Navigating within a navigation form

[tfurnivall]

I'm learning to use the new Navigation Form control in Access 2010. I think I like it. I have, however, run into a small problem.

I'm using the options/sub-options capabilities, with major options lined up across the top, and sub-options down the left-hand side.

At one point I need to be able to have a button on one of two sub-forms "call" another sub-form. If the target sub-form is access using the navigation buttons I want the form 'just as is", but if it is accessed from one of the other sub-forms, I have a button which will return me to the form whence I came. (Think procedures, where I call one procedure from within another, and when I exit the procedure, I know where to go back to. You probably have to be a COBOL programmer to even conceive of a procedure that can be accessed as in-line code, too - but then, history is what it is ;-)

I'm storing the calling form in the tag area of the button used for the return function. This is set up as part of the calling process. I also save the context of the calling form in the tag of the button that does the actual "call". Here's a more specific example.

Calling Button on Form 1 is called cmdCallTargetForm

Sub Form1.cmdCallTargetForm_Click

dim ReturnContext as string

...  Return Context is built using various controls ...

Me.cmdCallTargetForm.Tag=ReturnContext

'   Now navigate using the BrowseTo command
DoCmd.BrowseTo acForm, "TargetForm"
Form_TargetForm.cmdReturnButton.visible=true
TargetForm.cmdReturnButton.Tag="Form1"
TargetForm.cmdReturnButton.Caption="Return to Form1"

End Sub

Same thing for a similarly named button on Form2

The ReturnButton on TargetForm is coded as follows:

Sub cmdReturnButton_Click

dim ReturnTag as string
dim ReturnContext as string   ' Already available in the calling form

ReturnTag=me.cmdReturnButton.Tag
if ReturnTag="Form1" then
   ReturnContext=Form_Form1.cmdCallTargetButton.Tag
elseif ReturnTag="Form2" then
   ReturnContext=Form_Form2.cmdCallTargetButton.Tag
else
endif

'   Now use BrowseTo to get back to the calling form

DoCmd.BrowseTo acForm, ReturnTarget

End Sub

There is also much debug.printing around this.

What actually happens is that the first (calling) BrowseTo remains within the NavigationForm, and 'switches' to the TargetForm properly, including making the ReturnButton visible. The caption is properly set, and if I examine the Tag, it contains the proper return address. I also examine the ReturnContext, and during the execution of the TargetForm it is correctly set.

The problem is that on return, using substantially identical code (identical in concept, at least), rather than navigating withon the Navigation Form, Access pops up the sub-form independently. In other words, the first BrowseTo goes to the TargetForm within the Navigation Form, but the second form goes to the Calling Form as an independent form.

Obviously I am misunderstanding the way in which this is meant to work (using as my mental model the navigation within a tab control). What I don't understand is why one works, and the other doesn't!

Some things have occurred to me - but I'm at a loss to see how I can test them.
1) calling BrowseTo using a variable rather than a literal doesn't work (but if not, why did VBA accept it?)
2) The Navigation Form was never meant to be used in this way (but if not, why not? It's a perfectly rational way of using it)
3) Microsoft didn't think far enough through.....Nah, that would never be the case (!)


Any ideas?

(The db is available if wanted).

Tony

 

[tfurnivall]

I discovered the solution to this, so I'm posting it here in the hopes that others may find it useful.

First, the general condition within which I am working is that all of the forms used as sub-forms within the Navigation Form are independent forms. In other words they all operate just fine without the Navigation Form.

The problem arises in the sequence of code:

Sub cmdReturnButton_Click  
dim ReturnTag as string 
dim ReturnContext as string   ' Already available in the calling form ReturnTag=me.cmdReturnButton.Tag 
if ReturnTag="Form1" then
   ReturnContext=Form_Form1.cmdCallTargetButton.Tag 
elseif ReturnTag="Form2" then
    ReturnContext=Form_Form2.cmdCallTargetButton.Tag
else
endif  '   Now use BrowseTo to get back to the calling form  
DoCmd.BrowseTo acForm, ReturnTarget  
End Sub

I'm setting up the return context before browsing to the form. (This seemed pretty intuitive to me, but then, again, this is Microsoft ;-)
This resulted in the target form (the ReturnTarget) being loaded independently of the navigation form. Then, when I wanted to browse to it, it was this independently load instance of the form that became visible.

The other complicating thing is that when you BrowseTo a new form, that form is loaded without any saved values. In other words, not only was the early reference to the target form causing it to be loaded outside the navigation form, but even then, the data I was looking for was not available!

As counter-intuitive as it seems (at least to me), to save state between forms you have to:
1) Create the state before calling the new form
2) Browse to the new form
3) Save the return information (original form name) in the new form (I used the Return button)
4) Save the state information in the new form - either as a visible control,. or as a Tag attribute somewhere.

To return to the original form:
1) Get the name of the form (from the place where you saved it earlier)
2) Browse to the original form - at which point you are still in the procedure on the target form!
3) Retrieve the state information (from the place where you saved it earlier)
4) Recreate the state on the original form which is now loaded and ready for manipulation.

HTH

Tony