myEditText.addTextChangedListener(new TextWatcher() {
        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            //check count and do something
        }

        @Override
        public void afterTextChanged(Editable arg0) {
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }
    });