vb.net关于线程中修改界面文本框没有反应

Question

#1 问题概述

Imports System.Threading
Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim objTest1 As New Form1
        Dim thread1 As New Thread(New ThreadStart(AddressOf objTest1.count))
        thread1.Name = "线程1"
        Dim objTest2 As New Form1
        Dim thread2 As New Thread(New ThreadStart(AddressOf objTest2.count))
        thread2.Name = "线程2"
        Dim objTest3 As New Form1
        Dim thread3 As New Thread(New ThreadStart(AddressOf objTest3.count))
        thread3.Name = "线程3"
        thread1.Start()
        thread2.Start()
        thread3.Start()
    End Sub
    Public Sub count()
        Dim cnt As Integer = 1
        While cnt < 6

            cnt += 1
            TextBox1.Text += Thread.CurrentThread.Name + "数到" + Str(cnt) + vbCrLf
            Thread.Sleep(100)
        End While
    End Sub
End Class

为何运行无反应

Answer 1

这段代码不能实现主要有两个问题，这个跨线程了所以要使用invoke从主线程中修改ui，同时改完后如下会发现

Imports System.Threading
Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim objTest1 As New Form1
        Dim thread1 As New Thread(New ThreadStart(AddressOf objTest1.count1))
        thread1.Name = "线程1"
        Dim objTest2 As New Form1
        Dim thread2 As New Thread(New ThreadStart(AddressOf objTest2.count1))
        thread2.Name = "线程2"
        Dim objTest3 As New Form1
        Dim thread3 As New Thread(New ThreadStart(AddressOf objTest3.count1))
        thread3.Name = "线程3"
        thread1.Start()
        thread2.Start()
        thread3.Start()
    End Sub
    Public Sub count1()
        Dim cnt As Integer
        cnt = 0
        While cnt < 6
            cnt += 1

            Me.Invoke(New showDelegate(AddressOf show1), cnt)
            Application.DoEvents()
        End While

    End Sub

    Public Delegate Sub showDelegate(ByVal cnt As Integer)
    Public Sub show1(ByVal cnt As Integer)
        TextBox1.Text += Thread.CurrentThread.Name + "数到" + Str(cnt) + vbCrLf
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub
End Class

这时会发现

这主要是由于objTest继承了form1的text box1的属性但是还并没有创建text box1
这时将objTest1删除从form1调用即可成功
代码如下

Imports System.Threading
Public Class Form1

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

        Dim thread1 As New Thread(New ThreadStart(AddressOf count1))
        thread1.Name = "线程1"
        Dim objTest2 As New Form1
        Dim thread2 As New Thread(New ThreadStart(AddressOf count1))
        thread2.Name = "线程2"
        Dim objTest3 As New Form1
        Dim thread3 As New Thread(New ThreadStart(AddressOf count1))
        thread3.Name = "线程3"
        thread1.Start()
        thread2.Start()
        thread3.Start()
    End Sub
    Public Sub count1()
        Dim cnt As Integer
        cnt = 0
        While cnt < 6
            cnt += 1

            Me.Invoke(New showDelegate(AddressOf show1), cnt)
            Application.DoEvents()
        End While

    End Sub

    Public Delegate Sub showDelegate(ByVal cnt As Integer)
    Public Sub show1(ByVal cnt As Integer)
        TextBox1.Text += Thread.CurrentThread.Name + "数到" + Str(cnt) + vbCrLf
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub
End Class

但是线程名字还是无法显示,后来摸索了下在invoke中线程是主线程的名字，所以可以在while循环中添加一个变量来代表threadName
代码如下

Imports System.Threading
Public Class Form1

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

        Dim thread1 As New Thread(New ThreadStart(AddressOf count1))
        thread1.Name = "线程1"
        Dim objTest2 As New Form1
        Dim thread2 As New Thread(New ThreadStart(AddressOf count1))
        thread2.Name = "线程2"
        Dim objTest3 As New Form1
        Dim thread3 As New Thread(New ThreadStart(AddressOf count1))
        thread3.Name = "线程3"
        thread1.Start()
        thread2.Start()
        thread3.Start()
    End Sub
    Public Sub count1()
        Dim cnt As Integer
        Dim threadName As String
        cnt = 0
        While cnt < 6
            cnt += 1
            threadName = Thread.CurrentThread.Name
            Me.Invoke(New showDelegate(AddressOf show1), threadName, cnt)
            Application.DoEvents()
        End While

    End Sub

    Public Delegate Sub showDelegate(ByVal threadName As String, ByVal cnt As Integer)
    Public Sub show1(ByVal threadName As String, ByVal cnt As Integer)
        TextBox1.Text += threadName + "数到" + Str(cnt) + vbCrLf
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub
End Class

结果

这是可已完成目的，也可完全掌握过程中出现的错误