横幅广告出现在每个屏幕上。如何在选定的屏幕上放置横幅广告？

Question

我在堆栈溢出时发现了相同的问题，但未得到回答。我加载横幅广告并仅在一个屏幕上显示，但是横幅广告出现在项目的每个屏幕上。 如何在选定的屏幕上放置横幅广告，如何在选定的屏幕上设置横幅广告的位置？我想在屏幕的右上方显示横幅广告。

import 'package:flutter/material.dart';
import 'package:firebase_admob/firebase_admob.dart';
import 'dart:async';
import 'package:video_player/video_player.dart';
import 'chewielistitem.dart';



class videoPlayer extends StatefulWidget {
  @override
  _videoPlayerState createState() => _videoPlayerState();
}

class _videoPlayerState extends State<videoPlayer> {
  int counter=0;
  static final MobileAdTargetingInfo targetingInfo = MobileAdTargetingInfo(
    keywords: ['Games', 'Puzzles'],
  );

  BannerAd bannerAd;
  InterstitialAd interstitialAd;
  RewardedVideoAd rewardedVideoAd;

  BannerAd buildBanner() {
    return BannerAd(
        adUnitId: BannerAd.testAdUnitId,
        size: AdSize.banner,
        listener: (MobileAdEvent event) {
          print(event);
        });
  }

  InterstitialAd buildInterstitial() {
    return InterstitialAd(
        adUnitId: InterstitialAd.testAdUnitId,
        targetingInfo: targetingInfo,
        listener: (MobileAdEvent event) {
          if (event == MobileAdEvent.failedToLoad) {
            interstitialAd..load();
          } else if (event == MobileAdEvent.closed) {
            interstitialAd = buildInterstitial()..load();
          }
          print(event);
        });
  }
  @override
  void initState() {
    super.initState();
    FirebaseAdMob.instance.initialize(appId: FirebaseAdMob.testAppId);
//    bannerAd = buildBanner()..load();
    interstitialAd = buildInterstitial()..load();
  }
  @override
  Widget build(BuildContext context) {

    Future<bool> _onBackPressed() {
      if(counter<1){
        interstitialAd
          ..load()
          ..show();
        counter++;
      }
      else{
        Navigator.pop(context, true);
      }

    }
//    Orientatoin();
    return WillPopScope(
      child: Scaffold(
          backgroundColor: Colors.black,
          body: Stack(
            children: <Widget>[
              ),

              ),
            ],
          )
      ),
      onWillPop: _onBackPressed,
    );
  }
}