Bug 30655 [DND] Check selection in NavigatorDragAdapter.dragStart
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/navigator/NavigatorDragAdapter.java
LocalSelectionTransfer.getInstance().setSelection(selection);
		event.doit = true;
	}
	
	private IResource[] getSelectedResources(int resourceTypes) {
		List resources = new ArrayList();
		IResource[] result = new IResource[0];
		ISelection selection = selectionProvider.getSelection();
		if (!(selection instanceof IStructuredSelection) || selection.isEmpty()) {
			return null;
		}
		IStructuredSelection structuredSelection = (IStructuredSelection) selection;
		if (structuredSelection == null)
			return null;
		
		Iterator enum = structuredSelection.iterator();
		while (enum.hasNext()) {
			Object obj = enum.next();
			if (obj instanceof IResource) {
				IResource res = (IResource) obj;
				if ((res.getType() & resourceTypes) == res.getType()) {
					resources.add(res);
				}
			}
		}
		result = new IResource[resources.size()];
		resources.toArray(result);
		return result;
	}
}