Bug 127105 Package explorer hierarchical mode calls ICompilationUnit#getChildren() in PackageExplorerProblemTreeViewer#isExpandable
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
new ResourceTransferDragAdapter(fViewer),
			new FileTransferDragAdapter(fViewer)
		};
		fViewer.addDragSupport(ops, transfers, new JdtViewerDragAdapter(fViewer, dragListeners));
	}
	private void initDrop() {
		int ops= DND.DROP_COPY | DND.DROP_MOVE | DND.DROP_LINK | DND.DROP_DEFAULT;
		Transfer[] transfers= new Transfer[] {
			LocalSelectionTransfer.getInstance(), 
			FileTransfer.getInstance()};
		TransferDropTargetListener[] dropListeners= new TransferDropTargetListener[] {
			new SelectionTransferDropAdapter(fViewer),
			new FileTransferDropAdapter(fViewer),
			new WorkingSetDropAdapter(this)
		};
		fViewer.addDropSupport(ops, transfers, new DelegatingDropAdapter(dropListeners));
	}
	/**
	 * Handles post selection changed in viewer.
	 * 
	 * Links to editor (if option enabled).
	 */
	private void handlePostSelectionChanged(SelectionChangedEvent event) {
		ISelection selection= event.getSelection();
		
		
		if (isLinkingEnabled() && !selection.equals(fLastOpenSelection)) {
			linkToEditor((IStructuredSelection)selection);
		}
		fLastOpenSelection= null;