problem drag&drop with the framework netBeans

Hello,
     I develop an IHM with the framework netBeans, approximately a treeTableView in an Explorer (inside a TopComponent)... I am setting up the drag&drop.  According to what I saw, all is already set up in the framework of netbeans. 
But in my application the drag&drop is "blocked" or inhibited. (I have the icon interdiction)
 I however authorized the drag and the drop (myTreeTableView.setDragSource(true) and myTreeTableView. setDropTarget(true), even I checked with isDragSource() and isDropTarget() = > ok) but nothing....  :-(

I surely forgot something ...  If you can help me or give me an example for implementation of the D&D with the platform netbeans.



Thank you in advance.

 Erwan.