Flutter Dart-无法从连接流捕获异常

我无法捕获在

connectivity.onConnectivityChanged.listen函数中引发的异常。
我尝试过使用try-catch块和
onError
函数，但无法让它们工作。
有人知道我做错了什么吗

import 'package:flutter/foundation.dart';
import 'dart:async';

import 'package:connectivity/connectivity.dart';
import 'package:dio/dio.dart';

class DioConnectivityRequestRetrier {
  final Dio dio;
  final Connectivity connectivity;

  DioConnectivityRequestRetrier({
    @required this.dio,
    @required this.connectivity,
  });

  Future<Response> scheduleRequestRetry(RequestOptions requestOptions) async {
    StreamSubscription streamSubscription;
    final responseCompleter = Completer<Response>();
    try {
      connectivity.onConnectivityChanged.listen(
        (connectivityResult) {
          if (connectivityResult != ConnectivityResult.none) {
            // streamSubscription.cancel();

            // An exception when dio.request fails
            throw Exception;

            responseCompleter.complete(
              dio.request(
                requestOptions.path,
                cancelToken: requestOptions.cancelToken,
                data: requestOptions.data,
                onReceiveProgress: requestOptions.onReceiveProgress,
                onSendProgress: requestOptions.onSendProgress,
                queryParameters: requestOptions.queryParameters,
                options: requestOptions,
              ),
            );
          }
        },
      ).onError((e) {
        throw e;
      });
    } catch (e) {
      rethrow;
    }

    return responseCompleter.future;
  }
}


试着这样做：

try {
     /// YOUR CODE HERE ///
    } on PlatformException catch (e) {
      print(e.toString());
    }

试着这样做：

try {
     /// YOUR CODE HERE ///
    } on PlatformException catch (e) {
      print(e.toString());
    }

您可以在我的代码示例中看到，我已经尝试使用try-catch块，但这不起作用。在异常上添加
也没有什么不同。在我的代码示例中，您可以看到我已经尝试使用try-catch块，但这不起作用。在异常情况下添加
，
也没有什么区别。