Xamarin.Forms - Fingerprint Authentication In your App

Introduction

 

Xamarin.Forms code runs on multiple platforms - each of which has its own filesystem. This means that reading and writing files is most easily done using the native file APIs on each platform. Alternatively, embedded resources are a simpler solution to distribute data files with an app.

 

Plugin.Fingerprint

 

Authenticate a user via fingerprint, face id or any other biometric / local authentication method from a cross platform API.

 

Prerequisites

• Visual Studio 2017 or later (Windows or Mac)

Setting up a Xamarin.Forms Project

 

Start by creating a new Xamarin.Forms project. You wíll learn more by going through the steps yourself.

 

Create a new or existing Xamarin forms(.Net standard) Project. With Android and iOS Platform.

 

 

Nuget

 

Install the following Nuget from Nuget Manager In your Visual Studio.

• Plugin.Fingerprint

 

iOS Setup

 

Add NSFaceIDUsageDescription to your Info.plist to describe the reason your app uses Face ID. Otherwise the App will crash when you start a Face ID authentication on iOS 11.3+.

 

<key>NSFaceIDUsageDescription</key> 

<string>Need your face to unlock secrets!</string> 

 

Android Setup

 

Request the permission in AndroidManifest.xml

 

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

 

Add the below code in MainActivity.cs OnCreate Method.

CrossFingerprint.SetCurrentActivityResolver(() => this);

Install Android X Migration

 

Since version 2, this plugin uses Android X. You have to install Xamarin.AndroidX.Migration in your Android project.

 

FingerPrint Authentication

private async Task AuthenticateAsync(string reason, string cancel = null, string fallback = null, string tooFast = null)
        {
            _cancel = false ? new CancellationTokenSource(TimeSpan.FromSeconds(10)) : new CancellationTokenSource();

            var dialogConfig = new AuthenticationRequestConfiguration("My App", reason)
            {
                CancelTitle = cancel,
                FallbackTitle = fallback,
                AllowAlternativeAuthentication = true,
                ConfirmationRequired = false
            };

            dialogConfig.HelpTexts.MovedTooFast = tooFast;
            var result = await Plugin.Fingerprint.CrossFingerprint.Current.AuthenticateAsync(dialogConfig, _cancel.Token);
            await SetResultAsync(result);
        }

Enable AlternativeAuthentication

 

If you need to allow alternate authentication such as Pin, Pattern and password set AlternativeAuthentication=true

var dialogConfig = new AuthenticationRequestConfiguration("My App", reason)
            {
                CancelTitle = cancel,
                FallbackTitle = fallback,
                AllowAlternativeAuthentication = true,
                ConfirmationRequired = false
            };

Full code

protected override async void OnAppearing()
        {
            base.OnAppearing();

            var authType= await Plugin.Fingerprint.CrossFingerprint.Current.GetAuthenticationTypeAsync();
            if(authType==AuthenticationType.Fingerprint)
            {
                lblAuthenticationType.Text = "Auth Type: " + authType;

                await AuthenticateAsync("Authendicate with Touch ID");
            }

        }

        private async Task AuthenticateAsync(string reason, string cancel = null, string fallback = null, string tooFast = null)
        {
            _cancel = false ? new CancellationTokenSource(TimeSpan.FromSeconds(10)) : new CancellationTokenSource();

            var dialogConfig = new AuthenticationRequestConfiguration("My App", reason)
            {
                CancelTitle = cancel,
                FallbackTitle = fallback,
                AllowAlternativeAuthentication = true,
                ConfirmationRequired = false
            };

            dialogConfig.HelpTexts.MovedTooFast = tooFast;
            var result = await Plugin.Fingerprint.CrossFingerprint.Current.AuthenticateAsync(dialogConfig, _cancel.Token);
            await SetResultAsync(result);
        }

Run

 

 

 

 

 

I hope you have understood and learned how to implement fingerprint, password and facelock authentication in your XamarinApp.

 

Thanks for reading. Please share your comments and feedback. Happy Coding :)