Clarifying Questions

[hyperpau]

I just have some stupid questions but really want to know to fully understand vba more.


What are the arguments for in some of the events?

For example, the click event has the arguments (Shift As Integer, Cancel as Integer)


Then the DblClick event have (Cancel as Integer)

what are these for? specifically about these events. I am just curious as to why these appears although I do not use these variables in any of my procedures when I call these events.

The only argument I understand is the response in the NotInList event.

(Response As Integer) since I use it in the code as
Response = DataErrContinue


but regarding Shift and Cancel as Integer, what are these for?

where can I use them? does that mean the shift key? what about the Cancel argument?


Hope somebody can help me clear things up.

[FishVal]

Hi, hyperpau.

It depends on particular event.
Usually
Shift - represents Ctrl/Alt/Shift buttons state
Cancel - ByRef variable used to tell to the object that has raised the event whether to perform default action or no.
e.g.

Private Sub Text0_BeforeUpdate(Cancel As Integer)
    If IsNull(Me.Text0) Then Cancel = True
End Sub
 

This will tell Text0 object than update must be cancelled.

I recommend you to use object browser to get help on particular object events.

Regards,
Fish

[hyperpau]

Wow. thanks.
gives me more interest though.
I am very curious about the Shift.

Does this mean I can call different procedures depending on the key combination pressed with the mouse click?

if yes, please give me an example code.

let's say call a different message box when a button is clicked, then another message box when the button is clicked with the Shift, Ctl or Alt key.

please?.. :) Thanks in advance.

Hi, hyperpau.

It depends on particular event.
Usually
Shift - represents Ctrl/Alt/Shift buttons state
Cancel - ByRef variable used to tell to the object that has raised the event whether to perform default action or no.
e.g.

Private Sub Text0_BeforeUpdate(Cancel As Integer)
If IsNull(Me.Text0) Then Cancel = True
End Sub
 

This will tell Text0 object than update must be cancelled.

I recommend you to use object browser to get help on particular object events.

Regards,
Fish

[FishVal]

Wow. thanks.
gives me more interest though.
I am very curious about the Shift.

Does this mean I can call different procedures depending on the key combination pressed with the mouse click?

if yes, please give me an example code.

let's say call a different message box when a button is clicked, then another message box when the button is clicked with the Shift, Ctl or Alt key.

please?.. :) Thanks in advance.

Hmm.

Don't know what object raises Click event passing Shift argument.
The following example is for Form_KeyDown event.
Form object passes keyboard state in integer argument "Shift" having the following format.

Bit#       Set to 1 when pressed
0            Shift
1            Ctrl
2            Alt
 

additionally Access has constants corresponding to keys
acShiftMask = 1
acCtrlMask=2
acAltMask = 4
So to retrieve particular key state you may use bitwise logical operators AND and OR.

e.g.

if Shift AND acShiftMask = 1 Then 'Shift pressed
if Shift AND acCtrlMask = 0 Then 'Ctrl not pressed
if Shift AND (acCtrlMask OR acAltMask) = 1 Then MsgBox "Press DEL and go drink beer"

[hyperpau]

Wow. very cool.

but what scenarios can we use that Shift in the Click() event?

Hmm.

Don't know what object raises Click event passing Shift argument.
The following example is for Form_KeyDown event.
Form object passes keyboard state in integer argument "Shift" having the following format.

Bit# Set to 1 when pressed
0 Shift
1 Ctrl
2 Alt
 

additionally Access has constants corresponding to keys
acShiftMask = 1
acCtrlMask=2
acAltMask = 4
So to retrieve particular key state you may use bitwise logical operators AND and OR.

e.g.

if Shift AND acShiftMask = 1 Then 'Shift pressed
if Shift AND acCtrlMask = 0 Then 'Ctrl not pressed
if Shift AND (acCtrlMask OR acAltMask) = 1 Then MsgBox "Press DEL and go drink beer"

[FishVal]

Wow. very cool.

but what scenarios can we use that Shift in the Click() event?

Hmm.

There is no Click event which passes keyboard state to event handler.
This requires some play around.

The following code distinguish between Click and Ctrl+Click on Listbox.
MouseUp event handler checks whether Ctrl key is pressed, so far ListBox.Value is not yet set to item clicked. Then on Click event when ListBox.Value is set properly, Click event handler checks whether Ctrl key was pressed when mouse button was released. ;)

The form mentioned contains two controls:
Text2: unbound Textbox
List0: Listbox with RowSourceType = ValueList

Private blnCtrlPressed As Boolean
 
Private Sub CheckKeyboardState(Shift As Integer)
    If (Shift And acCtrlMask) <> 0 Then
        blnCtrlPressed = True
    Else
        blnCtrlPressed = False
    End If
End Sub
 
 
Private Sub List0_Click()
    With Me
        If blnCtrlPressed Then
            .Text2 = "Ctrl + " & .List0
        Else
            .Text2 = .List0
        End If
    End With
 
End Sub
 
Private Sub List0_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
    CheckKeyboardState (Shift)
End Sub