Freetutes.com

VB6 beginners tutorial - Learn VB6

Advanced VB6 tutorial - Learn Advanced VB6

VB .NET - Learn Visual Basic .NET

Systems Analysis - System analysis and Design tutorial for Software Engineering


You are here: Visual Basic > Advanced VB6 tutorial > Chapter 6

Manipulating a Form From Another Form's Load Event Procedure

It might seem that using a current form's Load event procedure to call another form's methods or loading another form implicitly or explicitly would be asking for trouble.

However, it's perfectly possible to do so, and in fact you can accomplish some tasks in a simple and elegant fashion by loading and activating a second form from a first form's Load event procedure.

For instance, consider a form that is the main data input form for an application. Perhaps this form needs a preliminary dialog box, such as a login screen, just before it appears. One very simple way to achieve this effect is by performing the following steps:

  1. In the Load event of the main form, put a modal call to the Show method of the login dialog box form with a statement such as

    Secondform.Show vbModal

  2. Let the login dialog box expose a custom flag property through a Public variable or through Property procedures. This property will be a Boolean value that indicates whether or not the login has been successful.

  3. Just before the login hides itself, it sets the flag property appropriately.

  4. The Load event procedure of the main form has not finished running in all the time that the login dialog box was running because the login dialog box was running modally, and therefore the main form's Load event procedure was paused.

  5. The code in the main form's Load event that follows the modal call to the login dialog box can check the dialog box form's Boolean flag property to decide what action to take. After retrieving this information, the calling code in the main form should manage memory efficiently by setting the login dialog box form to Nothing.

  6. If the main form decides not to unload itself, then it will continue loading and will become the application's active form.

Perhaps the key point to bear in mind is step 4 above: Actions you take to manipulate other forms from within a given form's Load event procedure have their effect regardless of where you call them from. If you call the secondary form modally (as described in step 1 above), then the current form_Load pauses until the secondary form is dismissed.

Conversely, if you were to call the Show method of a main form and you were to call up a second form in a modeless state from within the first form's Load event, using code such as Secondform.Show vbModeless or simply

Secondform.Show

then the second form would load implicitly (if it were not already loaded) and would display.

However, the main form's Load event procedure would continue to run (because the second form was modeless), and so the first form would eventually load and display as well. The net result would be that you would end up with both forms visible, and the first form would end up as the active form in the application.


  

<< Previous | Contents | Next (Chapter 7) >>

Home | About Us | Privacy Policy | Contact Us

Copyright © Freetutes.com | All Rights Reserved