[AccessD] Filtered combos - Events don't fire

John,

    There is an interesting reason for the problem faced by you. It has to do with the weird behavior of a control's GotFocus and LostFocus events, making such events unsuitable for the objective sought by you.

    With focus on combo box, if you progress through the records by pressing PgDn / PgUp keys, GotFocus and LostFocus events of this control keep firing alternately, in step with record change and nothing appears amiss.

    However, if an attempt is made to step through records by clicking navigation buttons on the subform, Lost focus event fires and you are stuck with it (visually, the combo appears to have focus, but it is in LostFocus state). There is no further firing of GotFocus or LostFocus events. Drop down list of combo box shows the unfiltered state. Again, if PgUp / PgDn is done, normal firing of these events resumes and things are back to normal.

    If you move out of the subform (say by clicking a control on parent form), while the focus was on its combo, exit event of subform control fires. LostFocus event of combo does not yet fire at this stage. Now, if you click a navigation button on the subform, combo's LostFocus event will fire (preceded by subform control's enter event) and you are stuck with combo in LostFocus state, even though it looks like having focus. 

    Similar phenomenon takes place, if after moving out of the subform, you try to step through its records via some control on the parent form (In such a case, subform control's enter event won't fire).

    In short, use of GotFocus / LostFocus events can not ensure consistent results as their firing can be sporadic, with the potential to get stuck in LostFocus state (in this state, even direct clicking on combo box does not cause firing of GotFocus event and full unfiltered drop down list gets displayed).

    Solution:
    ---------
    The solution is drastically simple. Use enter and exit events of combo box. Alternate firing of these events is consistent under all circumstances and remains in synch with record navigation.

Best wishes,
A.D. Tejpal
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  ----- Original Message ----- 
  From: jwcolby 
  To: Access Developers discussion and problem solving 
  Sent: Friday, March 06, 2009 18:43
  Subject: Re: [AccessD] Filtered combos - Events don't fire


  Yep, this is where I am headed.

  This is the reason that I keep the clsFrm public in a form header, it allows other objects to reach into the form, grab a pointer to the clsFrm and tell it to do things (like reset the combo queries).

  Unfortunately this is a little over the head of my target audience in the Classes and Events lecture series.

  John W. Colby
  www.ColbyConsulting.com


  Gustav Brock wrote:

  > Hi John
  > 
  > Use the OnEnter and OnExit events of the subform control of the main form to track this.
  > 
  > /gustav
  > 
  > 
  >>>> jwcolby at colbyconsulting.com 05-03-2009 21:52 >>>
  > I ran into something that I don't remember, or perhaps I never quite figured out.
  > 
  > In a subform, the Exit and LostFocus events of a control do not fire if you click entirely out of the subform into the parent form or into a control on another subform.  That is a PITA!
  > 
  > It appears that the logic is simply that the control never lost the focus IN IT'S FORM. 
  > Unfortunately this wreaks havoc with setting the unfiltered sql back into the combo's RowSource property.
  > 
  > What a PITA.
  > 
  > John W. Colby
  > www.ColbyConsulting.com