未处理的异常：“String”类型不是“List”类型的子类型<dynamic> &#39;

Question

我试图从解析图像images从JSON响应，但我得到的错误，指出为未处理的异常：类型“字符串”不是类型的子类型“列表”

{
    "status": true,
    "record": {
        "adid": "3",
        "adsubcatid": "7",
        "aduserid": "2",
        "adname": "wfw fw",
        "adcoverimg": "http://codecell.in/girrivi/assets/adcover/ic_service_search.png",
        "addesc": "e fe fe ",
        "ads_price": "5000",
        "ads_location": "mysuru",
        "created_date": "13/10/2020",
        "user_name": "sunil",
        "images": "{'adsimg_img':'http://codecell.in/girrivi/assets/adimgs/carpenter.png'},{'adsimg_img':'http://codecell.in/girrivi/assets/adimgs/electrician.png'},{'adsimg_img':'http://codecell.in/girrivi/assets/adimgs/gardner.png'}"
    }
}

List images;
Future<String> getProductDetails() async {
    String productDetailsUrl = Constant.productDetailsUrl+widget.id;
    print(productDetailsUrl);
    Map<String, String> headers = {'Content-Type' : 'application/json'};

    final response = await http.get(productDetailsUrl, headers: headers);
    print(response.body);
    if(response.statusCode == 200){
      jsonResponse = json.decode(response.body);
      print('Response in Profile Screen: ' + response.body);
      print("Price - "+jsonResponse['record']['ads_price']);
      setState(() {
        price = jsonResponse['record']['ads_price'];
        title = jsonResponse['record']['adname'];
        description = jsonResponse['record']['addesc'];
        location = jsonResponse['record']['ads_location'];
        publishedOn = jsonResponse['record']['created_date'];
        postedBy = jsonResponse['record']['user_name'];
        adId = jsonResponse['record']['adid'];
        postedById = jsonResponse['record']['aduserid'];
        images = jsonResponse['record']['images'];
      });
    }
  }

除了图像，我以正确的方式获取所有细节

Answer 1

正如我在您的图片回复中看到的那样，您有这个 {'adsimg_img': 'some_url'}。

所以我会在你的代码中这样做

setState(() {
  .
  .
  .
  adId = jsonResponse['record']['adid'];
  postedById = jsonResponse['record']['aduserid'];
  images = (jsonResponse['record']['images'] as List)
    ?.map((i) => i['adsimg_img'])
    ?.toList();
});

所以最后的图像看起来像 ['url1', 'url2', ...] // 字符串列表

我没有测试它，但它应该可以解决问题:)

Answer 2

在您添加的 json 响应片段中， images的值应该是一个数组，但它在双引号中，基本上是一个字符串。

如果将该片段放入像这样的 jsonValidator 中，它会显示关键images的值是一个字符串，而不是您期望的数组。

json 中的一组对象的格式与此类似

{
  "user_name": "sunil",
  "images": [
    {
      "adsimg_img":"http://codecell.in/girrivi/assets/adimgs/carpenter.png"
    },
    {
      "adsimg_img":"http://codecell.in/girrivi/assets/adimgs/carpenter.png"
    },
    {
      "adsimg_img":"http://codecell.in/girrivi/assets/adimgs/carpenter.png"
    }
  ]
}