Question

正如我的标题所述，当我滚动浏览表格视图时，我的tableView中的图片会移动并且不会显示在正确的帖子上。在我停止滚动后，它们似乎又回到原位。

我一直试图从以下文章中理解：

new Firebase retrieve data and put on the tableview swift

retrieve image from Firebase storage to show on tableview swift

swift Firebase sort posts in tableview by date

但我无法弄清楚如何让图片更好地显示。这就是我所拥有的：

    import UIKit
    import FirebaseAuth
    import FirebaseDatabase
    import FirebaseStorage

    class MainFeedTableViewController: UITableViewController {

        var posts = [Post]()

        let alert = AlertsViewController()

        var databaseRef: FIRDatabaseReference! {
            return FIRDatabase.database().reference()
        }

        var storageRef: FIRStorage! {
            return FIRStorage.storage()
        }

    override func viewDidLoad() {
        super.viewDidLoad()

        fetchPosts()

    }

    // populates the tableView with posts content in real time
    private func fetchPosts(){

        let postRefs = databaseRef.child("posts")

        postRefs.observe(.value) { (snapshot: FIRDataSnapshot) in
            var newPost = [Post]()

            for post in snapshot.children{
                let postObject = Post(snapshot: post as! FIRDataSnapshot)
                newPost.insert(postObject, at: 0)
            }

            self.posts = newPost
            self.tableView.reloadData()
        }

    }

    // MARK: - Table view data source

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

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

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

        let postsAtIndexPath = posts[indexPath.row]

        if postsAtIndexPath.postWithImage == true {

            let cell = tableView.dequeueReusableCell(withIdentifier: "postWithImage", for: indexPath) as! PostWithImageTableViewCell

            let postUser = postsAtIndexPath.uid

            let userRef = databaseRef.child("users/\(postUser!)")

            userRef.observe(.value, with: { (snapshot) in

                let user = User(snapshot: snapshot)

                DispatchQueue.main.async(execute: {
                    cell.userRealNameLabel.text = user.name
                    cell.usernameLabel.text = "@" + user.username
                    cell.postTextView.text = postsAtIndexPath.postText
                    cell.timeStampLabel.text = postsAtIndexPath.date
                })

                self.storageRef.reference(forURL: user.photoURL).data(withMaxSize: 1 * 1024 * 1024, completion: { (data, error) in

                    if error == nil{

                        DispatchQueue.main.async(execute: {
                            if let data = data{
                                cell.userProfilePicture.image = UIImage(data: data)
                            }
                        })

                    }
                    else{

                        print(error!.localizedDescription)
                    }
                })

                self.storageRef.reference(forURL: postsAtIndexPath.postPictureURL).data(withMaxSize: 1 * 1024 * 1024, completion: { (data, error) in

                    if error == nil{

                        DispatchQueue.main.async(execute: {
                            if let data = data{
                                cell.postImage.image = UIImage(data: data)

                            }
                        })

                    }
                    else{
                        self.alert.displayAlert(alertTitle: "Error", alertMessage: error!.localizedDescription, fromController: self)
                    }
                })

            }) { (error) in
                self.alert.displayAlert(alertTitle: "Error", alertMessage: error.localizedDescription, fromController: self)
            }

            return cell
        }
        else{

            let cell = tableView.dequeueReusableCell(withIdentifier: "postWithText", for: indexPath) as! PostTableViewCell

            let postUser = postsAtIndexPath.uid

            let userRef = databaseRef.child("users/\(postUser!)")

            userRef.observe(.value, with: { (snapshot) in

                let user = User(snapshot: snapshot)

                DispatchQueue.main.async(execute: {
                    cell.userRealNameLabel.text = user.name
                    cell.usernameLabel.text = "@" + user.username
                    cell.postTextView.text = postsAtIndexPath.postText
                    cell.timestampLabel.text = postsAtIndexPath.date

                })

                self.storageRef.reference(forURL: user.photoURL).data(withMaxSize: 1 * 1024 * 1024, completion: { (data, error) in

                    if error == nil{

                        DispatchQueue.main.async(execute: {
                            if let data = data{
                                cell.userProfilePicture.image = UIImage(data: data)
                            }
                        })

                    }
                    else{

                        print(error!.localizedDescription)
                    }
                })

            }) { (error) in
                self.alert.displayAlert(alertTitle: "Error", alertMessage: error.localizedDescription, fromController: self)
            }

            return cell
        }

    }

}

我之所以遇到困难，是因为我希望用户的用户名，姓名和个人资料图片能够在编辑信息时随时随地进行更改。这就是我根据帖子的用户uid检索用户信息的原因。

实施此更好的方法是什么？

Answer 1

您必须覆盖prepareForReuse中的PostWithImageTableViewCell功能。

示例

override func prepareForReuse() { super.prepareForReuse() self.userProfilePicture.image = nil //reset the rest of the values on your `UITableViewCell` subclass }

修改

由于重用问题已经解决，我建议使用以下缓存框架Kingfisher，以获得更方便的图像显示体验。

Kingfisher在UIImageView上有一个很好的扩展，会为你的缓存提供什么。

在这里你将如何使用它：

let url = URL(string: "https://domain.com/image.jpg")! imageView.kf.setImage(with: url)

您只需设置为URL，唯一标识图像资源的内容，并且只下载一次。这是一个cheat sheet，如何使用它。

从Firebase检索后，图片在UITableView中随机移动

1 个答案: