The
KeyDown and
KeyUp
events happen when the user respectively presses and releases a key on the keyboard.
Their event procedures take the following two parameters:
-
KeyCode
contains an integer code for the physical
key that the user pressed. You can check
for a particular key by comparing KeyCode
with one of the special VB internal constants
for physical key codes. Each constant name
begins with the string "vbKey"
followed by an obvious name for the key
(the letter of the key if it's an
alphabetic key or some other obvious name
for other keys). Examples of vbKey constants
would be vbKeyA, vbKeyW, vbKeyF1, vbKeyPgUp,
and so forth.
-
Shift
indicates if any of the three shift keys
(Alt, Ctrl, or Shift) is pressed at the
moment. This parameter works in the same
way as the Shift parameter for the MouseDown
and MouseUp event procedures. That is, Shift
is an integer representing a bit mask. You
can extract information concerning the state
of each of the three control keys by ANDing
the Shift parameter with one of the three
VB constants for the control keys.
In Listing 5.3, the KeyDown
event procedure is used to detect when the user
keys Shift+F10. Note the use of internal VB constants
to detect the keystroke and the state of the Shift
key.
LISTING 5.3
DETECTING A SHIFTED KEYSTROKE IN THE KEYDOWN EVENT PROCEDURE
Private Sub Form_KeyDown(KeyCode As Integer,
Shift As Integer)
Dim blnIsShift As Boolean
blnIsShift = Shift And vbShiftMask
If blnIsShift And (KeyCode = vbKeyF10) Then
'take some action for Shift+F10
End If
End Sub
NOTE :- How to Discover
the Names of VB Keystroke Constants When
in design mode, you can see the names of the internal
VB keystroke constants by invoking the Object
Browser with the F2 key, choosing All Libraries
or VBRun from the Libraries/Projects list, and
then choosing KeyCodeConstants from the Classes
list, as shown in Figure 5.1
FIGURE 5.1 Finding the names of VB KeyCode
constants in the Object Browser
In the event procedure code, you can modify the values of the KeyCode and Shift
parameters to change the keystroke information that the system sees, just as you
can modify the KeyAscii parameter in the KeyPress event procedure.
Keystroke Events at Field and Form Level topics
