Loading and unloading only bring the form into
memory or remove the form from memory. If the
programmer wants to display the form for the
user to interact with, another set of commands
must be used. The Show and Hide methods affect
the form's visibility. Unlike the Load
and Unload statements, which you write in code
before the form name, Show and Hide follow standard
method syntax and precede the object name, separated
from it by a period (.).
When a form is to appear on-screen for the
user to interact with, the Show statement causes
the form to appear. Hide will make the form
invisible, but allows it to remain in memory.
If the form is to be directly shown to the
user, only the Show method is required. The
loading of the Form object will take place automatically.
The following lines of code are all that is
required to both load the form and have it displayed:
Form1.Show
To understand why the form does not have to
be explicitly loaded, first always remember
that any programmatic reference to an object
will cause it to automatically load. That explains
why using the object name followed by the Show
method causes the form to load first and then
display onscreen. For further discussion of
implicit loading, see the previous section in
this chapter "Loading and Unloading Forms."
Calling a form's Show method will also
cause the form to become the application's
active form—that is the form where focus
resides in the application. Usually the form
itself does not have focus but rather a control
on the form. This is because a form object itself
cannot get focus unless the form contains no
controls that are currently able to receive
focus.
If the form is no longer required to be on-screen,
it can be removed from display by just using
the Hide method. This keeps the form loaded
but removes it from display. The following code
demonstrates this:
Form1.Hide
frmTest.Hide
The first line of code removes the form named
Form1 from the onscreen display. The second
line of code removes the object named frmTest.
Both prevent user interaction with the form
and help you avoid a very busy screen.
Forms can be hidden instead of being unloaded.
If a form is hidden without being unloaded and
destroyed, then the values of controls will
remain as the user entered them. Other code
in the project can then refer to the contents
of the controls on that form.
If the form were unloaded, this would re-initialize
the controls on the form. Every time the user
wanted the settings, they would either have
to be loaded from an external source or reset
by the user.
The relationship between Show and Hide methods and the Loading and Unloading
of forms is also discussed in Chapter 6, "Writing Code that Processes Data Entered
on a Form," in the sections "Show/Hide Methods Versus Load/Unload Statements"
and "How Significant Form Methods Affect Form Events." It is also discussed in
this chapter in the previous section "Loading and Unloading
Forms."
Creating Data Input Forms and Dialog Boxes topics
