A simple, unified fingerprint authentication library for Android with ReactiveX extensions.

Fingerprint authentication on Android is a mess. This library unifies the different available APIs, deals with the idiosyncrasies of each, and adds an optional reactive interface.

Reprint is distributed with jitpack and split up into several libraries, so you can include only the parts that you use.

First, add jitpack to your gradle repositories.

repositories {
    maven { url "https://jitpack.io" }
}

Then add the core library and optionally the Samsung Pass interface and the ReactiveX interface.

dependencies {
   compile 'com.github.ajalt.reprint:core:2.0.0@aar' // required, supports marshmallow devices
   compile 'com.github.ajalt.reprint:reprint_spass:2.0.0@aar' // optional: support for pre-marshmallow Samsung devices
   compile 'com.github.ajalt.reprint:reactive:2.0.0@aar' // optional: the ReactiveX interface
}

Reprint requires the following permissions be declared in your AndroidManifest.xml

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

<!-- Samsung fingerprint permission, only reqiured if you include the spass module -->
<uses-permission android:name="com.samsung.android.providers.context.permission.WRITE_USE_APP_FEATURE_SURVEY"/>

See the sample app for a complete example.

In your Application.onCreate, initialize Reprint with Reprint.initialize(this). This will load the Marshmallow module, and the Spass module if you included it.

Then, anywhere in your code, you can call Reprint.authenticate to turn on the fingerprint reader and listen for a fingerprint. You can call Reprint.cancelAuthentication to turn the reader off before it finishes normally.

There are two ways to be notified of authentication results: traditional callback, and a ReactiveX Observable..

Pass an AuthenticationListener to authenticate, and it's callbacks will be called with results. The onFailure callback will be called repeatedly until the sensor is disabled or a fingerprint is authenticated correcty, at which point onSuccess will be called.

Reprint.authenticate(new AuthenticationListener() {
    @Override
    public void onSuccess(int moduleTag) {
        showSuccess();
    }

    @Override
    public void onFailure(AuthenticationFailureReason failureReason, boolean fatal,
                          @Nullable CharSequence errorMessage, int moduleTag, int errorCode) {
        showError(failureReason, fatal, errorMessage, errorCode);
    }
});

The failureReason is an enum value with general categories of reason that the authentication failed. This is useful for displaying help messages in your UI.

The fatal parameter is true if the sensor has stopped and cannot be restarted, such as when it's locked out. It's false if the sensor is still running, such as when a finger was moved over the sensor too quickly.

The errorMessage is a string that, if it's not null, will contain some help text provided by the underlying SDK about the failure. You should show this text to the user. The underlying SDK might not provide help text, in which case you should show your own message.

The moduleTag and errorCode can be used to find out the SDK-specific reason for the failure.

If you include the reactive reprint library, you can be notified of authentication results through an Observable by calling RxReprint.authenticate. In this case, the subscriber's onNext will be called at most once, after a successful authentication. When the onError method is called, the sensor will already be stopped.

RxReprint.authenticate().subscribe(::showSuccess, ::showError);

You probably want to use the retry operator to restart the sensor when a non-fatal error occurs.

RxReprint.authenticate()
         .doOnError(::showHelp)
         .retry((count, t) -> {
            AuthenticationFailure e = (AuthenticationFailure) t;
            return !e.fatal || e.failureReason == AuthenticationFailureReason.TIMEOUT && count < 5;
         })
         .subscribe(::showSuccess, ::showError);

One advantage that this interface has is that when the subscriber unsubscribes, the authentication request is automatically canceled. So you could, for example, use the RxLifecycle library to bind the observable, and the authentication will be canceled when your activity pauses.

Copyright (c) 2015 AJ Alt


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