無法從線程中的類函數更新控件

Question

從調用類中的函數的線程更新文本框不起作用。我試圖讓這個在DLL中工作（但我沒有嘗試）。 DLL正在接受一個對象作爲參數，就像這樣;

Sub New(ByVal theObject As Object) 

這讓我送的對象，如這一個：

Public Class anObject 
    Public Sub doSomething() 
     Form1.TextBox1.Text = "test" 
    End Sub 
End Class 

所以我會打電話像這樣的DLL：

Dim theObject As New anObject 
Dim theDLL As New SO_TBFromDLL.UpdateTB(theObject) 

這之後，DLL將啓動線程，然後稱爲「doSomething」

Public Class UpdateTB 
    Dim theObjectSet As Object 

    Sub New(ByVal theObject As Object) 
     theObjectSet = theObject 

     'Try to update TB from Thread within current class 
     Dim ctThread As Threading.Thread = New Threading.Thread(AddressOf bghandler) 
     ctThread.Start() 
    End Sub 

    'Try to update TB from Thread within current class 
    Sub bghandler() 
     theObjectSet.doSomething() 
    End Sub 
End Class 

但這不起作用。我也嘗試使用委託（代碼如下）。

除了這兩個之外，我一直在嘗試其他兩種變體;

從不在Class/DLL中的線程嘗試3。這工作得很好。

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click 
    Dim ctThread As Threading.Thread = New Threading.Thread(AddressOf receiverFunction) 
    ctThread.Start() 
End Sub 

隨着receiverFunction之中：

'Receiver for Thread that's not in DLL (Button 3) 
Private Sub receiverFunction() 
    generaldelegatesN("tb1", "test") 
End Sub 

嘗試從4線程，這不是在DLL，但使用類內的功能。這也行不通。

Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click 
    Dim theObject As New anObjectWithDelegate 
    Dim ctThread As Threading.Thread = New Threading.Thread(AddressOf theObject.doSomething) 
    ctThread.Start() 
End Sub 

隨着anObjectWithDelegate之中：

'Unfortunately, with a delegate it still doesn't work (Button2 & Button4) 
Public Class anObjectWithDelegate 
    Public Sub doSomething() 
     Form1.generaldelegatesN("tb1", "test") 
    End Sub 
End Class 

爲什麼嘗試3個工作，但嘗試4不？這是doSomething()功能實際上與receiverFunction隨着加入Form1.

代表團代碼的異常：（如果它的事項）

'The Delegate functions 
Delegate Sub generaldelegates(ByVal param1 As String, ByVal param2 As String) 
Public generaldelegatesM As generaldelegates 
Public Sub generaldelegatesN(ByVal param1 As String, ByVal param2 As String) 
    'Updates control on main thread: 
    If Me.InvokeRequired Then 
     generaldelegatesM = New generaldelegates(AddressOf generaldelegatesN) 
     Me.BeginInvoke(generaldelegatesM, New Object() {param1, param2}) 
    Else 
     Select Case param1 
      Case "tb1" 
       TextBox1.Text = param2 
     End Select 
    End If 
End Sub 

Answer 1

你試圖硬編碼到外部對象的引用在一個單獨的類中，不知道什麼對象在其他地方被實例化。你的類對象需要將文本框引用傳遞給它：

Public Class Form1 

    Private myObject = New anObject 

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 
     myObject.doSomething(TextBox1, "test") 
    End Sub 

End Class 

Public Class anObject 
    Public Sub doSomething(ByRef obj As Object, ByVal message as String) 
     Dim objType = obj.GetType() 

     If objType Is GetType(TextBox) Then obj.Text = message 

    End Sub 
End Class