Face Authentication using androidx Biometric API in Android

Question

I need to integrate Biometric authentication using Fingerprint and Face authentication. Fingerprint authentication works perfectly but when I set only Face authentication I am getting Biometric not enrolled response from BiometricManager.from(context) method as follows,

val biometricManager = BiometricManager.from(context)
    when(biometricManager.canAuthenticate()){
        BiometricManager.BIOMETRIC_SUCCESS ->{
            Log.e(TAG, "App can authenticate using biometrics.")
        }
        BiometricManager.BIOMETRIC_ERROR_NO_HARDWARE ->{
            Log.d(TAG, "Hardware not available")
        }
        BiometricManager.BIOMETRIC_ERROR_HW_UNAVAILABLE ->{
            Log.d(TAG, "Biometric features are currently unavailable.")
        }
        BiometricManager.BIOMETRIC_ERROR_NONE_ENROLLED ->{
            Log.d(TAG, "The user hasn't associated any biometric credentials with their account.")
        }
        else ->{
            Log.d(TAG, "Nothing supported")
        }
    }

Answer 1

Android Biometric APIs would only work on the devices which have their biometric features (face,fingerprint, iris) compatible with Android Biometric stack. I have a set of devices with Face feature support, among them only few support Android Biometrics.

Answer 2

After looking at all the hurdles implementing the biometric for Android, I have chosen not to use BiometricManager.from(context) method to check if Biometric authentication is enabled, instead of that checked if KEYGUARD_SERVICE is enabled and used following prompt info

BiometricPrompt.PromptInfo.Builder().apply {
            setTitle(getString(R.string.title))
            setSubtitle(getString(R.string.sub_title))
            setConfirmationRequired(true)
            setDeviceCredentialAllowed(true)
        }.build()

through which even if only face ID is set and is not supporting the current callbacks, application fallbacks to devices PIN authentication method.