就像他们的文件里提到的，
当发生错误时，Dio会将Error/Exception Package 为DioException：
您可以使用try/ catch来捕获它们。

try {
  // 404
  await dio.get('https://api.pub.dev/not-exist');
} on DioException catch (e) {
  // The request was made and the server responded with a status code
  // that falls out of the range of 2xx and is also not 304.
  if (e.response != null) {
    print(e.response.data)
    print(e.response.headers)
    print(e.response.requestOptions)
  } else {
    // Something happened in setting up or sending the request that triggered an Error
    print(e.requestOptions)
    print(e.message)
  }
}

和DioException包含这些字段，

/// The request info for the request that throws exception.
RequestOptions requestOptions;

/// Response info, it may be `null` if the request can't reach to the
/// HTTP server, for example, occurring a DNS error, network is not available.
Response? response;

/// The type of the current [DioException].
DioExceptionType type;

/// The original error/exception object;
/// It's usually not null when `type` is [DioExceptionType.unknown].
Object? error;

/// The stacktrace of the original error/exception object;
/// It's usually not null when `type` is [DioExceptionType.unknown].
StackTrace? stackTrace;

/// The error message that throws a [DioException].
String? message;

就我个人而言，我会使用switch语句来捕获所有DioExceptionType，并相应地处理/返回错误消息。

if (error is DioException) {
      switch (error.type) {
        case DioExceptionType.connectionTimeout:
        case DioExceptionType.receiveTimeout:
        case DioExceptionType.sendTimeout:
          networkFailure = const NetworkFailure.requestTimeout();
          break;
        case DioExceptionType.badCertificate:
          networkFailure = const NetworkFailure.badCertificate();
    ...

你可以找到所有的异常类型here，或者你可以简单地转到flutter应用程序中的插件源代码。

响应有两个因素：statusMessage和statusCode。
你为什么不试试这个
把A改成B
一个

} else {
      print('error');
    }

B

} else {
      print('${response.statusMessage}');
      print('${response.statusCode}');
    }

或

import 'dart:developer';
...
} else {
      log(response);
      log('${response.statusMessage}');
      log('${response.statusCode}');
    }