Checkbox is not firing event when onClick or onChange

I don't know why my checkbox is not firing event on jQuery. Here is my table structure:

div id=example1
--table
  --tr
      --td + icon to check line item
      --td setOff select box
      --td checkbox class="fill"

and I'm doing this:

jQuery('#example1').on('click','.fill',function(){
    alert($(this).is(":checked"));
   });

but it's not working, it doesn't alert(Hello) and i also tried onChange but still no alert.