Question

我刚刚在vb.net中进行了ftp聊天，它从ftp服务器的文件更新消息所以我用这段代码添加一个间隔为1000的计时器

 Try
            Dim client As New Net.WebClient
            client.Credentials = New Net.NetworkCredential("fnet_1355****", "******")
            RichTextBox1.Text = client.DownloadString("ftp://185.**.***.**/htdocs/chat.txt")
        Catch ex As Exception
        End Try

所以..文件被下载并且它更新文本成功但是有一个问题..每次下载表格都有点滞后...我不喜欢那样：D我能做什么？

Answer 1

RichTextBox1.Text = client.DownloadString("ftp://185.**.***.**/htdocs/chat.txt")

而不是尝试异步方法。

client.DownloadStringAsync(new Uri("ftp://185.**.***.**/htdocs/chat.txt"))

然后处理下载字符串已完成的事件。

示例代码

client.DownloadStringAsync(new Uri("ftp://185.**.***.**/htdocs/chat.txt"));
client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted); 

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
     RichTextBox1.Text =e.Result;
}

您还可以通过处理进度更改事件来添加进度指示器。

Answer 2

最好的方法是使用Framework提供的ThreadPool在不同的线程上进行I / O绑定操作。

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    ThreadPool.QueueUserWorkItem(New WaitCallback(AddressOf DownloadFromFtp))
End Sub

Private Sub DownloadFromFtp()
    Try
        Dim client As New Net.WebClient
        client.Credentials = New Net.NetworkCredential("fnet_1355****", "******")
        Dim response As String = client.DownloadString("ftp://185.**.***.**/htdocs/chat.txt")

        Me.Invoke(New MethodInvoker(Function() RichTextBox1.Text = response))
    Catch ex As Exception
    End Try
End Sub

Answer 3

在我学习PHP之前，这个程序是我设计的。

这里试试这个：

Dim thrd As Threading.Thread
Dim tmr As New Timer
Dim tempstring As String
Private Sub thread_start()
    thrd = New Threading.Thread(Sub() check_for_changes())
    tmr.Interval = 50
    AddHandler tmr.Tick, AddressOf Tick
    tmr.Enabled = True
    tmr.Start()
    thrd.Start()
End Sub
Private Sub Tick(sender As Object, e As EventArgs)
    If Not thrd.IsAlive Then
        tmr.Stop() : tmr.Enabled = False
        RichTextBox1.Text = tempstring
    End If
End Sub
Private Sub check_for_changes()
    Try
        Dim client As New Net.WebClient
        client.Credentials = New Net.NetworkCredential("fnet_1355****", "******")
        tempstring = client.DownloadString("ftp://185.**.***.**/htdocs/chat.txt")
    Catch ex As Exception
    End Try
End Sub

希望它有所帮助。

如何从ftp下载没有形式滞后vb.net

3 个答案: