Should every screen check for authentication before loading or should it be done only in the main.dart file?

Question

This might be a very basic question but I wanted to understand the best practices followed around the industry.

Right now I am doing this in the build method of the main.dart file.

@override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: new StreamBuilder(
        stream: auth.onAuthStateChanged,
        builder: (context, snapshot)  {
          if (snapshot.hasData) {
            return MainScreen();
          }
          return AuthScreen();
        },
      ),
    );
  }

I always do this in `main.dart`, because It's the most important thing in the app, and easy to switch to `AuthScreen` If the token outdated or server is down. — Tokenyet, Oct 17 '19 at 06:37
this might help you `https://stackoverflow.com/questions/51027858/route-guards-in-flutter` — nmanikiran, Oct 17 '19 at 06:43

score 1 · Answer 1 · answered Oct 17 '19 at 06:51

i don't think anything is wrong with this method, i also use something similar for restarting my app, however there is a problem. when you change the route and get unauthorized it won't open main screen ( because you are no longer in Home widget )

you can try these solutions :

use Builder:

@override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: MainScreen(),
      builder: (context, widget) {
          return StreamBuilder(
            stream: auth.onAuthStateChanged,
            builder: (context, snapshot)  {
              if (snapshot.hasData) {
                return widget;
              }
              return AuthScreen();
            },
          ),
        },
    );
  }

it fixes the issue but you may have data in your widget that may be invalid due to Unauthentication so my suggestion is to restart app like this :


  double appKey = 0;
  @overrdie
  initState() {
    super.initState();
    auth.onAuthStateChanged.listen(() {
      setState(() { appKey++; });
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      key: Key('$appKey'),
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: new StreamBuilder(
        stream: auth.onAuthStateChanged,
        builder: (context, snapshot)  {
          if (snapshot.hasData) {
            return MainScreen();
          }
          return AuthScreen();
        },
      ),
    );
  }

but if you are sure you handle invalid data it's better to listen to onAuthStateChanged ( like in code above ) and push AuthScreen via navigator and block user from exiting screen using WillPopScope widget in AuthScreen. It feels better because of transition animation.

Should every screen check for authentication before loading or should it be done only in the main.dart file?

1 Answers1