Flutter :- 这个 AdWidget 已经在 Widget 树中了。如何禁用此异常。这是什么意思？

Question

所以我在列表中插入了 admob 广告。我在列表视图中添加了无限滚动的功能。因此，当用户滚动到列表末尾时，新项目将添加到列表中。对于这些项目，我还在其中添加了 admob 广告。

因此，当用户滚动到末尾时，新项目和广告将添加到列表中。那时捕获了以下异常。那么如何解决这个异常。

======== Exception caught by widgets library =======================================================
The following assertion was thrown building AdWidget-[#53ef3](dirty, state: _AdWidgetState#850ac):
This AdWidget is already in the Widget tree


If you placed this AdWidget in a list, make sure you create a new instance in the builder function with a unique ad object.
Make sure you are not using the same ad object in more than one AdWidget.

The relevant error-causing widget was: 
  AdWidget-[#53ef3] file:///D:/flutter%20project/memer/lib/pages/TimeLinePage.dart:198:42
When the exception was thrown, this was the stack: 
#0      _AdWidgetState.build (package:google_mobile_ads/src/ad_containers.dart:371:7)
#1      StatefulElement.build (package:flutter/src/widgets/framework.dart:4612:27)
#2      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4495:15)
#3      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4667:11)
#4      Element.rebuild (package:flutter/src/widgets/framework.dart:4189:5)

代码：-

return ListView.builder(itemBuilder: (context, index){
        //print(posts);
        if(posts[index] is Post){
          return posts[index];
        }
        else{
          final Container adContainer = Container(
                                  alignment: Alignment.center,
                                  child: AdWidget(key: UniqueKey(), ad: posts[index] as BannerAd),//AdmobService.createBannerAd()..load()
                                  height: 50,
                              );
                      return adContainer;
        }
      },itemCount: posts.length,
          controller: scrollController,physics: const BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics()));
    }

Answer 1

当您想添加一个新横幅时，您必须为其分配一个新 ID：

BannerAd(adUnitId: 'somethingDifferentThanTheOneInTheTree')

正如错误日志中明确指出的那样：

If you placed this AdWidget in a list, make sure you create a new instance in the builder function with a unique ad object. Make sure you are not using the same ad object in more than one AdWidget.

Answer 2

问题是您一次又一次地放置同一个小部件。您可以通过创建一个新的 StatefulWidget class 并返回 Adwidget 来解决这个问题，这将多次构建相同的小部件，它的工作方式类似于 Builder。这解决了我的问题，希望它也对你有用！ :)

您也不必为单个广告单元提供多个 ID。

Answer 3

除了 Kafil Khan 的，您还可以使用 StatefulBuilder 包装容器小部件。

示例：

Widget bannerAdWidget() {
    return StatefulBuilder(
      builder: (context, setState) => Container(
        child: AdWidget(ad: _bannerAd),
        width: _bannerAd.size.width.toDouble(),
        height: 100.0,
        alignment: Alignment.center,
      ),
    );
  }

Answer 4

如上，只是我将我的实现放在这里，以便将来的新手对他们来说更容易。

首先，让我们创建一个名为 ad_helper 的助手 class 来隐藏我们 UI 的所有内容，其中包含两个辅助方法：

第一个方法是 buildBannerWidget，它是一个 public 方法来按照我们的意愿构建我们的广告小部件。

第二个方法是 _instantiateBanner，它是一个私有方法，每次我们调用 buildBannerWidget 方法时都会构建我们的 bannerAd 对象。

class Ads {
 static BannerAd? _banner;

  static Future<Widget> buildBannerWidget({
    required BuildContext context,
  }) async {
    final mediaQuery = MediaQuery.of(context);

    await _instantiateBanner(
      mediaQuery.orientation,
      mediaQuery.size.width.toInt(),
    );

    return Container(
      width : MediaQuery.of(context).size.width,
      height : 70,
      child: AdWidget(ad: _banner!),
    );
  }

  static Future<BannerAd> _instantiateBanner(orientation, width) async {
    _banner = BannerAd(
      adUnitId: BannerAd.testAdUnitId,
      //  size: AdSize.banner,
      size: (await AdSize.getAnchoredAdaptiveBannerAdSize(orientation, width))!,
      request: _getBannerAdRequest(),
      listener: _buildListener(),
    );
    await _banner?.load();
    return _banner!;
  }

  static AdRequest _getBannerAdRequest() {
    return AdRequest();
  }

  static BannerAdListener _buildListener() {
    return BannerAdListener(
      onAdOpened: (Ad ad) {
        print('${Constants.Tag} BannerAdListener onAdOpened ${ad.toString()}.');
      },
      onAdClosed: (Ad ad) {
        print('${Constants.Tag} BannerAdListener onAdClosed ${ad.toString()}.');
      },
      onAdImpression: (Ad ad) {
        print(
            '${Constants.Tag} BannerAdListener onAdImpression ${ad.toString()}.');
      },
      onAdWillDismissScreen: (Ad ad) {
        print(
            '${Constants.Tag} BannerAdListener onAdWillDismissScreen ${ad.toString()}.');
      },
      onPaidEvent: (
        Ad ad,
        double valueMicros,
        PrecisionType precision,
        String currencyCode,
      ) {
        print('${Constants.Tag} BannerAdListener PaidEvent ${ad.toString()}.');
      },
      onAdLoaded: (Ad ad) {
        print('${Constants.Tag} BannerAdListener onAdLoaded ${ad.toString()}.');
      },
      onAdFailedToLoad: (Ad bannerAd, LoadAdError error) {
        bannerAd.dispose();
        print(
            '${Constants.Tag} BannerAdListener onAdFailedToLoad error is ${error.responseInfo} | ${error.message} | ${error.code} | ${error.domain}');
      },
    );
  }

  static void disposeBanner() {
   _banner?.dispose();
  }
 }

第二步是我们的 UI 将是我们的小部件：

FutureBuilder<Widget>(
      future: Ads.buildBannerWidget(
        context: context,
      ),
      builder: (_, snapshot) {
        if (!snapshot.hasData)return Text("No Banner yet");

          return Container(
            height: 90,
            width: MediaQuery.of(context).size.width,
            child: snapshot.data,
          );
    
      },
    )

Answer 5

我尝试了所有这些，但只有以下对我有用。我在每个页面上添加了 myBanner.dispose() 到 iniState。

void initState(){
  myBanner.dispose();
  myBanner.load();
  super.initState();
}

Answer 6

#Step-1：创建有状态 Class 如下所示：

import 'package:flutter/cupertino.dart';
import 'package:google_mobile_ads/google_mobile_ads.dart';

class BannerAdmob extends StatefulWidget{
  @override
  State<StatefulWidget> createState() {
    return _BannerAdmobState();
  }
}

class _BannerAdmobState extends State<BannerAdmob>{

  late BannerAd _bannerAd;
  bool _bannerReady = false;

  @override
  void initState() {
    super.initState();
    _bannerAd = BannerAd(
      adUnitId: "ca-app-pub-3940256099942544/6300978111",
      request: const AdRequest(),
      size: AdSize.largeBanner,
      listener: BannerAdListener(
        onAdLoaded: (_) {
          setState(() {
            _bannerReady = true;
          });
        },
        onAdFailedToLoad: (ad, err) {
          setState(() {
            _bannerReady = false;
          });
          ad.dispose();
        },
      ),
    );
    _bannerAd.load();
  }

  @override
  void dispose() {
    super.dispose();
    _bannerAd.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return _bannerReady?SizedBox(
      width: _bannerAd.size.width.toDouble(),
      height: _bannerAd.size.height.toDouble(),
      child: AdWidget(ad: _bannerAd),
    ):Container();
  }
}

#Step-2：如下使用：

@override
Widget build(BuildContext context){
  return BannerAdmob();
}

Flutter :- 这个 AdWidget 已经在 Widget 树中了。如何禁用此异常。这是什么意思？

Flutter :- This AdWidget is already in the Widget tree. How to disable this exception. And what does it mean?

flutter

admob

flutter-dependencies

firebase-admob