flutter http post "type 'int‘is not a subtype of type 'String’in type cast“

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

void postData() async {
  var url = 'https://example.com/api/endpoint';
  var data = {'id': 1, 'name': 'John Doe'};
  
  var response = await http.post(
    Uri.parse(url),
    headers: {'Content-Type': 'application/json'},
    body: jsonEncode(data),
  );
  
  if (response.statusCode == 200) {
    // 请求成功
    var responseData = jsonDecode(response.body);
    // 处理返回的数据
  } else {
    // 请求失败
    print('请求失败: ${response.statusCode}');
  }
}