ON DROP block
Syntax
ON DROP (dnd-object)
instruction [...]
Usage
To enable drop actions on a list, you must define the ON DROP
block; otherwise
the list will not accept drop actions.
The ON DROP
block is executed after the end user has released the mouse button
to drop the dragged object. ON DROP
will not occur if drop has been disallowed in
the previous ON DRAG_OVER
event or in ON DRAG_ENTER
with a call to
ui.DragDrop.setOperation(NULL)
.
When ON DROP
executes, the MIME type of the dragged object can be checked with
ui.DragDrop.getSelectedMimeType()
. Then call the ui.DragDrop.getBuffer()
method to
retrieve drag & drop data from external applications.
Ideally, the drop operation is accepted (there is no need for additional calls to ui.DragDrop.setOperation()
).
In this block, the ui.DragDrop.getLocationRow()
method returns the index of the row in the
target array, and can be used to execute the code to get the drop data / object into the row that
has been chosen by the user.
DEFINE dnd ui.DragDrop
...
DISPLAY ARRAY arr TO sr.* ...
...
ON DROP (dnd)
LET arr[dnd.getLocationRow()].capacity == dnd.getBuffer()
...
END DISPLAY
If the drag & drop operations are local to the same list or tree-view controller, you can use
the ui.DragDrop.dropInternal()
method to simplify the code. This method
implements the typical move of the dragged rows or tree-view node. This is especially useful in case
of a tree-view, but is also the preferred way to move rows around in simple tables.
ON DROP
code example uses the dropInternal()
method:DEFINE dnd ui.DragDrop
...
DISPLAY ARRAY arr_tree TO sr_tree.* ...
...
ON DROP (dnd)
CALL dnd.dropInternal()
...
END DISPLAY
If you want to implement by hand the code to drop a node in a tree-view, you must check the index
returned by the ui.DragDrop.getLocationParent()
method to detect if the object was dropped
as a sibling or as a child node, and execute the code corresponding to the drop
operation. If the drop target row index returned by getLocationRow()
is a child of
the parent row index returned by getLocationParent()
, the new row must be inserted
before getLocationRow()
; otherwise the new row must be added as a child of the
parent node identified by getLocationParent()
.