I'm using a BackgroundWorker and I need to use a Delegate Function to see if a ListViewItem is checked or not but I keep recieving a cross-thread error. It must be the way I'm writing it. Any help?
Dim delListViewItemChecked As ListViewItemCheckedDelegate = AddressOf ListViewItemChecked
delListViewItemChecked.Invoke(ListViewPhotos, 0)
Private Delegate Function ListViewItemCheckedDelegate(ByVal listView As ListView, ByVal index As Integer) As Boolean
Private Function ListViewItemChecked(ByVal listView As ListView, ByVal index As Integer) As Boolean
If listView.Items(index).Checked = True Then
Return True
Else
Return False
End If
End Function
Try this:
Do not pass the listView as a parameter to ListViewItemCheckedDelegate.
Declare a new delegate instance inside the DoWork handler of your background worker.
This sample seems to work OK:
Private Delegate Function ListViewItemCheckedDelegate(ByVal index As Integer) As Boolean
Private Function ListViewItemChecked(ByVal index As Integer) As Boolean
Return ListView1.Visible
End Function
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
bkg1.RunWorkerAsync()
End Sub
Private Sub bkg1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bkg1.DoWork
Dim delListViewItemChecked As New ListViewItemCheckedDelegate(AddressOf ListViewItemChecked)
MsgBox(Me.Invoke(delListViewItemChecked, 3)) ' arbitrary 3
End Sub
Related
I want to know if there a way around writing
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
End Sub
over and over again.
This is what I tried:
Public Class Ship
Public Property name As String
Public Property image As PictureBox
Public Property length As Integer
Public Property direction As String
Public Property selected As Boolean
Public Property placed As Boolean
Public Property location As Array
Public Sub New(ByVal namep As String, ByVal imagep As PictureBox, ByVal lengthp As Integer, ByVal directionp As String, ByVal selectedp As Boolean, ByVal placedp As Boolean, ByVal locationp As Array)
name = namep
image = imagep
length = lengthp
direction = directionp
selected = selectedp
placed = placedp
location = locationp
End Sub
Private Sub Ship_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.image.MouseMove
'Events here
End Sub
End Class
but I got the errors: Event 'image' cannot be found and End of statement expected
You can use WithEvents here:
Public WithEvents image As PictureBox
And then only
... Handles image.MouseMove
After that, look up AddHandler, too.
AddHandler can do at runtime what the Handles directive does at design time, i.e. it enables you to assign a method to the events of multiple / runtime-created objects.
A few weeks ago I wrote a wrapper for the ServiceController control to enhance and streamline the base ServiceController. One of the changes I made was to add a monitoring component using the System.Threading.Timer object. On any change of status, an event is raised to the parent class. The actual monitoring works fine, but when the event is handled in the main form, my program abruptly ends - no exceptions, no warning, it just quits. Here's a skeleton version of the control:
Public Class EnhancedServiceController
Inherits ServiceController
Public Event Stopped(ByVal sender As Object, ByVal e As System.EventArgs)
Public Event Started(ByVal sender As Object, ByVal e As System.EventArgs)
Private _LastStatus As System.ServiceProcess.ServiceControllerStatus
Private serviceCheckTimer as System.Threading.Timer
Private serviceCheckTimerDelegate as System.Threading.TimerCallback
...
Private Sub StartMonitor()
MyBase.Refresh()
_LastStatus = MyBase.Status
serviceCheckTimerDelegate = New System.Threading.TimerCallback(AddressOf CheckStatus)
serviceCheckTimer = New System.Threading.Timer(serviceCheckTimerDelegate, Nothing, 0, 60*1000)
End Sub
Private Sub CheckStatus()
MyBase.Refresh()
Dim s As Integer = MyBase.Status
Select Case s
Case ServiceControllerStatus.Stopped
If Not s = _LastStatus Then
RaiseEvent Stopped(Me, New System.EventArgs)
End If
Case ServiceControllerStatus.Running
If Not s = _LastStatus Then
RaiseEvent Started(Me, New System.EventArgs)
End If
End Select
_LastStatus = s
End Sub
End Class
And the form:
Public Class Form1
Private Sub ServiceStarted(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Started
Me.TextBox1.Text = "STARTED"
End Sub
Private Sub ServiceStopped(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Stopped
Me.TextBox1.Text = "STOPPED"
End Sub
End Class
If I had to guess, I'd say that there's some sort of thread problem, but I'm not sure how to handle that in the form. Any ideas?
IF it is a threading issue then you are probably trying to update the UI from a non-UI thread.
So something like this should solve that...
Private Delegate Sub UpdateTextBoxDelegate(byval tText as String)
Private Sub UpdateTextBox(byval tText As String)
If Me.InvokeRequired Then
Me.Invoke(New UpdateTextBoxDelegate(AddressOf UpdateTextBox), tText)
Exit Sub
End If
TextBox1.Text = tText
End Sub
Private Sub ServiceStarted(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Started
UpdateTextBox ("STARTED")
End Sub
Private Sub ServiceStopped(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Stopped
UpdateTextBox("STOPPED")
End Sub
Hey all i am trying to figure out why my 2nd form is not displaying the value i recived in my first form.
The code for the first form is:
Private Sub scannerOnCom_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
responceBack = scannerOnCom.ReadLine
Call frm1110.clickButton(responceBack)
End Sub
The second form code is this:
Public Sub clickButton(ByRef theResponse As String)
txtNumber.Text = theResponse
'Call cmdNextFinish_Click(Nothing, Nothing)
End Sub
However, when i debug it to make sure there is something stored for theResponse, there is but for some reason it does not put it into the textbox. It's blank.
Any help would be great!
David
UPDATE
Ok so Form1:
Dim tmpForm3020 As New frm3020
Private Sub cmd3020_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd3020.Click
tmpForm3020.Show()
Me.WindowState = FormWindowState.Minimized
End Sub
Private Sub scannerOnCom_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
responceBack = scannerOnCom.ReadLine
tmpForm3020.txtNumber.Text = responceBack
End Sub
If thats correct then i get an error on line:
xForm.txtNumber.Text = responceBack
Saying:
Cross-thread operation not valid: Control 'txtNumber' accessed from a thread other than the thread it was created on.
Are you explicitly creating an instance of your second form, or relying on the default instance? I.e. is "frm1110" the second form's class name, or an instance that you have new'd up? Make sure in either case that it is the same instance that is actually being displayed.
Dim tmpForm3020 As New frm3020
Private Sub cmd3020_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd3020.Click
tmpForm3020.Show()
Me.WindowState = FormWindowState.Minimized
End Sub
Private Sub scannerOnCom_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
responceBack = scannerOnCom.ReadLine
TestData(responceBack)
End Sub
Private Sub TestData(ByVal xVal As String)
If InvokeRequired Then
Me.Invoke(New MethodInvoker(AddressOf TestData))
' change Me to tmpForm3020 (if it does not work)
' tmpForm3020.Invoke(New MethodInvoker(AddressOf TestData))
Else
tmpForm3020.txtNumber.Text = xVal
End If
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.
I need to report progress changed. Consider the following code:
Public Class Calculator
Public Event CalculationProgress (ByVal sender As Object, ByVal e As MyCalculationProgressEventArgs)
Public Function Calculate(..)..
' Perform calculation here ...
' Reporting proggress
Dim args As New MyCalculationProgressEventArgs(myobj, myValue)
RaiseEvent CalculationProgress (Me, args)
...
End Class
*** Another class
Private WithEvents calculator As Calculator
Private Function PerformCalculation(ByVal obj As Object) As CalcParams
Dim params As CalcParams = CType(obj, CalcParams)
calculator = GetCalculator()
....
Return params.result = calculator.Calculate
End Function
Private Sub calculationWorker_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) _
Handles calculationWorker.DoWork
Dim calcResult As MyType = PerformCalculation(CType(e.Argument, MyType ))
e.Result = calcResult
End Sub
Private Sub calculationWorker_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs) _
Handles calculationWorker.ProgressChanged
CType(Parent.Parent, MainWindow).pbcCurrentProgress.Value = e.ProgressPercentage
End Sub
How and where should I subscribe to CalculationProgress event to call
calculationWorker.ReportProgress(MyCalculationProgressEventArgs.Percent)
?
Are you using a BackgroundWorker object here? If so what you want to do is to subscribe to the CalculationProgress event inside of the calculationWorker_DoWork event handler. You didn't post any information on MyType, so I'll assume you'll need to alter my code to get the Calculator instance.
Private Sub calculationWorker_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) _
Handles calculationWorker.DoWork
Dim calcResult As MyType = PerformCalculation(CType(e.Argument, MyType ))
Dim calc = calcResult.Calculator
AddHandler calc.CalculationProgress, AddressOf HandleCalculationProgress
...
RemoveHandler calc.CalculationProgress, AddressOf HandleCalculationProgress
e.Result = calcResult
End Sub
You would do this after your GetCalculator call, and before calling Calculate.