Question

我正在尝试运行此代码，但是当仅运行前n个列表框循环时，其他代码仍为空。我想同时为表单中的每个列表框运行子例程代码（无限循环）

这是主要表格：

Public Class Form1
  Private listSettings As New List(Of ListBox)
  Private nameSettings As New List(Of Label)
  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    'Variabili Grafiche
    Dim lSettings As ListBox
    Dim i As Integer
    i = 0
    Dim n As Integer
    Dim width As Integer
    Dim height As Integer
    'Variabili Lettura File
    Dim path As New IO.DirectoryInfo("C:\BatchDomoLake\config\")
    Dim diar1 As IO.FileInfo() = path.GetFiles()
    Dim dra As IO.FileInfo
    'Lettura File e Grafica
    For Each dra In diar1
        n = n + 1
    Next
    Dim T(n) As Thread
    width = (Me.Size.Width() / n)
    height = (Me.Size.Height() / 2)
    For Each dra In diar1
        lSettings = New ListBox
        With lSettings
            .Location = New Point(10 + (width * i), 40)
            .Name = "lst" & dra.Name.Replace(".conf", "")
            .Size = New Size(width - 35, height - 40)
            .Visible = True
        End With
        Me.listSettings.Add(lSettings)
        Me.Controls.Add(lSettings)
        Dim reader As StreamReader = My.Computer.FileSystem.OpenTextFileReader(dra.FullName)
        Dim a As String
        Do
            a = reader.ReadLine
            If a IsNot Nothing Then
                lSettings.Items.Add(a)
            End If
        Loop Until a Is Nothing
        'Thread
        T(i) = New Threading.Thread(AddressOf snmpThread)
        T(i).Start(lSettings)
        i = i + 1
    Next
End Sub

这是我想为每个创建的列表框使用的子程序：

Private Delegate Sub snmpThreadDelegate(ByVal list As ListBox)
Private Sub snmpThread(ByVal list As ListBox)
    If list.InvokeRequired Then
        list.Invoke(New snmpThreadDelegate(AddressOf snmpThread), New Object() {list})
    Else
        Dim count As Integer
        Dim i As Integer
        count = list.Items.Count - 1
        Do
            For i = 0 To count Step 1
                list.SetSelected(i, True)
                Thread.Sleep(100)
            Next
        Loop
    End If
End Sub

Answer 1

您无法从后台线程访问/更新UI元素。只有主UI线程才能对UI对象执行操作。这适用于WinForms和WPF。

对于WinForms，您可以使用BeginInvoke方法并传入将在UI线程中调用的委托。对于WPF，您可以使用Dispatcher对象。

无法启动多个线程

1 个答案: