Question

import 'package:flutter/material.dart';
import 'package:flutter_staggered_animations/flutter_staggered_animations.dart';
import 'package:http/http.dart' as http;
import 'package:html/parser.dart' as parser;
import 'package:html/dom.dart' as dom;
import 'package:plant_app/constants.dart';
import 'package:url_launcher/url_launcher.dart';

class Post extends StatefulWidget {
  @override
  _PostState createState() => _PostState();
}

class _PostState extends State<Post> {
  List<String> post = List();

  void _getDataFromWeb() async {
    String str = "http://yongwon-h.gne.go.kr/yongwon-h/main.do#";
    Uri uri = Uri.parse(str);

    final response = await http.get(uri);
    dom.Document document = parser.parse(response.body);
    final elements = document.getElementsByClassName('meal_list');
    setState(() {
      post = elements
          .map((element) => element.getElementsByTagName("p")[0].innerHtml)
          .toList();
    });
  }

  @override
  // ignore: must_call_super
  void initState() {
    _getDataFromWeb();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: kPrimaryColor,
      body: post.length == 0
          ? Text("No data", style: TextStyle(color: Colors.white))
          : ListView.builder(
              itemCount: post.length,
              itemBuilder: (context, index) {
                return AnimationConfiguration.staggeredList(
                  position: index,
                  duration: const Duration(milliseconds: 375),
                  child: SlideAnimation(
                      child: FadeInAnimation(
                    child: GestureDetector(
                      onTap: () async {
                        dynamic url = post[index];
                        if (await canLaunch(url))
                          launch(url);
                        else {
                          print('error');
                        }
                      },
                      child: Padding(
                        padding: const EdgeInsets.all(8.0),
                        child: Card(
                          child: Container(
                            child: Column(
                              children: <Widget>[
                                Align(
                                  alignment: Alignment.centerLeft,
                                  child: Text(
                                    post[index],
                                    style: TextStyle(
                                      fontWeight: FontWeight.bold,
                                      color: Colors.red,
                                      fontSize: 20,
                                    ),
                                  ),
                                ),
                              ],
                            ),
                          ),
                        ),
                      ),
                    ),
                  )),
                );
              }),
    );
  }
}

<块引用>

[RangeError(RangeError (index): Invalid value: Valid value range is empty: 0)]

有什么问题吗？看完this YouTube video后我正在应用它。

我认为 0 是问题所在。

Answer 1

根据 API 的响应，.meal_list 类被分配给一个段落标签。因此，在通过地图应用任何转换之前，您需要检查 elements 的值。

final elements = document.getElementsByClassName('meal_list') 返回一个单项的 Node 列表，你可以像这样访问它的内容 elements[0].innerText。

RangeError (RangeError (index): Invalid value: Valid value range is empty: 0)

1 个答案: