how to download android app from google drive and install in flutter

Question

I'm beginner for flutter. I built An android App(called "DCS"). A new version of that app(replace.apk) is stored in google drive and shared for public. Size of the app is 20MB. When touch a button, download the apk file from given URL and install the app replacing existing one. I tried using this code. But I was unable to succeed. As I identified, apk file downloading is not complete. Can't find this apk file in device. Please help me.

AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES"/>

main.dart

import 'package:http/http.dart' as http;
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:dio/dio.dart';
import 'package:path_provider/path_provider.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:open_file/open_file.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String apkUrl =
      'https://drive.google.com/uc?export=download&id=1qh2axZcDbj_OZn_4NHI5CUWTR0ocNFiN'; // Replace with your actual Google Drive file ID

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('DCS App'),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            downloadAndInstallApk();
          },
          child: Text('Download and Install DCS App'),
        ),
      ),
    );
  }

  Future<void> downloadAndInstallApk() async {
    if (await _requestPermission()) {
      final directory = await getExternalStorageDirectory();
      final savePath = directory!.path + '/replace.apk';

      try {
        await Dio().download(apkUrl, savePath);
        OpenFile.open(savePath);
      } catch (e) {
        // Handle the error
        print('Failed to download APK: $e');
      }
    } else {
      // Handle the scenario where the user denies storage permission
      print('Permission Denied');
    }
  }

  Future<bool> _requestPermission() async {
    var status = await Permission.storage.status;

    if (status.isDenied) {
      status = await Permission.storage.request();
    }

    return status.isGranted;
  }
}