[2005] Showing another form

[manavo11]

I have a loading form that i want to show when i'm reading something from the serial port. My only problem is that i'm not 100% sure what's with the new stuff like delegates, but i've got it to work with a MyDelegate sub. But to invoke on the loading form, it throws an exception that the window needs a handle before you can invoke... So if I make it visible and then hide it again in the main form load, it works... Any ideas how i could avoid the flicker of the form showing and hiding and how it actually should be done?

Thanks

[bmahler]

Can't you just call the show and hide method?
Form1.Show()
Form1.Hide()

[manavo11]

Here is what i have so far... Any comments would be useful

[bmahler]

There is no need to call the visible properties in the for load.
Just change you Show and Hide functions to call

Private Sub ShowRead()
        fRead.Show()
    End Sub
 
    Private Sub HideRead()
        fRead.Hide()
    End Sub
 
    Private Sub Form_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Serial.IsOpen = True Then
            Serial.Close()
        End If
 
        Index = 0
 
        fRead.pbRead.Minimum = 0
        fRead.pbRead.Maximum = 63
        fRead.pbRead.Value = 0
 
        Try
            With Serial
                .BaudRate = 9600
                .Parity = IO.Ports.Parity.None
                .DataBits = 8
                .StopBits = IO.Ports.StopBits.One
            End With
            Serial.Open()
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub

[manavo11]

I get an exception :

Invoke or BeginInvoke cannot be called on a control until the window handle has been created.

on this line :

fRead.Invoke(New myDelegate(AddressOf ShowRead))

[bmahler]

Question, why are you using delegates to show the form? Why not just call the show method in your DataRecieved sub like so

Private Sub DataReceived( _
       ByVal sender As Object, _
       ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _
       Handles Serial.DataReceived
 
        If fRead.Visible = False Then
            fRead.Show()
        End If
 
        fRead.pbRead.Invoke(New myDelegate(AddressOf ChangePB))
 
        Tdata(Index) = Serial.ReadByte
        Index += 1
 
        If Index = 64 Then
            Index = 0
 
            Call Display()
        End If
    End Sub

[manavo11]

Cross-thread operation not valid: Control 'frmRead' accessed from a thread other than the thread it was created on.

[manavo11]

Have I worded it wrong? I can't be the first to run into this, can I?

[manavo11]

Someone? Anyone? Please?

[manavo11]

Please?

[Aspnot]

Here is something similiar out of an application that I have done.

My ShowProcessing.vb class

Imports System.ComponentModel

Public Class ShowProcessing
    Implements IDisposable

    Private _TextToDisplay As String
    Private WithEvents _bw As New BackgroundWorker

#Region " IDisposable Support "
    Private disposedValue As Boolean = False        ' To detect redundant calls

    ' IDisposable
    Protected Overridable Sub Dispose(ByVal disposing As Boolean)
        If Not Me.disposedValue Then
            If disposing Then

            End If

            _bw.Dispose()
        End If
        Me.disposedValue = True
    End Sub
    ' This code added by Visual Basic to correctly implement the disposable pattern.
    Public Sub Dispose() Implements IDisposable.Dispose
        ' Do not change this code.  Put cleanup code in Dispose(ByVal disposing As Boolean) above.
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub
#End Region

#Region " Property Declarations "
    Friend Property TextToDisplay() As String
        Get
            Return _TextToDisplay
        End Get
        Set(ByVal value As String)
            _TextToDisplay = value
        End Set
    End Property
#End Region

    Public Sub New()
        _bw.WorkerSupportsCancellation = True
    End Sub

    Friend Sub StartProcessing()
        _bw.RunWorkerAsync()
    End Sub

    Friend Sub StopProcessing()
        _bw.CancelAsync()
    End Sub

    Private Sub _bw_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles _bw.DoWork
        Dim worker As BackgroundWorker = CType(sender, BackgroundWorker)

        e.Result = DisplayForm(worker, _TextToDisplay, e)
    End Sub

    Private Function DisplayForm(ByVal worker As BackgroundWorker, ByVal inText As String, ByVal e As System.ComponentModel.DoWorkEventArgs) As Boolean
        Dim frm As New frmProcessing

        With frm
            .Text = inText
            .ShowDialog(worker, e)
            .Dispose()
        End With
    End Function
End Class

My ProgressBar form:

Public Class frmProcessing

    Private _worker As System.ComponentModel.BackgroundWorker
    Private _e As System.ComponentModel.DoWorkEventArgs

    Private Sub frmProcessing_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
        _e.Cancel = True
    End Sub

    Private Sub frmProcessing_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        With ProgressBar1
            .Minimum = 0
            .Maximum = 100
            .Value = 0
        End With

        With Timer1
            .Interval = 500
            .Start()
        End With

        Cursor = Cursors.WaitCursor

    End Sub

    Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        If _worker.CancellationPending Then
            Me.Close()
        End If

        If ProgressBar1.Value = 100 Then
            ProgressBar1.Value = 0
        Else
            ProgressBar1.Value += 1
        End If
    End Sub

    Public Overloads Function ShowDialog(ByVal worker As System.ComponentModel.BackgroundWorker, ByVal e As System.ComponentModel.DoWorkEventArgs) As System.Windows.Forms.DialogResult
        _worker = worker
        _e = e
        MyBase.ShowDialog()
    End Function
End Class

[Aspnot]

The example above is shown by FormA when it starts a SQL Stored Procedure that takes about 5 minutes to run. I just wanted the user to understand that it was still working.

That should give you a push in the right direction.

PS - Why all of the Delegates in your code? Is there something I am missing?

[manavo11]

I had the Delegates, so I could change the values of the label and the progressbar without getting the errors I've written above (Cross-thread operation not valid) I might be going about this the wrong way... I'll look at your code, try and compare. So thanks, I'll have a look