Firebase 引发了另一个异常：type'_MapStream<；查询快照、列表<；会计摘要>&燃气轮机'；不是类型为'；列表<；会计摘要>'；

这是firestore的服务

  Stream<List<AccountSummary>> get accountsStream {
    CollectionReference _accountReference = FirebaseFirestore.instance
        .collection('borrowers')
        .doc(uid)
        .collection('accounts');
    return _accountReference.snapshots().map((snapshot) => snapshot.docs
        .map((document) => AccountSummary.fromMap(document.data()))
        .toList());
  }

Stream获取帐户Stream{
CollectionReference\u accountReference=FirebaseFirestore.instance
.托收（“借款人”）
.doc（uid）
.收款（“账户”）；
返回_accountReference.snapshots（）.map（（snapshot）=>snapshot.docs
.map（（document）=>AccountSummary.fromMap（document.data（））
.toList（））；
}

这是小部件代码

  Widget build(BuildContext context) {
    final borrowerService =
        Provider.of<BorrowerService>(context, listen: false);
    final List<AccountSummary> accountlist =
        borrowerService.accountsStream ?? [];
    print(accountlist.length);
    return StreamBuilder<List<AccountSummary>>(
      stream: borrowerService.accountsStream,
      builder: (context, AsyncSnapshot<List<AccountSummary>> snapshot) {
        final List<AccountSummary> summary = snapshot.data;
        if (summary != null) {
          return ListView.builder(
            itemCount: summary.length,
            itemBuilder: (context, int index) {
              return AccountTile(summary[index]);
            },
          );
        }
        return Center(
          child: Text('Loading'),
        );
      },
    );
  }

小部件构建（构建上下文）{
最终借用服务=
Provider.of（上下文，listen:false）；
最终清单会计清单=
借款服务.accountsStream？？？[]；
打印（accountlist.length）；
返回流生成器(
stream:borrowerService.accountsStream，
生成器：（上下文，异步快照）{
最终列表摘要=snapshot.data；
如果（摘要！=null）{
返回ListView.builder(
itemCount:summary.length，
itemBuilder：（上下文，int索引）{
返回账户（汇总[索引]）；
},
);
}
返回中心(
子项：文本（'Loading'），
);
},
);
}

我在UI上收到此错误消息

引发了另一个异常：“映射流”类型不是“列表”类型的子类型 如何修复代码

这就是我在调试控制台中遇到的错误，我在面向对象编程方面做得不多，我认为这与没有获得所需的类有关，或者请提供帮助

═╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following _TypeError was thrown building AccountList(dirty):
type '_MapStream<QuerySnapshot, List<AccountSummary>>' is not a subtype of type
'List<AccountSummary>'
The relevant error-causing widget was:
  AccountList
  
lib\…\Borrowings\borrow_profile_screen.dart:66
When the exception was thrown, this was the stack:
#0      AccountList.build 
package:paisa/widgets/account_list.dart:12
#1      StatelessElement.build 
package:flutter/…/widgets/framework.dart:4620
#2      ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4546

#564    ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:4525
#565    ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4520
...     Normal element mounting (7 frames)
#572    SingleChildWidgetElementMixin.mount 
package:nested/nested.dart:223
...     Normal element mounting (7 frames)
#579    _NestedHookElement.mount 
package:nested/nested.dart:188
...     Normal element mounting (7 frames)
#586    SingleChildWidgetElementMixin.mount 
package:nested/nested.dart:223
#587    Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3490
#588    Element.updateChild 
package:flutter/…/widgets/framework.dart:3255
#589    ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4571
#590    StatefulElement.performRebuild 
package:flutter/…/widgets/framework.dart:4719
#591    Element.rebuild 
package:flutter/…/widgets/framework.dart:4262
#592    BuildOwner.buildScope 
package:flutter/…/widgets/framework.dart:2667
#593    WidgetsBinding.drawFrame 
package:flutter/…/widgets/binding.dart:866
#594    RendererBinding._handlePersistentFrameCallback 
package:flutter/…/rendering/binding.dart:286
#595    SchedulerBinding._invokeFrameCallback 
#596    SchedulerBinding.handleDrawFrame 
package:flutter/…/scheduler/binding.dart:1056
#597    SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> 
package:flutter/…/scheduler/binding.dart:865
(elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and dart:async-patch)
════════════════════════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by widgets library ═══════════════════════════════════
The following _TypeError was thrown building AccountList(dirty):
type '_MapStream<QuerySnapshot, List<AccountSummary>>' is not a subtype of type 'List<AccountSummary>'

The relevant error-causing widget was
    AccountList 
lib\…\Borrowings\borrow_profile_screen.dart:66
When the exception was thrown, this was the stack
#0      AccountList.build 
package:paisa/widgets/account_list.dart:12
#1      StatelessElement.build 
package:flutter/…/widgets/framework.dart:4620
#2      ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4546
#3      Element.rebuild 
package:flutter/…/widgets/framework.dart:4262
#4      ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:4525
...
═══════ Exception caught by widgets library ═══════════════════════════════════
type '_MapStream<QuerySnapshot, List<AccountSummary>>' is not a subtype of type 'List<AccountSummary>'
The relevant error-causing widget was
    AccountList 
lib\…\Borrowings\borrow_profile_screen.dart:66
════════════════════════════════════════════════════════════════════════════════

═╡ WIDGETS库捕获到异常╞═══════════════════════════════════════════════════════════
生成AccountList（脏）时引发了以下类型错误：
类型“\u MapStream”不是类型的子类型
“列表”
导致错误的相关小部件是：
会计清单
lib\…\Borrowings\borrow\u profile\u屏幕。省道：66
引发异常时，这是堆栈：
#0 AccountList.build
包：paisa/widgets/account\u list.dart:12
#1.build元素
包：flatter/../widgets/framework.dart:4620
#2 ComponentElement.PerformBuild
包：flatter/../widgets/framework.dart:4546
#564组件元素。\u首次构建
包：flatter/../widgets/framework.dart:4525
#565 ComponentElement.mount
包：flatter/../widgets/framework.dart:4520
...     正常元件安装（7个机架）
#572 SingleChildWidgetElement混合安装
包：嵌套/嵌套。省道：223
...     正常元件安装（7个机架）
#579 _NestedHookElement.mount
包装：嵌套/嵌套。省道：188
...     正常元件安装（7个机架）
#586 SingleChildWidgetElementMixin.mount
包：嵌套/嵌套。省道：223
#587 Element.inflateWidget
包：flatter/../widgets/framework.dart:3490
#588 Element.updateChild
包：flatter/../widgets/framework.dart:3255
#589 ComponentElement.performRebuild
包：flatter/../widgets/framework.dart:4571
#590 StatefulElement.PerformBuild
包：flatter/../widgets/framework.dart:4719
#591.重建元素
包：flatter/../widgets/framework.dart:4262
#592 BuildOwner.buildScope
包：flatter/../widgets/framework.dart:2667
#593 WidgetsBinding.drawFrame
包：flatter/../widgets/binding.dart:866
#594渲染器绑定。\u handlePersistentFrameCallback
包：flatter/../rendering/binding.dart:286
#595 SchedulerBinding.\u调用远程回调
#596 SchedulerBinding.handleDrawFrame
包：flatter/../scheduler/binding.dart:1056
#597 SchedulerBinding.scheduleWarmUpFrame。
包：flatter/../scheduler/binding.dart:865
（从类RawReceivePortImpl、类计时器、dart:async和dart:async补丁中删除了11帧）
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ widgets库捕获到异常═══════════════════════════════════
生成AccountList（脏）时引发了以下类型错误：
类型“\u MapStream”不是“List”类型的子类型
导致错误的相关小部件已被删除
会计清单
lib\…\Borrowings\borrow\u profile\u屏幕。省道：66
当抛出异常时，这是堆栈
#0 AccountList.build
包：paisa/widgets/account\u list.dart:12
#1.build元素
包：flatter/../widgets/framework.dart:4620
#2 ComponentElement.PerformBuild
包：flatter/../widgets/framework.dart:4546
#3.重建
包：flatter/../widgets/framework.dart:4262
#4组件元素。\u第一次构建
包：flatter/../widgets/framework.dart:4525
...
═══════ widgets库捕获到异常═══════════════════════════════════
类型“\u MapStream”不是“List”类型的子类型
导致错误的相关小部件已被删除
会计清单
lib\…\Borrowings\borrow\u profile\u屏幕。省道：66
════════════════════════════════════════════════════════════════════════════════

我发现代码有问题

    final List<AccountSummary> accountlist =
        borrowerService.accountsStream ?? [];
    print(accountlist.length);

最终清单会计清单=
借贷者服务.帐户流？？[];
打印（accountlist.length）；

这段代码就是问题所在。当我把它取下来的时候。它开始工作了

以前我尝试在没有StreamBuild的情况下构建小部件，但我忘记了清理代码。

您可以共享跟踪吗