Flutter: type 'Future<Dynamic>' is not a subtype of type widget

Question

I’m trying to run a check through the token:

If there is a token, display the page Home and, if not, displays the page Login.

I tried this way:

main.Dart:

class MyApp extends StatelessWidget {

    // Create storage
    final storage = new FlutterSecureStorage();
    checkHome() async {
    // Read value 
    String token = await storage.read(key: 'token');
    if(token != null){
      return HomePage();
    }else{
      return LoginPage();
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Cadê meu pet?',
      theme: ThemeData(primarySwatch: Colors.yellow),
      home: checkHome(),
    );
  }
}

However, I am getting:

type 'Future' is not a subtype of type 'Widget'

I cannot return to home/login through this function?

I also tried to:

void main() async {
  // Set default home.
  Widget _defaultHome = new LoginPage();

  // Read value 
  final storage = new FlutterSecureStorage();
  String token = await storage.read(key: 'token');
  if (token != null) {
    _defaultHome = new HomePage();
  }

  // Run app!
  runApp(new MaterialApp(
    title: 'Cadê meu pet?',
    theme: ThemeData(primarySwatch: Colors.yellow),
    home: _defaultHome,
  ));
}

Answer 1

Its return shows that the component expects to be passed to it an element of the type Widget but you’re passing an element of the kind Future<Widget>. Futures are returned whenever the method has in its signature the declaration async.

In your case an example you can use is:

Example with Statefulwidget

import 'package:flutter/material.dart';
import 'package:flutter_secure_storage/flutter_secure_storage.dart';

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

class MyApp extends StatefulWidget {
  // Create storage
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  // Variável de controle
  bool temToken = false;

  final storage = new FlutterSecureStorage();

  checkHome() async {
    // Read value
    String token = await storage.read(key: 'token');
    setState(() {
      temToken = token != null;
    });
  }

  @override
  void initState() {
    super.initState();

    checkHome();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Cadê meu pet?',
      theme: ThemeData(primarySwatch: Colors.yellow),

      /// Declaração do ternário para escolher qual page exibir
      home: temToken ? HomePage() : LoginPage(),
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Center(
        child: Text("Home"),
      ),
    );
  }
}

class LoginPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Center(
        child: Text("Login"),
      ),
    );
  }
}

There are other approaches that could be used, but given the example that passed the question, this is one of the simple ways for this specific scenario that presented.