2

我正在开发一个从给定 URL 下载视频的应用程序。问题是我没有收到整个文件内容，然后无法播放文件。例如，尝试下载大小约为 2.23 MB 的视频，我只能得到 ~2.11 MB。当我在浏览器中使用 URL 时，它会显示一个对话框来保存视频并且文件已成功下载。

我尝试过使用WebClient类并且它可以工作，但我想分块下载文件以便能够报告状态（完成百分比）。这是我使用的代码：

private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
    int bufferSize = 1024 * 300;
    string filePath = saveFileDialog.FileName;
    if (File.Exists(filePath))
        File.Delete(filePath);
    int totalBytes = 0;
    HttpWebRequest webRequest = (HttpWebRequest)HttpWebRequest.Create(DownloadUrl);
    long contentLength = webRequest.GetResponse().ContentLength;
    using (Stream webStream = webRequest.GetResponse().GetResponseStream())
    using (StreamReader reader = new StreamReader(webStream))
    using (BinaryWriter fileWriter = new BinaryWriter(File.Create(filePath)))
    {
        do
        {
            char[] buffer = new char[bufferSize];
            bytesRead = reader.ReadBlock(buffer, 0, bufferSize); // also tried with Read(buffer, 0, bufferSize);
            totalBytes += bytesRead;
            Console.WriteLine("Bytes read: " + bytesRead + " Total Bytes: " + totalBytes + " Content length: " + contentLength);
            if (bytesRead > 0)
                fileWriter.Write(buffer, 0, bytesRead);
        } while (!reader.EndOfStream);
    }
}

我也尝试阅读 until bytesRead = 0，但结果相同。有什么我想念的吗？

4

2 回答 2

2

我建议您改用DownloadFileAsync。这为您提供了两个事件，使您可以更轻松地跟踪下载进度。

下载ProgressChangedEventHandler

下载文件完成

一个非常简单的实现看起来像这样。

WebClient client = new WebClient();

client.DownloadProgressChanged += 
        new DownloadProgressChangedEventHandler(DownloadProgressCallback);

client.DownloadFileAsync(DownloadUrl, filePath);

然后有一个更新进度条的功能。

private void DownloadProgressCallback(object sender, 
                                      DownloadProgressChangedEventArgs e)
{
     myProgressBar.Value = e.ProgressPercentage;
}

您还可以访问 和 等e.BytesReceived数据e.TotalBytesToReceive。

编辑：

我必须做的主要更改是将缓冲区从 更改char[]为byte[]，然后使用 Stream 而不是 StreamReader。

我们还通过检查是否有任何字节要写入我们的硬盘驱动器来检查文件的结尾。如果没有东西可写，我们就知道我们已经完成了。

private static void download()
{
    int bufferSize = 1024 * 300;
    string filePath = "Test.exe";

    if (File.Exists(filePath))
        File.Delete(filePath);
    int totalBytes = 0;
    HttpWebRequest webRequest =
        (HttpWebRequest)
        HttpWebRequest.Create(
            @"http://www.rarlab.com/rar/wrar420.exe");
    long contentLength = webRequest.GetResponse().ContentLength;
    Console.WriteLine(totalBytes);

    using (WebResponse webResponse = webRequest.GetResponse())
    using (Stream reader = webResponse.GetResponseStream())
    using (BinaryWriter fileWriter = new BinaryWriter(File.Create(filePath)))
    {
        int bytesRead = 0;
        byte[] buffer = new byte[bufferSize];
        do
        {
            bytesRead = reader.Read(buffer, 0, buffer.Length);
            totalBytes += bytesRead;
            fileWriter.Write(buffer, 0, bytesRead);
            Console.WriteLine("BytesRead: " + bytesRead + " -- TotalBytes: " + totalBytes);

        } while (bytesRead > 0);
    }
}
于 2013-04-17T18:08:27.157 回答
0

尝试

private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
    int bufferSize = 1024 * 300;
    string filePath = saveFileDialog.FileName;
    if (File.Exists(filePath))
        File.Delete(filePath);
    int totalBytes = 0;
    HttpWebRequest webRequest = (HttpWebRequest)HttpWebRequest.Create(DownloadUrl);
    long contentLength = webRequest.GetResponse().ContentLength;
    using (Stream webStream = webRequest.GetResponse().GetResponseStream())
    using (StreamReader reader = new StreamReader(webStream))
    using (BinaryWriter fileWriter = new BinaryWriter(File.Create(filePath)))
    {
        do
        {
            char[] buffer = new char[bufferSize];
            bytesRead = reader.ReadBlock(buffer, 0, bufferSize); // also tried with Read(buffer, 0, bufferSize);
            totalBytes += bytesRead;
            Console.WriteLine("Bytes read: " + bytesRead + " Total Bytes: " + totalBytes + " Content length: " + contentLength);
            if (bytesRead > 0)
                fileWriter.Write(buffer, 0, bytesRead);
        } while (!reader.EndOfStream);
        fileWriter.flush();
    }
}

嗨，那是我的错，我刚刚添加了fileWriter.flush(); 循环外

于 2013-04-17T18:16:04.700 回答