This blog was originally published on RavSam blog.

In any production app, the user is directed to a route based on some authentication logic whenever the app is opened. In our Flutter App, we have at least two routes, Login and Dashboard. The problem is how can we decide which route should a user be redirected to?

In this app, we will check the value of a locally stored boolean variable to dynamically decide the home route. We can use any method for writing our authentication logic, like checking the validity of the API token, but for the sake of simplicity, we will explore a simple logic.

Flutter Dynamic Home Route Flowchart

Installing Dependencies

In our pubspec.yaml, let us add the following dependencies that we will be using in our Flutter application:

dependencies:
  shared_preferences: ^0.5.12+4
  async: ^2.4.2

Make sure to install the latest version of the dependencies.

Shared Preferences is a simple Flutter plugin for reading and writing simple key-value pairs to the local storage. Async contains the utility functions and classes related to the dart:async library.

After adding these dependencies, it is now time to install them. In the terminal, let us execute the following command:

flutter pub get

2. Writing Code

In our main.dart, let us add the following code:

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

void main() async {

  // handle exceptions caused by making main async
  WidgetsFlutterBinding.ensureInitialized();

  // init a shared preferences variable
  SharedPreferences prefs = await SharedPreferences.getInstance();

  // get the locally stored boolean variable
  bool isLoggedIn = prefs.getBoolean('is_logged_in');

  // define the initial route based on whether the user is logged in or not
  String initialRoute = isLoggedIn ? '/' : 'login';

  // create a flutter material app as usual
  Widget app = MaterialApp(
    ...
    initialRoute: initialRoute,
  );

  // mount and run the flutter app
  runApp(app);
}

The code is pretty self-explanatory. All we are doing is getting the value of the is_logged_in boolean variable, and then decide the value of the initialRoute in our Flutter Material App.

One important thing in the above code is the use of the async-await pattern. We can also use then but it makes the code a little messy and that’s what we are trying to avoid here. Making our main() function asynchronous can cause some exceptions, so to solve this, we need to add WidgetsFlutterBinding.ensureInitialized().

Results

That’s it. We have successfully written a code that allows us to redirect the user to the Dashboard page if they are logged in, otherwise to the Login page.

Thanks for reading 💜

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