颤振DioError [DioErrorType.response]：XMLHttpRequest错误

Question

我有一个Localhoset，希望从这个本地主机获得数据，然后点击按钮显示。get请求成功完成，但与打印结果相反，我收到以下错误！

> Running with unsound null safety
For more information see https://dart.dev/null-safety/unsound-null-safety
Debug service listening on ws://127.0.0.1:59432/vuDMHfesIRs=/ws
DioError [DioErrorType.response]: XMLHttpRequest error.
dart-sdk/lib/_internal/js_dev_runtime/patch/core_patch.dart 909:28   get current
packages/dio/src/dio_mixin.dart 819:20                               assureDioError
packages/dio/src/dio_mixin.dart 678:13                               _dispatchRequest
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 60:31   <fn>
dart-sdk/lib/async/zone.dart 1618:54                                 runBinary
dart-sdk/lib/async/future_impl.dart 169:20                           handleError
dart-sdk/lib/async/future_impl.dart 719:46                           handleError
dart-sdk/lib/async/future_impl.dart 740:13                           _propagateToListeners
dart-sdk/lib/async/future_impl.dart 550:5                            [_completeError]
dart-sdk/lib/async/future_impl.dart 606:7                            callback
dart-sdk/lib/async/schedule_microtask.dart 40:11                     _microtaskLoop
dart-sdk/lib/async/schedule_microtask.dart 49:5                      _startMicrotaskLoop
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 166:15  <fn>

我用它正在工作的api测试相同的代码和相同的进程！会是什么？

下面是get方法：

    Dio dio = new Dio();
  void getCountries() async{
    try {
      var response = await dio.get('http://b21dfa1ea157.ngrok.io/gettest'
      );

      dio.options.headers['content-Type'] = 'text/plain; charset=UTF-8';
      dio.options.headers['Access-Control-Allow-Origin'] = '*';
      dio.options.headers['Access-Control-Allow-Methods'] = 'GET , POST';

      print(response.data);
    } catch (e) {
      print(e);
    }
  }

此外，通过单击Button，它调用了方法：

RaisedButton(onPressed: getMethod)

有人能帮我吗？

Answer 1

这似乎是一个CORS (跨来源资源共享)问题。这里为开发构建创建的常见解决方案是在应用程序运行时使用disabling security使用--disable-web-security参数。

对于生产构建，您需要启用服务器端的CORS请求来修复这个问题。根据您的设置，您将不需要对客户端应用程序进行更改。