交叉线无法正常工作 [英] Crossthreading not working

问题描述

这是我的代码：

Hi,

This is my code:

Private Delegate Sub UpdateListInvoker(ByVal WhatToWrite As String)
  Private Sub UpdateListBox(ByVal WhatToWrite As String)
      If Form1.ListBox2.InvokeRequired Then
          Form1.ListBox2.Invoke(New UpdateListInvoker(AddressOf UpdateListBox), WhatToWrite)
      Else
          Form1.ListBox2.Items.Add(WhatToWrite)
      End If
  End Sub

使用：UpdateListBox（你好）



它只是没有做任何事情。为什么？



-Rixterz

To use: UpdateListBox("Hello")

It just isn't doing anything. Why?

-Rixterz

推荐答案

好的，所以看起来你试图调用一个委托form1来自你项目中的另一种形式，当我测试那个（而不是从form1开始的线程）时，我遇到了同样的问题。



你需要对后台线程（或来自form2）的form1进行引用。这是我在快速测试应用程序中工作的方式（在form2上调用form1上的委托）：



试试这个：

Ok, so it looks like your trying to invoke a delegate on form1 from a different form in your project, and when I tested THAT (as opposed to a thread started from form1), I had the same problem you did.

You need to make a refrence to form1 available to the background thread (or from form2). This is how I got it to work (calling a delegate on form1 from form2) in my quick test app:

Try this:

' Form1 code:

' Define your delegate:
Public Delegate Sub UpdateListInvoker(ByVal whatToWrite As String)

' Create your reference object:
Public UpdateListBox As UpdateListInvoker

' Your callback:
Public Sub ListBoxUpdater(ByVal WhatToWrite As String)
   If Me.InvokeRequired Then
        Me.Invoke(UpdateListBox, WhatToWrite)
   Else
        Me.ListBox2.Items.Add(WhatToWrite)
    End If
End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    UpdateListBox = AddressOf ListBoxUpdater
    Form2.f1 = Me
    Form2.Show()
End Sub


' Form2 code:
Public f1 As Form1

Private Sub bgThread()
    ' Elsewhere in your code...
    f1.UpdateListBox("what you're adding to the listbox")
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim t As New Threading.Thread(AddressOf bgThread)
    t.Start()
End Sub

你看到在form2中，当我点击一个按钮时，我正在启动后台线程，然后从后台线程我正在使用它的参考更新form1上的列表框（f1）。



这应该适合你。



-Pete

You see that in form2, I'm starting a background thread when I click a button, and then from the background thread I'm updating a listbox on form1 by using it's reference (f1).

This should do the trick for you.

-Pete

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