UICollectionViewCells不填充

Question

我正在嘗試創建消息應用程序。當我嘗試顯示包含UICollectionView中的消息的單元格時，它們沒有顯示出來。 我首先想給單元格一個紅色的背景並顯示我的模型中的項目。我有消息數組。誰能告訴我爲什麼他們不填充？

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() 
       } 
      }) 
     }) 
    } 

} 

這裏是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

嘗試檢查，如果你的消息從陣火力地堡數據庫中獲取後不爲空..把破發點中的observeMessages func。如果你陣列不是空的，你成功地從Firebase數據庫中獲取數據，那麼你有設置collectionView的問題..