优化 UICollectionView 插入和更新

如何解决优化 UICollectionView 插入和更新

我有一个使用 firebase 的聊天应用程序，每次用户接收或发送消息时，我都会插入一个单元格并更新上一个单元格。但是，它非常缓慢且滞后。如您所见 here，执行批量更新需要很长时间。我发了 10 条短信，耗时 4.16 秒。

我花了很长时间试图弄清楚为什么需要这么长时间，但似乎无法弄清楚。

我有一个 firebase 监听器，每次在聊天中添加帖子时，我都会这样做：

 self.collectionView.performBatchUpdates {
            self.collectionView.insertSections(IndexSet(integer: self.posts.count - 1))
            self.collectionView.reloadSections(IndexSet(integer: self.posts.count - 2))
            
        } completion: { (bool) in
            self.collectionView.scrollToItem(at: IndexPath(row: 0,section: self.posts.count - 1),at: .bottom,animated: false)
        }

（我更新上一个单元格以查看最后一个帖子是否来自同一用户，以便我可以将帖子粘贴在一起）

数据源：

//MARK: - Datasource
extension ChatController {
    override func collectionView(_ collectionView: UICollectionView,numberOfItemsInSection section: Int) -> Int {
        return 1
    }
    
    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return isFiltering ? filteredPosts.count : posts.count
    }
    
    func collectionView(_ collectionView: UICollectionView,layout collectionViewLayout: UICollectionViewLayout,referenceSizeForHeaderInSection section: Int) -> CGSize {
        if section == 0 {return CGSize(width: UIScreen.main.bounds.width,height: 50)}
        
        if isFiltering {
            if filteredPosts[section].createdAt - filteredPosts[section - 1].createdAt > 3600000 {
                return CGSize(width: UIScreen.main.bounds.width,height: 15)
            }
            
            if filteredPosts[section - 1].isLastPostInARowFromUser {
                return CGSize(width: UIScreen.main.bounds.width,height: -16)
            } else {
                return CGSize(width: UIScreen.main.bounds.width,height: -31)
            }
        } else {
            if posts[section].createdAt - posts[section - 1].createdAt > 3600000 {
                return CGSize(width: UIScreen.main.bounds.width,height: 15)
            }
            
            if posts[section - 1].isLastPostInARowFromUser {
                return CGSize(width: UIScreen.main.bounds.width,height: -31)
            }
        }
    }
    
    override func collectionView(_ collectionView: UICollectionView,viewForSupplementaryElementOfKind kind: String,at indexPath: IndexPath) -> UICollectionReusableView {
        if kind == UICollectionView.elementKindSectionHeader {
            let sectionHeader = collectionView.dequeueReusableSupplementaryView(ofKind: kind,withReuseIdentifier: headerReuseIdentifier,for: indexPath) as! TimeStampCollectionViewHeader
            
            let createdAt = isFiltering ? filteredPosts[indexPath.section].createdAt : posts[indexPath.section].createdAt
            let date = Date(timeIntervalSince1970: TimeInterval(createdAt/1000))
            
            let startOfToday = Calendar.current.startOfDay(for: Date()).timeIntervalSince1970 * 1000
            let startOfYesterday = Calendar.current.startOfDay(for: Date()).timeIntervalSince1970 * 1000 - (3600000 * 24)
            let startOfDayOneWeekAgo = Calendar.current.startOfDay(for: Date()).timeIntervalSince1970 * 1000 - (3600000 * 24 * 7)
            let dateformat = DateFormatter()
            if createdAt > Int(startOfToday) {
                dateformat.dateFormat = "h:mm a"
                sectionHeader.timeStampLabel.text = "Today \(dateformat.string(from: date))"
            } else if createdAt > Int(startOfYesterday) {
                dateformat.dateFormat = "h:mm a"
                sectionHeader.timeStampLabel.text = "Yesterday \(dateformat.string(from: date))"
            } else if createdAt > Int(startOfDayOneWeekAgo) {
                dateformat.dateFormat = "EEEE h:mm a"
                sectionHeader.timeStampLabel.text = " \(dateformat.string(from: date))"
            } else {
                dateformat.dateFormat = "E,MMM,dd h:mm a"
                sectionHeader.timeStampLabel.text = dateformat.string(from: date)
            }
            return sectionHeader
        } else {
            return UICollectionReusableView()
        }
    }
    func collectionView(_ collectionView: UICollectionView,minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
    
    func collectionView(_ collectionView: UICollectionView,minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
    
    override func collectionView(_ collectionView: UICollectionView,cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier,for: indexPath) as! PostCell
  
        if isFiltering {
            cell.post = filteredPosts[indexPath.section]
        } else {
            cell.post = posts[indexPath.section]
        }
        
        cell.chatController = self
        cell.delegate = self
        return cell
    }
}

//MARK: - UICollectionViewDelegateFlowLayoutz
extension ChatController: UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView,insetForSectionAt section: Int) -> UIEdgeInsets {
        return .init(top: 16,left: 0,bottom: 16,right: 0)
    }
    
    func collectionView(_ collectionView: UICollectionView,sizeForItemAt indexPath: IndexPath) -> CGSize {
        let frame = CGRect(x: 0,y: 0,width: view.frame.width,height: 50)
       let estimatedSizeCell = PostCell(frame: frame)
        if isFiltering {
            estimatedSizeCell.post = filteredPosts[indexPath.section]
        } else {
            estimatedSizeCell.post = posts[indexPath.section]
        }
        estimatedSizeCell.layoutIfNeeded()

        let targetSize = CGSize(width: view.frame.width,height: 1000)
        let estimateSize = estimatedSizeCell.systemLayoutSizeFitting(targetSize)
        
        return .init(width: view.frame.width,height: estimateSize.height)
    }
}

这是我的 PostCell 类的链接。它又长又乱，肯定有问题。 https://github.com/SebastianDanson/PostCell/blob/main/PostCell.swift

我对编码比较陌生，任何帮助将不胜感激！