Error: The getter 'title' isn't defined for the type 'RSSParser'

Question

我想实现一个关于如何使用 Flutter 解析 Rss Feed 的简单教程，这是我的代码：

import 'package:flutter/material.dart';
import 'package:webfeed/webfeed.dart';
import 'package:http/http.dart' as http;
import 'package:url_launcher/url_launcher.dart';
import 'package:cached_network_image/cached_network_image.dart';

 class RSSParser extends StatefulWidget {
  @override
    _RSSParserState createState() => _RSSParserState();
 }

 class _RSSParserState extends State<RSSParser> {
  final String url = "https://www.90min.com/posts.rss";
  RssFeed _feed;
  String _title;
  static const String loadingFeedMsg = 'Loading Feed...';
  static const String feedLoadErrorMsg = 'Error Loading Feed.';
  static const String feedOpenErrorMsg = 'Error Opening Feed.';

   Future<RssFeed> loadFeed() async{
    try{
    final client = http.Client();
    final response = await client.get(url);
     return RssFeed.parse(response.body);

  }
    catch(e){

   }
   return null;

 }

updateTitle(title){
  setState(() {
  _title = title;
});
}

@override
void initState() {
// TODO: implement initState
super.initState();
updateTitle(widget.title);
}


updateFeed(feed){
 setState(() {
  _feed = feed;
 });
}

@override
 Widget build(BuildContext context) {
 return Scaffold(
  appBar: AppBar(
    title: Text(_title),
  ),
 );
 }
}

问题是我在该指令中遇到编译错误

 updateTitle(widget.title);

出现以下错误消息：

The getter 'title' isn't defined for the type 'RSSParser'

在教程中，效果很好！！

你知道如何解决这个问题吗？谢谢

Answer 1

这不起作用，因为 RSS class 中没有标题。

我觉得你对widget.something的用法不是很清楚。这意味着在扩展 StatefulWidget 的 class 中有一个 something 参数，我需要在 stateObject 中获取该参数。

看代码就明白了

class YellowBird extends StatefulWidget {
  const YellowBird({ Key? key }) : super(key: key);
  String someData = 'SomeData'; // Some data 

  @override
  _YellowBirdState createState() => _YellowBirdState();
}


//This is the state object
class _YellowBirdState extends State<YellowBird> {

 // Now that if you need some data from the above class. You use use this widget.someData to get it here
  String getHere = widget.someData ; 
  @override
  Widget build(BuildContext context) {
    return Container(color: const Color(0xFFFFE306));
  }
}

Answer 2

您还没有为您的 RSS 小部件声明 title。它应该看起来像这样：

 class RSSParser extends StatefulWidget {
final String title;
const RSSParser({required this.title});

这应该可以解决您的错误。

Error: The getter 'title' isn't defined for the type 'RSSParser'

Error: The getter 'title' isn't defined for the type 'RSSParser'

widget

flutter

statefulwidget