android TextWatcher

    private class SearchFieldWatcher implements TextWatcher {
        @Override
        public void afterTextChanged(Editable s) {
        }

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

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            mSearchButton.setEnabled(s.length() > 0);
        }
    }