Visual Basic responds to various mouse events, which are recognized by most of
the controls. The main events are
MouseDown, MouseUp and
MouseMove.
MouseDown occurs
when the user presses any mouse button and
MouseUp
occurs when the user releases any mouse button. These events use the arguments
button, Shift, X, Y and they contain information about the mouse's condition when
the button is clicked.
The first argument is an integer called Button. The value of the argument indicates
whether the left, right or middle mouse button was clicked. The second argument
in an integer called shift. The value of this argumnet indicates whether the mouse
button was clicked simultaneously with the Shift key, Ctrl key or Alt key. The
third and fourth arguments X and Y are the coordinates of the mouse location at
the time the mouse button was clicked. As the Form_MouseDown(
) is executed automatically whenever the mouse button is clicked inside
the Form's area the X, Y co-ordinates are referenced to the form.
Positioning a control
MouseDown is the commonly used event and it is combined
wiyth the move method to move an Image control to different locations in a Form.
The following application illustrates the movement of objects responding to move
events. it makes use of two OptionButton Controls,
two image controls and a CommandButton. The application
is designed in such a way that when an OptionButton is selected, the corresponding
image control is placed anywhere in the form whenever it is clicked.
Open a new standard EXE project and save the Form as Move.frm
and save the project as Move.vbp Design the
Form as shown below.
Object |
Property |
Setting |
Form
|
Caption
Name |
MouseDown
frmMouseDown |
OptionButton
|
Caption
Name
Value |
Credit card is selected
optCredit
True |
OptionButton
|
Caption
Name |
Cash is selected
optCash |
Image
|
Name
Picture |
imgCredit
c:/credit.jpg |
Image
|
Name
Picture |
imgCash
c:/cash.jpg |
The follwoing code is entered in the general declarations section of the Form.
Option Explicit
The following code is entered in the Form_MouseDown( ) event
Private Sub Form_MouseDown(Button As Integer, Shift As Integer,
X As Single, Y As Single)
If optCredit = True Then
imgCredit.Move X, Y
Else
imgCash.Move X, Y
End If
End Sub
Run the application by keying in F5. You can notice that when the mouse is
clicked on the form somewhere, the selected image moves to that clicked location.
This is shown in the below figure.
( Download the source code )
