komplettes async Beispielt

asyncbsp3.dart

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

void main() => runApp(AsyncBeispiel());

class AsyncBeispiel extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HauptSeite(),
    );
  }
}


class HauptSeite extends StatefulWidget {
  @override
  _HauptSeiteState createState() => _HauptSeiteState();
}

class _HauptSeiteState extends State<HauptSeite> {
  String zeichenKette = "";
  @override
  initState(){
   textVomServer();
   super.initState();
  }

  textVomServer() async{
    String url = "https://rickandmortyapi.com/api/character/?name=pencil";
    http.Client client = http.Client();
    http.Response response = await client.get(url,);
    Map decodedJson = json.decode(response.body);
    setState((){
    zeichenKette = decodedJson["results"][0]["name"];
    });
  }
@override

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Async Beispiel"),
      ),
      body: Container(
        child: Center(
          child: Text(
            zeichenKette
          ),
        ),
      ),
    );
  }
}