如何从json中获取数据到flutter中的字符串

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

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  String data = '';

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

  Future<void> fetchData() async {
    final response = await http.get('https://example.com/api/data.json');
    if (response.statusCode == 200) {
      final jsonData = jsonDecode(response.body);
      final String extractedData = jsonData['key'];
      setState(() {
        data = extractedData;
      });
    } else {
      throw Exception('Failed to load data');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('JSON Data'),
      ),
      body: Center(
        child: Text(data),
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyWidget(),
  ));
}