start method Null safety

Implementation

void start() async {
  Map<String, String> reportParams = {};
  DateTime startTime = DateTime.now();
  _state = SMHTaskState.processing;
  stateStream.add(_state);
  receivePort = ReceivePort();
  receivePort.listen((data) {
    SendPort? subSencPort;
    if (data['code'] == 'finish') {
      if (finishCalBack != null) {
        SMHError? error = data['error'];

        reportParams['took_time'] =
            DateTime.now().difference(startTime).inMilliseconds.toString();
        reportParams['space_id'] = getTaskInfo().spaceId;
        reportParams['host'] = SMHServicesManager
                .servicesManager.serviceMap[SMHAPIServiceKey]?.baseUrl ??
            '';
        reportParams['smh_key'] = SMHServicesManager
                .servicesManager.serviceMap[SMHAPIServiceKey]?.baseUrl +
            getTaskInfo().filePath;
        if (error != null) {
          reportParams['error_service_name'] = SMHRequest.getServiceName();
          reportParams['error_status_code'] = error.statusCode.toString();
          reportParams['error_message'] = error.statusMessage.toString() +
              ':' +
              error.smhMessage.toString();
          reportParams['error_code'] = error.smhCode.toString();
          reportParams['error_type'] = error.error.toString();
          reportParams['cos_request_id'] = error.cosRequestId ?? '';
          reportParams['request_id'] = error.requestId ?? '';
          _state = SMHTaskState.error;
          if (getTaskInfo().option == SMHTaskOption.upload) {
            reportParams['size'] = getTaskInfo().length.toString();
            SMHBeaconManager.manager
                .reportFail(params: reportParams, eventCode: 'smh_upload');
          } else {
            reportParams['size'] =
                File(getTaskInfo().localPath).lengthSync().toString();
            SMHBeaconManager.manager
                .reportFail(params: reportParams, eventCode: 'smh_download');
          }
        } else {
          _state = SMHTaskState.success;
          if (getTaskInfo().option == SMHTaskOption.upload) {
            reportParams['name'] = 'SMHTransferService.upload';
            reportParams['size'] = getTaskInfo().length.toString();
            SMHBeaconManager.manager.reportSuccess(
              params: reportParams,
              eventCode: 'smh_upload',
            );
          } else {
            reportParams['name'] = 'SMHTransferService.download';
            reportParams['size'] =
                File(getTaskInfo().localPath).lengthSync().toString();
            SMHBeaconManager.manager.reportSuccess(
              params: reportParams,
              eventCode: 'smh_download',
            );
          }
        }
        stateStream.add(_state);
        finishCalBack!(data['result'], error);
      }
      finish();
      return;
    }

    if (data['code'] == 'confirmKey') {
      String confirmKey = data['result'];
      if (confirmKeyCalBack != null) {
        confirmKeyCalBack!(confirmKey);
      }
      return;
    }

    if (data['code'] == 'processing') {
      Map value = data['result'];
      if (onSendProgress != null) {
        onSendProgress!(value['count'], value['total']);
      }

      if (onReceiveProgress != null) {
        onReceiveProgress!(value['count'], value['total']);
      }
      return;
    }

    if (data['code'] == 'init') {
      subSencPort = data['result'];
      SMHServicesManager servicesManager = SMHServicesManager.servicesManager;
      Map<String, dynamic> envMap = {
        'currentHost': servicesManager.currentHost,
        'currentType': servicesManager.currentType,
      };
      final info = getTaskInfo();
      subSencPort!.send({'data': info, 'env': envMap});
      return;
    }
  });
  isolate = await createIsolate(receivePort.sendPort);
}