firebase - Flutter Cloud Firestore Map 错误

Question

我正在尝试使用 Flutter 和 Firestore 构建应用程序。使用 StreamBuilder 从 Firestore 加载集合以在 ListView 中显示时，出现以下错误

The following assertion was thrown building StreamBuilder<QuerySnapshot>(dirty, state:
I/flutter (26287): _StreamBuilderBaseState<QuerySnapshot, AsyncSnapshot<QuerySnapshot>>#d5638):

I/flutter (26287): type '_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, dynamic>'

I/flutter (26287): where

I/flutter (26287):   _InternalLinkedHashMap is from dart:collection

I/flutter (26287):   Map is from dart:core

I/flutter (26287):   String is from dart:core

这就是我想要从 DocumentSnapshot 获取数据的方式

class Creator {
  const Creator({this.creatorId, this.name});

  Creator.fromDoc(DocumentSnapshot doc) : this.fromMap(doc.data);

  Creator.fromMap(Map<String, dynamic> map) :
    assert(map.containsKey('creatorId'),
    assert(map.containsKey('name'),
    this ( creatorId: map['creatorId'], name: map['name'] );

  /*

  ...

  */
}

以及我想如何使用它

return Scaffold(
  appBar: AppBar(title: new Text('Creators')),
  body: StreamBuilder<QuerySnapshot>(
    stream: CreatorRepo.getCreators().map<List<Creator>>((creators) {
      return creators.documents.map<Creator>((c) => Creator.fromSnapshot(c)).toList();
    }),
    builder: (BuildContext context, snapshot) {
      if ( snapshot.hasData ) {
        return ListView.builder(
          itemCount: snapshot.data.length,
          builder: (context, index) {
            final creator = snapshot.data[index];

            return ExpansionTile(
              title: Text(creator.name),
              children: [
                Text(creator.creatorId),
              ],
            );
          },
        );
      }

      return const CircularProgressIndicator();
    },
  ),
);

依赖关系:

dependencies:
  flutter:
    sdk: flutter

  cloud_firestore: ^0.6.3
  firebase_messaging: ^0.2.4

Firestore 仅允许 String键和 dynamic值是，Timestamp 除外，核心语言类型。 cloud_firestore插件将文档数据保存在 _InternalLinkedHashMap<dynamic, dynamic> 中.我以为 Map全部DocumentSnapshot将是 Map<String, dynamic> .我该如何解决这个问题？更改所有功能以获取 Map<dynamic, dynamic>并假设 key 是 String是一个相当丑陋的解决方法。

Answer 1

我相信这是因为从 Firebase 返回的 map 不是 Map<String, dynamic>而是 Map<dynamic, dynamic> .

见 https://github.com/flutter/flutter/issues/17417相关问题。