FlutterでAndroid実機のcurrent directoryが取得できません

前提・実現したいこと

FlutterでAndroid実機を用いて、CSVファイルを生成、メールで添付して送るコードを作っております。
その際に、Android実機のcurrentなDirectoryにcsvファイルを吐き出すことになるのですが、
これがどうもうまくいっていない様子です。

Windows10で下記関数を実行するとちゃんとCSVファイルが生成されるのですが、
Android実機だとうまくいかず、その理由と解決方法がわかれば幸いです。

発生している問題・エラーメッセージ

E/MethodChannel#flutter_mailer(17274): Failed to handle method call
E/MethodChannel#flutter_mailer(17274): java.lang.IllegalArgumentException: Failed to find configured root that contains /sample.csv
E/MethodChannel#flutter_mailer(17274): 	at androidx.core.content.FileProvider$SimplePathStrategy.getUriForFile(FileProvider.java:739)
E/MethodChannel#flutter_mailer(17274): 	at androidx.core.content.FileProvider.getUriForFile(FileProvider.java:418)
E/MethodChannel#flutter_mailer(17274): 	at com.dataxad.fluttermailer.FlutterMailerPlugin.mail(FlutterMailerPlugin.java:116)
E/MethodChannel#flutter_mailer(17274): 	at com.dataxad.fluttermailer.FlutterMailerPlugin.onMethodCall(FlutterMailerPlugin.java:50)
E/MethodChannel#flutter_mailer(17274): 	at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:222)
E/MethodChannel#flutter_mailer(17274): 	at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:96)
…

該当のソースコード

//ファイルを作る関数
import 'dart:async';
import 'dart:io';

import 'package:flutter/material.dart';
import 'package:flutter_mailer/flutter_mailer.dart';

void main() => runApp(new MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {

  final GlobalKey<ScaffoldState> _scafoldKey = GlobalKey<ScaffoldState>();
  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> send() async {
    // Platform messages may fail, so we use a try/catch PlatformException.
    final MailOptions mailOptions = MailOptions(
      body: null,
      subject: 'ファイル添付',
      recipients: [' '],
      isHTML: true,
      // bccRecipients: ['other@example.com'],
      ccRecipients: [' '],
      attachments: [_createFile().path],
    );

    String platformResponse;

    try {
      await FlutterMailer.send(mailOptions);
      platformResponse = 'success';
    } catch (error) {
      platformResponse = error.toString();
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;
    _scafoldKey.currentState.showSnackBar(SnackBar(
      content: Text(platformResponse),
    ));
  }

  @override
  Widget build(BuildContext context) {

    return new MaterialApp(
      theme: ThemeData(primaryColor: Colors.red),
      home: new Scaffold(
        key: _scafoldKey,
        appBar: new AppBar(
          title: const Text('Plugin example app'),
          actions: <Widget>[
            IconButton(
              onPressed: send,
              icon: const Icon(Icons.send),
            )
          ],
        ),
        body: SingleChildScrollView(
          child: new Center(
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: Column(
                mainAxisSize: MainAxisSize.max,
                // mainAxisAlignment: MainAxisAlignment.spaceBetween,
                crossAxisAlignment: CrossAxisAlignment.center,

              ),
            ),
          ),
        ),
      ),
    );
  }


//ファイルを作る関数
  File _createFile(){
    Directory current = Directory.current;

    String fileName = current.path    +"\sample.csv";
    print(fileName);

    File file = new File(fileName);
    file.writeAsString("Hello World!!");

    return file;
  }
}