Question

Form1.vb的

Imports System.Threading

Public Class Form1

Dim demoThread As Thread

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    Dim Start As New Class1
    Me.demoThread = New Thread( _
            New ThreadStart(AddressOf Start.ThreadProcSafe))

    Me.demoThread.Start()

End Sub
Delegate Sub SetTextCallback([text] As String)
Public Sub SetText(ByVal [text] As String)

    ' InvokeRequired required compares the thread ID of the 
    ' calling thread to the thread ID of the creating thread. 
    ' If these threads are different, it returns true. 
    If Me.textBox1.InvokeRequired Then
        Dim d As New SetTextCallback(AddressOf SetText)
        Me.Invoke(d, New Object() {[text]})
    Else
        Me.textBox1.Text = [text]
    End If
End Sub
End Class

Class1.vb

Public Class Class1

Public Sub ThreadProcSafe()
    Form1.SetText("This text was set safely.")
End Sub
End Class

有人可以告诉我为什么这不会更新文本框？

当ThreadProcSafe在Form1内部（并且仍然由一个线程启动）被调用时，它可以工作，但是当它被移到另一个类之外时，没有警告或错误，但是没有更新。< / p>

Answer 1

原因是您指的是第二个代码段中的默认实例。默认实例是特定于线程的，因此第二个代码段将创建Form1类型的新实例，而不是使用现有实例。您的Class1需要引用Form1的原始实例。

如果这不实用，那么解决方案是不在表单中进行委派，而是使用SynchronizationContext类在访问表单的类中执行。

从线程设置标签

1 个答案: