I'm referring to this post (https://social.msdn.microsoft.com/Forums/vstudio/en-US/1bc71779-4b08-4d85-aaf1-531ed836a008/how-to-run-task-on-specified-timer-from-list-of-structure?forum=vbgeneral) but while deploying the program I realized that the Timer fires 2 or 3 times which results to open the file twice even three times.
I searched for a solution and found here (Run method every specified time within a service without repeating) one is explaining we need to use "SynchronizingObject" (https://msdn.microsoft.com/en-us/library/system.timers.timer.synchronizingobject(v=vs.110).aspx) but I'm able to apply it.
and I also noticed that sometimes the Timer is not accurate (it is short), I installed .Net 4.5.1 on deployement computer but it's still not working properly.
Can you please help?
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
StartTimer(1000, "c:\myfile1.txt")
StartTimer(1500, "c:\myfile2.txt")
End Sub
Private TimerList As New List(Of Timer)
Private Sub StartTimer(ByVal RunTime As Integer, ByVal FileName As String)
TimerList.Add(New Timer With {.Interval = RunTime, .Tag = FileName, .Enabled = True})
AddHandler TimerList(TimerList.Count - 1).Tick, AddressOf myTimer_Tick
End Sub
Private Sub myTimer_Tick(sender As Object, e As EventArgs)
Dim theUsedTimer = DirectCast(sender, Timer)
Dim runtime = theUsedTimer.Interval
Dim filename = theUsedTimer.Tag
theUsedTimer.Stop()
End Sub
End Class
The below code is the one I use on the real Program
Public TimerList As New List(Of Timer)
Public Sub StartTimer(ByVal RunTime As Integer, ByVal FileName As String)
TimerList.Add(New Timer With {.Interval = RunTime, .Tag = FileName, .Enabled = True})
AddHandler TimerList(TimerList.Count - 1).Tick, AddressOf myTimer_Tick
End Sub
==========
Public Sub myTimer_Tick(sender As Object, e As EventArgs)
Dim theUsedTimer = DirectCast(sender, Timer)
Dim runtime = theUsedTimer.Interval
Console.WriteLine(" ********************* File to open using Timer : " & theUsedTimer.Tag)
End Sub
==========
StartTimer(millisecond, FullPathfile)
Related
I need to add some controls to a Visual Basic 2017 form programmatically. One of the controls is a textbox that needs a changetext event handler. Below is some code that accomplishes that task.
HOWEVER, the changetext event handler seems to fire right away, before the form even loads... before the textbox itself even loads! A "click" handler works fine, as expected. But changetext? Nope.
I've thrown together a simplified version to demonstrate. The line with the "DIES RIGHT HERE" comment causes the problem (not the comment, but the code to the left of it).
A textbox that is added at design time will work fine, not cause this problem, but that isn't an option.
What's causing this the changetext handler to be run early? How do I work around this?
Public Class Form1
Dim txtTest As TextBox
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim pntTextBox As Point
pntTextBox.X = 100
pntTextBox.Y = 100
txtTest = New TextBox
With txtTest
.Location = pntTextBox
.Width = 100
AddHandler txtTest.TextChanged, AddressOf txtTest_TextChanged
End With
Me.Controls.Add(txtTest)
End Sub
Private Sub txtTest_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyClass.TextChanged
Dim strTest As String
strTest = Str(txtTest.Width) ' ****** DIES RIGHT HERE
MsgBox(strTest)
End Sub
End Class
Made a few changes. Works.
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
For x As Integer = 1 To 2 'create multiple TB's
Dim pntTextBox As Point
pntTextBox.X = 100 * x
pntTextBox.Y = 100
Dim txtTest As TextBox = New TextBox
With txtTest
txtTest.Name = "tb_" & x.ToString
AddHandler txtTest.TextChanged, AddressOf txtTest_TextChanged
.Location = pntTextBox
.Width = 100
End With
Me.Controls.Add(txtTest)
Next
End Sub
Private Sub txtTest_TextChanged(ByVal sender As Object,
ByVal e As System.EventArgs) 'no handler at design time
Dim tb As TextBox = DirectCast(sender, TextBox)
Dim strTest As String
strTest = tb.TextLength.ToString
Debug.WriteLine("{0} {1}", tb.Name, strTest) 'put breakpoint here
End Sub
End Class
I am trying to use a single handler to cover the end of multiple backgroundworker activities and cannot find a way to get the information about the specific backgroundworker using the backgroundworkercompleted event.
My code to catch the event is as below:
Private Sub BGx_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted, BackgroundWorker2.RunWorkerCompleted, BackgroundWorker3.RunWorkerCompleted, BackgroundWorker4.RunWorkerCompleted, BackgroundWorker5.RunWorkerCompleted, BackgroundWorker6.RunWorkerCompleted, BackgroundWorker7.RunWorkerCompleted, BackgroundWorker8.RunWorkerCompleted
'Do work here based on completed Backgroundworker
For BG = 1 To 8
If Not DSWorkers(BG).IsBusy Then
If DStatus(BG) = -2 Then : DStatus(BG) = -1 : End If
End If
Next
Complete()
End Sub
There is nothing on the "Do Work Here" section because I do not know how to capture and have been unable to find details of the backgroundworkercompleted event id.
Please - any pointers as to how I can identify the specific completed BackgroundWorker
As with all event handlers, the sender parameter is a reference to the object that raised the event, so you can access the actual BackgroundWorker that has completed its work via that. If you need some data other than that, you assign it to the e.Result property in the DoWork event handler and get it back from the e.Result property in the RunWorkerCompleted event handler. e.Result works for getting data out of the DoWork event handler much as e.Argument works for getting data in.
Check this out for some examples of using BackgroundWorker objects, including passing data out using e.Result. You might also like to checkout my own BackgroundMultiWorker class, which basically combines the functionality of multiple BackgroundWorker objects into a single BackgroundMultiWorker object. It identifies each task using a token.
EDIT:
Here's an example that may help with this issue and your task in general:
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private ReadOnly resultsByWorker As New Dictionary(Of BackgroundWorker, BackgroundWorkerResult)
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = 9
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 1 To 10
Dim worker As New BackgroundWorker
resultsByWorker.Add(worker, New BackgroundWorkerResult)
AddHandler worker.DoWork, AddressOf workers_DoWork
AddHandler worker.RunWorkerCompleted, AddressOf workers_RunWorkerCompleted
worker.WorkerSupportsCancellation = True
worker.RunWorkerAsync()
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
Dim worker = resultsByWorker.Keys.ToArray()(index)
If worker.IsBusy Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync()
End If
End Sub
Private Sub workers_DoWork(sender As Object, e As DoWorkEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.CancellationPending Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
Dim result = resultsByWorker(worker)
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
Dim workers = resultsByWorker.Keys.ToArray()
If Not workers.Any(Function(bgw) bgw.IsBusy) Then
'All work has completed so display the results.
Dim results As New List(Of String)
For i = 0 To workers.GetUpperBound(0)
worker = workers(i)
result = resultsByWorker(worker)
results.Add($"Worker {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, results))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Here is that example reworked to use a single instance of the BackgroundMultiWorker is linked to instead of multiple instances of the BackgroundWorker class.
Imports System.Threading
Public Class Form1
Private WithEvents worker As New BackgroundMultiWorker With {.WorkerSupportsCancellation = True}
Private ReadOnly results(9) As BackgroundWorkerResult
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = results.GetUpperBound(0)
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 0 To results.GetUpperBound(0)
results(i) = New BackgroundWorkerResult
worker.RunWorkerAsync(i)
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
If worker.IsBusy(index) Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync(index)
End If
End Sub
Private Sub worker_DoWork(sender As Object, e As DoWorkEventArgs) Handles worker.DoWork
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.IsCancellationPending(e.Token) Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles worker.RunWorkerCompleted
Dim result = results(CInt(e.Token))
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
If Not worker.IsBusy() Then
'All work has completed so display the results.
Dim output As New List(Of String)
For i = 0 To results.GetUpperBound(0)
result = results(i)
output.Add($"Task {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, output))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
First off, pardon me if my English is bad, I'm not a native English speaker.
I'm fairly new to programming and I'm trying to teach myself VB.NET
I came across a problem while trying to learn about Delegates. (see code below)
What I'm trying to accomplish is to update a specified Control's text property via a thread. However, as soon as I start the thread, I get an ArgumentException Error. I have completely no idea what's wrong. Anybody have an idea what i've done wrong here?
Public Class Form1
Delegate Sub myDelegate1(ByVal s_Name As Control, ByVal s_txt As String)
Public txtUpdate As New myDelegate1(AddressOf upd_ControlTextProperty)
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Label1.Text = vbnullstring
End Sub
Private Sub upd_ControlTextProperty(ByVal ControlName As Control, ByVal txt As String)
ControlName.Text = txt
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim thread1 As New Threading.Thread(AddressOf threadstart)
thread1.IsBackground = True
thread1.Start()
End Sub
Private Sub threadstart()
Me.Invoke(Me.txtUpdate, New Object(), {Label1, "This is Label 1"})
End Sub
End Class
As TheValyreanGroup said, your delegate is supposed to accept two arguments, and you pass it three :
Me.Invoke(Me.txtUpdate, New Object(), {Label1, "This is Label 1"})
^-1--------^ ^-2--------^ ^-3-----------------------^
So just remove the New Object() thing, and transform this {Label1, ...} into just a string :
Me.Invoke(Me.txtUpdate, "This is Label 1")
OK Better that way.
On a second hand, what you are doing is not very usefull.
You create a new Thread from your UI Thread.
With this new Thread, you invoke back the UI Thread and you stop your Thread...
Remember that a Control can be updated only by the Thread who created the Form (the UI thread).
Unless you have a good reason to work with your background thread, you can resume your code to :
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Label1.Text = vbnullstring
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Label1.Text = "This is Label 1"
End Sub
End Class
UPDATE
(from comments)
To make it more clear, here is a schema (that I took on https://androidkennel.org/android-networking-tutorial-with-asynctask/, if any restrictions apply I will remove the image)
The Main UI Thread is used for things :
React to user events (clicks, inputs...) and start background threads that will do the process
Update the User Interface when the background thread is over or during the task.
When I say what you're doing is not usefull is because your background thread does not do any processing, it just signals the UI thread to update the UI...
I would try this approach. upd_ControlTextProperty can be called successfully either from the UI thread or your new thread.
Public Class Form1
Delegate Sub myDelegate1(ByVal s_Name As Control, ByVal s_txt As String)
Public txtUpdate As New myDelegate1(AddressOf upd_ControlTextProperty)
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Label1.Text = ""
End Sub
Private Sub upd_ControlTextProperty(ByVal ControlName As Control, ByVal txt As String)
If Me.InvokeRequired = True Then
Me.Invoke(txtUpdate, New Object() {ControlName, txt})
Else
ControlName.Text = txt
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim thread1 As New Threading.Thread(AddressOf threadstart)
thread1.IsBackground = True
thread1.Start()
End Sub
Private Sub threadstart()
upd_ControlTextProperty(Label1, "This is Label 1")
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
I'm having trouble getting a progress bar to update. I'd be okay just with a moving marquee bar. Basically, I'm reading a database routine in a SqliteReader.vb class. I'm new to visual basic, and I'm sure I need to use the worker_DoWork routine, but I'm not sure how to expose my variables coming from Form1: graphData, graphComputations, m_debug to the worker_DoWork sub. How is this usually done?
Public Class SqliteReader
Public Sub ReadDataBase
End Sub
End Class
This is updating a graph (zedgraph element) on the main form, Form1.vb. I call the progressbar from the main form like this:
ProgressBar.Initialize(channelArray, computationArray, m_debug)
ProgressBar.vb below:
Partial Public Class ProgressBar
Dim DataAcquisition As New SqliteReader
Dim WithEvents worker As New BackgroundWorker
Public Sub Initialize(ByRef graphData As Channels(), ByRef graphComputations As Computations(), ByVal m_debug As Integer)
DataAcquisition = SqliteReader.GetInstance()
Me.Show()
Me.Update()
Dim Update_Thread As Thread(AddressOf Update_ThreadExecute)
Update_Thread.Priority = ThreadPriority.Normal
Update_Thread.Start()
DataAcquisition.ParseEntireDatabase(graphData, graphComputations, m_debug)
Me.Close()
End Sub
Private Sub ProgressBarStart(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
DataAcquisition = SqliteReader.GetInstance()
progress.Style = ProgressBarStyle.Marquee
worker.WorkerReportsProgress = True
worker.WorkerSupportsCancellation = True
worker.RunWorkerAsync()
End Sub
Private Sub worker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles worker.DoWork
Dim worker As BackgroundWorker = DirectCast(sender, BackgroundWorker)
DataAcquisition = SqliteReader.GetInstance()
' I probably need
' DataAcquisition.ParseEntireDatabase(graphData, graphComputations, m_debug)
' here... but how do I expose graphdata, graphcomputations and m_debug to this sub?
End Sub
Private Sub worker_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles worker.ProgressChanged
dataProgress = CInt(((DataAcquisition.currentRow + 1) / DataAcquisition.totalRows) * 100)
progress.Value = dataProgress
End Sub
RunWorkerAsync has a second version that takes a parameter. You can use that to pass any values (or references) your worker needs.
That said, you shouldn't be updating form elements from inside the worker. Your worker should fire the ProgressChanged event when you want the UI to update, and you handle it there. That one also has a version that can send a value back. (Or many values if you send back an array, list, or custom class.)
The last step in this is that you need to actually fire ProgressChanged. DataAcquisition.ParseEntireDatabase may not do that, in which case using it won't allow this method to work.
If graphData, graphComputations, m_debug are already members of ProgressBar and worker_DoWork is a member of ProgressBar, then you have nothing more to do. You should be able to access them directly.
For Rapunzo, above.. My Final Solution was this:
Partial Public Class ProgressBar
Dim _mDataAcquisition As New SqliteReader
Public Property DataProgress As Integer = 0
Dim WithEvents _mProgressWorker As New BackgroundWorker
Public Sub Initialize(ByRef graphData As List(Of Channels), ByRef auxData As List(Of Channels), _
ByRef graphComputations As List(Of Computations))
_mDataAcquisition = SqliteReader.GetInstance()
Show()
Update()
_mDataAcquisition.ParseEntireDatabase(graphData, auxData, graphComputations)
Close()
End Sub
Private Sub ProgressBarStart(ByVal sender As System.Object, ByVal e As EventArgs) Handles MyBase.Load
progress.Style = ProgressBarStyle.Blocks
_mProgressWorker.WorkerReportsProgress = True
_mProgressWorker.WorkerSupportsCancellation = True
_mProgressWorker.RunWorkerAsync()
progress.Visible = True
progress.Maximum = 100
progress.Value = 0
End Sub
Public Sub WorkerProgressChanged()
progress.Value = DataProgress
Invalidate()
End Sub
Private Sub WorkerRunWorkerCompleted(ByVal sender As Object, _
ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) _
Handles _mProgressWorker.RunWorkerCompleted
progress.Visible = False
progress.Value = 0
Close()
End Sub
From there, just call ProgressBar.Initialize to start it
To update:
ProgressBar.DataProgress = CInt((currentIt / totalIt) * 100)
ProgressBar.WorkerProgressChanged()
and to end:
ProgressBar.DataProgress = 100
ProgressBar.WorkerProgressChanged()
Hope this helps.