Drag & Drop start event

Vaadin 6 / 7 / 8 Framework UI
1

Hi,

Is there a way to know when a drag event is started?
I only found the

DropHandler.drop(DragAndDropEvent event)

but I need something like:

DropHandler.drag(DragAndDropEvent event)

Thanks for this great framework!
Mihai Cazacu

2

You could try and checkout this interface:
http://vaadin.com/api/com/vaadin/terminal/gwt/client/ui/dd/VDropHandler.html

I think this is what you were looking for.

3

The drag can come from somewhere outside the component with a drop handler, even from outside the browser, so it does not really make sense for drop handlers to be notified when someone starts a drag operation somewhere, nor would it always be possible.

The drag source component (if of a suitable type) could provide such an interface, but I guess it does not at the moment.

4

You’ve right, but this is not my case. I’am working on a chess application and, when a player drag the piece from own square, I need that piece to be removed from the current location while the drop is not finished.

The current behavior is this:

  1. player drag the piece
    1.1 Vaadin creates a copy of that (@see DragAndDropWrapper#setDragStartMode) - but it doesn’t remove the component from the original location
  2. player drop the piece
    2.1 Vaadin call DropHandler#drop method of the destionation component (in this method I can remove the piece from the initial location and put it in the destination)

Please see
Demo 10
 .

Yes, indeed but I think that is a must feature to have (of course, only for Vaadin components).

Thanks!

5

Hi,

DragAndDropWrapper should indeed have a mode that hides the component on dragstart (and makes it visible again if drop was not handled). Have you searched for an enhancement ticket in dev.vaadin.com ? If there ain’t one, feel free to create it.

If you end up implementing the feature by yourself, I’m happy to review and commit your patch.

cheers,
matti

6

Perhaps you could use ServerSideCriterion and on first accept() call make the component invisible, or something like that.