I am trying to call a thread on a button click event. i dont fell my code is not making any syntax error. but its not working.
Private Sub btnHisStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnHisStart.Click
thrHis = New Thread(AddressOf threadHistorical)
thrHis.Start()
End Sub
Private Sub threadHistorical()
'code
End Sub
Add this line and check it
System.Windows.Forms.Control.CheckForIllegalCrossThreadCalls = False
Related
Having a small issue.
I am receiving a Cannot access a disposed object error for Form1
Upon clicking a menu item on the main form - the below Sub is called, which opens another form Form1
Private Sub ToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ToolStripMenuItem.Click
If (Not Form1.Visible) Then
Form1.Show(Me)
End If
End Sub
Within Form1, there is a Try block. If it isn't passed, Form1 should show a message box, before closing down. The message appears, but it's then that I receive the error (where it says Form1.Show(Me))
Private Sub Form1_Load(ByVal sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Try
'DO STUFF
Catch
MsgBox("Error loading in data. Please contact an administrator")
Me.Close()
Return
End Try
End Sub
I am quite new to this type of programming, and struggling to fix the problem even after searching similar problems. Could someone please assist or point me in the right direction?
EDIT: So looks like this is due to trying to close the form during the Load event. So my question now is, are there any simple alternatives? I've found ways of doing this in C#, but not a lot for vb.net
Here is one option:
Private loadFailed As Boolean = False
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Try
'...
Catch ex As Exception
loadFailed = True
End Try
End Sub
Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
If loadFailed Then
MessageBox.Show("Load failed")
Close()
End If
End Sub
In that case, the form will show with the message over it, then it will close when the message is dismissed. Here's an option that will not display the form:
Friend Module Form1Manager
Public Sub ShowForm1(owner As Form)
If Not Form1.Visible Then
Try
'...
'Pass data to Form1 here.
Form1.Show(owner)
Catch ex As Exception
MessageBox.Show("Load failed")
End Try
End If
End Sub
End Module
and, to use that:
Private Sub ToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ToolStripMenuItem.Click
Form1Manager.ShowForm1(Me)
End Sub
I'm working on a custom GUI, my last step is for the button to change automatically check if the file exists or not on startup. The method below is my download/open button. Any help is appreciated!
Private Sub Button7_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button7.Click
If Dir("DownloadedFile.zip") <> "" Then
Process.Start("DownloadedFile.zip")
Else
WC.DownloadFileAsync(New Uri("http://download852.mediafire.com/3a688rz1a6ig/dk71cs34ihs3v6x/Devil+went+down+to+georgia.rar"), "DownloadedFile.zip")
MsgBox("Starting Download")
End If
End Sub
A subroutine is a seperate method that does not return a value. I would take the If statement out of your click eventhandler and put it in its own method as I stated like this.
Private Sub CheckForFile()
If Dir("DownloadedFile.zip") <> "" Then
Process.Start("DownloadedFile.zip")
Else
WC.DownloadFileAsync(New Uri("http://download852.mediafire.com/3a688rz1a6ig/dk71cs34ihs3v6x/Devil+went+down+to+georgia.rar"), "DownloadedFile.zip")
MsgBox("Starting Download")
End If
End Sub
Call it from your button like this.
Private Sub Button7_Click(sender As Object, e As EventArgs) Handles Button7.Click
CheckForFile()
End Sub
Then handle the Shown Event and call it from there. It will run as soon as the initial form is shown
Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
CheckForFile()
End Sub
Responding to your comment You need to use the WebClient DownloadFileCompleted Event and the WebClient DownloadProgressChanged Event
I'm quite confused about progress bar in VB.net, here is my code
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
ProgressBar_my.Minimum = 0
ProgressBar_my.Maximum = 10
ProgressBar_my.Step = 1
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
ProgressBar_my.PerformStep()
Threading.Thread.Sleep(5000)
If 1 = 1 Then
ProgressBar_my.PerformStep()
ProgressBar_my.PerformStep()
End If
'Threading.Thread.Sleep(2000)
End Sub
For the above code, what I expected is that after I click Button1, the progress bar will increase the progress status by 1, then it will pause for 5 sec, then it will increase the progress status by 2 at once.
However, after I ran the above code, what I saw was that after I click Button1, the progress bar will increase by 3 continually after 5 sec.
Can someone tell me why it behaves like this and How should I program my code so that I can increase by 1, then pause 5 sec and then increase by 2?
Thanks in advance!
I think what you are seeing (or not seeing) is the fact that the progress bar takes a finite amount of time to advance each step.
When you call Threading.Thread.Sleep on the UI thread this stops the progress bar from being redrawn until after the Sleep
What you should do is update the progress bar on a background worker instead, then I think you will see the effect you desire.
Add a BackgroundWorker to your form
Change your button click code to start the worker:
Private Sub frmSO_Load(sender As Object, e As EventArgs) Handles MyBase.Load
ProgressBar_my.Minimum = 0
ProgressBar_my.Maximum = 10
ProgressBar_my.Step = 1
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
BackgroundWorker1.RunWorkerAsync
End Sub
Then perform the update in the DoWork event:
'define a delegate to handle updates to the UI thread
Private Delegate Sub PerformStepCallback()
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Dim cb As PerformStepCallback = AddressOf ProgressBar_my.PerformStep
Me.BeginInvoke(cb)
Threading.Thread.Sleep(5000)
Me.BeginInvoke(cb)
Me.BeginInvoke(cb)
End Sub
The problem is that you call Threading.Thread.Sleep(5000), which will, well, pause the current thread. But that also means that the window won't be redrawn, so you see the effect of the first call to PerformStep only after the thread is no longer paused.
You can use another thread for wait and the second update; the easiest way in this case is using the Task Parallel Library:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
ProgressBar1.PerformStep()
Task.Delay(5000).ContinueWith(Sub()
ProgressBar1.PerformStep()
ProgressBar1.PerformStep()
End Sub, TaskScheduler.FromCurrentSynchronizationContext)
End Sub
Thanks Matt Wilko for giving me the clue. Here is my code.
From the Components tab of the Toolbox, add a BackgroundWorker component named backgroundWorker2. Create DoWork and ProgressChanged event handlers for the BackgroundWorker.
The following code will initiate the Component.
Public Sub New()
InitializeComponent()
BackgroundWorker2.WorkerReportsProgress = True
BackgroundWorker2.WorkerSupportsCancellation = True
End Sub
Call RunWorkerAsync when the button is clicked and the background worker is not running.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If BackgroundWorker2.IsBusy <> True And ProgressBar_my.Value < 6 Then
BackgroundWorker2.RunWorkerAsync()
End If
End Sub
Private Sub BackgroundWorker2_DoWork_1(ByVal sender As System.Object, _
ByVal e As System.ComponentModel.DoWorkEventArgs) _
Handles BackgroundWorker2.DoWork
Dim worker As BackgroundWorker = CType(sender, BackgroundWorker)
worker.ReportProgress(1)
System.Threading.Thread.Sleep(2000)
worker.ReportProgress(1)
worker.ReportProgress(1)
End Sub
The following event is raised when every time the ReportProgress method is called.
Private Sub backgroundWorker2_ProgressChanged(ByVal sender As System.Object, _
ByVal e As System.ComponentModel.ProgressChangedEventArgs) _
Handles BackgroundWorker2.ProgressChanged
ProgressBar_my.PerformStep()
End Sub
More information about the BackgroundWorker:
http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker(v=vs.110).aspx
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
Here's the deal. I tried using classes instead of the usual modules(in an attempt to try a different approach[aside from what I know that is] to OOP). So I used classes and in a simple showing and hiding of forms, I got an InvalidOperationsException error. Weirded out, I removed the OOP parts and just tried calling the other form directly on the form itself and still got the same error.
Here's the error I get:
An error occurred creating the form. See Exception.InnerException for details. The error is: The form referred to itself during construction from a default instance, which led to infinite recursion. Within the Form's constructor refer to the form using 'Me.'
Here's the code:
Private Sub btnNewSales_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnNewOrder.Click
'This ought to have opened the new form via a method in the class
'order.NewOrder()
frmNewOrder.Show()
Me.Hide()
End Sub
either way, I get the same error.
Tried using modules instead. Here's the code:
Public Sub ShowForm(ByVal frmName As String)
If frmName = "Order" Then
frmOrders.Show()
ElseIf frmName = "AddOrder" Then
frmAddOrder.Show()
End If
End Sub
Now so far (in all my programming experience) this ought to work just fine, but it still returns the same error..
Update!
Tried removing all OOP aspects in form calling and left a module to simply show or hide some controls in one form.
Here's the code in the module:
Public Sub DesignSelect(ByVal design As String)
If design = "Basic" Then
frmAddOrder.lblD3.Hide()
frmAddOrder.cmbD3Color.Hide()
frmAddOrder.cmbD3Type.Hide()
frmAddOrder.lblD4.Hide()
frmAddOrder.cmbD4Color.Hide()
frmAddOrder.cmbD4Type.Hide()
Else
End If
End Sub
Now correct me if I'm wrong, but I do believe nothing is wrong with it right?
Now here's the code of the form where the module was used:
Dim selectedDesign As String = ""
Private Sub frmSalesTrans_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub
Private Sub frmSalesTrans_FormClosing(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Me.FormClosing
'ShowForm("Order")
frmOrders.Show()
End Sub
Private Sub rdbBasic_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles rdbBasic.CheckedChanged
selectedDesign = "Basic"
DesignSelect(selectedDesign)
End Sub
And here's the code of the form that calls the form above:
Private Sub frmSales_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub
Private Sub btnNewSales_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnNewOrder.Click
Me.Hide()
frmAddOrder.Show()
End Sub
Now it just boggles me why I get this error.. If I removed all OOP (including the subprocedure DesignSelect), it works fine. Kindly enlighten me on this...