Prevent flutter_admod banner from reloading

I use the banner in the admob_flutter package. I placed a banner on the first page. I initialize it in initState. When I go back from the sub-pages, the banner on the main page is recalled again. What can I do to have it already loaded when I come back? How do I keep loaded banner on the previous page.

AdmobBanner admobBanner;
AdmobBannerSize bannerSize;

@override
void initState() {

  bannerSize = AdmobBannerSize.BANNER;
  admobBanner = AdmobBanner(
    adUnitId: getBannerAdUnitId(),
    adSize: bannerSize,
  );
}

body: Stack(
  children: <Widget>[
    Align(
     alignment: Alignment.bottomCenter,
         child: admobBanner)
   ],
),