新的多线程不起作用

Question

我正在尝试创建一个线程，所以当我点击一个按钮时它会从一个类创建一个新的PictureBox，这就是我已经走了多远但屏幕上什么也没有出现。

Form1代码：

Public Class Form1

Private pgClass As New SecondUIClass

Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
    pgClass = New SecondUIClass
    pgClass.x += 100
    pgClass.thread()
End Sub
End Class

班级代码：

Imports System.Threading

Public Class SecondUIClass
Public Const count As Integer = 1000
Public emeny(count - 1) As PictureBox
Public counter As Integer = 0
Public x As Integer = 0
Private trd As Thread

Public Sub thread()
    trd = New Thread(AddressOf NewUIThread)
    trd.SetApartmentState(ApartmentState.STA)
    trd.IsBackground = False
    trd.Start()
End Sub

Private Sub NewUIThread()
    emeny(counter) = New PictureBox
    emeny(counter).BackColor = Color.Red
    emeny(counter).Visible = True
    emeny(counter).Location = New System.Drawing.Point(x, 100)
    emeny(counter).Size = New System.Drawing.Size(10, 50)
    Form1.Controls.Add(emeny(counter))
    For z = 0 To 13
        emeny(counter).Location = New Point(emeny(counter).Location.X + 10, emeny(counter).Location.Y)
        Application.DoEvents()
        Threading.Thread.Sleep(100)
    Next
    counter += 1
End Sub
End Class

我之前在这里贴了类似的东西，但它有所不同，图片盒子在屏幕上显示但是我试图让它们同时移动但是它们不会移动，它们只移动了一个一时间我之前问过的问题是Multi threading classes not working correctly

Answer 1

我对这个答案做了一些假设，所以它可能不适合你开箱即用，但我认为它会让你走在正确的轨道上而不使用任何Thread.Sleep电话，因为我个人并不是比如为我的应用程序建立故意减速但这确实是个人偏好。

所以对于我的例子，我只是使用了一堆textboxes，因为我没有任何便于摆弄的图片。但基本上为了让用户在移动过程中仍然可以与程序进行交互，我使用了一个由用户启动的后台工作线程，一旦启动它就会将textboxes向下移动到表单直到用户告诉它停止或它击中我组成的任意边界。因此理论上，开始将是您的应用程序中的空格键，我的停止将添加另一个控件到集合。对于你的东西，你需要在添加任何内容之前锁定集合，同时更新位置，但这取决于你自己的判断。

所以肉和土豆：

在表单设计器中我有三个按钮，btnGo，btnStop和btnReset。下面的代码处理这些按钮上的click事件，因此您需要在此之前创建它们。

Public Class Move_Test
    'Flag to tell the program whether to continue or to stop the textboxes where they are at that moment.
    Private blnStop As Boolean = False
    'Worker to do all the calculations in the background
    Private WithEvents bgWorker As System.ComponentModel.BackgroundWorker
    'Controls to be moved.
    Private lstTextBoxes As List(Of TextBox)
    'Dictionary to hold the y positions of the textboxes.
    Private dtnPositions As Dictionary(Of Integer, Integer)

    Public Sub New()
        ' Default code. Must be present for VB.NET forms when overwriting the default constructor.
        InitializeComponent()

        ' Here I instantiate all the pieces. The background worker to do the adjustments to the position collection, the list of textboxes to be placed and moved around the form
        ' and the dictionary of positions to be used by the background worker thread and UI thread to move the textboxes(because in VB.NET you can not adjust controls created on the UI thread from a background thread.
        bgWorker = New System.ComponentModel.BackgroundWorker()
        Me.lstTextBoxes = New List(Of TextBox)
        Me.dtnPositions = New Dictionary(Of Integer, Integer)
        For i As Integer = 0 To 10
            Dim t As New TextBox()
            t.Name = "txt" & i
            t.Text = "Textbox " & i
            'I used the tag to hold the ID of the textbox that coorelated to the correct position in the dictionary, 
            ' technically you could use the same position for all of them for this example but if you want to make the things move at different speeds 
            ' you will need to keep track of each individually and this would allow you to do it.
            t.Tag = i
            dtnPositions.Add(i, 10)
            'Dynamically position the controls on the form, I used 9 textboxes so i spaced them evenly across the form(divide by 10 to account for the width of the 9th text box).
            t.Location = New System.Drawing.Point(((Me.Size.Width / 10) * i) + 10, dtnPositions(i))
            Me.lstTextBoxes.Add(t)
        Next
        'This just adds the controls to the form dynamically
        For Each r In Me.lstTextBoxes
            Me.Controls.Add(r)
        Next
    End Sub

    Private Sub Move_Test_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Try
            'Don't need to do anything here. Placeholder
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message)
        End Try
    End Sub

    Private Sub btnGo_Click(sender As Object, e As EventArgs) Handles btnGo.Click
        Try
            If Not bgWorker.IsBusy Then
                'User starts the movement.
                bgWorker.RunWorkerAsync()
            End If
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message)
        End Try
    End Sub

    Private Sub btnReset_Click(sender As Object, e As EventArgs) Handles btnReset.Click
        Try
            'Reset the positions and everything else on the form for the next time through
            ' I don't set the blnStop value to true in here because it looked cooler to keep reseting the textboxes 
            ' and have them jump to the top of the form and keep scrolling on their own...
            For Each r In Me.lstTextBoxes
                r.Location = New System.Drawing.Point(r.Location.X, 10)
            Next
            For i As Integer = 0 To dtnPositions.Count - 1
                dtnPositions(i) = 10
            Next
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message)
        End Try
    End Sub

    Private Sub bgWorker_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles bgWorker.DoWork
        Try
            'This is where we do all the work.
            ' For this test app all its doing is scrolling through each value in the dictionary and incrementing the value
            ' You could make the dictionary hold a custom class and have them throttle themselves using variables on the class(or maybe travel at an angle?)
            For i As Integer = 0 To dtnPositions.Count - 1
                dtnPositions(i) += 1
            Next
        Catch ex As Exception
            blnStop = True
        End Try
    End Sub

    Private Sub bgWorker_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles bgWorker.RunWorkerCompleted
        Try
            'Once the background worker is done updating the positions this function scrolls through the textboxes and assigns them their new positions.
            ' We have to do it in this event because we don't have access to the textboxes on the backgroun thread.
            For Each r In Me.lstTextBoxes
                r.Location = New System.Drawing.Point(r.Location.X, dtnPositions(CInt(r.Tag)))
            Next
            'use linq to find any textboxes whose position is beyond the threshhold that signifies they are down far enough.
            ' I chose the number 100 arbitrarily but it could really be anything.
            Dim temp = From r In Me.lstTextBoxes Where r.Location.Y > (Me.Size.Height - 100)

            'If we found any textboxes beyond our threshold then we set the top boolean
            If temp IsNot Nothing AndAlso temp.Count > 0 Then
                Me.blnStop = True
            End If
            'If we don't want to stop yet we fire off the background worker again and let the code go otherwise we set the stop boolean to false without firing the background worker
            ' so we will be all set to reset and go again if the user clicks those buttons.
            If Not Me.blnStop Then
                bgWorker.RunWorkerAsync()
            Else
                Me.blnStop = False
            End If
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message)
        End Try
    End Sub

    Private Sub btnStop_Click(sender As Object, e As EventArgs) Handles btnStop.Click
        Try
            'The user clicked the stop button so we set the boolean and let the bgWorker_RunWorkerCompleted handle the rest.
            Me.blnStop = True
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message)
        End Try
    End Sub
End Class

那里有很多代码，但很多都是评论，我试图尽可能清楚，所以他们可能有点啰嗦。但是您应该能够在新表单上填充该代码，并且无需任何更改即可运行。我的表单大小非常大（1166 x 633）。所以我认为这是最好的，但任何尺寸都应该有效（较小的形式会更加混乱）。

如果这对您的申请不起作用，请告诉我。

Answer 2

这是一个非常适合async / await的问题。 Await允许您暂停代码以处理特定时间段内的其他事件。

Private Async Function Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) As Task Handles Button1.Click
    pgClass = New SecondUIClass
    pgClass.x += 100
    await pgClass.NewUIThread()
End Sub
End Class

班级代码：

Imports System.Threading

Public Class SecondUIClass
Public Const count As Integer = 1000
Public emeny(count - 1) As PictureBox
Public counter As Integer = 0
Public x As Integer = 0

Private Async Function NewUIThread() As Task
    emeny(counter) = New PictureBox
    emeny(counter).BackColor = Color.Red
    emeny(counter).Visible = True
    emeny(counter).Location = New System.Drawing.Point(x, 100)
    emeny(counter).Size = New System.Drawing.Size(10, 50)
    Form1.Controls.Add(emeny(counter))
    For z = 0 To 13
        emeny(counter).Location = New Point(emeny(counter).Location.X + 10, emeny(counter).Location.Y)
        await Task.Delay(100) 'The await state machine pauses your code here in a similar way to application.doevents() until the sleep has completed.
    Next
    counter += 1
End Sub
End Class