flutter - 在应用运行时从URL读取数据

下面的flutter代码运行良好，该代码很简单，是自动生成的示例，带有从url读取数据的velow语句已添加到void _incrementCounter()函数中:

      new HttpClient().getUrl(Uri.parse('https://docs.google.com/spreadsheets/d/e/2PACX-1vQvf9tp4-fETDJbC-HRmRKvVFAXEAGO4lrYPpVeiYkB6nqqXdSs3CjX0eBMvjIoEeX9_qU6K2RWmzVk/pub?gid=0&single=true&output=csv'))
          .then((HttpClientRequest request) => request.close())
          .then((HttpClientResponse response) => response.transform(new Utf8Decoder()).listen(print));

完整的代码是:

import 'package:flutter/material.dart';
import 'dart:convert';
import 'dart:io';
import 'package:csv/csv.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
//////// Here is the statement /////
      new HttpClient().getUrl(Uri.parse('https://docs.google.com/spreadsheets/d/e/2PACX-1vQvf9tp4-fETDJbC-HRmRKvVFAXEAGO4lrYPpVeiYkB6nqqXdSs3CjX0eBMvjIoEeX9_qU6K2RWmzVk/pub?gid=0&single=true&output=csv'))
          .then((HttpClientRequest request) => request.close())
          .then((HttpClientResponse response) => response.transform(new Utf8Decoder()).listen(print));
///////////////////////////////////
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

我实际上需要执行的功能是，通过在应用启动时从URL读取数据，我尝试将其放在class _MyHomePageState extends State<MyHomePage>下，但出现错误，如下所示，如何调用它而不等待用户的操作:

最佳答案

像这样创建函数:

getApiParsing()async{
var url = 'https://example.com/whatsit/create';
var response = await http.post(url, body: {'name': 'doodle', 'color': 'blue'});
print('Response status: ${response.statusCode}');
print('Response body: ${response.body}');

print(await http.read('https://example.com/foobar.txt'));
}

然后像这样调用 initState :-

class _MyHomePageState extends State<MyHomePage> {

  @override
  void initState() {
    super.initState();
    getApiParsing();
  }

  @override
  Widget build(BuildContext context) { //... // }
}