在Dart中未获得所需的json响应

问题描述

我目前正在构建一个应用程序，以从json API获取数据。
我想从json代码中获取数字54。

I am currently building an app to get a data from a json api.I want to get the number 54 from the json code.

这是json

我尝试在此处制作json api的模型类

I have tried making model class of the json api here

class TeerModel{
  String text;
  TeerModel(this.text);
  TeerModel.fromJson(Map<String, dynamic>parsedJson){
    text = parsedJson['text'];
  }
}

但是我无法得到结果，所以我删除了

But I can't get the result so i removed it

这是代码

import 'package:flutter/material.dart';
import 'package:http/http.dart' show get;
import 'models/teer_model.dart';
import 'dart:convert';


class Appss extends StatefulWidget {
  @override
  _AppssState createState() => _AppssState();
}

class _AppssState extends State<Appss> {

  String result = "1S";

  void fetchData ()async{
    var response1 = await get("http://motyar.info/webscrapemaster/api/?url=http://teertoday.com/&xpath=/html/body/div[5]/div/table/tbody/tr[3]/td[1]#vws");
    var teerModel =  json.decode(response1.body);
    var line = teerModel["text"].replaceAll(new RegExp(r"(\s\n)"), "");
    print(line);

  }


  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text("Teer result"),),
        floatingActionButton: FloatingActionButton(
          onPressed: fetchData,
        ),
        body: Center(
          child: Text("The result is: $result"),
        ),
      ),
    );
  }
}

我只想从文本中获取数字54 所以我使用正则表达式

I only want to get the number 54 from "text" so I use regex

我希望输出为54，但我却收到此错误

I expected the output will be 54 but instead I get this error

推荐答案

如果您查看json，您会发现它完全被 [...] 包围，这意味着它是一个json数组。 json.decode 会将其转换为Dart List< Map< String，dynamic>> 。看来您想要此数组/列表的第一个/第零个元素。

If you look at your json, you will see that it is entirely surrounded by [...], meaning that it is a json array. json.decode will convert this into a Dart List<Map<String, dynamic>>. It looks like you want the first / zero'th element of this array/list.

更改：

var line = teerModel["text"].replaceAll(new RegExp(r"(\s\n)"), "");

到

var line = teerModel[0]["text"].replaceAll(new RegExp(r"(\s\n)"), "");

别忘了调用 setState 您的小部件会自行重建。

Don't forget to call setState so that your widget rebuilds itself.

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