A control's Click event
fires when the control is enabled and the user
both presses and releases a mouse button while
the mouse pointer is over the control. If the
mouse pointer is over a disabled control or
if the mouse cursor is over a blank area of
the form, then the form receives the Click event.
The Click event is easy to
understand, because it represents a common user
action that occurs dozens of times during a
single session in any Windows-based application.
Notice that in our definition
of the Click event in the first paragraph, the
user must both press and release the mouse button
over the same control. The Click event won't
occur if the user presses the mouse button over
one control and then moves the mouse pointer
off the control to release it. The same goes
for a form's Click event:
The user must both press and
release the mouse button over an exposed area
of the form or over a disabled control in order
for the form to receive the Click event.
The Click event can also fire when the user presses a control's access key.
The following controls support the Click event as noted:
-
CommandButton
Only the left (or, for left-handed
mice, the primary) mouse button fires a Click
event for this control. Pressing Enter or
SpaceBar when a CommandButton has focus will
fire the Click event. Programmatically setting
its Value property to True will cause the
Click event procedure to run but will not
fire the Click event.
-
Label
Left or right mouse button fires a Click event.
-
TextBox
Left or right mouse button fires a Click event.
NOTE1: Choosing the Proper Mouse Event
Procedure One of the tricks to learning
Visual Basic is to determine which events to use
in a given situation.
When attempting to determine which mouse button
was selected, many new programmers do not see
much difference between the Click, MouseUp, and
MouseDown events. The difference between any two
events within VB lies in when they occur with
respect to each other. The Click event procedure
is the preferred place to detect a user's
intentions.
The reason for using the Click event is to allow
the user forgiveness. If the user did not mean
to click on your object, or has pressed the button
and then realized he did not want to, the mouse
could still be removed from the object. If the
mouse is dragged outside the area of the object,
the MouseUp event will still occur. The Click
event, however, will not occur.
Allowing your program to be forgiving means
the user will have an easier time using the software,
instead of fearing the next mistake.
NOTE2: Pressing and Releasing the Mouse Button To distinguish
between pressing and releasing the mouse button, see the discussion of MouseUp
and MouseDown events later in this
