final TreeViewer viewer = new TreeViewer(shell, SWT.NONE);
		
		DelegatingDragAdapter dragAdapter = new DelegatingDragAdapter();		
		dragAdapter.addDragSourceListener(new TransferDragSourceListener() {
			public Transfer getTransfer() {
				return TextTransfer.getInstance();
			>to 
 every listener, and checking if the {@link DragSourceEvent#doit doit} field is left 
 set to true.
 
 
 The DragSource's set of supported Transfer types ({@link
 DragSource#setTransfer(Transfer[])}) is updated to reflect the Transfer types
 corresponding to the active listener subset.
 

 If and when {@link #dragSetData(DragSourceEvent)} is called, a single
 TransferDragSourceListener is chosen, and only it is allowed to set the
 drag data. The chosen listener is the first listener in the subset of active listeners
 whose Transfer supports ({@link Transfer#isSupportedType(TransferData)}) the 
 dataType in the DragSourceEvent.
 
 

 The following example snippet shows a DelegatingDragAdapter with two
 TransferDragSourceListeners. One implements drag of text strings, 
 the other supports file transfer and demonstrates how a listener can be disabled using
 the dragStart method. 
 
 
		final TreeViewer viewer = new TreeViewer(shell, SWT.NONE);
		
		DelegatingDragAdapter dragAdapter = new DelegatingDragAdapter();		
		dragAdapter.addDragSourceListener(new TransferDragSourceListener() {
			public Transfer getTransfer() {
				return TextTransfer.getInstance();
			 55 
			public void dragStart(DragSourceEvent event) {
				// always enabled, can control enablement based on selection etc.
			}
			public void dragSetData(DragSourceEvent event) {
				event.data = "Transfer data";
			}
			public void dragFinished(DragSourceEvent event) {
				// no clean-up required
			}
		});
		dragAdapter.addDragSourceListener(new TransferDragSourceListener() {
			public Transfer getTransfer() {
				return FileTransfer.getInstance();
			}
			public void dragStart(DragSourceEvent event) {
				// enable drag listener if there is a viewer selection
				event.doit = !viewer.getSelection().isEmpty();
			}
			public void dragSetData(DragSourceEvent event) {
				File file1 = new File("C:/temp/file1");
				File file2 = new File("C:/temp/file2");
				event.data = new String[] {file1.getAbsolutePath(), file2.getAbsolutePath()};
			}
			public void dragFinished(DragSourceEvent event) {
				// no clean-up required
			}
		});
		viewer.addDragSupport(DND.DROP_COPY | DND.DROP_MOVE, dragAdapter.getTransfers(), dragAdapter);
 
 

 NOTE: This API is experimental and subject to change including removal.
 




Since:
  
2.2













Field Summary



private  java.util.List
activeListeners



           



private  TransferDragSourceListener
currentListener



           



private  java.util.List
listeners



           


 






Constructor Summary


DelegatingDragAdapter()



           


 






Method Summary



 void
addDragSourceListener(TransferDragSourceListener listener)



          Adds the given TransferDragSourceListener.



 void
dragFinished(org.eclipse.swt.dnd.DragSourceEvent event)



          The drop has successfully completed.



 void
dragSetData(org.eclipse.swt.dnd.DragSourceEvent event)



          The drop data is requested.



 void
dragStart(org.eclipse.swt.dnd.DragSourceEvent event)



          A drag operation has started.



 org.eclipse.swt.dnd.Transfer[]
getTransfers()



          Returns the Transfers from every TransferDragSourceListener.



 boolean
isEmpty()



          Returns true if there are no listeners to delegate drag events to.



 void
removeDragSourceListener(TransferDragSourceListener listener)



          Removes the given TransferDragSourceListener.



private  void
updateCurrentListener(org.eclipse.swt.dnd.DragSourceEvent event)



          Updates the current listener to one that can handle the drag.


 


Methods inherited from class java.lang.Object


clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait


 








Field Detail




listeners
private java.util.List listeners







activeListeners
private java.util.List activeListeners







currentListener
private TransferDragSourceListener currentListener











Constructor Detail




DelegatingDragAdapter
public DelegatingDragAdapter()









Method Detail




addDragSourceListener
public void addDragSourceListener(TransferDragSourceListener listener)

Adds the given TransferDragSourceListener.











dragFinished
public void dragFinished(org.eclipse.swt.dnd.DragSourceEvent event)

The drop has successfully completed. This event is forwarded to the current 
 drag listener.
 Doesn't update the current listener, since the current listener  is already the one
 that completed the drag operation.


Specified by:
dragFinished in interface org.eclipse.swt.dnd.DragSourceListener








dragSetData
public void dragSetData(org.eclipse.swt.dnd.DragSourceEvent event)

The drop data is requested.
 Updates the current listener and then forwards the event to it.


Specified by:
dragSetData in interface org.eclipse.swt.dnd.DragSourceListener








dragStart
public void dragStart(org.eclipse.swt.dnd.DragSourceEvent event)

A drag operation has started.
 Forwards this event to each listener. A listener must set event.doit 
 to false if it cannot handle the drag operation. If a listener can  
 handle the drag, it is added to the list of active listeners.  
 The drag is aborted if there are no listeners that can handle it.


Specified by:
dragStart in interface org.eclipse.swt.dnd.DragSourceListener








getTransfers
public org.eclipse.swt.dnd.Transfer[] getTransfers()

Returns the Transfers from every TransferDragSourceListener.











isEmpty
public boolean isEmpty()

Returns true if there are no listeners to delegate drag events to.











removeDragSourceListener
public void removeDragSourceListener(TransferDragSourceListener listener)

Removes the given TransferDragSourceListener.
 Listeners should not be removed while a drag and drop operation is in progress.











updateCurrentListener
private void updateCurrentListener(org.eclipse.swt.dnd.DragSourceEvent event)

Updates the current listener to one that can handle the drag. There can 
 be many listeners and each listener may be able to handle many TransferData 
 types.  The first listener found that supports one of the TransferData 
 types specified in the DragSourceEvent will be selected.

















  

  
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