Firebase 如何从带有flatter的文档的firestore数组中获取数据？

这是我在cloud fire store中的用户集合：

这是从firestore中的用户集合获取用户的函数

 Stream<QuerySnapshot> fetchUsersInSearch() {
    return Firestore.instance.collection('users').snapshots();
  }

在下面的streamBuilder中，通过电子邮件获取用户

我有这个streamBuilder来填充屏幕上的数据

return StreamBuilder<QuerySnapshot>(
        stream: DatabaseService().fetchUsersInSearch(),
        builder: (context, AsyncSnapshot<QuerySnapshot> snapshot) {

          final emailResults = snapshot.data.documents
              .where((u) => u['email'].contains(query));

          if (!snapshot.hasData) {
            return Container(
              color: Theme.of(context).primaryColor,
              child: Center(
                child: Text(
                  '',
                  style: TextStyle(
                      fontSize: 16, color: Theme.of(context).primaryColor),
                ),
              ),
            );
          }
          if (emailResults.length > 0) {
            return Container(
              color: Theme.of(context).primaryColor,
              child: ListView(
                children: emailResults
                    .map<Widget>((u) => GestureDetector(
                          child: Padding(
                            padding: const EdgeInsets.all(0.1),
                            child: Container(
                              padding: EdgeInsets.symmetric(vertical: 5),
                              decoration: BoxDecoration(
                                  color: Theme.of(context).primaryColor,
                                  border: Border(
                                      bottom: BorderSide(
                                          width: 0.3, color: Colors.grey[50]))),
                              child: ListTile(
                                leading: CircleAvatar(
                                        backgroundColor:
                                            Theme.of(context).primaryColor,
                                        backgroundImage:
                                            NetworkImage(u['userAvatarUrl']),
                                        radius: 20,
                                      ),
                                title: Container(
                                  padding: EdgeInsets.only(left: 10),
                                  child: Column(
                                    crossAxisAlignment:
                                        CrossAxisAlignment.start,
                                    children: [
                                      Text(u['email'],
                                          style: TextStyle(
                                              fontSize: 16,
                                              color: Theme.of(context)
                                                  .accentColor),
                                          overflow: TextOverflow.ellipsis),
                                      SizedBox(
                                        height: 5,
                                      ),
                                
                                    ],
                                  ),
                                ),
                                
                              ),
                            ),
                          ),
                          onTap: () {
                            showUserProfile(u['id']);
                          },
                        ))
                    .toList(),
              ),
            );
          } else {
            return Container(
              color: Theme.of(context).primaryColor,
              child: Center(
                child: Text(
                  'No results found',
                  style: TextStyle(
                    fontSize: 16,
                    color: Theme.of(context).accentColor,
                  ),
                ),
              ),
            );
          }
        });

但它返回了这个错误：

The method 'contains' was called on null.
Receiver: null
Tried calling: contains("#username1")

我做错了什么

任何帮助都将不胜感激。

试试以下方法：-

Stream<QuerySnapshot> getUsers() {
  final usersCollection = FirebaseFirestore.instance.collection('users');
  return usersCollection.where('otherUsernames', arrayContainsAny: ['username1', 'username2']);
}

Stream getUsers（）{
final usersCollection=FirebaseFirestore.instance.collection（'users'）；
返回usersCollection.where（'otherUsernames'，arrayContainsAny:['username1'，'username2']）；
}

---

对于firestore 0.16.0版

我对您的答案做了一些更正以使其生效：Stream getUsers（）{final users collection=firestore.instance.collection（'users'）.snapshots（）；return users collection.where（'otherUsernames'，arrayContainsAny:['username1'，'username2']）；}但至少这种方法让我很高兴，我们可以通过子集合搜索用户

The method 'contains' was called on null.
Receiver: null
Tried calling: contains("#username1")

Stream<QuerySnapshot> getUsers() {
  final usersCollection = FirebaseFirestore.instance.collection('users');
  return usersCollection.where('otherUsernames', arrayContainsAny: ['username1', 'username2']);
}