Question

所以我用Xamarin在iOS中编写了一个下载程序，使用'WebClient'下载文件等。当用户添加要下载的新文件时，它将使用自定义单元格添加到UITableView中，并带有名称，大小和百分比之类的信息。但是我想知道随着下载进度的变化，如何更改文件特定单元格中的百分比？好吧，这是代码：

首先，我为下载创建了一个名为“ download”的类，以获取文件名，文件大小和百分比：

using System;

namespace iDownloader
{
    internal class download
    {
        public string FileName
        {
            get;
            set;
        }

        public Uri uri
        {
            get;
            set;
        }

        public string FileSize
        {
            get;
            set;
        }

        public double percentage
        {
            get;
            set;
        }
    }
}

然后在这里，我得到了tableview的源代码：

using System;
using System.Collections.Generic;
using Foundation;
using UIKit;

namespace iDownloader
{
    internal class downloadsTVS : UITableViewSource
    {
        private List<download> downloadFile;

        public downloadsTVS(List<download> downloadFile)
        {
            this.downloadFile = downloadFile;
        }

        public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
        {
            var cell = (DownloadCell) tableView.DequeueReusableCell("Cell", indexPath);

            var currentDownload = downloadFile[indexPath.Row];

            cell.updateCell(currentDownload);

            return cell;
        }

        public override nint RowsInSection(UITableView tableview, nint section)
        {
            return downloadFile.Count;
        }
    }
}

然后在这里，我有了tableviewcell的类：

using Foundation;
using System;
using UIKit;

namespace iDownloader
{
    public partial class DownloadCell : UITableViewCell
    {
        public DownloadCell(IntPtr handle) : base(handle)
        {
        }

        internal void updateCell(download currentDownload)
        {
            FileNameLabel.Text = currentDownload.FileName;
            FileSizeLabel.Text = currentDownload.FileSize.ToString();
            lblPercentage.Text = currentDownload.percentage.ToString();
        }

    }
}

这是视图控制器中的代码（我已经删除了不必要的部分）：在课程部分，我列出了下载列表（如果您记得，还提供了文件详细信息）以填充我的tablview。而且，我有我的网络客户端。

List<download> downloadFile = new List<download>
        {

        };
        WebClient webClient = new WebClient();

然后是主要部分：

private async void DownloadAsync(Uri uri, string fileName)
        {
            downloadsint++;
            TabBarItem.BadgeValue = downloadsint.ToString();
            var fileNameandPath = Path.Combine(System.Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), fileName);
            //UITableView cell adding
            download download = new download();
            download.FileName = fileName;
            webClient = new WebClient();
            webClient.OpenRead(uri.ToString());
            Int64 totalbytes = System.Convert.ToInt64(webClient.ResponseHeaders["Content-Length"]) / 1000000;
            download.FileSize = totalbytes.ToString() + " MB";
            downloadFile.Add(download);
            tableview.Source = new downloadsTVS(downloadFile);
            tableview.RowHeight = UITableView.AutomaticDimension;
            tableview.EstimatedRowHeight = 70f;
            tableview.ReloadData();
            //UITableView cell adding
            webClient = new WebClient();
            await webClient.DownloadFileTaskAsync(uri, fileName);
            btnPause.Enabled = true;
            webClient.DownloadProgressChanged += WebClient_DownloadProgressChanged(fileName);
            webClient.DownloadFileCompleted += DownloadFileCompleted(fileName);
        }
public DownloadProgressChangedEventHandler WebClient_DownloadProgressChanged(string filename)
        {
            Action<object, DownloadProgressChangedEventArgs> action = (sender, e) =>
            {
                double received = e.BytesReceived;
                double total = e.TotalBytesToReceive;
                double percentage = received / total * 100;
                download download = downloadFile.Find((download obj) => obj.FileName == filename);
                downloadFile.Remove(download);
                download.percentage = percentage;
                downloadFile.Add(download);
                tableview.Source = new downloadsTVS(downloadFile);
            };
            return new DownloadProgressChangedEventHandler(action);
        }

        public AsyncCompletedEventHandler DownloadFileCompleted(string filename)
        {
            Action<object, AsyncCompletedEventArgs> action = (sender, e) =>
            {
                if (e.Error.Message == "Request Aborted")
                {
                    var alert = UIAlertController.Create("Download(s) has been cancelled.", null, UIAlertControllerStyle.Alert);
                    alert.AddAction(UIAlertAction.Create("Okay", UIAlertActionStyle.Cancel, null));
                    alert.View.Subviews[0].Subviews[0].Subviews[0].BackgroundColor = UIColor.DarkGray;
                    alert.View.TintColor = UIColor.White;
                    PresentViewController(alert, true, null);
                }

                if (e.Error != null)
                {
                    var alert = UIAlertController.Create("The operation has faced a problem.", null, UIAlertControllerStyle.Alert);
                    alert.AddAction(UIAlertAction.Create("Okay", UIAlertActionStyle.Cancel, null));
                    alert.View.Subviews[0].Subviews[0].Subviews[0].BackgroundColor = UIColor.DarkGray;
                    alert.View.TintColor = UIColor.White;
                    PresentViewController(alert, true, null);
                }

                if (e.Cancelled)
                {
                    var alert = UIAlertController.Create("The operation has been cancelled", null, UIAlertControllerStyle.Alert);
                    alert.AddAction(UIAlertAction.Create("Okay", UIAlertActionStyle.Cancel, null));
                    alert.View.Subviews[0].Subviews[0].Subviews[0].BackgroundColor = UIColor.DarkGray;
                    alert.View.TintColor = UIColor.White;
                    PresentViewController(alert, true, null);
                }

                else
                {
                    downloadsint--;
                    TabBarItem.BadgeValue = downloadsint.ToString();
                    //Show finished downloades notification
                    var alert = UIAlertController.Create("File has been downloaded:", "'" + filename + "' has been downloaded!", UIAlertControllerStyle.Alert);
                    alert.AddAction(UIAlertAction.Create("Okay", UIAlertActionStyle.Cancel, null));
                    PresentViewController(alert, true, null);
                    //Show finished downloades notification

                    if (downloadsint == 0)
                    {
                        TabBarItem.BadgeValue = null;
                        btnPause.Enabled = false;
                    }
                }
                download file = new download()
                {
                    FileName = filename
                };

            };
            return new AsyncCompletedEventHandler(action);
        }

所以现在这里出现了问题：我尝试使用“ Lambada”将文件名传递给“ DownloadProgressChanged”，但找不到文件并将其百分比更改并添加到“ downloadFile”中无效（*请注意，我已经下载了多个文件因此，我希望它们的百分比也能得到更新。）最后，在“ DownloadFileCompeleted”中，我还尝试使用“ Lambada”做同样的事情，并找到文件名等于下载文件的位置，并在下载完成后删除该单元格。完成。

因此，总而言之，我需要解决以下问题： 1-更改下载文件的百分比（有多个文件正在下载。） 2-下载文件后删除单元格。

谢谢大家！！！感谢您的帮助。

Answer 1

刷新UI（更新DownloadProgress和Delete单元格）的代码应该在主线程中，因此最好在主线程上调用它。 InvokeOnMainThread(() => { //update tableviewcell });

更新UITableViewCell的对象值-Xamarin.iOS

1 个答案: