为什么htttp.get在Flutter中给我一个错误

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('HTTP GET Example')),
        body: Center(child: HttpGetExample()),
      ),
    );
  }
}

class HttpGetExample extends StatefulWidget {
  @override
  _HttpGetExampleState createState() => _HttpGetExampleState();
}

class _HttpGetExampleState extends State<HttpGetExample> {
  String _response = 'Waiting for response...';

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

  Future<void> fetchData() async {
    try {
      var response = await http.get(Uri.parse('https://jsonplaceholder.typicode.com/posts/1'));
      if (response.statusCode == 200) {
        setState(() {
          _response = response.body;
        });
      } else {
        setState(() {
          _response = 'Failed to load data: ${response.statusCode}';
        });
      }
    } catch (e) {
      setState(() {
        _response = 'Error: $e';
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Text(_response);
  }
}