Adds the listener to the collection of listeners who will be notified when a drag and drop operation is in progress, by sending it one of the messages defined in the
DragSourceListener interface.
dragStart is called when the user has begun the actions required to drag the widget. This event gives the application the chance to decide if a drag should be started. dragSetData is called when the data is required from the drag source. dragFinished is called when the drop has successfully completed (mouse up over a valid target) or has been terminated (such as hitting the ESC key). Perform cleanup such as removing data from the source side on a successful move operation.
@param listener the listener which should be notified
@exception IllegalArgumentException
- ERROR_NULL_ARGUMENT - if the listener is null
@exception SWTException
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
@see DragSourceListener
@see #getDragListeners
@see #removeDragListener
@see DragSourceEvent