code: private void sendBeforeTextChanged(CharSequence text, int start, int before, int after) {
          final List<TextWatcher> list = mExternalTextWatchers;
          final int count = list.size();
          for (int i = 0; i < count; i++) {
              TextWatcher watcher = list.get(i);
              if (watcher != this) {
                  watcher.beforeTextChanged(text, start, before, after);
              }
          }
      }
docs: Notify external text watchers that the text is about to change.
  See {@link TextWatcher#beforeTextChanged(CharSequence, int, int, int)}.