {

        let listName = wishLists[section]["listname"] as! String

        return listName
       }
    }

Answer 1

在 awakeFromNib 中实例化后，您似乎没有将 Collection View 添加到 View 层次结构中。您需要在单元格的内容 View 上调用 addSubview。

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

    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    layout.itemSize = CGSize(width: screenWidth, height: ((screenWidth / 4) * Constants.IMAGE_ASPECT_RATIO))
    layout.minimumInteritemSpacing = 0
    layout.minimumLineSpacing = 0
    layout.estimatedItemSize.height = ((screenWidth / 4) * Constants.IMAGE_ASPECT_RATIO)
    layout.estimatedItemSize.width = screenWidth

    collectionView = UICollectionView(frame: contentView.frame, collectionViewLayout: layout)

    collectionView.delegate = self

    collectionView.dataSource = self

    self.contentView.addSubview(collectionView) // <-- Need this        
}

如果重复使用表格单元格，您可能还会遇到一些问题。您必须确保您的 Collection View 委托(delegate)在每次被重新使用时都得到设置——可能在 prepareForReuse 中。