Failed assertion: line 133 pos 12: 'file.absolute.existsSync()': is not true

Hello I am a beginner and I am trying to record audio and upload it to firebase but I am facing an error which probably says that file does not exists.

Currently Flutter Audio Recorder is reading audio data but when Audio Recorder is set to stop and the process of uploading begins then the error is generated. I have checked file existence using existsSync() method which returned false

Kindly help me out in this. Here is my code

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:avatar_glow/avatar_glow.dart';
import 'package:flutter_audio_recorder/flutter_audio_recorder.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:path_provider/path_provider.dart';

class HomeView extends StatefulWidget {
  @override
  _HomeViewState createState() => _HomeViewState();
}

class _HomeViewState extends State<HomeView> {

  bool _isRecording;
  String _convertedText;
  String _fileName;

  String _filePath;
  FlutterAudioRecorder _audioRecorder;

  @override
  void initState() {
    super.initState();
    _isRecording = false;
    _fileName = "";
    _convertedText = "Press the Record button to convert text";
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Urdu Speech to Text Converter"),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
      floatingActionButton: AvatarGlow(
        animate: _isRecording,
        glowColor: Theme
            .of(context)
            .primaryColor,
        endRadius: 75.0,
        duration: const Duration(milliseconds: 2000),
        repeatPauseDuration: const Duration(milliseconds: 100),
        repeat: true,
        child: FloatingActionButton(
          onPressed: _onRecordButtonPressed,
          child: Icon(_isRecording ? Icons.mic : Icons.mic_none),
        ),
      ),
      body: SingleChildScrollView(
        reverse: true,
        child: Container(
            padding: const EdgeInsets.fromLTRB(30.0, 30.0, 30.0, 150.0),
            child: Text(_convertedText)
        ),
      ),
    );
  }

  Future<void> _uploadFile() async {
    FirebaseStorage firebaseStorage = FirebaseStorage.instance;

    try {
      await firebaseStorage
          .ref()
          .child(_fileName)
          .putFile(File(_filePath));
    } catch (error) {
      print('Error occured while uplaoding to Firebase ${error.toString()}');
      // Scaffold.of(context).showSnackBar(
      //   SnackBar(
      //     content: Text('Error occured while uplaoding'),
      //   ),
      // );
    }
  }

  Future<void> _onRecordButtonPressed() async {
    if (_isRecording) {
      _audioRecorder.stop();
      _isRecording = false;
      File(_filePath).existsSync() ? _uploadFile() : print("*************** File Doesn't Exists **************");
    } else {
      _isRecording = true;
      await _startRecording();
    }
    setState(() {});
  }

  Future<void> _startRecording() async {
    final bool hasRecordingPermission =
    await FlutterAudioRecorder.hasPermissions;
    if (hasRecordingPermission) {
      Directory directory = await getApplicationDocumentsDirectory();
      String filepath = directory.path +
          '/' +
          DateTime
              .now()
              .millisecondsSinceEpoch
              .toString() +
          '.wav';
      _audioRecorder =
          FlutterAudioRecorder(filepath, audioFormat: AudioFormat.WAV);
      await _audioRecorder.initialized;
      _audioRecorder.start();
      _filePath = filepath;
      _fileName = _filePath.substring(_filePath.lastIndexOf('/') + 1, _filePath.length);
      _convertedText = _fileName;
      setState(() {});
    } else {
      print("*************************** No Permissions *****************************");
    }
  }

}