swift - UICollectionViewCells 未填充

Question

我正在尝试创建一个消息应用程序。当我尝试显示包含 UICollectionView 中的消息的单元格时，它们没有显示。我首先想为单元格提供红色背景并显示模型中的项目。我有消息数组。谁能告诉我为什么他们没有填充？

import UIKit
import Firebase

class ChatLogController: UICollectionViewController, 
UITextFieldDelegate, UICollectionViewDelegateFlowLayout{

    var messages = [Message]()

    var user: User?{
        didSet{
            navigationItem.title = user?.name
            navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Back", style: .plain, target: self, action: #selector(handleBackBtnPressed))



            observeMessages()
        }
    }

    lazy var inputTextField: UITextField = {
        let textField = UITextField()
        textField.placeholder  = "Enter Message..."
        textField.translatesAutoresizingMaskIntoConstraints = false
        textField.delegate = self

        return textField
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        collectionView?.backgroundColor = UIColor.white
         collectionView?.register(ChatMessageCell.self, forCellWithReuseIdentifier: "cell")
        collectionView?.delegate = self
        collectionView?.dataSource = self
        setupInputComponents()

    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return messages.count
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! ChatMessageCell

        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        //set the size
        return CGSize(width: self.view.frame.width, height: 80)
    }


    func setupInputComponents(){
        let containerView = UIView()
        containerView.translatesAutoresizingMaskIntoConstraints = false

        view.addSubview(containerView)

        //constraints
        containerView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        containerView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        containerView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
        containerView.heightAnchor.constraint(equalToConstant: 50).isActive = true
        containerView.backgroundColor = UIColor.white

        let sendBtn = UIButton(type: .system)
        sendBtn.setTitle("Send", for: .normal)
        sendBtn.translatesAutoresizingMaskIntoConstraints = false
        sendBtn.addTarget(self, action: #selector(handleSend), for: .touchUpInside)
        containerView.addSubview(sendBtn)
        sendBtn.rightAnchor.constraint(equalTo: containerView.rightAnchor).isActive = true
        sendBtn.centerYAnchor.constraint(equalTo: containerView.centerYAnchor).isActive = true
        sendBtn.widthAnchor.constraint(equalToConstant: 80).isActive = true
        sendBtn.heightAnchor.constraint(equalTo: containerView.heightAnchor).isActive = true

        containerView.addSubview(inputTextField)

        inputTextField.leftAnchor.constraint(equalTo: containerView.leftAnchor, constant: 8).isActive = true
        inputTextField.centerYAnchor.constraint(equalTo: containerView.centerYAnchor).isActive = true
        inputTextField.rightAnchor.constraint(equalTo: sendBtn.leftAnchor).isActive = true
        inputTextField.heightAnchor.constraint(equalTo: containerView.heightAnchor).isActive = true

        let separator = UIView()
        separator.backgroundColor =  UIColor.lightGray
        separator.translatesAutoresizingMaskIntoConstraints = false
        containerView.addSubview(separator)

        separator.leftAnchor.constraint(equalTo: containerView.leftAnchor).isActive = true
        separator.topAnchor.constraint(equalTo: containerView.topAnchor).isActive = true
        separator.widthAnchor.constraint(equalTo:containerView.widthAnchor).isActive = true
        separator.heightAnchor.constraint(equalToConstant: 1).isActive = true


    }

    func handleSend(){
        let reference = FIRDatabase.database().reference().child("messages")
        let childRef = reference.childByAutoId()
        let toId = user!.id!
        let fromId = FIRAuth.auth()!.currentUser!.uid
        let timeStamp = Date().timeIntervalSince1970
        let values = ["text":inputTextField.text!,"toId":toId,"fromId":fromId,"timeStamp":timeStamp] as [String : AnyObject]
        childRef.updateChildValues(values) { (error, ref) in
            if error != nil{
                print(error?.localizedDescription ?? "")
                return
            }
            let userMessagesRef = FIRDatabase.database().reference().child("user-messages").child(fromId)
            let messageId = childRef.key
            userMessagesRef.updateChildValues([messageId:1])

            let recipientUserMessageRef = FIRDatabase.database().reference().child("user-messages").child(toId)
            recipientUserMessageRef.updateChildValues([messageId:1])
        }
    }

    func handleBackBtnPressed(){
        let messageController = MessagesVC()
        let navController = UINavigationController(rootViewController: messageController)
        self.present(navController, animated: true, completion: nil)
    }

    func observeMessages(){
        guard let uid = FIRAuth.auth()?.currentUser?.uid else{
            return
        }

        let ref = FIRDatabase.database().reference().child("user-messages").child(uid)
        ref.observe(.childAdded, with: { (snapshot) in

            let messageId = snapshot.key
            let messagesRef = FIRDatabase.database().reference().child("messages").child(messageId)
            messagesRef.observeSingleEvent(of: .value, with: { (snapshot) in

                guard let dictionary = snapshot.value as? [String:AnyObject] else{
                    return
                }

                let message = Message()
                message.setValuesForKeys(dictionary)
                self.messages.append(message)

                DispatchQueue.main.async {
                    self.collectionView?.reloadData()
                }
            })
        })
    }

}

这是 ChatMessageCell

import UIKit

class ChatMessageCell: UICollectionViewCell {
    let textView: UITextView = {
        let tv = UITextView()
        tv.text = "my text"
        tv.font = UIFont.systemFont(ofSize: 16)
        return tv
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)

        backgroundColor = UIColor.red
    }
}

Answer 1

从 Firebase 数据库获取数据后，尝试检查您的消息数组是否不为空。在 observeMessages func 中放置断点。如果您的数组不为空并且您成功从 firebase 数据库获取数据，那么您在设置 collectionView 时遇到问题..