flutter

Question

自从更新到 Firebase 9.0.5 后，我在 event.snapshot.value 上遇到错误。我有很多这样的功能，在 firebase 8.X.

中运行良好

  Stream<List<MentorModel>> mentorStream() {
    final stream = _database.onValue;

    final Stream<List<MentorModel>> resultStream = stream.map((event) {
      List<MentorModel> _mentorList = [];
      Map<String, dynamic>.from(event.snapshot.value).forEach((key, value) => _mentorList.add(MentorModel.fromRTDB(key, value)));
      return _mentorList;
    });

    return resultStream;
  }

现在我在 event.snapshot.value 上有错误标记，android 工作室说

Error: The argument type 'Object?' can't be assigned to the parameter type 'Map<dynamic, dynamic>'.
 - 'Object' is from 'dart:core'.
 - 'Map' is from 'dart:core'.
      Map<String, dynamic>.from(event.snapshot.value).forEach((key, value) => _mentorList.add(MentorModel.fromRTDB(key, value)));

当我尝试时

Map<String, dynamic>.from(event.snapshot.value as Map<String, dynamic>).forEach((key, value) =>

然后错误标记消失了，但是当我运行应用程序时 returns

E/flutter (16737): [ERROR:flutter/shell/common/shell.cc(93)] Dart Unhandled Exception: type '_InternalLinkedHashMap<Object?, Object?>' is not a subtype of type 'Map<String, dynamic>' in type cast, stack trace:

Firebase 9.0 到底有什么变化？如何在 firebase 9.0 中遍历 event.snapshot.value？

Answer 1

从 Firebase v9 开始，他们从使用 dynamic 转移到 Object? 并且开始将 Object? 转换为 Map 可能会很麻烦，正如您所经历的那样。 .只需制作对象 dynamic 即可消除麻烦。

尝试：

Map<String, dynamic>.from(event.snapshot.value as dynamic).forEach((key, value) => _mentorList.add(MentorModel.fromRTDB(key, value)));

Answer 2

状态：json['statut'] != null ? (json['statut'] as List).map((i) => Statut.fromJson(Map.from(i as dynamic))).toList() ：空，

flutter - 自更新到 firebase 9 以来出现错误 event.snapshot.value。0.X

flutter - errors event.snapshot.value since updating to firebase 9.0.X

firebase

firebase-realtime-database