UIcollectionview 中未显示数据。我做错了什么[关闭]

Question

我的UICollectionView 没有显示数据，我做错了什么？

这里是集合视图控制器类：

class SongfeedViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDataSource {

    @IBOutlet weak var collectionview: UICollectionView!
    
    var posts = [Post]()
    
    private var song = [songs]()
    private var songsCollection : CollectionReference!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        songsCollection = Firestore.firestore().collection("Songs")
    }
    
    override func viewWillAppear(_ animated: Bool) 
    {
        songsCollection.getDocuments { (snapshot, error) in
            if let err = error{
                print("Error Fetching Docs:\(err)")
            
            } else {
                guard let snap = snapshot else{return}
                for document in snap.documents{
                    let data = document.data()
                    let fullname = data["fullname"] as? String ?? "Anonymous"
                    let songname = data["songname"] as? String ?? "Anonymous"
                    let youtubelink = data["youtubelink"] as? String ?? "Anonymous"
                    let moneyoffer = data["moneyoffer"] as? String ?? "Anonymous"
                    let instalink = data["instalink"] as? String ?? "Anonymous"
                    
                    let newsong = songs(fullname: fullname, songname: songname, moneyoffer: moneyoffer, youtubelink: youtubelink, instalink: instalink)
                    
                    self.song.append(newsong)
                }

                self.collectionview.reloadData()
            }
        }
    }
    
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.posts.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionview.dequeueReusableCell(withReuseIdentifier: "postCell", for: indexPath) as! postCell
        
        cell.artistnamelabel.text = self.posts[indexPath.row].fullname
        cell.moneyofferlabel.text = self.posts[indexPath.row].moneyoffer
        cell.instaUsernnamelabel.text = self.posts[indexPath.row].instalink
        cell.songnamelabel.text = self.posts[indexPath.row].songname
        cell.youtubelinklabel.text = self.posts[indexPath.row].youtubelink
        
        return cell
    }

来自 firestore 的数据未显示在 UI 集合视图上。

我的邮箱中的代码如下：

import UIKit

class postCell: UICollectionViewCell {
    @IBOutlet weak var artistnamelabel: UITextField!
    @IBOutlet weak var moneyofferlabel: UITextField!
    @IBOutlet weak var songnamelabel: UITextField!
    
    @IBOutlet weak var youtubelinklabel: UITextField!
    @IBOutlet weak var instaUsernnamelabel: UITextField! 
}

Answer 1

尝试将您的SongfeedViewController 更改为：

class SongfeedViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {

    @IBOutlet weak var collectionview: UICollectionView!
    
    var posts = [Post]()
    
    private var song = [songs]() {
        didSet {
            self.collectionview.reloadData()
        }
    }
    private var songsCollection : CollectionReference!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        songsCollection = Firestore.firestore().collection("Songs")
    }
    
    override func viewWillAppear(_ animated: Bool) 
    {
        songsCollection.getDocuments { (snapshot, error) in
            if let err = error {
                print("Error Fetching Docs:\(err)")
            } else {
                guard let snap = snapshot else { return }

                var songList = [songs]()

                for document in snap.documents 
                {
                    let data = document.data()
                    let fullname = data["fullname"] as? String ?? "Anonymous"
                    let songname = data["songname"] as? String ?? "Anonymous"
                    let youtubelink = data["youtubelink"] as? String ?? "Anonymous"
                    let moneyoffer = data["moneyoffer"] as? String ?? "Anonymous"
                    let instalink = data["instalink"] as? String ?? "Anonymous"
                    
                    let newsong = songs(
                        fullname: fullname, 
                        songname: songname, 
                        moneyoffer: moneyoffer, 
                        youtubelink: youtubelink, 
                        instalink: instalink
                    )
                    
                    songList.append(newsong)
                }

                self.song = songList
            }
        }
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.song.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionview.dequeueReusableCell(withReuseIdentifier: "postCell", for: indexPath) as! postCell
        let song = self.song[indexPath.row]

        cell.artistnamelabel.text = song.fullname
        cell.moneyofferlabel.text = song.moneyoffer
        cell.instaUsernnamelabel.text = song.instalink
        cell.songnamelabel.text = song.songname
        cell.youtubelinklabel.text = song.youtubelink
        
        return cell
    }

    // -- Add this delegate method --
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        // Change this values as you want
        let numberOfItemsPerRow: CGFloat = 2 
        let spacingBetweenCells: CGFloat = 12
        let cellHeight: CGFloat = 200
        
        let totalSpacing = (2 * spacingBetweenCells) + ((numberOfItemsPerRow - 1) * spacingBetweenCells)
        
        let width = (collectionView.bounds.width - totalSpacing) / numberOfItemsPerRow
        
        return CGSize(width: width, height: cellHeight)
    }

Answer 2

您的 numberOfItemsInSection 和 cellForItemAt 函数正在查看 posts 数组

但在您的闭包中，您将数据插入到song 变量中

当重新加载集合时，posts 仍然为空