vb.net 如何下载带有进度条的 .exe 文件 - VB 2012
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How to download .exe file with progress bar - VB 2012
提问by user2839828
I am trying to create an updater for my program which automatically download's the latest version of my program from the web. Now I want this process to be done using a progress bar (so when the download progress is at 50% the progress bar is half-way through). This is my code:
我正在尝试为我的程序创建一个更新程序，它会自动从网络下载我的程序的最新版本。现在我希望使用进度条来完成这个过程（所以当下载进度为 50% 时，进度条是中途）。这是我的代码：
Private Sub client_ProgressChanged(ByVal sender As Object, ByVal e As DownloadProgressChangedEventArgs)
Dim bytesIn As Double = Double.Parse(e.BytesReceived.ToString())
Dim totalBytes As Double = Double.Parse(e.TotalBytesToReceive.ToString())
Dim percentage As Double = bytesIn / totalBytes * 100
client.Value = Int32.Parse(Math.Truncate(percentage).ToString())
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim url As String = "MY DOWNLOAD LINK"
'Download
Dim client As WebClient = New WebClient
AddHandler client.DownloadProgressChanged, AddressOf client_ProgressChanged
AddHandler client.DownloadFileCompleted, AddressOf client_DownloadCompleted
client.DownloadFileAsync(New Uri(url), "C:\Users\User\Desktop\BACKUP\TESTING\New folder.exe")
End Sub
End Class
Now I know that the place where the file is saved has been inputed manually by me , but I will change that later. My problem currently is that the file is not being downloaded. However when I change the DownloadFileAsync method to DownloadFile , my program downloads the file. However with the DownloadFile method I will not be able to use the progress bar to track the download progress. Any help is much appreciated :-)
现在我知道保存文件的位置是我手动输入的，但我稍后会更改。我目前的问题是文件没有被下载。但是，当我将 DownloadFileAsync 方法更改为 DownloadFile 时，我的程序会下载文件。但是，使用 DownloadFile 方法，我将无法使用进度条来跟踪下载进度。任何帮助深表感谢 ：-）
采纳答案by igrimpe
Don't know what you mean, when you say that the file isn't downloaded? You get an Error/Exception? Nothing happens at all? Did you place breakpoints, debug.prints etc?
不知道你说的文件没有下载是什么意思？您收到错误/异常？什么都没有发生？您是否放置了断点、debug.prints 等？
With VS2012 and asyn/await you can put everything into one method an keep a "linear code-flow". Import System.Threading and System.Threading.Tasks
使用 VS2012 和 asyn/await，您可以将所有内容放入一个方法中，并保持“线性代码流”。导入 System.Threading 和 System.Threading.Tasks
Private Async Function DownloadWithProgress(ByVal url As String, ByVal p As ProgressBar) As Task(Of Integer)
Dim wc As Net.HttpWebRequest = DirectCast(Net.HttpWebRequest.Create(url), Net.HttpWebRequest)
Dim resp = Await (New TaskFactory(Of Net.WebResponse)).StartNew(AddressOf wc.GetResponse)
p.Value = 0
p.Maximum = CInt(resp.ContentLength)
Dim rqs = resp.GetResponseStream
Dim bufsize As Integer = 1 << 16
Dim buffer(bufsize) As Byte
Dim got As Integer = 0
Dim total As Integer = 0
Do
got = Await (New TaskFactory(Of Integer)).FromAsync(AddressOf rqs.BeginRead, AddressOf rqs.EndRead, buffer, 0, bufsize, Nothing)
total += got
Me.Label1.Text = "got: " & total.ToString
p.Increment(got)
Loop Until got = 0
Return total
End Function
In this sample, the data from the web is downloaded into an array, but you can of course also write it into a file, or do whatever you want with the data.
在这个示例中，来自 Web 的数据被下载到一个数组中，但您当然也可以将其写入一个文件，或者对数据进行任何您想做的事情。
Sample for usage:
使用示例：
Private running As Boolean = False
Private Async Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
If running Then
MessageBox.Show("Cant you see, I'm working?")
Exit Sub
Else
running = True
End If
Await DownloadWithProgress("http://download.thinkbroadband.com/5MB.zip", ProgressBar1)
running = False
End Sub
