Adds the listener to the collection of listeners who will
be notified when a drag gesture occurs, by sending it
one of the messages defined in the <code>DragDetectListener</code>
interface.
@param listener the listener which should be notified
@exception IllegalArgumentException <ul>
<li>ERROR_NULL_ARGUMENT - if the listener is null</li>
</ul>
@exception SWTException <ul>
<li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
<li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
</ul>
Adds the listener to the collection of listeners who will be notified when a drag gesture occurs, by sending it one of the messages defined in the <code>DragDetectListener</code> interface.
@param listener the listener which should be notified
@exception IllegalArgumentException <ul> <li>ERROR_NULL_ARGUMENT - if the listener is null</li> </ul> @exception SWTException <ul> <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> </ul>
@see DragDetectListener @see #removeDragDetectListener
@since 3.3