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DragAndDropCommand move objects between different owners [message #1272822]

Tue, 18 March 2014 21:23

Dmitry Spiridenok

Messages: 12
Registered: August 2011

Junior Member

I'm trying to understand how org.eclipse.emf.edit.command.DragAndDropCommand class works.

I have the following EMF model:

Application
____|-> Node Element A
_______|-> Leaf Element 1
_______|-> Leaf Element 2
____|
____|-> Node Element B
_______|-> Leaf Element 10

What I would like is to move ("reparent") "Leaf Element 10" object from "Node Element B" to "Node Element A" in my Java code .
I can do that by creating 2 EMF commands for that:

    Command cmd = RemoveCommand.create(domain, NodeElement_B_Object, feature, LeafElement10Object);
    Command cmd = AddCommand.create(domain, NodeElement_A_Object, feature, LeafElement10Object, 0);

What I would like is move the object in 1 command, something like that:

    List coll = new ArrayList();
    coll.add(LeafElement10Object);
    Command cmd = DragAndDropCommand.create(domain, NodeElement_A_Object, 0.0F, DragAndDropFeedback.DROP_MOVE, DragAndDropFeedback.DROP_MOVE, coll);

However the drag&drop command canExecute() method returns false and the command does not get executed.
After some basic debugging of the class I see that prepare*() methods retrieve the parent of the owner object provided to the class (in my case the parent of "Node Element B" which is "Application") and try to operate on the parent instead of the owner object itself.

I've also read the Javadoc of the DragAndDropCommand class but it did not make it more clear to me how to work with this class.

So could you please tell me how I can perform such a model object move between different parents using an EMF command?
Also real-life examples on how to use DragAndDropCommand would be appreciated.

I'm new to EMF so I would really appreciate any support on this topic. Thank you in advance!

P.S. I've tried to use MoveCommand for that but as far as I can understand it moves only objects within a single owner object (in my example it would be moving "Leaf Element 1" to another location within "Node Element A" which is not what I want).

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Re: DragAndDropCommand move objects between different owners [message #1272871 is a reply to message #1272822]

Wed, 19 March 2014 00:52

Ed Merks

Messages: 33140
Registered: July 2009

Senior Member

Dimitry,

Drag and drop command is really intended to deal with drag and drop
behavior in a UI. For what you describe, you should just use a compound
command that composes the basic things you want to do in the model,
i.e., a remove followed by and add rather than try to figure out what
magical arguments will make a drag and drop command do that same thing
under the covers.

On 18/03/2014 2:23 PM, Dmitry Spiridenok wrote:
> I'm trying to understand how
> org.eclipse.emf.edit.command.DragAndDropCommand class works.
>
> I have the following EMF model:
>
> Application
> ____|-> Node Element A
> _______|-> Leaf Element 1
> _______|-> Leaf Element 2
> ____|
> ____|-> Node Element B
> _______|-> Leaf Element 10
> What I would like is to move ("reparent") "Leaf Element 10"
> object from "Node Element B" to "Node Element A" in my Java code .
> I can do that by creating 2 EMF commands for that:
> Command cmd = RemoveCommand.create(domain, NodeElement_B_Object,
> feature, LeafElement10Object);
> Command cmd = AddCommand.create(domain, NodeElement_A_Object,
> feature, LeafElement10Object, 0);
> What I would like is move the object in 1 command, something like that:
> List coll = new ArrayList();
> coll.add(LeafElement10Object);
> Command cmd = DragAndDropCommand.create(domain,
> NodeElement_A_Object, 0.0F, DragAndDropFeedback.DROP_MOVE,
> DragAndDropFeedback.DROP_MOVE, coll);
>
> However the drag&drop command canExecute() method returns false and
> the command does not get executed.
> After some basic debugging of the class I see that prepare*() methods
> retrieve the parent of the owner object provided to the class (in my
> case the parent of "Node Element B" which is "Application") and try to
> operate on the parent instead of the owner object itself.
>
> I've also read the Javadoc of the DragAndDropCommand class but it did
> not make it more clear to me how to work with this class.
>
> So could you please tell me how I can perform such a model object move
> between different parents using an EMF command?
> Also real-life examples on how to use DragAndDropCommand would be
> appreciated.
>
> I'm new to EMF so I would really appreciate any support on this topic.
> Thank you in advance!
>
> P.S. I've tried to use MoveCommand for that but as far as I can
> understand it moves only objects within a single owner object (in my
> example it would be moving "Leaf Element 1" to another location within
> "Node Element A" which is not what I want).

Ed Merks
Professional Support: https://www.macromodeling.com/

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