I'm trying to change a few addresses. However, I need the code to update them almost consistently. The code WORKS, BUT, when the checkbox is checked, it freezes and wont let me Unchecked it. (To stop changing the addresses)
Iv'e also tryed:
Loop While CheckBox1.CheckState = 1
But that does not help the issue.
Code:
Private Sub CheckBox1_Click(sender As Object, e As EventArgs) Handles CheckBox1.Click
If IsProcessRunning("Notepad") = True Then
Do
Try
WriteInteger("Notepad", &H49E6CC, 99)
WriteInteger("Notepad", &H49E6D4, 99)
Catch ex As Exception
End Try
Loop While True
Else
CheckBox1.CheckState = 0
MessageBox.Show("Notepad Not Running!")
End If
End Sub
The application becomes unresponsive when you click on the checkbox because you have written an infinite loop in the event handler. The main thread of the application handles the execution of the UI events.
You need to create a separated mechanism that is going to continuously executes your logic, such as a BackgroundWorker or using a separated thread.
Thus, the event handler of the check box only enables/disables the BackgroundWorker or the separated Thread.
[Problem Solved] Appreciate everyone help!
Dim Timer1 As New Timer
Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged
If CheckBox1.CheckState = 1 Then
AddHandler Timer1.Tick, AddressOf Timer1_Tick
Timer1.Interval = 500
Timer1.Start()
Else
RemoveHandler Timer1.Tick, AddressOf Timer1_Tick
Timer1.Stop()
End If
End Sub
Private Sub Timer1_Tick(sender As Object, e As EventArgs)
WriteInteger("Notepad", &H49E6D4, 99)
WriteInteger("Notepad", &H49E6CC, 99)
End Sub
Related
I have come to learn that a module level variable's value will not be altered until a sub routine that changed it exits.
StopBackgroundWorker1 = True
Thread.Sleep(1500)
If BackgroundWorker1Complete = False Then
Exit Sub
End If
in this example, I added a long delay for testing. I'm simply trying to stop and start a background worker safely with vb 2017 new background worker class.
The example above with "StopBackgroundWorker1 = True", I was hoping to stop the worker at a safe place and then continue within that sub with other code.
But what is happening is that the "StopBackgroundWorker1 = True" is not being set "True" until the sub exits.
There must be another way to do what I am trying to do, please help
Ok here is a complete example,
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private flag As Boolean = False
Dim Completed As Boolean = False
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
flag = True
'Do
' do loop never see's a true flag
'Loop Until Completed
Thread.Sleep(500)
If Completed = True Then
Label1.BackColor = Color.Red
End If
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Do
Thread.Sleep(25)
Loop Until flag
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As
RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
Completed = True
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles
Button2.Click
Label1.Text = flag.ToString
End Sub
End Class
Now the concept is if you hit button1 and wait for background worker to complete, it should turn lable1 red. but it doesn't. The do loop looking for a true flag will spin forever locking the form up.
I have determined with this example that the flag is not set to true until you exit the sub. Hit Button1 again and lable1 turns red.
Thanks in advance for any answers.
This doesn't answer your question per se but I want to post a large code snippet so I'll post it as an answer. It demonstrates that what you think is the problem is not the problem, i.e. that a field's value changes as soon as you change it, even if that change is made from a BackgroundWorker.DoWork event handler.
Create a new Windows Forms application project, add a Button, a Label and a BackgroundWorker to your form and then paste in this code over the default code of the form:
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private flag As Boolean
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BackgroundWorker1.WorkerReportsProgress = True
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Label1.Text = flag.ToString()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Thread.Sleep(5000)
flag = True
BackgroundWorker1.ReportProgress(0)
Thread.Sleep(5000)
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
Label1.BackColor = Color.Green
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
Label1.BackColor = Color.Red
End Sub
End Class
Run the project and, when the form appears, start clicking the Button at a pace of a few times per second. You'll see that the value of the flag field, as displayed on the Label, changes from False to True as soon as the code to set it is executed in the DoWork event handler. The Label will turn green when that happens, so it's easy to spot. You'll know that it didn't wait until the DoWork event handler completes because the Label will turn red at that point.
EDIT: Now that you have provided all the relevant information, the issue is obvious. As I have already said, the moment you set a variable, that is the value of that variable. There's no waiting because there cannot be any waiting because there's nowhere to store a temporary value for the variable.
The reason that it looks otherwise is that your test code is faulty. If you use the debugger then you will see how. When you use a BackgroundWorker, the DoWork event handler is executed on a secondary thread but the RunWorkerCompleted event handler is executed on the UI thread. That means that your DoWork event handler can execute at the same time as your Click event handler for Button1 because they are on different threads, but the RunWorkerCompleted event handler cannot run at the same time, so it has to wait until the Click event handler completes before it can be executed. That means that the code to set the Completed field doesn't get executed until the Click event handler completes. It's not that the field value doesn't change when it's set but rather that it doesn't actually get set. If you place breakpoints on the two lines that access that Completed field then you'll see that.
The mistake you're making is trying to do something in that Click event handler after the DoWork event handler completes. That's wrong. That's exactly what the RunWorkerCompleted event handler is for. That's where you do UI work after the background work completes.
Also, you can get rid of that flag variable. Cancellation functionality is built into the BackgroundWorker class. Look at the CancelAsync method and the CancellationPending property.
Many thanks to "jmcilhinney" for his insights! I have figured out the code I was looking for!
This code allows me to stop and start a background thread safely by allowing the background thread to finish completely before restarting.
During the time that the background thread is stopped, user actions can perform operations without the worry of cross-threading or with thread.abort garbled code conditions.
Finally, stress-free threading!
I wish I could find the doc on MSDN that I read that stated the await async method was far superior to task.run but that's another argument.
This may not be the best code in the world but it works!
And in light of trying to rewrite all code in my project with async and await I'll stick with this!
Public Class Form1
Private flag As Boolean = False
Dim Completed As Boolean = False
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
flag = True
Await Task.Run(Sub()
Do
Loop Until Completed
End Sub)
If Completed = True Then
Label1.BackColor = Color.Red
End If
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Do
Thread.Sleep(250)
Loop Until flag
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As
RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
Completed = True
End Sub
End Class
For all of the academics out there this code is more appropriate.
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private Completed As Boolean = False
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BackgroundWorker1.WorkerSupportsCancellation = True
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles
Button1.Click
BackgroundWorker1.CancelAsync()
Await Task.Run(Sub()
Do
Loop Until Completed
End Sub)
If Completed = True Then
Label1.BackColor = Color.Red
End If
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Do
Thread.Sleep(250)
Loop Until BackgroundWorker1.CancellationPending
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
Completed = True
End Sub
End Class
The application is doing a lot more than this, but I have narrowed down the issue with the example below.
When bgwDone.WaitOne() is commented out, the progress bar works fine, cancel button is effective, but execution continues before the background process is complete.
When bgwDone.WaitOne() is applied, the ProgressForm is visible but not enabled, so processing cannot be cancelled and progress bar does not refresh, and the most confusing part, Msgbox("1") does not execute. I only see Msgbox("2") after the background worker finishes. I am utterly perplexed.
Imports System.ComponentModel
Public Class Form1
Private WithEvents bgw As BackgroundWorker
Private Event bgwCancelled()
Private bgwDone As New System.Threading.AutoResetEvent(False)
'Allows ProgressForm to cancel execution
Public Sub bgwCancelAsync()
RaiseEvent bgwCancelled()
End Sub
Private Sub bgw_Cancelled_by_ProgressForm() Handles Me.bgwCancelled
bgw.CancelAsync()
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Cursor = Cursors.WaitCursor
bgw = New BackgroundWorker
bgw.WorkerReportsProgress = True
bgw.WorkerSupportsCancellation = True
If bgw.IsBusy = False Then
ProgressForm.Show()
bgw.RunWorkerAsync(10)
End If
'********THIS LINE: bgwDone.WaitOne() MAKES A BIG DIFFERENCE*******
bgwDone.WaitOne()
MsgBox("1")
MsgBox("2")
Cursor = Cursors.Default
End Sub
'BackgroundWorker.RunWorkerAsync raises the DoWork event
Private Sub bgw_DoWork(sender As Object, e As DoWorkEventArgs) Handles bgw.DoWork
Dim numToDo As Integer = CInt(e.Argument)
For n As Integer = 1 To numToDo
If bgw.CancellationPending Then
Exit For
End If
System.Threading.Thread.Sleep(200)
bgw.ReportProgress(n * 10)
Next
bgwDone.Set()
End Sub
'ReportProgress raises the ProgressChanged event
Private Sub bgw_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles bgw.ProgressChanged
ProgressForm.UpdateProgress(e.ProgressPercentage)
End Sub
Private Sub bgw_RunWorkerCompleted(sender As Object,
e As RunWorkerCompletedEventArgs) Handles bgw.RunWorkerCompleted
ProgressForm.Close()
End Sub
And my form with the ProgressBar:
Public Class ProgressForm
Private Sub ButtonCancel_Click(sender As Object, e As EventArgs) Handles ButtonCancel.Click
Form1.bgwCancelAsync()
End Sub
Public Sub UpdateProgress(pct As Integer)
ProgressBar1.Value = pct
ProgressBar1.Refresh()
End Sub
End Class
I am not sure what you are trying to accomplish. But it almost seems like some of your code is trying to defeat the purpose of a BackGroundWorker:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Cursor = Cursors.WaitCursor
bgw = New BackgroundWorker
...
If bgw.IsBusy = False Then
ProgressForm.Show()
bgw.RunWorkerAsync(10)
End If
bgwDone.WaitOne()
MsgBox("1")
MsgBox("2")
Cursor = Cursors.Default
End Sub
The purpose of a BackgroundWorker is to do some long running task on another thread and leave the UI responsive. I am not sure that a task that only "takes several seconds" qualifies as a long running task.
Given that, why use the WaitCursor while the BGW runs? The point to leaving the UI resposive is to allow the user to do other things in the meantime.
The test for bgw.IsBusy can never, ever be true - you just created it 3 lines earlier. Click the button again and you will create another BGW.
The rest of the code in the click looks like you want or expect the code to continue on the next line after the BGW completes. That's not how it works.
If the app cannot continue without those tasks being completed, disable anything that lets the user go elsewhere until the worker completes or:
Forego the worker and put the form in wait mode (Me.UseWaitCursor) until the stuff is loaded. This doesn't rule out a ProgressBar.
A dedicated Progress Form can make sense in cases where the app will use various workers at various times. A StatusBar can contain a ProgressBar and is much more subtle (and perhaps appropriate since it is a status element).
So, revised and using a form instance for the progress reporter:
MainForm
Private WithEvents bgw As BackgroundWorker
Private frmProg As ProgressForm
Public Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
bgw = New BackgroundWorker
End Sub
Private Sub btnLoadAll_Click(sender As Object, e As EventArgs) Handles btnLoadAll.Click
bgw.WorkerReportsProgress = True
bgw.WorkerSupportsCancellation = True
If bgw.IsBusy = False Then
' create ProgressForm instance if needed
If frmProg Is Nothing Then frmProg = New ProgressForm
frmProg.Show()
bgw.RunWorkerAsync(78)
End If
btnLoadAll.Enabled = False
End Sub
Private Sub bgw_DoWork(sender As Object, e As DoWorkEventArgs) Handles bgw.DoWork
' multiple workers can use the same event
Dim thisWorker = DirectCast(sender, BackgroundWorker)
Dim count = Convert.ToInt32(e.Argument)
For n As Integer = 1 To count
If thisWorker.CancellationPending Then
Exit For
End If
' Fake work:
System.Threading.Thread.Sleep(50)
' dont assume the size of the job if
' there are multiple BGW or tasks
thisWorker.ReportProgress(Convert.ToInt32((n / count) * 100))
Next
End Sub
Private Sub bgw_ProgressChanged(sender As Object,
e As ProgressChangedEventArgs) Handles bgw.ProgressChanged
frmProg.UpdateProgress(e.ProgressPercentage)
End Sub
Private Sub bgw_RunWorkerCompleted(sender As Object,
e As RunWorkerCompletedEventArgs) Handles bgw.RunWorkerCompleted
If e.Error IsNot Nothing Then
'... ToDo
ElseIf e.Cancelled Then
'... ToDo
Else
frmProg.Close()
' avoid 'cannot access disposed object':
frmProg = Nothing
Me.btnNextStep.Enabled = True
btnLoadAll.Enabled = True
End If
End Sub
Rather than enabling a "Next" button, the app could automatically proceed. It depends on the app.
I have a main form with a progressbar at the bottom status strip. It is set to marquee style. I want it to keep animating when
I run a long function. But when the function hits, the form and everything on it freezes, so II used a backgroundworker
to run the long function. But this gave me the following error inside the MyClass.BigFunction() code.
Cross-thread operation not valid: Control 'frmMainNew' accessed from a thread other than the thread it was created on.
"frmMainNew" is the main form on which the progressbar and backgroundworker are. I pass the form as a parameter to the MyClass object
when I initialize it.
This is the first time I am using backgroundworker, so what else do I need?
I have already looked at these examples and tried them, but nothing works. (1, 2, 3, 4, 5, 6).
I have to use this for other functions too.
My code:
Private WithEvents bgw As BackgroundWorker
Private Sub frmMainNew_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Try
Me.SuspendLayout()
'Other Functions
w_AddBackgroundWorkerForProgressBar()
Me.ResumeLayout()
Catch ex As Exception
Scube.Planner.ErrorHandler.DisplayError(ex)
End Try
End Sub
Private Sub w_AddBackgroundWorkerForProgressBar()
bgw = New BackgroundWorker
AddHandler bgw.DoWork, AddressOf bgw_DoWork
AddHandler bgw.RunWorkerCompleted, AddressOf bgw_Completed
'AddHandler bgw.ProgressChanged, AddressOf bgw_ProgressChanged
End Sub
Private Sub MyButton_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyButton.Click
Try
bgw.WorkerSupportsCancellation = True
bgw.RunWorkerAsync()
'MyClass.BigFunction() <--- Originally called from here
Catch ex As Exception
Scube.Planner.ErrorHandler.DisplayError(ex)
Finally
Me.Cursor = Cursors.Default
End Try
End Sub
Private Sub bgw_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) Handles bgw.DoWork
'Do your lenghty operations here
MyClass.BigFunction()
System.Threading.Thread.Sleep(10000)
End Sub
Private Sub bgw_Completed(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) Handles bgw.RunWorkerCompleted
If Not IsNothing(e.Error) Then
MessageBoxEx.Show(e.Error.ToString)
End If
ProgressBar1.Hide()
End Sub
Private Sub w_ShowProgressBar()
ProgressBar1.Show()
Me.Refresh()
System.Windows.Forms.Application.DoEvents()
End Sub
You cant and should not access your frmMainNew from your 'BigFunction()'. It is working on a separate thread and does not have access to the UI thread. We need to see what you are doing inside your bigfunction to tell you the problem. Im going to take a guess and say you are trying to update the progressbar values from within that function? If this is so then is the incorrect way to do so.
What you need to do is, set the progress in your BigFunction like so:
bgw.ReportProgress(Progress/Percentage)
and have an event for the progress changed and inside of that event is where you update the progress bar.
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
Progressbar1.value = e.ProgressPercentage
End Sub
I have a loop that increases a a progress bar value every second. It works fine, but if you click anywhere in the form, the window turns white and it says "YOURTITLEHERE (No response)".
Here is the loop code:
Private Sub incprogress()
While ProgressBar1.Value < 1000
ProgressBar1.Value += 1
System.Threading.Thread.Sleep(1000)
End While
End Sub
Better yet, use a timer that ticks once per second. It's best not to play with Threads if you don't know what you are doing.
If you look in your toolbox, you'll find a Timer control that you can drag onto your form.
Set its interval to 1000, Enable it, and handle its Tick event to have something happen once per second.
If you want to do something more complicated than sleep between progress bar updates (like process lines in a file or wait for network traffic) you might use the BackgroundWorker instead of Timer. It is a little more complex to set up, but it will let you do all the heavy lifting off of your GUI thread so the GUI remains responsive.
Public Class Form1
Dim bgw As System.ComponentModel.BackgroundWorker
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
bgw = New System.ComponentModel.BackgroundWorker
bgw.WorkerReportsProgress = True
AddHandler bgw.DoWork, AddressOf bgw_DoWork
AddHandler bgw.ProgressChanged, AddressOf bgw_ProgressChanged
bgw.RunWorkerAsync()
End Sub
Private Sub bgw_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs)
While ProgressBar1.Value < 1000
System.Threading.Thread.Sleep(1000) 'Optionally do some useful work here off the UI thread
bgw.ReportProgress(0) 'optionally report a real percentage done
End While
End Sub
Private Sub bgw_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs)
If ProgressBar1.Value < 1000 Then
ProgressBar1.Value += 1 'optionally set progress bar to real percentage done
End If
End Sub
End Class
I have read other posts about this but I still can't seem to get it to work right.
Whenever my BackgroundWorker begins to do work, my function API.CheckForUpdate causes the GUI to hang. I can't click on anything. It only freezes for half a second, but is enough to notice.
How can I fix this? Should I dive deeper into API.CheckForUpdate and run individual threads on particular statements, or can I just have an all-inclusive thread that handles this? API.CheckForUpdate does not reference anything in Form1.
Also, I presume Form1_Load is not the best place to put the RunWorkerAsync call. Where is a better spot?
'Declarations
Dim ApplicationUpdate As BackgroundWorker = New BackgroundWorker
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
ApplicationUpdate.WorkerSupportsCancellation = True
ApplicationUpdate.WorkerReportsProgress = True
AddHandler ApplicationUpdate.DoWork, AddressOf ApplicationUpdate_DoWork
AddHandler ApplicationUpdate.ProgressChanged, AddressOf ApplicationUpdate_ProgressChanged
AddHandler ApplicationUpdate.RunWorkerCompleted, AddressOf ApplicationUpdate_RunWorkerCompleted
ApplicationUpdate.RunWorkerAsync()
End Sub
Private Sub ApplicationUpdate_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs)
'Check for an update (get the latest version)
Dim LatestVersion = API.CheckForUpdate
End Sub
Private Sub ApplicationUpdate_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs)
'Nothing here
End Sub
Private Sub ApplicationUpdate_RunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs)
'Work completed
MsgBox("Done")
End Sub
Its not a background worker Fix but if you don't mind walking around and not finding the answer, you can code like so:
Keep in mind when you first Start a Thread and you are coding in a Model you MUST pass (me) into the initial thread because of VB having a concept of "Default Form Instances". For every Form in the application's namespace, there will be a default instance created in the My namespace under the Forms property.
and that is just adding an additional parameter like so
----------------------/ Starting Main Thread /-----------------------------------
Private Sub FindCustomerLocation()
Dim Findcontractor_Thread As New Thread(AddressOf **FindContractor_ThreadExecute**)
Findcontractor_Thread.Priority = ThreadPriority.AboveNormal
Findcontractor_Thread.Start(me)
End Sub
------------------/ Running Thread /---------------
Private Sub **FindContractor_ThreadExecute**(beginform as *NameOfFormComingFrom*)
Dim threadControls(1) As Object
threadControls(0) = Me.XamDataGrid1
threadControls(1) = Me.WebBrowserMap
**FindContractor_WorkingThread**(threadControls,beginform) ' ANY UI Calls back to the Main UI Thread MUST be delegated and Invoked
End Sub
------------------/ How to Set UI Calls from a Thread / ---------------------
Delegate Sub **FindContractor_WorkingThread**(s As Integer,beginform as *NameOfFormComingFrom*)
Sub **FindContractor_WorkingThreadInvoke**(ByVal s As Integer,beginform as *NameOfFormComingFrom*)
If beginform.mouse.InvokeRequired Then
Dim d As New FindContractor_WorkingThread(AddressOf FindContractor_WorkingThreadInvoke)
beginform.Invoke(d, New Object() {s,beginform})
Else
beginform.Mouse.OverrideCursor = Cursors.Wait
'Do something...
beginform.Mouse.OverrideCursor = Nothing
End If
End Sub
Sources From Pakks Answer Tested!
Try starting the process outside the Load event. Create a Timer and start it on the Load event, and then handle the event for the tick:
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
Timer1.Enabled = False
ApplicationUpdate.RunWorkerAsync()
End Sub