code: public void setUsernameStyle(@UsernameStyle int style) {
          if (style == EMAIL || !usernameRequired) {
              setDataType(DataType.EMAIL);
          } else if (style == USERNAME) {
              setDataType(DataType.USERNAME);
              String errorDescription = isCustomDatabase ? getResources().getString(R.string.com_auth0_lock_input_error_username_empty) :
                      getResources().getString(R.string.com_auth0_lock_input_error_username, minUsernameLength, maxUsernameLength);
              setErrorDescription(errorDescription);
          } else if (style == DEFAULT) {
              setDataType(DataType.USERNAME_OR_EMAIL);
          }
      }
docs: Choose username or email DataType, according to the Username Style.
  
  @param style to use in this username field