@UiHandler("previousButton")
 void uiOnPreviousClick(ClickEvent event) {
   onPreviousClickCallback.onSuccess(null);
 }
 @UiHandler("firstButton")
 void uiOnFirstClick(ClickEvent event) {
   onFirstClickCallback.onSuccess(null);
 }
 @UiHandler("nextButton")
 void uiOnNextClick(ClickEvent event) {
   onNextClickCallback.onSuccess(null);
 }
 @UiHandler("countryCode")
 void uiOnCountryChange(ChangeEvent event) {
   onCountryChangeCallback.onSuccess(null);
 }