How to download files in Flutter WebView?

Question

I am working on Flutter webview apps using Flutter Webview.

import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';
import 'package:url_launcher/url_launcher.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: SafeArea(
          child : const WebView(
            initialUrl: 'https://google.com',
            javascriptMode: JavascriptMode.unrestricted,
          ),
        )
      )
    );
  }
}

I try to use launchURL plugin but that will open predefined url in external browser window.

if (url.contains('.pdf')) {
    launchURL(url);
  }

What I want is to download the file in-app webview.