Android fingerprint on SDK<23

Question

I have a project on Android with minSDK=17 and targetSDK=23. We have a fingerprint authentication in this project made using FingerprintManager class (it was added in SDK23). We added SDK version check, so we are not using anything related to fingerprint if SDK<23. But in older SDK versions app behaviour is unpredictable: on some versions app just crashing, on other -- fingerprint not working (so, it's ok).

My question:

1) Is it any good and easy-to-implement libraries for minSDK=17, that can recognize fingerprints? 2) How can I avoid app crashing in devices with SDK<23? Crash error:

E/dalvikvm: Could not find class 'android.hardware.fingerprint.FingerprintManager', referenced from method nl.intratuin.LoginActivity.loginByFingerprint
E/AndroidRuntime: FATAL EXCEPTION: main   java.lang.VerifyError:
LoginActivity at java.lang.Class.newInstanceImpl(Native Method)

---

Some new info: created HelloWorld fingerprint project using this tutorial: http://www.techotopia.com/index.php/An_Android_Fingerprint_Authentication_Tutorial Found the root of the problem: FingerprintDemoActivity->cipherInit:

try {
    keyStore.load(null);
    SecretKey key = (SecretKey) keyStore.getKey(KEY_NAME,
             null);
    cipher.init(Cipher.ENCRYPT_MODE, key);
    return true;
} catch (KeyPermanentlyInvalidatedException e) {
    return false;
} catch (KeyStoreException | CertificateException 
      | UnrecoverableKeyException | IOException
      | NoSuchAlgorithmException | InvalidKeyException e) {
   throw new RuntimeException("Failed to init Cipher", e);
}

First catch block breacking whole app with error I mentioned above. Of course, I can just remove this catch (this exception extends InvalidKeyException, so it will be handled), and return false in case of any exceptions. Is it any better way?

Answer 1

I think, I found acceptable solution: catch not KeyPermanentlyInvalidatedException, but InvalidKeyException. Everything working fine this way. Still have no idea how this exception crashed whole app...

Answer 2

It happened to me also..even when i used : if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M).. my app crashes on android 4.4- kitkat. so eventually the problem was in the initCipher method in the catches part - see the following code (even though i m not suppose to get there as it targeted to M and above... very strange behaviour..) :

@TargetApi(Build.VERSION_CODES.M)
private boolean initCipher() {
    try {
        mKeyStore.load(null);
        SecretKey key = (SecretKey) mKeyStore.getKey(KEY_NAME, null);
        mCipher.init(Cipher.ENCRYPT_MODE, key);

        return true;
    } catch (KeyStoreException | CertificateException | UnrecoverableKeyException | IOException
            | NoSuchAlgorithmException e) {
        throw new RuntimeException("Failed to init Cipher", e);
    } catch (InvalidKeyException e) {
        e.printStackTrace();
        return false;

    }
}

apparently the order off the catches matter..so just make sure to write it as i mentioned.