问题
I am programming an application for downloading articles from an SQL Database on the internet. I have programmed the Website for managing the articles. Now I'm downloading the article List in gzip Format and then I decompress them to a xml-File. When I'm done I want to insert the articles to the mobile phone. This works great. Now I want to add an progress Bar to see the state of the insertion. I tried with Threading but this doesn't work. I'm posting some pieces of code from my application and also the progressUpdate methods.
private void btn_send_Click(object sender, EventArgs e)
{
label1.Text = "Download started";
string ArticlesURL = "URLTOSITE";
InvokeAsync(ArticlesURL);
}
private void InvokeAsync(string URL)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.AllowWriteStreamBuffering = true;
allDone.Reset();
request.BeginGetRequestStream(new AsyncCallback(ReadArticlesCallback), request);
allDone.WaitOne();
request.BeginGetResponse(new AsyncCallback(ResponseArticlesCallback), request);
}
private static void ReadArticlesCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
//End the operation.
Stream postSream = request.EndGetRequestStream(asynchronousResult);
string postData = "articles=test";
//Convert the string into a byte array.
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
//Write to the request stream.
postSream.Write(byteArray, 0, postData.Length);
postSream.Close();
allDone.Set();
}
private static void ResponseArticlesCallback(IAsyncResult asynchronousResult)
{
Form1 f = new Form1();
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
HttpWebResponse resp = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
Stream streamResponse = resp.GetResponseStream();
StreamReader streamRead = new StreamReader(streamResponse);
string responseString = streamRead.ReadToEnd();
nbrArticles = Convert.ToInt16(responseString);
// Close the stream object.
streamResponse.Close();
streamRead.Close();
// Release the HttpWebResponse.
resp.Close();
f.truncate_articles();
f.get_articles();
}
private void get_articles()
{
string url = "URLTOSITE";
int startPoint = 0;
DownloadZipFile((object)startPoint, url);
DecompressFile();
getXmlAndInsertInDB();
}
private void getXmlAndInsertInDB()
{
int total = nbrArticles;
int count = total / 100; //How much articles are 1 percent
int i = 0;
String barcode = "";
String name = "";
bool state = false;
XmlTextReader reader = new XmlTextReader("Program Files\\SmartDeviceProject1\\articles.xml");
while (reader.Read())
{
switch (reader.NodeType)
{
case XmlNodeType.Element: //The node is an element
while (reader.MoveToNextAttribute()) //Get the attributes like barcode, lastname, firstname, pincode
switch (reader.Name)
{
case "barcode":
barcode = reader.Value.ToString();
state = false;
break;
case "name":
name = reader.Value.ToString();
state = true;
break;
}
break;
}
if (state == true)
{
cmd.CommandText = "INSERT INTO articles(barcode, name) " +
"VALUES('" + barcode + "','" + name + "');";
cmd.ExecuteNonQuery();
state = false;
i++;
if (i == count)
{
Thread t = new Thread(new ThreadStart(this.incrementProgressBar));
t.Start();
//incrementProgressBar();
i = 0;
}
}
}
reader.Close();
}
private void updateProgressBarMethod(int progress)
{
if (progressBar1.InvokeRequired)
{
//It was called from a non UI thread so we create a delegate
//and have the UI Thread call this method again
UpdateProgressBar = new UpdateProgressBarDelegate(updateProgressBarMethod);
this.Invoke(UpdateProgressBar, progress);
}
else
{
//Called from the UI Thread OK to update
//update your progress bar here
progressBar1.Value += progress;
}
}
private void incrementProgressBar()
{
//Call the method to update progress Bar on UI thread
//we do not need a delegate here that will be taken care of
//in the method
updateProgressBarMethod(1);
Application.DoEvents();
}
I think the problem is that I am using Callbacks. I have read that the Callbacks are also starting Threads. So I think the problem is there but I can't solve it.
I've found another very good site for threading with mobile applications: Updating the User Interface from a Worker Thread
Now with the new code, the debugger stops always at the same piece of code without any notification or exception :( Here is my new code:
if (i == count)
{
this.info_percent = "Synchro " + step.ToString() + "%";
this.Invoke(new EventHandler(WorkerUpdate)); //The Debugger stops here!
i = 0;
step++;
Thread.Sleep(700);
}
public void WorkerUpdate(object sender, EventArgs e)
{
this.lbl_percent.Text = this.info_percent;
this.lbl_percent.Update();
this.progressBar1.Value = step;
this.progressBar1.Update();
}
The Debugger stops at: this.Invoke(new EventHandler(WorkerUpdate));
回答1:
I would suggest using the Background worker class. I had a similar problem and implemented the Background worker and it fixed my problem. Hopefully it will fix yours also
http://www.dotnetperls.com/backgroundworker
http://msdn.microsoft.com/en-us/library/cc221403(v=vs.95).aspx
I found another thread discussing this and thought it would help:
Is there a BackgroundWorker replacement for .NET Compact Framework 3.5?
回答2:
Your code will always hang at this point:
if (i == count)
{
this.info_percent = "Synchro " + step.ToString() + "%";
this.Invoke(new EventHandler(WorkerUpdate)); //The Debugger stops here!
i = 0;
step++;
Thread.Sleep(700);
}
Make these changes:
public delegate void MethodInvoker(); // this is not defined in CF
if (i == count)
{
this.info_percent = "Synchro " + step.ToString() + "%";
object sender = null; // make this whatever you want/need
EventArgs e = new EventArgs();
if (this.InvokeRequired) {
MethodInvoker mi = delegate { WorkerUpdate(sender, e); } };
this.BeginInvoke(mi);
} else {
WorkerUpdate(sender, e);
}
i = 0;
step++;
// Thread.Sleep(700); Why is this here?
}
This should prevent those obnoxious freezes.
来源：https://stackoverflow.com/questions/8309193/c-sharp-progressbar-threading-mobile-6