Problem calling a Sub in another form

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  • Start date Start date
G

Guest

Hello.

I have 2 forms (Form1 and Form2). When i call the Sub placed in form1 from
form2, i get the error "object reference not set to an instance of an object"
!
What can i do to solve the problem?

Thanks
 
Here is the code:

' the code in form2
Private Sub DataGridView1_RowHeaderMouseClick(ByVal sender As Object, ByVal
e As System.Windows.Forms.DataGridViewCellMouseEventArgs) Handles
DataGridView1.RowHeaderMouseClick
dim exitvar as Integer
exitvar = DataGridView1.Rows(e.RowIndex).Cells(0).Value
Dim ff As New Form1
ff.BringToFront()
ff.soumavez(exitvar) ' this is the call to the sub in Form1
End Sub
 
Looks like it should work, when you step through the code where does
the exception occur? If the error occurs in somewhere other than this
sub please post that code too. Also what does "soumavez" mean?

Thanks,

Seth Rowe
 
ok....the name "soumavez" its a name that i called to the Sub...End Sub.

i put here the code of Sub(its about the Mapguide ActiveX to show a map in
VB). I'll send there to Sub in the other form the id of a polygon on the map,
and then the Sub localize the polygon and zoom the place!!!

Code of the Sub "soumavez" in the Form1:

Public Sub soumavez(ByVal varin As Integer)
' --->"varin" its the var that i send from Form2!!!
' --->"mgmap" its the name of the control (mapguide activex)
Try
Dim pubmapsel As MGMapControl.MGSelection
Dim pubvar2 As MGMapControl.MGMapLayer
Dim pubmapobjectos As MGMapControl.MGCollection
Dim pubmapobj As MGMapControl.MGMapObject
pubmapsel = mgmap.getSelection()
pubvar2 = mgmap.getMapLayer("SIG")
pubmapobjectos = mgmap.createObject("MGCollection")
pubmapobj = pubvar2.getMapObject(varin)
pubmapobjectos.add(pubmapobj)
pubmapsel.addObjectsEx(pubmapobjectos, False)
mgmap.zoomSelected()
mgmap.zoomScale(mgmap.getLat(), mgmap.getLon(), 1500)
mgmap.refresh()
Catch ex As Exception
MessageBox.Show(ex.Message, "Erro", MessageBoxButtons.OK,
MessageBoxIcon.Error)
End Try
End Sub
 
ok....the name "soumavez" its a name that i called to the Sub...End Sub.

It looked like a foreign langauge to me (is it?), so I was just making
sure it was a protected keyword in a foreign language edition of visual
studio.

Anyways, I have to apologize - my "visual" debugging skills must be
lacking today, as I still don't see anything obviously wrong. Which
line of the code raises the exception?

Thanks,

Seth Rowe
 
Yes....im portuguese....but I love America!!!!!

i forgot to tell U the line with the problem!!!Sorry

So, the problem "object reference not set to an instance of an object"
occurs in the line >>pubmapobj = pubvar2.getMapObject(varin)

Thanks
 
Hmm. The "object reference not set to an instance of an object"
exception is raised when you try to use an object that doesn't exist
yet, like if you left out the New keyword. However, everything looks
alright to me. The only thing I would try (outside of praying that
someone else happens on this thread and sees what we're missing!) is to
change this line:
pubmapobj = pubvar2.getMapObject(varin)
Click to expand...

To this:

pubmapobj = MGMapControl.MGMapLayer.getMapObject(varin)

That will take the pubvar2 variable out of the equation. Note, you may
also try throwing the "New" keyword into that line, I'm not sure if
you do or don't need it.

Hope that helps,

Seth Rowe
 
Hello rowe_newsgroups,

Your solutuion would not work. MGMapControl is the namespace.. MGMapLayer
is the type. getMapObject is not static (shared).
pubvar2 (GEEZ! Use some better freakin names next time wouldja, OP!) is
supposed to grab a reference to a specific map layer.

You are correct in that the OP is trying to use an object that is null.

OP: Check your MWF, make sure you have a layer actually called "SIG". Also,
ZoomSelected is a terrible way to get to an object. First, the selection
will only succeed if the object is visible at your current zoom scale. Second,
MapGuide is notorious for busystate collisions.

-Boo
 
What I see is that you do not show the form BringToFront does not make
a control a top-level control, and it does not raise the Paint event.

So with the knowledge of the last post, try following

- Check, if you can run the sub from form2 alone. Implement a button to
show what you want and make a test like this.
- If this does not work, first correct the sub until you are able to
let it run.
- After that, first show the new form and then let sub run from
form1...

Daniel
 
Daniel said:
What I see is that you do not show the form BringToFront does not make
a control a top-level control, and it does not raise the Paint event.

So with the knowledge of the last post, try following

- Check, if you can run the sub from form2 alone. Implement a button to
show what you want and make a test like this.
- If this does not work, first correct the sub until you are able to
let it run.
- After that, first show the new form and then let sub run from
form1...

Daniel
Click to expand...

Sorry, I did a mistake and mixed form1 and form2 :)
 
The SUB in form2:

Public Sub soumavez(ByVal varin As Integer)
Try
MessageBox.Show(varin)
Dim pubmapsel As MGMapControl.MGSelection
Dim pubvar2 As MGMapControl.MGMapLayer
Dim pubmapobjectos As MGMapControl.MGCollection
Dim pubmapobj As MGMapControl.MGMapObject
pubmapsel = mgmap.getSelection()
pubvar2 = mgmap.getMapLayer("SIG")
pubmapobjectos = mgmap.createObject("MGCollection")
pubmapobj = mgmap.getMapLayer("SIG").getMapObject(varin)
pubmapobjectos.add(pubmapobj)
mgmap.getSelection().addObjectsEx(pubmapobjectos, False)
mgmap.zoomSelected()
mgmap.zoomScale(mgmap.getLat(), mgmap.getLon(), 1500)
mgmap.refresh()
Catch ex As Exception
MessageBox.Show(ex.Message, "Erro", MessageBoxButtons.OK,
MessageBoxIcon.Error)
End Try

End Sub


this sub is called form Form2 with the following code:

exitvar = DataGridView1.Rows(e.RowIndex).Cells(0).Value
Dim ff As New Form1
ff.BringToFront()
ff.soumavez(exitvar)

PROBLEM:

if i dont put the codeline "MessageBox.Show(varin)", occurs the error at
line "pubmapobj = mgmap.getMapLayer("SIG").getMapObject(varin)".
If i put the message "MessageBox.Show(varin)", occurs the error at line
"mgmap.getSelection().addObjectsEx(pubmapobjectos, False)".

the test that u say to do (call the sub from a buttonclick within Form1)
occurs with NO Error!!!!

Thanks
 
Resume my problem:


if i call the Sub located in Form1 from Form1 i get no error. If i call the
Sub from Form2 i get error. Why?

Thanks
 
Thanks for coming to my rescue here Ghost, with no experience using
Mapguide (and not having it's SDK) I was getting in over my head!

Thanks,

Seth Rowe
 
Hello rowe_newsgroups,

I envy you, Seth. I have to use the abismal peice of crap every day.

-Boo
 
Can i force the execution of the Button_click located in Form1 from Form2?

i ask this because in Form1, if i execute the sub called from the
button_click everything goes right, but if i call the sub outside the Form1
(Form2) occurs the error!!!

Thanks
 
Now, have you tried to first SHOW the document with the command "show"
before let running the sub.

I realy believe that your problem just occurs because there is no valid
form available (because it's not yet shown and has it's window handle)
that can take the form handlings of your map software ...

Daniel
 
i have the form1 and form2 open....i dont have to do the show command to the
Form1...i think!!!!!
 
Have you tried?

Sometimes, software development is not about thinking but about trying.
So give it a try and place a ".show" instead of ".bringtofront" and
check out, what happens.

Daniel
 
it opens again the form1....i dont want this, and dont work anyway!!!
i think that i solved the problem. In form1 i open the form2 with the
command showdialog...just this!!!
 
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