Asynchronous action?

[cocoon_wls]

Hi all,

I have an application with will moving the record and display in the chart by click a button. Does anyone know how make sure the action is asynchronous?What i mean here is how to make sure the next action is going after the action before completely done.

Any tips are welcome.

regards
lswang

[leinad31]

Post your code

[Lord Orwell]

simplest way is disable the button at the beginning of your code and enable it again at the end.

[cocoon_wls]

Hi
Lord Orwell, thanks for your suggestion.And Leinail31, below is my part of code to implement the display chart action when click on button.

Private Sub Plot_QueryChart(action As Integer)
Dim data As Integer, MoveValue As Integer


On Error GoTo errorhandler

If Not QueryRecordSet.EOF Or Not QueryRecordSet.BOF Then

    QueryRecordSet.MoveLast
    JJ = QueryRecordSet.RecordCount
    '**********************load all record*********************
    If action = 0 Then
          '*****get recordset
           If JJ > 60 Then
              QueryRecordSet.Move -cTotal_Brecord   '***to search record
              EmptyRow = 0
              '***currentRecord is to calculate how many record should move
              '***cTotal_Brecord is const variable
              currentRecord = cTotal_Brecord
              '***menuMoveFlag aim to disable some menu button                
              menuMoveFlag False, True
           Else
              QueryRecordSet.MoveFirst
              EmptyRow = cTotal_Brecord - JJ
              currentRecord = 0
              menuMoveFlag False, False
           End If
        
    '*************move previous 1 record*********************
    ElseIf action = 1 Then
        If currentRecord + cMovePreOne < JJ Then
            currentRecord = currentRecord + cMovePreOne
            QueryRecordSet.Move -currentRecord
            EmptyRow = 0
                If currentRecord + cMovePreOne >= JJ Then
                    menuMoveFlag True, False
                Else
                    menuMoveFlag True, True
                End If
        End If
        
    '*************move previous page*************************
    ElseIf action = 2 Then
        If (currentRecord + movePrePage) <= JJ Then
            currentRecord = currentRecord + movePrePage
            QueryRecordSet.Move -currentRecord
            EmptyRow = 0
                If (currentRecord + 1) >= JJ Then
                    menuMoveFlag True, False
                Else
                    menuMoveFlag True, True
                End If
        Else
            currentRecord = JJ - 1
            QueryRecordSet.Move -currentRecord
            EmptyRow = 0
            menuMoveFlag True, False
        End If
        
    '***************move next 1 record*************************
    ElseIf action = 3 Then
        If currentRecord - cMoveNextOne >= cTotal_Brecord Then
            currentRecord = currentRecord - cMoveNextOne
            QueryRecordSet.Move -currentRecord
            EmptyRow = 0
                If currentRecord - cMoveNextOne < 60 Then
                    menuMoveFlag False, True
                Else
                    menuMoveFlag True, True
                End If
        End If
        
    '**************move next page*****************************
    ElseIf action = 4 Then
        If currentRecord - moveNextPage >= cTotal_Brecord Then
            currentRecord = currentRecord - moveNextPage
            QueryRecordSet.Move -currentRecord
            EmptyRow = 0
                If currentRecord = 60 Then
                    menuMoveFlag False, True
                Else
                    menuMoveFlag True, True
                End If
        Else
            QueryRecordSet.Move -moveNextPage
            currentRecord = moveNextPage
            EmptyRow = 0
            menuMoveFlag False, True
        End If
        
    '**************search record******************************
    ElseIf action = 5 Then
        '***SearchLocationPiont is the location of record found
        '***CurrentToTalPoint is the total record count
        If SearchLocationPoint - (CurrentToTalPoint - JJ) > JJ Then Exit Sub
         
        If SearchLocationPoint - (CurrentToTalPoint - JJ) <= JJ Then
            currentRecord = SearchLocationPoint - (CurrentToTalPoint - JJ)
            If currentRecord < cTotal_Brecord Then      '
                currentRecord = moveNextPage
                QueryRecordSet.Move -cTotal_Brecord
                EmptyRow = 0
                menuMoveFlag False, True
            ElseIf currentRecord > JJ - cTotal_Brecord Then
                currentRecord = JJ - 1
                QueryRecordSet.Move -currentRecord
                EmptyRow = 0
                menuMoveFlag True, False
            Else
                QueryRecordSet.Move -currentRecord
                EmptyRow = 0
                menuMoveFlag True, True
            End If
        End If
    
    '*********move to First Page********************************
    ElseIf action = 6 Then
        currentRecord = JJ - 1
        QueryRecordSet.Move -currentRecord
        EmptyRow = 0
        menuMoveFlag True, False
    
    '********move to Last page*********************************
    ElseIf action = 7 Then
        '***moveNextPage is a variable
        QueryRecordSet.Move -moveNextPage
        currentRecord = moveNextPage
        EmptyRow = 0
        menuMoveFlag False, True
    
    End If
    DoEvents
    
    '**************insert data,plot chart************************
        For data = 1 To cTotal_Brecord
            If data > EmptyRow Then
                If Not (QueryRecordSet.BOF) Then
                Debug.Print (Format$((QueryRecordSet("RDate")), "dd/mm/yy") & " " & Format$((QueryRecordSet("RTime")), "hh:mm:ss"))
                   QueryArrValues(data, 1) = Format$((QueryRecordSet("RDate")), "dd/mm/yy") & " " & Format$((QueryRecordSet("RTime")), "hh:mm:ss") ' Labels
                   QueryArrValues(data, 2) = IIf(IsNull(QueryRecordSet(PreFieldString)), 0, QueryRecordSet(PreFieldString)) ' Series 1 values.
                   QueryArrValues(data, 3) = IIf(IsNull(QueryRecordSet(ActFieldString)), 0, QueryRecordSet(ActFieldString)) ' Series 2 values.
        
                   QueryRecordSet.MoveNext
                End If
            Else
                   QueryArrValues(data, 1) = " " ' Labels
                   QueryArrValues(data, 2) = 0 ' Series 1 values.
                   QueryArrValues(data, 3) = 0 ' Series 2 values.
            End If
        Next data
        DoEvents
        MSChart1.TitleText = trendName & " -- " & trendPreriod
        MSChart1.ChartData = QueryArrValues
        MSChart1.Column = 1: MSChart1.ColumnLabel = "Pre."
        MSChart1.Column = 2: MSChart1.ColumnLabel = "Act."
        
        
        
    '*******************************************************************************
End If

Exit Sub
errorhandler:
Call ELogger("Plot_Chart" & "-" & action)
Resume Next
    
End Sub

[Lord Orwell]

You wouldn't have the problem if that doevents was not in there. why is it there?

[cocoon_wls]

hi

Actually my whole application are containts 4 timers and will run every 1.5 sec and 5 sec.So, i need to use doevents to release my cpu usage,and avoid lack up of application.Does it make a problem for my application if i put the doevents there?


regards
lswang

[Lord Orwell]

yes, but you can cut down on the problems with global variables at the start of each of your subroutines. Set it to a value when your sub starts, and the line before that checkes to see if the value is already set. If so, exit sub/function. Last line of sub (or any place you have an exit sub) you reset the value. This prevents a subroutine from running more than once at the same time.
As for having all of those timers. This is a bad idea. A program never needs more than one. You use counting loops with static variables to ensure that you have the time interval you want. I am positive you are doing this already since you have intervals greater than 100ms. This is the biggest problem. Timers are unreliable and if you have more than one firing at the same time, occasionally (but quite often) you will lose event triggers.

[cocoon_wls]

Hi,

Set it to a value when your sub starts, and the line before that checkes to see if the value is already set. If so, exit sub/function. Last line of sub (or any place you have an exit sub) you reset the value.

Did you mean set a flag before check the recordset and reset the flag?

As for having all of those timers. This is a bad idea.

I had no choice but have to do it because i need to get some data due com port and at the same time i need to plot the chart according to the value which i got. And yes, as you said, i may be lose the events triggers while the other timers run toghter.

Can you please briefly how can i use counting loops to get the intervals time i need in condition that i have 3 action (currently using timers to run the action)need to complete at the same time..


thanks

best regards
lswang

[Lord Orwell]

yes it just requires a global variable for each one.

(inside timer1_timer with interval of 100)
a = a + 1
b = b + 1
c = c + 1
if a = 100 then a = 0:  Call CodeThatTriggersEvery10Seconds
if b = 10 then b = 0:  Call CodeThatTriggersEverySecond
if c = 450 then c = 0 etc.
end sub

get the picture? You never need more than one timer, and it can be demonstrated pretty easily that as few as 3 or 4 timers will miss events.

[Al42]

As for having all of those timers. This is a bad idea.

I had no choice but have to do it because i need to get some data due com port and at the same time i need to plot the chart according to the value which i got.

The MSComm control is event-driven, you don't need timers. If you get your incoming data in the MSComm1_OnComm event, the event will fire when there's data to get, regardless of what else you're doing. If you're using a timer to look at MSComm1.Input, you're using the control the wrong way. There's almost never a good reason to poll an interrupting asynchronous input.

[cocoon_wls]

hi,

First,thanks for Loar Orvwell, i have got the pic and then i will try it in my program.So, that mean if i running these code in my application, the percentage of lost event triggers will be decrease,am I right?

Second, for the Al42,thanks for your suggestion.Basically, in my application i already running the concept you are mention, which is get data while the comm event fired.But at the same time i need another timer to get the data and continue my next action if i cant receive the complete data from comm in 100ms.Example,i need to get 10 char from comm in 100ms. If i cant complete get all the data in 100ms, i will give up and continue my next action (in my condition, i cant wait untill i get the complete data, i must move to next action after 100ms).

[Lord Orwell]

In theory, it should be more reliable.