Local Authentication with Flutter

In this post I am going to implement this feature using flutter and dart.

First of all download and install flutter SDK from

https://flutter.dev/docs/get-started/install/windows


Create a project:
Enter this command in command prompt  "flutter create signin_flutter"


Importing packages:
Now import the plug-in local_auth by adding the following line to your project's pubspec.yaml file.

"loacl_auth: ^0.4.0+1."

you can also find latest version on https://pub.dev/packages/local_auth

Adding Permissions:

In order to have authentication working correctly on android we have to update AndriodManifesto.xml file to include the USE_FINGERPRINT permission.

"<uses-permission android:name="android.permission.USE_FINGERPRINT"/>"

we can find the file here
Your project directory...\signin_flutter\android\app\src\main\AndroidManifest.xml


Adding local Authentication:

import local_auth package in main.dart file

import 'package:local_auth/local_auth.dart';

and create an instance

final LocalAuthentication _localAuthentication = LocalAuthentication();

Now we will be implementing 3 methods:

1. _checkBiometric()  for checking bio metric authentication hardware is available in the device.
2. _getListOfBiometricTypes()  for getting the list of available bio metric types.
3._authorizeNow()  for authenticating the user.

  bool _canCheckBiometric = false;  
  String _authorizedOrNot = "Not Authorized";  
  List<BiometricType> _availableBiometricTypes = List<BiometricType>();  
  Future<void> _checkBiometric() async {  
   bool canCheckBiometric = false;  
   try {  
    canCheckBiometric = await _localAuthentication.canCheckBiometrics;  
   } on PlatformException catch (e) {  
    print(e);  
   }  
   if (!mounted) return;  
   setState(() {  
    _canCheckBiometric = canCheckBiometric;  
   });  
  }  
  Future<void> _getListOfBiometricTypes() async {  
   List<BiometricType> listofBiometrics;  
   try {  
    listofBiometrics = await _localAuthentication.getAvailableBiometrics();  
   } on PlatformException catch (e) {  
    print(e);  
   }  
   if (!mounted) return;  
   setState(() {  
    _availableBiometricTypes = listofBiometrics;  
   });  
  }  
  Future<void> _authorizeNow() async {  
   bool isAuthorized = false;  
   try {  
    isAuthorized = await _localAuthentication.authenticateWithBiometrics(  
     localizedReason: "Please authenticate proceed",  
     useErrorDialogs: true,  
     stickyAuth: true,  
    );  
   } on PlatformException catch (e) {  
    print(e.message);  
   }  
   if (!mounted) return;  
   setState(() {  
    if (isAuthorized) {  
     _authorizedOrNot = "Authorized";  
    } else {  
     _authorizedOrNot = "Not Authorized";  
    }  
   });  
  }  

we need to import

import 'package:flutter/services.dart';

for getting PlatformExceptions.


Building a basic UI:

we are adding sample
3 text widgets and respective buttons.

 Scaffold(  
    appBar: AppBar(  
     title: Text(widget.title),  
    ),  
    body: Center(  
     child: Column(  
      mainAxisAlignment: MainAxisAlignment.center,  
      children: <Widget>[  
       Text("Can we check Biometric : $_canCheckBiometric"),  
       RaisedButton(  
        onPressed: _checkBiometric,  
        child: Text("Check Biometric"),  
        color: Colors.blue,  
        colorBrightness: Brightness.light,  
       ),  
       Text("List Of Biometric : ${_availableBiometricTypes.toString()}"),  
       RaisedButton(  
        onPressed: _getListOfBiometricTypes,  
        child: Text("List of Biometric Types"),  
        color: Colors.blue,  
        colorBrightness: Brightness.light,  
       ),  
       Text("Authorized : $_authorizedOrNot"),  
       RaisedButton(  
        onPressed: _authorizeNow,  
        child: Text("Authorize now"),  
        color: Colors.blue,  
        colorBrightness: Brightness.light,  
       ),  
      ],  
     ),  
    ),  
   );  

UI Screens:

Conclusion:

I hope this article will saves your time to integrate bio metric authentication with flutter.

you can find the source code from my GitHub repository here