How to add clickhandler on ImageCell in GWT CellTable?

I have tried this but didn't work

Column<ContactInfo, String> imageColumn = new Column<ContactInfo, String>(new ImageCell()) {
       @Override
       public String getValue(ContactInfo object) {
           return "contact.jpg";
          }
        };
        imageColumn.setFieldUpdater(new FieldUpdater<ContactInfo, String>() {

        @Override
        public void update(int index, ContactInfo object, String value) {
        Window.alert("You clicked " + object.firstName);
        }

    });
cellTable.addColumn(imageColumn, SafeHtmlUtils.fromSafeConstant("<br/>"));