code: private void adaptMessageTextSize() {
          if (getRootView() != null) {
              View messageView = getRootView().findViewById(android.R.id.message);
  
              if (messageView instanceof TextView) {
                  TextView messageTextView = (TextView) messageView;
  
                  if (TextUtils.isEmpty(getDialog().getTitle())) {
                      messageTextView.setTextSize(TypedValue.COMPLEX_UNIT_PX,
                              getContext().getResources()
                                      .getDimensionPixelSize(R.dimen.dialog_message_text_size_large));
                  } else {
                      messageTextView.setTextSize(TypedValue.COMPLEX_UNIT_PX,
                              getContext().getResources().getDimensionPixelSize(
                                      R.dimen.dialog_message_text_size_normal));
                  }
              }
          }
      }
docs: Adapts the text size of the dialog's message, depending on whether a title is shown.