The Load event fires when the
form loads into memory. This event's procedure
is the customary place for programmers to insert
code that sets form-level Private variables
(not associated with custom properties) and
performs other startup processes.
A form receives an Activate event
when it becomes the active form. A form is the
active form in an application when the focus
in the application is on the form itself or
(more likely) on a control within the form.
This could mean that either the form itself
has the focus or that a control on the form
has focus. The user can tell which form is active
because the title bar appears highlighted and
the form usually appears on top of the user's
desktop, as in Figure 6.1.
FIGURE 6.1 An Active form on the user's
desktop.
NOTE: Forms
as an Application's Startup Object
As mentioned in Chapter 4, "Creating Data
Input Forms and Dialog Boxes," a form
might be the application's startup object.
In such a case, you can count on the startup
form's Initialize, Load, and Activate
events to run when the application starts.
Focus can come to the form (and
fire the Activate event) either by user action
or through program code. For instance, the user
can activate the form from another form in the
application by clicking on the form with the
mouse. Your program can cause a form to become
the application's active form by calling
that form's Show method or by calling
the SetFocus method of one of the form's
controls.
The Activate event could therefore
fire many more times in an application than
either the Load or Initialize events (because
it could fire as often as the user returns to
the form with the mouse or as often as your
application makes it the active form).
Sometimes you will need to decide between putting code in the
form's Activate event procedure and putting it in the Load event procedure. The
following points can serve as guidelines for deciding between Activate and Load
event procedures:
-
The Load event procedure fires before the form is established visually and
before the data connections of any data controls that it contains have been established.
You will get runtime errors if you place code in form_Load that tries to use data
connections belonging to the form's own Data Controls. Code that attempts graphics
output to the form in form_Load will have no effect unless you set the form's
AutoRedraw property to True.
-
The Activate event can fire multiple times once the form is loaded, so you
should be cautious when placing code into the Activate event procedure if you
do not want that code to run more than once per form session. If such code must
go in the Activate event procedure (say, because it relies on an established data
connection), then you could put a Boolean Static variable in the Activate event
procedure to keep track of whether the Activate event has already run.
