how to add my button in refrence in java? : 
i want to add and sub counter but i can only added "add" in R.Java
[![enter image description here][1]][1]and can't added "sub" in R.Java .and i have this error in my program 
"btnsub cannot be resolved or is not a field"?
Thank you;


  [1]: http://i.stack.imgur.com/R6Gyd.jpg