Drag And Drop
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Basic |
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Setting the DragMode Property of a control to "Automatic",
allows a control to be dragged. For an action to be performed, a
corresponding DragDrop Event will need to exist.
For example, to reposition the control on a different
part of the Form, the Form would require a DragDrop event.
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Private Sub Form_DragDrop(Source As Control,
X As Single, Y As Single)
Source.Move X, Y
End Sub |
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If you try the above example, you'll notice that when you release
the mouse, the top left of the control being dragged is positioned
to the current mouse position, so jumps when dropped. You can alter
this by taking note of the relative position on the control when
it was clicked. When a control's DragDrop Property is set
to Automatic, you lose the MouseDown, MouseUp, and Click Events
for that control. The MouseMove Event is still available,
but you get more control by setting the DragDrop Property to
"Manual" (the default value for the Property), and
calling the Drag method explicitly.
The following example uses a PictureBox's MouseDown Event
to start the Drag operation, and get the relative position the
mouse was clicked on the control, so it's dropped exactly where
the mouse is released on the Form.
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Option Explicit
' Variables to store the relative position of a control on MouseDown
Dim dragX As Integer, dragY As Integer
Private Sub Form_DragDrop(Source As Control, X As Single, Y
As Single)
' Position the control with adjustments
Source.Move X - dragX, Y - dragY
End Sub
Private Sub picFace_MouseDown(Button As Integer, Shift As Integer,
X As Single, Y As Single)
' Store the relative coordinates
dragX = X
dragY = Y
picFace.Drag vbBeginDrag
End Sub |
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THE DRAGOVER EVENT
The DragOver Event can be used to detect whether an object
is being dragged over another object. The Event fires when the mouse
cursor enters the target. The Event has a State parameter which
can be used to determine whether it has entered the target, is over
the target or is leaving the target.
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Private Sub picTarget_DragOver(Source
As Control, X As Single, Y As Single, State As Integer)
' Only change the background colour
of the Target if the
' Source object is a PictureBox
If TypeOf Source Is PictureBox
Then
Select
Case State
Case
vbEnter
picTarget.BackColor
= RGB(0, 0, 0)
Case
vbOver
picTarget.BackColor
= RGB(128, 0, 0)
Case
vbLeave
picTarget.BackColor
= RGB(255, 255, 255)
End
Select
End If
End Sub |
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