Access Cookbook, 2nd Edition [Electronic resources] نسخه متنی

Recipe 2.2 Highlight the Current Field in Data-Entry Forms

2.2.1 Problem

The text cursor is too small in Access,
and you can't always tell which text box on a form
has the focus. You need some way to

really
highlight the current field.

2.2.2 Solution

There are many visual cues you can use to tell the user which text
box contains the cursor. You can change the color of the text or the
background, change the appearance of the text box, or change the
appearance of the text box's label.

The simplest solution, which works quite
well, is to change the BackColor and SpecialEffect properties of the
active control. This solution uses some simple VBA code, which is
attached to each control's Enter and Exit events, to
do the work. Figure 2-3 shows the sample form,
frmEffects, in use (with the City field currently selected).

Figure 2-3. frmEffects in use, showing the active field

Open

02-02.MDB and load frmEffects. As you move
from field to field on the form, note that the special effect and the
background color of each control change when you enter and again when
you leave the control.

Follow these steps to create a form with this same sort of
functionality:

1. Create a new module and name it basSpecialEffects. In the declaration
   section, create the following constants, which will represent the
   controls' SpecialEffect and BackColor property
   settings:

   Option Compare Database
   Option Explicit
   Private Const conWhite = 16777215
   Private Const conGray = -12632256
   Private Const conIndent = 2
   Private Const conFlat = 0

2. Create two functions named

   SpecialEffectEnter
   and

   SpecialEffectExit that will toggle the
   values of the BackColor and SpecialEffects properties for the text
   boxes. The completed module is shown in Figure 2-4.

   Here are the code listings for the two functions:

   Public Function SpecialEffectEnter( )
   On Error GoTo HandleErr
   ' Set the current control to be indented.
   Screen.ActiveControl.SpecialEffect = conIndent
   ' Set the current control's background color to be white.
   Screen.ActiveControl.BackColor = conWhite
   ExitHere:
   Exit Function
   HandleErr:
   MsgBox Err & ": " & Err.Description
   Resume ExitHere
   End Function
   Public Function SpecialEffectExit( )
   On Error GoTo HandleErr
   ' Set the current control to be flat.
   Screen.ActiveControl.SpecialEffect = conFlat
   ' Set the current control's background color to be gray.
   Screen.ActiveControl.BackColor = conGray
   ExitHere:
   Exit Function
   HandleErr:
   MsgBox Err & ": " & Err.Description
   Resume ExitHere
   End Function

Figure 2-4. The completed basSpecialEffects module

3. Create your input form, if
   you haven't already. In design mode, select all of
   the text boxes to which you'd like to attach this
   effect. (Shift-clicking with the mouse allows you to select multiple
   controls.) When you select a group of controls, you can set
   properties for all of them at once. Set the properties of this group
   of controls as shown in Table 2-1. Figure 2-5 shows the design surface with all the text
   boxes selected. (Note that once you select multiple controls, the
   properties sheet's title can no longer display the
   name of the selected control and it will only show
   "Multiple selection," as shown in
   Figure 2-5.)

Figure 2-5. frmEffects in design mode, with all the text boxes selected

4. Add the following code to the
   form's Load event procedure (see the Preface for
   information on creating event procedures):

   Sub Form_Open (Cancel As Integer)
   Me.SetFocus
   End Sub

2.2.3 Discussion

The

SpecialEffectEnter and

SpecialEffectExit functions do their work by
reacting to the events that occur when you enter or leave a control
on the form. Every time you enter one of the text boxes to which
you've attached a function, Access executes that
function. Therefore, whenever you enter one of these special text
boxes, Access will cause the text box to appear sunken and will
change its background color to white. When you leave the control (by
tab or mouseclick), Access will set it back to being flat and will
reset its background color to gray.

The pair of functions do their work for
any control by using the built-in Screen.ActiveControl object. This
object always provides a reference to the currently active control.
Therefore, when you enter a control, the function acts on that
particular control, setting the SpecialEffects and BackColor
properties.

The only problem with this mechanism
is that, when Access first opens a form, there

isn't a current control.
Attempting to refer to Screen.ActiveControl before the form is fully
loaded results in an Access error. Because Access attempts to enter
the first control on your form when it first opens the form and there
isn't yet a current control, the code
you've attached to that first text
box's OnGotFocus event property will fail. To work
around this problem, you need to use the code attached to the Open
event, as shown in Step 4. This tiny bit of code forces Access to
load the form completely before it attempts to enter the first text
box on the form. You may find this technique useful in other
applications you create that use Screen.ActiveControl.

The functions used in this solution
could be extended to include many other changes to the controls as
you enter and leave them. For example, you can change the font or its
size, or the foreground color. You might wonder why this example
calls functions directly from the Properties window, instead of using
the standard mechanism for setting up event handlers. In this case,
because multiple controls call the same procedures in reaction to the
same events, it's simpler to set up the function
calls directly from the Properties window. This
isn't the only solution, but it's a
quick and easy one, when you need to have multiple events of multiple
controls call the same procedure.

2.2.4 See Also

See How Do I Create a Module in
the Preface for information on creating a new module.