请问一下，在使用dio时，如何做https证书校验？ about dio HOT 13 CLOSED

import 'package:flutter/material.dart';
import 'dart:io';
import 'package:dio/dio.dart';

void main() async {
  HttpOverrides.global = new MyHttpOverrides();
  runApp(new MyApp());
}

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

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;
  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class MyHttpOverrides extends HttpOverrides{
  @override
  HttpClient createHttpClient(SecurityContext context){
    HttpClient client= super.createHttpClient(context); //<<--- notice 'super'
    client.badCertificateCallback = (X509Certificate cert, String host, int port ){
      print(cert.sha1);
      return false;
    };
    return client;
  }
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  Dio dio = Dio();
  void _incrementCounter() {
    setState(() {//
      _counter++;
    });
  }
  @override
  Widget build(BuildContext context) {
    this.dio.get("https://github.com/flutterchina/dio/issues/61").then((response){
      print(response);
    }, onError: (){

    });
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Text(
              'You have pushed the button this many times:',
            ),
            new Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: new Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

    dio.onHttpClientCreate = (HttpClient client) {
      print("dio xxxx");
      client.badCertificateCallback =
          (X509Certificate cert, String host, int port) {
        //校验逻辑
        return true;
      };
    };

@override
  void initState() {
    // TODO: implement initState
    super.initState();
    dio.onHttpClientCreate = (HttpClient client) {
      print("dio xxxx");
      client.badCertificateCallback =
          (X509Certificate cert, String host, int port) {
        //校验逻辑
        print("dio x509");
        return true;
      };
    };
  }