Flutter :- 这个 AdWidget 已经在 Widget 树中了.如何禁用此异常.这是什么意思? [英] Flutter :- This AdWidget is already in the Widget tree. How to disable this exception. And what does it mean?

问题描述

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，新项目会添加到列表中.对于这些项目，我还在其中添加了 admob 广告.

So I insert admob ads inside the List. And I added the functionality of infinity scroll inside the list view. So when the user scrolls to end of the list, new items are added into the list. With this items I also add admob ads inside it.

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

So when the users scroll to the end the new items and ads are added into the List. At that time the below exceptions are caught. So how to solve this exception.

======== 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()));
    }

推荐答案

除了 Kafil Khan 的 answer，您还可以将带有 StatefulBuilder 的容器小部件.

In addition to Kafil Khan's answer, you can wrap the Container widget with StatefulBuilder.

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,
      ),
    );
  }

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