What is onUnknownRoute in flutter

Question

I'm new to flutter, In MaterailApp Widget have an attribute called onUnknownRoute. What is the main use of onUnknownRoute?

Thanks for your help!

Answer 1

You can copy paste run full code below
In flutter web, when user manually key a undefine route, it can produce like 404 effect

full code

import 'package:flutter/material.dart';

void main() {
  runApp( MaterialApp(    
    initialRoute: "/screen1",
    routes: <String, WidgetBuilder>{
      '/screen1': (BuildContext context) =>  Screen1(),
      '/screen2': (BuildContext context) =>  Screen2(),
      '/screen3': (BuildContext context) =>  Screen3(),
      '/screen4': (BuildContext context) =>  Screen4()
    },
    onUnknownRoute: (RouteSettings settings) {
      return MaterialPageRoute<void>(
        settings: settings,
        builder: (BuildContext context) =>
            Scaffold(body: Center(child: Text('Not Found'))),
      );
    },
  )
  );
}

class Screen1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

class Screen2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

class Screen3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

class Screen4 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}