Flutterexperts

Introduction

Hello, I welcome you all to my new post on Local Authentication in Flutter. In this post, we shall discuss how to implement the FingerPrint in your flutter app for local authentication. So let’s start with the context.

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Table of content

1. Local Authentication
2. Required Plugin
3. Checking for biometric availability
4. Checking biometric type
5. Authentication using biometric
6. Designing a simple App

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Local Authentication

Verifying the user locally i.e. without the use of a web server, using facelock or fingerprint can be termed as Local Authentication.

1. biometric authentication on iOS
2. fingerprint APIs on Android

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Required Plugin

Fortunately, we have a plugin managed by the flutter team.

Just go to pub.dev and search for local_auth package.

Install the dependencies in your pubspec.yaml file.

dependencies:
  local_auth: ^latets version

install the dependence

Useflutter_pub_get command to install the dependence.

import the package

import 'package:local_auth/local_auth.dart';

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Checking for biometric availability

final LocalAuthentication auth = LocalAuthentication();
bool canCheckBiometrics = false;
try {
  canCheckBiometrics = await auth.canCheckBiometrics;
} catch (e) {
  print("error biome trics $e");
}

print("biometric is available: $canCheckBiometrics");

We are using the try and catch method for checking biometric and catching errors.

initializing LocalAuthentication

final LocalAuthentication auth = LocalAuthentication();

canCheckBiometrics

bool canCheckBiometrics = false;

We have made a bool variable canCheckBiometrics which is initially set to false.

We are using it to set/update the availability of biometric.

auth.canCheckBiometrics

Here canCheckBiometrics is a method of LocalAuthentication() object which returns a boolean value.

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Checking biometric type

List<BiometricType> availableBiometrics;
try {
  availableBiometrics = await auth.getAvailableBiometrics();
} catch (e) {
  print("error enumerate biometrics $e");
}

print("following biometrics are available");
if (availableBiometrics.isNotEmpty) {
  availableBiometrics.forEach((ab) {
    print("Avalible Biomatrics: $ab");
  });
} else {
  print("no biometrics are available");
}

getAvailableBiometrics() method returns the list of available Biometrics.

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Authentication using biometric

bool authenticated = false;
try {
  authenticated = await auth.authenticateWithBiometrics(
      localizedReason: 'Touch your finger on the sensor to login',
      useErrorDialogs: true,
      stickyAuth: false,
      androidAuthStrings:
          AndroidAuthMessages(signInTitle: "Login to HomePage"));
} catch (e) {
  print("error using biometric auth: $e");
}
print("authenticated: $authenticated");

authenticateWithBiometrics() is a method that returns a dialog box to provide a message to the user to press the fingerprint sensor for authentication.

To read more about each method you can press Ctrl+B in that particular method.

Full method

void _checkBiometric() async {
  final LocalAuthentication auth = LocalAuthentication();
  bool canCheckBiometrics = false;
  try {
    canCheckBiometrics = await auth.canCheckBiometrics;
  } catch (e) {
    print("error biome trics $e");
  }

  print("biometric is available: $canCheckBiometrics");

  List<BiometricType> availableBiometrics;
  try {
    availableBiometrics = await auth.getAvailableBiometrics();
  } catch (e) {
    print("error enumerate biometrics $e");
  }

  print("following biometrics are available");
  if (availableBiometrics.isNotEmpty) {
    availableBiometrics.forEach((ab) {
      print("\ttech: $ab");
    });
  } else {
    print("no biometrics are available");
  }

  bool authenticated = false;
  try {
    authenticated = await auth.authenticateWithBiometrics(
        localizedReason: 'Touch your finger on the sensor to login',
        useErrorDialogs: true,
        stickyAuth: false,
        androidAuthStrings:
            AndroidAuthMessages(signInTitle: "Login to HomePage"));
  } catch (e) {
    print("error using biometric auth: $e");
  }
  setState(() {
    isAuth = authenticated ? true : false;
  });

  print("authenticated: $authenticated");
}

Designing a simple App

Github link

anmolseth06/local_auth
A new Flutter application. This project is a starting point for a Flutter application. A few resources to get you…github.com

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Hi, I am Anmol Gupta, a Flutter Developer, content writer, and now udemy instructor. I am a passionate application developer and curious learner and I love sharing my knowledge with others that’s why I decided to write on medium, and now I am expanding my capabilities by creating a demanding udemy course that will help Flutter Developer to learn advanced functionalities that will directly help you in landing high paying job or getting high paying clients internationally.

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