firebase - 类型“_AssertionError”不是“字符串”类型的子类型

Question

我已经处理这个问题很长时间了。我正在尝试为每个用户（Uid）解析一组不受欢迎的项目。我得到了响应正文，它被转换为列表。但是我收到了这个错误：

======== Exception caught by widgets library =======================================================
The following _TypeError was thrown building FutureBuilder<dynamic>(dirty, state: _FutureBuilderState<dynamic>#7125a):
type '_AssertionError' is not a subtype of type 'String'

The relevant error-causing widget was: 
  FutureBuilder<dynamic> file:///C:/Users/arunb/AndroidStudioProjects/resplash/lib/pages/bookmark.dart:35:15
When the exception was thrown, this was the stack: 
#0      BookmarkPage.build.<anonymous closure> (package:resplash/pages/bookmark.dart:47:44)
#1      _FutureBuilderState.build (package:flutter/src/widgets/async.dart:775:55)
#2      StatefulElement.build (package:flutter/src/widgets/framework.dart:4691:27)
#3      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4574:15)
#4      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4746:11)
...

代码：

书签.dart

class BookmarkPage extends StatelessWidget {
  const BookmarkPage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final sb = context.watch<SignInBloc>();

    return RefreshIndicator(
      onRefresh: () async {
        await context.read<BookmarkBloc>().getData();
      },
      child: Scaffold(
        backgroundColor: Theme.of(context).primaryColor,
        appBar: AppBar(
          backgroundColor: Theme.of(context).primaryColor,
          centerTitle: false,
          title: Text('Saved Items'),
        ),
        body: sb.guestUser == true
            ? EmptyPage(
                icon: FontAwesomeIcons.heart,
                title: 'No wallpapers found.\n Sign in to access this feature',
              )
            : FutureBuilder(
                future: context.watch<BookmarkBloc>().getData(),
                builder: (BuildContext context, AsyncSnapshot snapshot) {
                  if (snapshot.hasData) {
                    if (snapshot.data.length == 0)
                      return EmptyPage(
                        icon: FontAwesomeIcons.heart,
                        title: 'No wallpapers found',
                      );
                    return _buildList(snapshot);
                  } else if (snapshot.hasError) {
                    return Center(
                      child: Text(snapshot.error),
                    );
                  }

                  return Center(
                    child: CupertinoActivityIndicator(),
                  );
                },
              ),
      ),
    );
  }

  Widget _buildList(snapshot) {
    return StaggeredGridView.countBuilder(
      crossAxisCount: 4,
      itemCount: snapshot.data.length,
      itemBuilder: (BuildContext context, int index) {
        List d = snapshot.data;

        return InkWell(
          child: Stack(
            children: <Widget>[
              Hero(
                  tag: 'bookmark$index',
                  child: cachedImage(d[index]['image url'])),
              Positioned(
                bottom: 15,
                left: 12,
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text(
                      d[index]['category'],
                      style: TextStyle(color: Colors.white, fontSize: 18),
                    )
                  ],
                ),
              ),
              Positioned(
                right: 10,
                top: 20,
                child: Row(
                  children: [
                    Icon(Icons.favorite,
                        color: Colors.white.withOpacity(0.5), size: 25),
                    Text(
                      d[index]['loves'].toString(),
                      style: TextStyle(
                          color: Colors.white.withOpacity(0.7),
                          fontSize: 16,
                          fontWeight: FontWeight.w600),
                    ),
                  ],
                ),
              ),
            ],
          ),
          onTap: () {
            Navigator.push(
                context,
                MaterialPageRoute(
                    builder: (context) => DetailsPage(
                          tag: 'bookmark$index',
                          imageUrl: d[index]['image url'],
                          catagory: d[index]['category'],
                          timestamp: d[index]['timestamp'],
                        )));
          },
        );
      },
      staggeredTileBuilder: (int index) =>
          new StaggeredTile.count(2, index.isEven ? 4 : 3),
      mainAxisSpacing: 10,
      crossAxisSpacing: 10,
      padding: EdgeInsets.all(15),
    );
  }
}

getData() 方法

final FirebaseFirestore firestore = FirebaseFirestore.instance;

  getData() async {
    SharedPreferences sp = await SharedPreferences.getInstance();
    String _uid = sp.getString('uid');

    final DocumentReference ref = firestore.collection('users').doc(_uid);
    DocumentSnapshot snap = await ref.get();
    List d = snap['loved items'];
    List filteredData = [];
    if (d.isNotEmpty) {
      await firestore
          .collection('contents')
          .where('timestamp', whereIn: d)
          .get()
          .then((QuerySnapshot snap) {
        filteredData = snap.docs;
      });
    }

    notifyListeners();
    return filteredData;
  }

我怎么解决这个问题？我不完全知道是什么原因以及如何解决这个问题。

标签： firebaseflutterdartgoogle-cloud-firestore

Answer 1

不能仅根据此信息确定，但我最好的猜测是

firestore
   .collection('contents')
   .where('timestamp', whereIn: d)
   .get() 

正在返回错误。

但是我建议您充分利用 await，因为您正在使用它。还要在 get() 方法上添加一个捕获。所以做类似的事情：

if (d.isNotEmpty) {
    try {
      const snapshot:QuerySnapshot = await firestore
          .collection('contents')
          .where('timestamp', whereIn: d)
          .get();
          (*)
      fiteredData = snapshot.docs
    }
    catch(e) {
      console.log(e)
      // or/and error handling
    }
}

(*)您还可以尝试在代码 ( (*)) 中的星号位置记录快照以尝试追踪错误（如果您认为分配有可能导致问题）

我不确定这是否能解决您的问题（如果没有可重现的示例，很难确切知道出了什么问题），但它至少应该可以帮助您找出问题所在。