[RESOLVED] Previous Instances Remaining

[DaWolf]

I am currently using VB6 with SP6 on XP Home to create a program that generates reports from text files. I have everything working fine within the program at this time, but there remains one problem. If you click the EXIT button then the program ends as it should and releases the memory and processes just as it should. I have viewed this activity in the Task Manager. If you exit by clicking the X in the upper right corner then the applications appears to have closed since the main window of the application goes away but if you view in Task Manager the prior instance of the application is still running. I have added the code

If App.PrevInstance Then
     End
End If

But if there is a previous instance running but not accessible by the user then another instance will not run either and then there is no way to close the prior instance or start a new instance without opening the Task Manager to "End Task" on the instance that was held over.

How do you get the instance to release properly when the X is clicked? I know I can remove that from the form in design but would rather keep it there for ease of transistion for users since it is similar to all other Windows applications.

Thanks in advance for your time and effort in this.
God Bless You All.

[RhinoBull]

How do you get the instance to release properly when the X is clicked?

There are number of thing to look upon closing your app the following "list" is just an idea:

- close all global connections, recordsets, etc (if any)
- destroy all global objects
- close all documents (if automation is in place)
- loop through forms collection and close each form individually
- for each form (form_unload or queryunload events can be used)
... - close any open local connection, etc...
... - destroy all form level objects

... and so on and so forth ...

[si_the_geek]

To expand a little on what RhinoBull said.. the problem is that not everything is being closed/unloaded, possibly because of using "End" (which is basically a forced crash, with some cleanup, but not enough).

What you should do instead is unload everything properly, which should usually be done a Form_Unload event.


In there you should close and release all object variables as appropriate (anything you "Set" or "Dim .. as New ...", which includes recordsets etc), disable all timers (as timers will reload the form!), and if appropriate stop any long-running loops (similar to timers).

If you have multiple forms, you can use code like this in your 'main' form to unload the others:

    Dim frmTemp As Form
    For Each frmTemp In Forms
        If Not frmTemp is Me Then
          Unload frmTemp
          Set frmTemp = Nothing
        End if
    Next frmTemp

(note that every form should have code in its _Unload event to close its own object variables, timers, etc).

[Edgemeal]

You can try something like this,

Option Explicit
Dim terminate_app As Boolean

Private Sub Form_Load()
    If App.PrevInstance Then
        terminate_app = True
        MsgBox "A copy of My Program is already loaded!", vbInformation
        Unload Me
        Exit Sub
    End If

' YOUR CODE HERE

End Sub


Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
	If terminate_app = True Then Exit Sub ' only run on normal exit

' Stop timers, close open files, save user settings, etc,etc,

End Sub

Private Sub Form_Unload(Cancel As Integer)

    Dim i As Integer
    ' unload forms 
    For i = Forms.Count - 1 To 0 Step -1
        Unload Forms(i)
    Next i
    
    'Set Form1 = Nothing
End Sub

[westconn1]

generally don't use End, use unload me to unload your form, as well as all the things rhino said, make sure no code runs after you unload a form that in any way may reference any property or control of the form, put exit sub, immediately after unload me

[DaWolf]

I have resolved this problem by just using the Form_QueryUnload event which is triggered when the user attempts to exit the application by either a method coded by the programmer or by using the X in the upper right corner. I just placed my calls to the subroutine(s) for cleaning up variables, files, and forms in the QueryUnload event. I then called the QueryUnload event upon the Exit Button be clicked. I watched in Task Manager and the program was released and ended from the lsit of tasks being run when exited in either fashion.
Thanks for everyones help.

[si_the_geek]

There is no need to call _QueryUnload or _Unload, as they will run automatically when you use "Unload Me", or the form closes some other way (like clicking the "X")

There is no reason to use _QueryUnload (which is the point where you can cancel the unload), rather than _Unload itself (which happens when unloading is actually going to happen).

[RhinoBull]

There is no reason to use _QueryUnload ...

There is very good reason to use it - mainly because it allows to trap the unloadmode - in other words what caused application to exit.

[isnoend07]

There is very good reason to use it - mainly because it allows to trap the unloadmode - in other words what caused application to exit.

All my forms have tons of checking isDirty code in the query_Unload, i would be lost with-out it. It's the best place to mange the unload process

[si_the_geek]

That is fair enough for choosing whether or not to show a message to the user (eg: only show "are you sure you want to exit?" if Windows isn't closing the app), but what part of the actual unload would you do differently depending on unloadmode?

[isnoend07]

That is fair enough for choosing whether or not to show a message to the user (eg: only show "are you sure you want to exit?" if Windows isn't closing the app), but what part of the actual unload would you do differently depending on unloadmode?

I have roof estimating software that mostly revolves around the main form. One unload mode i can think of off the top of my head is one i added recently.
If a user has a saved bid open from the main form this bid also fills a secondary
form that contains 5 flexigrid with saved information. If the user tries to unload the second form by clicking the X i only make the form invisible and show the main form. If i let them close the form the data will be gone so i do this:
If Not mGridsAreDirty Then
If gSavedBidIsOpen And UnloadMode = vbFormControlMenu Then
Cancel = 1
Me.Visible = False
MainForm.Show
GoTo bail
End If
End If
If unloaded from main form i allow if it's not dirty

[si_the_geek]

Yet again, please use code tags when posting code.

That's a good reason for using _QueryUnload, but not for putting your actual unload code (releasing objects etc) in it rather than in _Unload.

The point I tried to make (that RhinoBull partly quoted), and admittedly didn't explain clearly, is that the _QueryUnload event should just be used to determine if the unload should be cancelled or not (as in the snippet you posted), and the _Unload event is where the your unloading code should go.

[isnoend07]

Yet again, please use code tags when posting code.

That's a good reason for using _QueryUnload, but not for putting your actual unload code (releasing objects etc) in it rather than in _Unload.

The point I tried to make (that RhinoBull partly quoted), and admittedly didn't explain clearly, is that the _QueryUnload event should just be used to determine if the unload should be cancelled or not (as in the snippet you posted), and the _Unload event is where the your unloading code should go.

How do you use code tags?

[si_the_geek]

You can either select the code and then press the Code/VBCode button in the post editor screen (or at the top of the Quick Reply box), or by put them in manually, like this:
[code] code here [/code]

If you want to try it out, post a new thread in our Test area.