Conflict of "addSelectionChangedListener" and "addDoubleClickListener" for TableViewer

Conflict of "addSelectionChangedListener" and "addDoubleClickListener" for
TableViewer

all related
With JFace TableViewer,I want to select some entry(e.g select a file) by
single-click, and do some other operations(e.g go into a directory) by
double-click.
Noticing addSelectionChangedListener() and addDoubleClickListener() via a
webpage: http://javafact.com/2010/08/07/example-tableviewer-events/ , I
add "SelectionChangedListener" and "DoubleClickListener" for my
TableViwer, and find out: Either of the two listeners can work, but they
can't work together - actually it's DoubleClickListener that can't work.
What's the problem? How I should implement listeners for single-click and
double-clicks? Any comments is appreciated.
Regards & Thanks from Sunzen