How to check user's Bio-Metric Preference through Biometric api?

Question

As we all know, from android 9.0, android introduced BiometricPrompt Api to provide standard authentication experience across growing range of biometric sensors (E.g Fingerprint,Face ID etc).

Now with this new BiometricPrompt Api user can get authenticated via fingerprint, face scanner or iris scanned (depend on their biometric preference). BiometricPrompt api will take care of this and it will notify us via various callbacks.

Below is my code to display Biometric Prompt.

 biometricPrompt = new BiometricPrompt.Builder(context)
            .setTitle("FingerPrint Authentication")
            .setSubtitle("Login via Fingerprint")
            .setDescription("Touch Fingerprint Sensor")
            .setNegativeButton("Cancel", context.getMainExecutor(),
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            Log.d(TAG,"Cancelled");
                        }
                    })
            .build();

Now if you see my code, i am setting title as a Fingerprint Authentication. Now in device setting, if user had set a Biometric Preference as a Face ID instead of FingerPrint then this biometricPrompt will authenticate user via faceID and fingerprint sensor wont work even if user keep touching sensor. This would create confusion as Biometric title is saying that "Fingerprint authentication" and user is actually getting authenticated via faceID

Is there any way by which we can know what Biometric preference user has selected (e.g Fingerprint or FaceID)? So based upon that preference i can show appropriate message on BiometricPrompt so user wont get confused.

I already explored all api from BiometricPrompt but could find anything related to BiometricPreference.

Any help would be highly appreciated.

Answer 1

While not a perfect solution, you can use the PackageManager API to determine whether a device has the authenticator hardware, e.g.:

if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_FACE))
{
}

I've created a helper class as follows:

class BiometricAuthenticator
{
 public enum BiometricType
 {
  FINGERPRINT,
  FACE, 
  IRIS,
  NONE
 }

 public static boolean hasBiometricAuthenticator(Context context)
 {
    int biometry = BiometricManager.BIOMETRIC_ERROR_UNSUPPORTED;
    if (VERSION.SDK_INT >= 30)
        biometry = BiometricManager.from(context).canAuthenticate(Authenticators.BIOMETRIC_STRONG | Authenticators.BIOMETRIC_WEAK);
    else
        biometry = BiometricManager.from(context).canAuthenticate();

    switch (biometry)
    {
        case BiometricManager.BIOMETRIC_ERROR_HW_UNAVAILABLE:
        case BiometricManager.BIOMETRIC_ERROR_NONE_ENROLLED:
        case BiometricManager.BIOMETRIC_ERROR_NO_HARDWARE:
             return (false);
        case BiometricManager.BIOMETRIC_SUCCESS:
             return true;
    }
    return (false);
 }

 /**
  * biometricType()
  *
  * returns type of biometry supported
  */
 public static BiometricType biometricType(Context context)
 {
    if (VERSION.SDK_INT < 23)
        return BiometricType.NONE;

    PackageManager packageManager = context.getPackageManager();

    // SDK 29 adds FACE and IRIS authentication
    if (VERSION.SDK_INT >= 29)
    {
        if (packageManager.hasSystemFeature(PackageManager.FEATURE_FACE))
            return BiometricType.FACE;
        if (packageManager.hasSystemFeature(PackageManager.FEATURE_IRIS))
            return BiometricType.IRIS;
        if (packageManager.hasSystemFeature(PackageManager.FEATURE_FINGERPRINT))
            return BiometricType.FINGERPRINT;
        return BiometricType.NONE;
    }

    // SDK 23-28 offer FINGERPRINT only
    return (packageManager.hasSystemFeature(PackageManager.FEATURE_FINGERPRINT) ? BiometricType.FINGERPRINT : BiometricType.NONE);
 }
}

This allows you to determine if a biometric authenticator is present (hasBiometricAuthenticator), and if so, return the type of authenticator as a BiometricType enum.

A device could theoretically have multiple authenticators, and biometricType() will return FACE, IRIS, then FINGERPRINT in that order of preference on API30+ devices.

Hopefully Google will expose better API in the future, but these tricks will at least help get appropriate prompts on the dialog

Answer 2

There is no mean of knowing this type of information for now, an issue had been opened last year to ask for it (https://issuetracker.google.com/issues/111315641). As Android tried to simplify the path for developer to implement authentication in their apps, there is a lack of options in the BiometricPrompt implementation (see the Android document for BiometricPrompt implementation).