ios - Xcode中UICollectionsView的单元格没有出现

Question

我正在开发一个应用程序并设置一个 UICollectionView。下面是 UICollectionView 所在的视图控制器的代码：

import UIKit
import Firebase
import FirebaseFirestoreSwift
import FirebaseFirestore

class scrollCollectionViewController: UICollectionViewController{
    var tournaments = [String]()
    @IBOutlet weak var collectionview: UICollectionView!
    override func viewDidLoad() {
        fetchTourneys()
        super.viewDidLoad()
        
        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        // Register cell classes
        

        // Do any additional setup after loading the view.
    }
    
    func fetchTourneys() {
       let db = Firestore.firestore()
       db.collection("Tournaments").getDocuments() { (querySnapshot, err) in
               if let err = err {
                   print("Error getting documents: \(err)")
               } else {
                   for document in querySnapshot!.documents {
                       print("\(document.documentID) => \(document.data())")
                       self.tournaments.append(document.documentID)
                   }
               }
       }
    }
    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using [segue destinationViewController].
        // Pass the selected object to the new view controller.
    }
    */

    // MARK: UICollectionViewDataSource

    override func numberOfSections(in collectionView: UICollectionView) -> Int {
    // #warning Incomplete implementation, return the number of sections
       return self.tournaments.count
    }


    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    // #warning Incomplete implementation, return the number of items
       return 5
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
       let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "tourneyIdentifier", for: indexPath) as! ScrollCollectionViewCell
       cell.tournamentTitle.text = tournaments[indexPath.row]
       print(cell.tournamentTitle.text)
    // Configure the cell

       return cell
    }

    // MARK: UICollectionViewDelegate

    /*
    // Uncomment this method to specify if the specified item should be highlighted during tracking
    override func collectionView(_ collectionView: UICollectionView, shouldHighlightItemAt indexPath: IndexPath) -> Bool {
        return true
    }
    */

    /*
    // Uncomment this method to specify if the specified item should be selected
    override func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
        return true
    }
    */

    /*
    // Uncomment these methods to specify if an action menu should be displayed for the specified item, and react to actions performed on the item
    override func collectionView(_ collectionView: UICollectionView, shouldShowMenuForItemAt indexPath: IndexPath) -> Bool {
        return false
    }

    override func collectionView(_ collectionView: UICollectionView, canPerformAction action: Selector, forItemAt indexPath: IndexPath, withSender sender: Any?) -> Bool {
        return false
    }

    override func collectionView(_ collectionView: UICollectionView, performAction action: Selector, forItemAt indexPath: IndexPath, withSender sender: Any?) {
    
    }
    */
}

细胞只是没有最终出现。在包含一些打印语句后，我注意到 numberOfSections 的任何覆盖函数或集合视图似乎都没有运行。为什么这些没有运行，以及为什么细胞没有出现，可能是什么问题？

标签： iosswiftxcodefirebaseuicollectionview

Answer 1

请fetchTourneys() 在super.viewDidLoad() 之后移动。此外，您需要确保正确设置单元格标识符并在您的 collectionView 中注册

private let reuseIdentifier = "tourneyIdentifier"

class scrollCollectionViewController: UICollectionViewController {
    var tournaments = [String]()

    @IBOutlet weak var collectionview: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Register cell classes
        self.collectionview!.register(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)
        fetchTourneys()
    }

然后，在创建单元格时，重新使用reuseIdentifier

.dequeueReusableCell(withReuseIdentifier: reuseIdentifier

此外，在您的 Firebase 函数中，确保在填充数据源后告诉 collectionView 进行更新

if let err = err {
    print("Error getting documents: \(err)")
} else {
    for document in querySnapshot!.documents {
        print("\(document.documentID) => \(document.data())")
        self.tournaments.append(document.documentID)
    }
    self.collectionview.reloadData()
}

你还说

我注意到 numberOfSections 的任何覆盖函数或集合视图似乎都没有运行

这表明您的 UICollectionView 不知道此代码是 viewController。确保您已在 XCode Inspector 中进行设置。一般来说，Classes 和 Structs 应该以大写字母开头，vars 是小写的