(1) net::ERR_UNKNOWN_URL_SCHEME

main.dart

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

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

class Sys extends StatelessWidget {
  const Sys({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) => MaterialApp(
    onGenerateRoute: (RouteSettings route) => MaterialPageRoute(
      settings: RouteSettings(name: MainPage.path),
      builder: (context) => MainPage()
    ),
  );
}

class MainPage extends StatefulWidget {
  const MainPage({Key? key}) : super(key: key);
  static const String path = "/";

  @override
  _MainPageState createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  
  bool check = false;

  /// net::ERR_UNKNOWN_URL_SCHEME
  @override
  Widget build(BuildContext context) => Scaffold(
    appBar: AppBar(),
    body: this.check ? Center(child: Text("Load")) : WebView(
      initialUrl: "http://192.168.25.46:3000",
      javascriptMode: JavascriptMode.unrestricted,
      onPageStarted: (String url){
        print("📌");
        /// Example
        // if(url.indexOf("inapt://") >= 0){
        //   try{
        //     await launch(url);
        //   }
        //   catch(e){}
        // }

        /// TEST
        if(url.indexOf("sms") >= 0){
          setState(() => this.check = true);
          try{ launch(url); }
          catch(e){}
        }
      }
    ),
    floatingActionButton: !this.check
      ? null
      : FloatingActionButton(
          child: Icon(Icons.check),
          onPressed: () => setState(() => this.check = false)
        ),
  );
}