[英]I cant update progress bar while downloading a file
我正在尝试制作一个简单的下载管理器,并且它可以工作。问题是,如果我添加一个进度条来通知用户,我将收到此异常
此流不支持搜索操作
while ((readed = ReadFrom.Read(read, 0, read.Length)) > 0)
{
strLocal.Write(read, 0, readed);
**UpdateProgress(ReadFrom.Length, strLocal.Length);// throws exception**
}
这是所有代码
private void button1_Click(object sender, EventArgs e)
{
req = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
res = (HttpWebResponse)req.GetResponse();
Int64 contentlength = res.ContentLength;
WebClient wc = new WebClient();
Stream ReadFrom= wc.OpenRead(new Uri(url));
strLocal = new FileStream(@"E:\\xxx.tar.gz", FileMode.Create, FileAccess.Write, FileShare.None);
byte[]read=new byte[1024];
int readed = 0;
while ((readed = ReadFrom.Read(read, 0, read.Length)) > 0)
{
strLocal.Write(read, 0, readed);
UpdateProgress(ReadFrom.Length, strLocal.Length);
}
strLocal.Close();
ReadFrom.Close();
}
private void UpdateProgress(long Filesize, long readedBytes)
{
// progressBar1.Maximum = 100;
int downloaded =Convert.ToInt32((readedBytes * 100) / Filesize);
progressBar1.Value = downloaded;
}
怎么了
@编辑
HttpWebRequest req;
HttpWebResponse res;
Stream strLocal;
Stream ResponseStr;
byte[] bytes = null;
Thread thr;
delegate void UpdateCallBack(long l1, long l2);
public Form1()
{
InitializeComponent();
}
string url="https://www.unrealircd.org/downloads/Unreal3.2.10.3.tar.gz";
////string url2 = "http://www.microsoft.com/en-us/download/confirmation.aspx?id=34794&6B49FDFB-8E5B-4B07-BC31-15695C5A2143=1";
string filename = @"C:\\Unreal3.2.10.3.tar.gz";
private void Form1_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
thr = new Thread(download);
thr.Start();
}
private void download()
{
req = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
res = (HttpWebResponse)req.GetResponse();
Int64 contentlength = res.ContentLength;
ResponseStr = res.GetResponseStream();
strLocal = new FileStream(@"E:\\xxx.tar.gz", FileMode.Create, FileAccess.Write, FileShare.None);
byte[]read=new byte[1024];
int readed = 0;
while ((readed = ResponseStr.Read(read, 0, read.Length)) > 0)
{
strLocal.Write(read, 0, readed);
this.Invoke(new UpdateCallBack(this.UpdateProgress), new object[] {ResponseStr.Length,strLocal.Length });
}
strLocal.Close();
ResponseStr.Close();
}
private void UpdateProgress(long Filesize, long readedBytes)
{
int updated =Convert.ToInt32((readedBytes * 100) / Filesize);
progressBar1.Value = updated;
}
@ EDIT2
private void download()
{
req = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
res = (HttpWebResponse)req.GetResponse();
Int64 contentlength = res.ContentLength;
ResponseStr = res.GetResponseStream();
strLocal = new FileStream(@"E:\\xxx.tar.gz", FileMode.Create, FileAccess.Write, FileShare.None);
byte[]read=new byte[1024];
int readed = 0;
while ((readed = ResponseStr.Read(read, 0, read.Length)) > 0)
{
strLocal.Write(read, 0, readed);
backgroundWorker1.RunWorkerAsync();
// this.Invoke(new UpdateCallBack(this.UpdateProgress), new object[] {ResponseStr.Length,strLocal.Length });
}
strLocal.Close();
ResponseStr.Close();
}
private void UpdateProgress(long Filesize, long readedBytes)
{
int updated =Convert.ToInt32((readedBytes * 100) / Filesize);
progressBar1.Value = updated;
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
UpdateProgress(ResponseStr.Length, strLocal.Length);
}
您的所有操作都在同一线程上进行。 在进行下载时,该应用程序将停止UI更新。 对于这种情况,我通常使用BackgroundWorker更新进度条。
根据您的编辑,以下是适合您的代码:
// At the class level, put this:
BackgroundWorker bw = new BackgroundWorker();
bw.WorkerReportsProgress = true; // This means we want to send updates from the background worker.
// The DoWork method handles your time consuming task, which in this case is your download method. So you can try this:
private void Download()
{
bw.RunWorkerAsync();
}
// This should be called as a result:
private void bw_DoWork(object sender, DoWorkEventArgs e)
{
// The worker who's progress will be updated.
BackgroundWorker worker = sender as BackgroundWorker;
req = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
res = (HttpWebResponse)req.GetResponse();
Int64 contentLength = res.ContentLength;
ResponseStr = res.GetResponseStream();
strLocal = new FileStream(@"E:\xxx.tar.gz", FileMode.Create, FileAccess.Write, FileShare.None);
byte[] read = new byte[1024];
int readed = 0;
while((readed = ResponseStr.Read(read, 0, read.Length)) > 0)
{
strLocal.Write(read, 0, readed);
// Update the worker (this uses the number you calculated)
worker.ReportProgress(Convert.ToInt32((ResponseStr.Length * 100) / strLocal.Length));
strLocal.Close();
ResponseStr.Close();
}
}
// This is called via worker.ReportProgress
private void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
您需要在您的课程中定义后台工作程序,并允许其接受进度更新。
然后,无论此方法需要后台工作人员在哪里,都需要调用RunWorkerAsync
。 您可以在下载方法中执行此操作,也可以替换调用下载的位置。
在do work类中,您可以执行通常的所有工作,但是在要更新进度的情况下,可以使用必要的值调用ReportProgress
。
如果您查看上面的链接,还有其他可以实现的方法-如果您担心取消后台工作程序或出现错误或其他任何情况。
编辑
如果您仍然收到错误,我只是意识到您可能正在尝试从Stream
对象提取长度。 如果错误仍然存在,请看这个问题 。
如上所述,它与线程有关。 因此,您需要将操作分开在多个线程上才能更新UI。 您还可以使用异步并等待以解决此问题。 以下是一篇不错的文章,该文章是关于执行一些操作和更新UI的。
http://www.i-programmer.info/programming/c/1514-async-await-and-the-ui-problem.html
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