pausing a while loop using code

[Andy]

If you have a loop running and you would like to pause it using a button and start it running again from that point, how could that be done? think of it as a tape that gets a pause button pressed and unpressed.

[pvbangera]

why dont u pop-up a msgbox when the button is pressed?

[alextyx]

I think your problem is how to know if button is pressed, isn't it?
You have to use:

Application.DoEvents()

It forces application to serve events occurred and so the event ButtonClick will be served. Put the instruction on every cicle, or any ten turns or....as you prefer
Was this the problem, Andy?

[janis]

Try somthing like this:

Private stopFlag As Boolean
    Private counter As Integer = 0
 
    Private Sub cmdLoop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdLoop.Click
        stopFlag = False
        cmdStop.Focus()
        While counter < 2000000
            counter += 1
            Application.DoEvents()
            If stopFlag = True Then
                MsgBox("stop")
                Exit While
            End If
        End While
 
    End Sub
    Private Sub cmdStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdStop.Click
        stopFlag = True
    End Sub

regard j

[Negative0]

Something like this:

Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click
        blnStop = False
        blnPause = False
        btnStart.Enabled = False
        MyLoop()
    End Sub
 
    Private Function MyLoop()
        Dim i As Int16
        Dim j As Int16
        i = 0
        j = 1
        While i < j
            i = i + 1
            j = j + 1
            Label1.Text = i.ToString
            Me.Refresh()
            Application.DoEvents()
            Do While blnPause
                Application.DoEvents()
                If blnStop Then Exit Function
            Loop
            If blnStop Then Exit Function
        End While
    End Function
 
    Private Sub btnPause_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPause.Click
        If blnPause Then
            btnPause.Text = "Pause"
        Else
            btnPause.Text = "Resume"
        End If
        blnPause = Not blnPause
    End Sub
 
    Private Sub btnStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStop.Click
        blnStop = True
        btnPause.Text = "Pause"
        btnStart.Enabled = True
    End Sub

[taxes]

Hi janis,

I know that your code will not work without

Appplication.DoEvents()

but I cant see why. I would have thought that the loop would function without it, but it doesn't.

Any ideas anyone?


EDIT

Sorry. I've worked it out. The Application.DoEvents() is needed to enable outside events to be recognised during the application of the loop.

[carlblanchard]

Yo andy, you know the best way to do this is using threading

Imports System.Threading

On the form/class that contains the loop stick

Public myThreadDelegate As New ThreadStart(AddressOf SUB_WHICH_CONTAINS_LOOP)
 
Public myThread As New Thread(myThreadDelegate)

on the button start event stick

myThread.Start()

on the pause button event stick

myThread.Suspend()

how u handle starting the loop again is up to you, you could on the start button have an event to check the state of the thread if paused then resume it, if not then start it

If myThread.ThreadState = ThreadState.Suspended Then
myThread.resume()
else
myThread.start()
end if

This is a really nice way to handle pausing stuff, because it keeps the UI active during the pause period....
Of course if you want to run other stuff while this thread is paused then your need to do that in another thread or just make this one a background thread......

Syntax is hopefully correct, if not it ant going to be too far off

[dimonique]

Hi carlblanchard,
I have a problem on this part:
Public myThreadDelegate As New ThreadStart(AddressOf SUB_WHICH_CONTAINS_LOOP) <--- my sub contains parameter mysub(parameter), how can i resolve this?

[carlblanchard]

ok this is where it gets hard...

You cant use parameters, so this is what i do to work arround

Public myThreadDelegate As New ThreadStart(AddressOf RunProg)
Public myThread As New Thread(myThreadDelegate)

imagine this is a button event

Sub onClick blah blah (sorry just woke up)

myThread.start()

end

Private Sub RunProg
'Call your sub with the parameters here
myParamSub(blah,blah,blah)
end sub

See what this will do is execute the subs (its a chain reaction) so even if you had more subs within myParamSub they will all be executed in the new thread.....

Dynamic params will still work just assign then the myParamSub

hope this makes sense after all its 9am sunday morning and i havnt had my coffee yet