不是转换类型的子类型（字符串，动态）=>MapEntry）

Question

我取一些产品从服务器，但我得到了一个错误，说明另一个例外被抛出：不正确使用家长DataWidget。同步快照

Incorrect use of ParentDataWidget.
The ParentDataWidget Flexible(flex: 1) wants to apply ParentData of type FlexParentData to a RenderObject, which has been set up to accept ParentData of incompatible type ParentData.

Usually, this means that the Flexible widget has the wrong ancestor RenderObjectWidget. Typically, Flexible widgets are placed directly inside Flex widgets.
The offending Flexible is currently placed inside a RepaintBoundary widget.

The ownership chain for the RenderObject that received the incompatible parent data was:
  RichText ← Text ← FutureBuilder<List<ProductsModel>> ← Container ← Flexible ← RepaintBoundary ← IndexedSemantics ← NotificationListener<KeepAliveNotification> ← KeepAlive ← AutomaticKeepAlive ← ⋯
When the exception was thrown, this was the stack: 
#0      RenderObjectElement._updateParentData.<anonymous closure> (package:flutter/src/widgets/framework.dart:5689:11)
#1      RenderObjectElement._updateParentData (package:flutter/src/widgets/framework.dart:5705:6)
#2      ParentDataElement._applyParentData.applyParentDataToChild (package:flutter/src/widgets/framework.dart:4939:15)
#3      ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:4600:14)
#4      ParentDataElement._applyParentData.applyParentDataToChild (package:flutter/src/widgets/framework.dart:4942:15)
...
Another exception was thrown: Incorrect use of ParentDataWidget.
AsyncSnapshot<List<ProductsModel>>(ConnectionState.waiting, null, type '(dynamic) => ProductsModel' is not a subtype of type '(String, dynamic) => MapEntry<dynamic, dynamic>' of 'transform')

这是我的ProductModel课程

class ProductsModel {
  String adid;
  String adsubcatid;
  String aduserid;
  String adname;
  String adcoverimg;
  String addesc;
  String adsPrice;
  String adsLocation;
  String createdDate;
  String userName;
  String images;

  ProductsModel(
      {this.adid,
        this.adsubcatid,
        this.aduserid,
        this.adname,
        this.adcoverimg,
        this.addesc,
        this.adsPrice,
        this.adsLocation,
        this.createdDate,
        this.userName,
        this.images});

  factory ProductsModel.fromJson(Map<String, dynamic> json) {
    return ProductsModel(
      adid: json['adid'],
      adsubcatid: json['adsubcatid'],
      aduserid: json['aduserid'],
      adname: json['adname'],
      adcoverimg: json['adcoverimg'],
      addesc: json['addesc'],
      adsPrice: json['ads_price'],
      adsLocation: json['ads_location'],
      createdDate: json['created_date'],
      userName: json['user_name'],
      images: json['images']
    );
  }
}

这是主页

@override
  void initState() {
    getProducts();
    super.initState();
  }

@override
  Widget build(BuildContext context) {
    print("Home");
    return Scaffold(
      appBar: AppBar(
        leading: Image.asset('assets/images/ic_logo.png'),
        actions: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: FlatButton.icon(
              onPressed: () {},
              icon: Icon(Icons.location_on),
              label: Text('Mysuru, India'),
              textColor: Colors.white,
            ),
          ),
        ],
      ),
      body: CustomScrollView(
        slivers: [
          SliverToBoxAdapter(
            child: SizedBox(
              child: _search(),
            ),
          ),
          SliverToBoxAdapter(
            child: SizedBox(
              child: HorizontalCategories(),
            ),
          ),
          SliverGrid(
            gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount: 2,
              childAspectRatio: 0.7,
            ),
            delegate: SliverChildBuilderDelegate(
                (context, index) => _products(context)),
          )
        ],
      ),
    );
  }

 Widget _products(BuildContext context) {
    print("Inside products");
    return Flexible(
      child: Container(
        child: FutureBuilder<List<ProductsModel>>(
          future: _fetchProducts(),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              print("Has data");
              List<ProductsModel> data = snapshot.data;
              return _productsList(data);
            } else if (snapshot.hasError) {
              print("Error");
              print(snapshot.hasError);
              print(snapshot);
              return Text('${snapshot.hasError}');
            } else {
              return Center(
                child: CircularProgressIndicator(),
              );
            }
          },
        ),
      ),
    );
  }

  Future<List<ProductsModel>> _fetchProducts() async {
    String productsUrl = Constant.productsUrl;
    Map<String, String> headers = {'Content-Type': 'application/json'};

    final response = await http.get(productsUrl, headers: headers);
    if (response.statusCode == 200) {
      var jsonResponse = json.decode(response.body);
      print(jsonResponse);
      return jsonResponse
          .map((products) => new ProductsModel.fromJson(products))
          .toList();
    } else {
      throw Exception('Failed to load Categories from API');
    }
  }

这是JsonResorts

{
    "status": true,
    "record": [
        {
            "adid": "1",
            "adsubcatid": "1",
            "aduserid": "2",
            "adname": "Ads",
            "adcoverimg": "Royal Enfield Classic 350 Images Classic 350 Photos & 360 View_files.JPG",
            "addesc": "vsv dsv  sd fds fd fdsf dsf s fds fdssfdf c sfdf sd",
            "ads_price": "3000",
            "ads_location": "mysore",
            "created_date": "06/10/2020",
            "user_name": "sunil",
            "images": "{'adsimg_img':'2.JPG'},{'adsimg_img':'3.JPG'},{'adsimg_img':'4.JPG'}"
        }
    ]
}

Answer 1

映射函数不能应用于jsonResponse。

return jsonResponse
          .map((products) => new ProductsModel.fromJson(products))
          .toList();

在记录字段中包含记录，这些记录应该映射到产品模型。

return jsonResponse
          .record
          .map((products) => new ProductsModel.fromJson(products))
          .toList();