Bug 5774 Unpredicatable behaviour on double click in packages view
from EC: If you double click a file in the packages view, it opens the file (technically, compilation unit I believe) -- if not already open. However, if the file is already open, a single click selects it as the active editor tag; a double click expands its structure in the packages view. This is unpredictable behavior ;
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
if (! clazz.isInstance(resource))
					return false;
			}
		}
		return true;	
	}
	
	
	
	private void initDragAndDrop() {
		int ops= DND.DROP_COPY | DND.DROP_MOVE;
		final LocalSelectionTransfer lt= LocalSelectionTransfer.getInstance();
		Transfer[] transfers= new Transfer[] {lt, FileTransfer.getInstance()};
		
		
		TransferDropTargetListener[] dropListeners= new TransferDropTargetListener[] {
			new SelectionTransferDropAdapter(fViewer),
			new FileTransferDropAdapter(fViewer)
		};
		fViewer.addDropSupport(ops, transfers, new DelegatingDropAdapter(dropListeners));
		
		
		Control control= fViewer.getControl();
		TransferDragSourceListener[] dragListeners= new TransferDragSourceListener[] {
			new SelectionTransferDragAdapter(fViewer),
			new FileTransferDragAdapter(fViewer)
		};
		DragSource source= new DragSource(control, ops);
		
		source.addDragListener(new DelegatingDragAdapter(dragListeners));