Mega Code Archive
Demonstrates using threads in a GUI
<![CDATA[
'Visual Basic(R) 2005 for Programmers (2nd Edition) (Deitel Developer Series) (Paperback)
'by Harvey M. Deitel (Author), Paul J. Deitel (Author)
'Publisher: Prentice Hall PTR; 2 edition (June 6, 2006)
'Language: English
'ISBN-10: 013225140X
'ISBN-13: 978-0132251402
'**************************************************************************
'* (C) Copyright 1992-2006 by Deitel & Associates, Inc. and *
'* Pearson Education, Inc. All Rights Reserved. *
'* *
'* DISCLAIMER: The authors and publisher of this book have used their *
'* best efforts in preparing the book. These efforts include the *
'* development, research, and testing of the theories and programs *
'* to determine their effectiveness. The authors and publisher make *
'* no warranty of any kind, expressed or implied, with regard to these *
'* programs or to the documentation contained in these books. The authors *
'* and publisher shall not be liable in any event for incidental or *
'* consequential damages in connection with, or arising out of, the *
'* furnishing, performance, or use of these programs. *
'**************************************************************************
Imports System.Threading
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms
public class UsingThreadInGUI
public Shared Sub Main
Application.Run(New frmGUIThreads)
End Sub
End class
Public Class frmGUIThreads
Private letter1 As RandomLetters ' first randomLetters object
Private letter2 As RandomLetters ' second randomLetters object
Private letter3 As RandomLetters ' third randomLetters object
Private Sub frmGUIThreads_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
' create first thread
letter1 = New RandomLetters(lblThread1)
Dim firstThread As New Thread(New ThreadStart( _
AddressOf letter1.Run))
firstThread.Name = "Thread 1"
firstThread.Start()
' create second thread
letter2 = New RandomLetters(lblTread2)
Dim secondThread As New Thread(New ThreadStart( _
AddressOf letter2.Run))
secondThread.Name = "Thread 2"
secondThread.Start()
' create third thread
letter3 = New RandomLetters(lblThread3)
Dim thirdThread As New Thread(New ThreadStart( _
AddressOf letter3.Run))
thirdThread.Name = "Thread 3"
thirdThread.Start()
End Sub ' frmGUIThreads_Load
' close all threads associated with this application
Private Sub frmGUIThreads_FormClosing(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.FormClosingEventArgs) _
Handles MyBase.FormClosing
System.Environment.Exit(System.Environment.ExitCode)
End Sub ' frmGUIThreads_FormClosing
Private Sub chkThread_CheckedChanged(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles chkThread1.CheckedChanged, _
chkThread3.CheckedChanged, chkThread2.CheckedChanged
If sender.Equals(chkThread1) Then
letter1.Toggle()
ElseIf sender.Equals(chkThread2) Then
letter2.Toggle()
ElseIf sender.Equals(chkThread3) Then
letter3.Toggle()
End If
End Sub ' chkThread_CheckedChanged
End Class ' frmGUIThreads
Public Class RandomLetters
Private Shared generator As New Random() ' for random letters
Private suspended As Boolean = False ' true if thread is suspended
Private output As Label ' Label for output
Private threadName As String ' name of the current thread
' constructor
Public Sub New(ByVal label As Label)
output = label
End Sub ' New
' delegate that allows method DisplayCharacter to be called
' in the thread that creates and maintains the GUI
Delegate Sub DisplayDelegate(ByVal displayChar As Char)
' method DisplayCharacter sets the Label's Text property
' in a thread-safe manner
Private Sub DisplayCharacter(ByVal displayChar As Char)
' output character in Label
output.Text = threadName + ": " + displayChar
End Sub ' DisplayCharacter
' place random characters in GUI
Public Sub Run()
' get name of executing thread
threadName = Thread.CurrentThread.Name
While True ' infinite loop; will be terminated from outside
' sleep for up to 1 second
Thread.Sleep(generator.Next(1001))
SyncLock Me ' obtain lock
While suspended ' loop until not suspended
Monitor.Wait(Me) ' suspend thread execution
End While
End SyncLock
' select random uppercase letter
Dim displayChar As Char = ChrW(generator.Next(26) + 65)
' display character on corresponding Label
output.Invoke(New DisplayDelegate(AddressOf DisplayCharacter), _
New Object() {displayChar})
End While
End Sub ' Run
' change the suspended/running state
Public Sub Toggle()
suspended = Not suspended ' toggle bool controlling state
' change label color on suspend/resume
If suspended Then
output.BackColor = Color.Red
Else
output.BackColor = Color.LightGreen
End If
SyncLock Me ' obtain lock
If Not suspended Then ' if thread resumed
Monitor.Pulse(Me)
End If
End SyncLock
End Sub ' Toggle
End Class ' RandomLetters
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Public Class frmGUIThreads
Inherits System.Windows.Forms.Form
'Form overrides dispose to clean up the component list.
<System.Diagnostics.DebuggerNonUserCode()> _
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing AndAlso components IsNot Nothing Then
components.Dispose()
End If
MyBase.Dispose(disposing)
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> _
Private Sub InitializeComponent()
Me.lblThread1 = New System.Windows.Forms.Label
Me.lblTread2 = New System.Windows.Forms.Label
Me.lblThread3 = New System.Windows.Forms.Label
Me.chkThread1 = New System.Windows.Forms.CheckBox
Me.chkThread2 = New System.Windows.Forms.CheckBox
Me.chkThread3 = New System.Windows.Forms.CheckBox
Me.SuspendLayout()
'
'lblThread1
'
Me.lblThread1.AutoSize = True
Me.lblThread1.BackColor = System.Drawing.Color.LightGreen
Me.lblThread1.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle
Me.lblThread1.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.lblThread1.Location = New System.Drawing.Point(13, 9)
Me.lblThread1.Name = "lblThread1"
Me.lblThread1.Size = New System.Drawing.Size(63, 18)
Me.lblThread1.TabIndex = 0
Me.lblThread1.Text = "Thread 1:"
'
'lblTread2
'
Me.lblTread2.AutoSize = True
Me.lblTread2.BackColor = System.Drawing.Color.LightGreen
Me.lblTread2.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle
Me.lblTread2.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.lblTread2.Location = New System.Drawing.Point(13, 34)
Me.lblTread2.Name = "lblTread2"
Me.lblTread2.Size = New System.Drawing.Size(63, 18)
Me.lblTread2.TabIndex = 1
Me.lblTread2.Text = "Thread 2:"
'
'lblThread3
'
Me.lblThread3.AutoSize = True
Me.lblThread3.BackColor = System.Drawing.Color.LightGreen
Me.lblThread3.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle
Me.lblThread3.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.lblThread3.Location = New System.Drawing.Point(13, 59)
Me.lblThread3.Name = "lblThread3"
Me.lblThread3.Size = New System.Drawing.Size(63, 18)
Me.lblThread3.TabIndex = 2
Me.lblThread3.Text = "Thread 3:"
'
'chkThread1
'
Me.chkThread1.AutoSize = True
Me.chkThread1.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.chkThread1.Location = New System.Drawing.Point(116, 8)
Me.chkThread1.Name = "chkThread1"
Me.chkThread1.Size = New System.Drawing.Size(93, 20)
Me.chkThread1.TabIndex = 3
Me.chkThread1.Text = "Suspended"
'
'chkThread2
'
Me.chkThread2.AutoSize = True
Me.chkThread2.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.chkThread2.Location = New System.Drawing.Point(116, 33)
Me.chkThread2.Name = "chkThread2"
Me.chkThread2.Size = New System.Drawing.Size(93, 20)
Me.chkThread2.TabIndex = 4
Me.chkThread2.Text = "Suspended"
'
'chkThread3
'
Me.chkThread3.AutoSize = True
Me.chkThread3.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.chkThread3.Location = New System.Drawing.Point(116, 58)
Me.chkThread3.Name = "chkThread3"
Me.chkThread3.Size = New System.Drawing.Size(93, 20)
Me.chkThread3.TabIndex = 5
Me.chkThread3.Text = "Suspended"
'
'frmGUIThreads
'
Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
Me.ClientSize = New System.Drawing.Size(221, 86)
Me.Controls.Add(Me.chkThread3)
Me.Controls.Add(Me.chkThread2)
Me.Controls.Add(Me.chkThread1)
Me.Controls.Add(Me.lblThread3)
Me.Controls.Add(Me.lblTread2)
Me.Controls.Add(Me.lblThread1)
Me.Name = "frmGUIThreads"
Me.Text = "GUI Threads"
Me.ResumeLayout(False)
Me.PerformLayout()
End Sub
Friend WithEvents lblThread1 As System.Windows.Forms.Label
Friend WithEvents lblTread2 As System.Windows.Forms.Label
Friend WithEvents lblThread3 As System.Windows.Forms.Label
Friend WithEvents chkThread1 As System.Windows.Forms.CheckBox
Friend WithEvents chkThread2 As System.Windows.Forms.CheckBox
Friend WithEvents chkThread3 As System.Windows.Forms.CheckBox
End Class
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