Dart错误：未处理的异常：类型'_InternalLinkedHashMap <string，dynamic =“”>'不是类型'Map <string，map <string，=“” dynamic =“” >>>>'

时间：2019-03-16 09:55:31

标签： dart flutter

我正在开发一个flutter项目，并且被困在必须从firebase检索数据的地方。 我想获取“产品”的数据，这些是我产品中的字段。

class Product {
  final String product_id;
  final String title;
  final String description;
  final double price;
  final String image;
  final bool isFavorite;
  final String id;
  final String email;

  Product({
    @required this.product_id,
    @required this.title,
    @required this.description,
    @required this.image,
    @required this.price,
    @required this.email,
    @required this.id,
    this.isFavorite = false,
  });
}

这就是我存储数据的方式。

Map<String, dynamic> productdata = {
      'title': title,
      'description': description,
      'image':
      'https://upload.wikimedia.org/wikipedvdkfjngjsdnga/a5.jpg',
      'price': price,
      'id': _authenticatedUser.id,
      'email':_authenticatedUser.email,
    };
    http
        .post('https://flutter-blah_blah.firebaseio.com/products.json',
        body: json.encode(productdata));

当我运行get命令以检索数据时 得到赞扬：

http.get('https://flutter-blah_blah.firebaseio.com/products.json')
        .then((http.Response response) {
          print(json.decode(response.body));

我得到上面代码的输出

{-L_x5_aGpDN-bbrqqqqi: {description: kkkkkkk, email: abc@gmail.com, id: fghjdgf, image: https://upload.wikimedia.org/wikipedia/commons/a/a5/Red_Kitten_01.jpg, price: 111.0, title: kitten}, -L_x7ffhrotslg4vS: {description: kkkkkkkk, email: abc@gmail.com, id: fghjdgf, image: https://upload.wikimedia.org/wikipedia/commons/a/a5/Red_Kitten_01.jpg, price: 111.0, title: kitten 2}}

您可以清楚地看到，我的firebase表中已经有2行。 但是之后，我在函数的下一个命令中遇到了问题，即：

final Map<String, Map<String, dynamic>> productListData = json.decode(response.body);

我遇到了一个大错误 错误：

I/flutter ( 6106): _InternalLinkedHashMap<String, dynamic>
E/flutter ( 6106): [ERROR:flutter/shell/common/shell.cc(186)] Dart Error: Unhandled exception:
E/flutter ( 6106): type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Map<String, Map<String, dynamic>>'
E/flutter ( 6106): #0      _MainModel&Model&ConnectedProduct&UserModel&ProductsModel.fetchProducts.<anonymous closure> (package:udemy/scoped_models/connected_product.dart:109:47)
E/flutter ( 6106): #1      _RootZone.runUnary (dart:async/zone.dart:1379:54)
E/flutter ( 6106): #2      _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
E/flutter ( 6106): #3      Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
E/flutter ( 6106): #4      Future._propagateToListeners (dart:async/future_impl.dart:668:32)
E/flutter ( 6106): #5      Future._complete (dart:async/future_impl.dart:473:7)
E/flutter ( 6106): #6      _SyncCompleter.complete (dart:async/future_impl.dart:51:12)
E/flutter ( 6106): #7      _AsyncAwaitCompleter.complete (dart:async/runtime/libasync_patch.dart:28:18)
E/flutter ( 6106): #8      _completeOnAsyncReturn (dart:async/runtime/libasync_patch.dart:294:13)
E/flutter ( 6106): #9      _withClient (package:http/http.dart)
E/flutter ( 6106): <asynchronous suspension>
E/flutter ( 6106): #10     get (package:http/http.dart:46:5)
E/flutter ( 6106): #11     _MainModel&Model&ConnectedProduct&UserModel&ProductsModel.fetchProducts (package:udemy/scoped_models/connected_product.dart:104:5)
E/flutter ( 6106): #12     _ProductPageState.initState (package:udemy/pages/products.dart:21:18)
E/flutter ( 6106): #13     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3830:58)
E/flutter ( 6106): #14     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3696:5)
E/flutter ( 6106): #15     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #16     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #17     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4860:14)
E/flutter ( 6106): #18     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #19     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #20     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3732:16)
E/flutter ( 6106): #21     Element.rebuild (package:flutter/src/widgets/framework.dart:3547:5)
E/flutter ( 6106): #22     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3701:5)
E/flutter ( 6106): #23     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3696:5)
E/flutter ( 6106): #24     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #25     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #26     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4860:14)
E/flutter ( 6106): #27     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #28     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #29     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4860:14)
E/flutter ( 6106): #30     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #31     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #32     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4860:14)
E/flutter ( 6106): #33     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #34     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #35     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4860:14)
E/flutter ( 6106): #36     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #37     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #38     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3732:16)
E/flutter ( 6106): #39     Element.rebuild (package:flutter/src/widgets/framework.dart:3547:5)
E/flutter ( 6106): #40     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3701:5)
E/flutter ( 6106): #41     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3848:11)
E/flutter ( 6106): #42     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3696:5)
E/flutter ( 6106): #43     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2950:14)
E/flutter ( 6106): #44     Element.updateChild (package:flutter/src/widgets/framework.dart:2753:12)
E/flutter ( 6106): #45     ComponentElement.performRebuild (packag

该如何解决？ 我需要将解码后的响应存储在Map <\ string，Map <\ string，dynamic >>变量中，使用forEach命令遍历每个元素/行，并将其存储在“ Product”类型的列表中（Product类为并在我的应用页面上显示。 我该怎么办？

1 个答案:

答案 0 :(得分：0)

只需更改

final Map<String, Map<String, dynamic>> productListData = json.decode(response.body)

到

final Map<String, Map<String, dynamic>> productListData = json.decode(response.body)?.cast<String, Map<String, dynamic>>();

希望有帮助！

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