当它们不可见时，如何更新UITableView单元格中的进度条

如何解决当它们不可见时，如何更新UITableView单元格中的进度条

我遇到了一个问题：我有一个表视图，其中显示了云存储中用户文件的列表。通过单击单元格上的按钮，我已成功实现了将这些文件下载到设备的操作。单击它之后，进度条将出现在单元格上，其中显示了文件下载的进度。 现在，我需要通过单击全部下载按钮来实现下载所有文件的功能。但是我遇到了一个问题：我可以一起下载所有文件，但是无法在Table View之外的单元格中显示下载进度。我希望进度条即使在单元格不可见的情况下也能显示当前进度。当我向下滚动“表格视图”以便出现新单元格时，我会看到当前的加载进度。我怎样才能做到这一点？我尝试了很多选择，但是没有一个能正常工作。 在下面您可以看到我的代码：

class SourceFileListViewController: UIViewController {
    private var isDownloadAllButtonPressed: Bool = false
    private var cellsWithFilesIndexPathes: [IndexPath] = []
    private var currentProgress: [IndexPath : Double] = [:]
    ...
    @objc private func barButtonAction() {
    isDownloadAllButtonPressed = true
    for indexPath in cellsWithFilesIndexPathes {
        fileListSource?.downloadFile(path: fileListSource?.files[indexPath.row].path,pathComponent: fileListSource?.files[indexPath.row].name,completion: { progress in
                                        self.currentProgress[indexPath] = progress
                              
        },callback: {
            self.getTrackNames {
                self.tableView.reloadRows(at: [indexPath],with: .automatic)
            }
        })
    }
}

extension SourceFileListViewController: UITableViewDelegate,UITableViewDataSource {
    func tableView(_ tableView: UITableView,cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: SourceFileListCell.reuseId,for: indexPath) as! SourceFileListCell
        cell.progressBar.isHidden = true
        cell.delegate = self
        cell.progressBar.setProgress(to: 0)
        ....
        //Here I check the file this or folder
        let entry = fileListSource?.unreformedFileList[indexPath.row]
        switch entry {
        case _ as Files.FileMetadata:
            cell.downloadButton.isHidden = false
            cell.artworkImageView.image = UIImage(systemName: "music.note")

            //If this is a file,I put its indexPath in an array so that it can be downloaded by the Download All button
            cellsWithFilesIndexPathes.append(indexPath)
            if isDownloadAllButtonPressed {
            cell.progressBar.isHidden = false
            guard let progress = currentProgress[indexPath] else { return cell }
            cell.progressBar.setProgress(to: progress)
        }
        case _ as Files.FolderMetadata:
            cell.downloadButton.isHidden = true
            cell.artworkImageView.image = UIImage(systemName: "folder.fill")
        default:
            break
        }
        
        //Here I check if there is such a file in the user library
        guard let fileName = fileListSource?.files[indexPath.row].name else { return cell }
        if trackNames.contains(fileName) {
            cell.downloadButton.setImage(UIImage(systemName: "checkmark.circle.fill"),for: .normal)
        } else {
            cell.downloadButton.setImage(UIImage(systemName: "icloud.and.arrow.down"),for: .normal)
        }
        
        return cell
        
    }
}

解决方法

您的数据源需要存储当前进度，以便您可以在cell.progressBar.setProgress中调用cellForRowAt:IndexPath:

您可以使用初始值0来显示所有显示的项数来初始化数组，并在downloadFile完成块中以新进度更新indexPath.row处的数组