Flutter Class不工作

Question

我是Flutter/Dart的新手,所以可能没有使用所有正确的关键词,但我遇到了一个问题,我在类'FirstPageState'扩展State 下获得了一条红线.这使我无法调试应用程序,所以我来到这里希望得到一个解决方案!

这是我的'FirstPage.dart'代码

import 'dart:async';

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

String _FirstPageText = 'Exchange Rates';

class First extends StatefulWidget {
  // This widget is the root of your application.
  @override
  FirstPageState createState() => new FirstPageState();
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text(_FirstPageText),
          centerTitle: true,
          backgroundColor: Colors.black,
        ),
        body: new FeedWidget(),
        ),
      );
  }
}

class FirstPageState extends State<First> {

Future<String> getData() async {
  var response = await http.get(
    'https://jsonplaceholder.typicode.com/posts'
  );

}

}

谢谢 :)

Answer 1

如果您阅读"红线",您将看到一个错误,可能State是一个抽象类,需要定义一个或多个方法:

实例,getter和setter方法可以是抽象的,定义一个接口,但将其实现留给其他类

在这种情况下,我相信State期望这种build方法.您可能需要查看后面StatefulWidget的文档,其中描述了必要的内容:

class YellowBird extends StatefulWidget {
  const YellowBird({ Key key }) : super(key: key);

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

class _YellowBirdState extends State<YellowBird> {
  @override
  Widget build(BuildContext context) {
    return new Container(color: const Color(0xFFFFE306));
  }
}