I agree with @youssef and @user17726418 answer, just adding extension to it if you are working with multiple states.

 BlocBuilder<UploadPhotoBloc, UploadPhotoState>(
      builder: (context, state) {
        if (state is UploadPhotosLoading) {
          return const LoadingButton();
        }
        return BlocBuilder<UserProfileBloc, UserProfileState>(
            builder: (context, state) {
          if (state is UserProfileLoading) {
            return const LoadingButton();
          } else {
            return CustomButton(
              title: 'Submit',
              onTapCallBack: () async {
                 // your logic
                },
               ),
            }
           })
        }),