Continuously listen for fingerprints on android device in background

Question

I am developing a fingerprint gesture application which should work in the background and continuously listen for fingerprint input from user to perform desired actions. So far, I have tried to use IntentService to make fingerprint scanner work in the background but as soon as I close the activity or minimize it, fingerprint scanner stops working. Is there any way where I can use fingerprint scanner in the background even after my activity is closed? Here is my code

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private static final String KEY_NAME = "secretkey";
    private Cipher cipher;
    private KeyStore keyStore;
    private KeyGenerator keyGenerator;
    private FingerprintManager.CryptoObject cryptoObject;

    private TextView textView;
    private Button auth_button,stop_button;
    private FingerprintManager fingerprintManager;
    private KeyguardManager keyguardManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            keyguardManager = (KeyguardManager) getSystemService(KEYGUARD_SERVICE);
            fingerprintManager = (FingerprintManager) getSystemService(FINGERPRINT_SERVICE);
            textView=(TextView)findViewById(R.id.authStatus);
            auth_button=(Button)findViewById(R.id.auth_button);
            stop_button=(Button)findViewById(R.id.stop_button);

            if (!fingerprintManager.isHardwareDetected()) {
                textView.setText("Your device doesn't support fingerprint authentication");
            }

            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
                textView.setText("Please enable the fingerprint permission");
            }

            if (!fingerprintManager.hasEnrolledFingerprints()) {
                textView.setText("No fingerprint configured. Please register at least one fingerprint in your device's Settings");
            }

            if (!keyguardManager.isKeyguardSecure()) {
                textView.setText("Please enable lockscreen security in your device's Settings");
            }

            else {
                auth_button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Toast.makeText(MainActivity.this, "Starting service", Toast.LENGTH_SHORT).show();
                        try
                        {
                            generateKey();
                        }
                        catch(Exception e)
                        {
                            e.printStackTrace();
                        }
                        if(initCipher())
                        {
                            Provider provider=new Provider(fingerprintManager,cryptoObject,MainActivity.this);
                            Intent intent=new Intent(MainActivity.this,AsyncService.class);
                            startService(intent);
                        }
                    }
                });

                stop_button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        stopService(new Intent(MainActivity.this,AsyncService.class));
                        Toast.makeText(MainActivity.this, "Service stopped", Toast.LENGTH_SHORT).show();
                    }
                });
            }
        }
    }

    private void generateKey() {
        try
        {
            keyStore = KeyStore.getInstance("AndroidKeyStore");
            keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore");
            keyStore.load(null);
            keyGenerator.init(new

                    KeyGenParameterSpec.Builder(KEY_NAME,
                    KeyProperties.PURPOSE_ENCRYPT |
                            KeyProperties.PURPOSE_DECRYPT)
                    .setBlockModes(KeyProperties.BLOCK_MODE_CBC)
                    .setUserAuthenticationRequired(true)
                    .setEncryptionPaddings(
                            KeyProperties.ENCRYPTION_PADDING_PKCS7)
                    .build());

            keyGenerator.generateKey();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    public boolean initCipher() {
        try
        {
            cipher = Cipher.getInstance(KeyProperties.KEY_ALGORITHM_AES + "/" + KeyProperties.BLOCK_MODE_CBC + "/" + KeyProperties.ENCRYPTION_PADDING_PKCS7);
        }
        catch (Exception e)
        {
            throw new RuntimeException("Failed to get Cipher", e);
        }

        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 (Exception e)
        {
            throw new RuntimeException("Failed to init Cipher", e);
        }
    }
}

AsyncService.java

public class AsyncService extends IntentService {

    private int ONGOING_NOTIFICATION_ID=2346712;

    public AsyncService() {
        super(AsyncService.class.getName());
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        showNotification();
        new FingerprintHandler().startAuth(Provider.fpManager,Provider.cryptoObj);
    }

    public void showNotification() {

        Intent notificationIntent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent =
                PendingIntent.getActivity(this, 0, notificationIntent, 0);

        Notification notification =
                new Notification.Builder(this)
                        .setContentTitle(getText(R.string.notification_title))
                        .setContentText(getText(R.string.notification_message))
                        .setSmallIcon(R.drawable.launcher)
                        .setContentIntent(pendingIntent)
                        .build();

        startForeground(ONGOING_NOTIFICATION_ID, notification);
    }

    public class FingerprintHandler extends FingerprintManager.AuthenticationCallback {

        private CancellationSignal cancellationSignal;
        public void startAuth(FingerprintManager manager, FingerprintManager.CryptoObject cryptoObject)
        {
            cancellationSignal = new CancellationSignal();
            if (ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED)
            {
                return;
            }
            manager.authenticate(cryptoObject, cancellationSignal, 0, this, null);
        }

        @Override
        public void onAuthenticationError(int errMsgId, CharSequence errString)
        {

        }

        @Override
        public void onAuthenticationFailed()
        {
           //some action to perform
        }

        @Override
        public void onAuthenticationHelp(int helpMsgId, CharSequence helpString)
        {

        }

        @Override
        public void onAuthenticationSucceeded(FingerprintManager.AuthenticationResult result)
        {
            //some action to perform
        }
    }
}

Provider.java

public class Provider {

    public static FingerprintManager fpManager;
    public static FingerprintManager.CryptoObject cryptoObj;
    public static Context mContext;

    public Provider(FingerprintManager fingerprintManager, FingerprintManager.CryptoObject cryptoObject, Context context) {
        fpManager=fingerprintManager;
        cryptoObj=cryptoObject;
        mContext=context;
    }
}

Answer 1

Look at my answer here

Finally, After hours of trying I found the problem, The solution is you must create AccessibilityService and enable the permission from settings, After enabling the permission, Callback will work.

Answer 2

try this, worked for me

@Override
public int onStartCommand(@Nullable Intent intent, int flags, int startId) {

    startForeground(ONGOING_NOTIFICATION_ID, showNotification());
    new FingerprintHandler().startAuth(Provider.fpManager,Provider.cryptoObj);
    return START_STICKY;
}

@Override
protected void onHandleIntent(Intent intent) {

}

public Notification showNotification() {

    Intent notificationIntent = new Intent(this, MainActivity.class);
    PendingIntent pendingIntent =
            PendingIntent.getActivity(this, 0, notificationIntent, 0);

    Notification notification =
            new Notification.Builder(this)
                    .setContentTitle(getText(R.string.notification_title))
                    .setContentText(getText(R.string.notification_message))
                    .setSmallIcon(R.drawable.launcher)
                    .setContentIntent(pendingIntent)
                    .build();
    notificationChannel().notify(ONGOING_NOTIFICATION_ID, notification);
    return notification;

}

@TargetApi(Build.VERSION_CODES.O)
private NotificationManager notificationChannel() {
    NotificationManager notificationMgr =(NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {

        NotificationChannel notificationChannel =(NotificationChannel) new NotificationChannel("channel_name", BuildConfig.APPLICATION_ID, NotificationManager.IMPORTANCE_MIN);
        notificationChannel.setDescription("desc");
        notificationChannel.setLightColor(ContextCompat.getColor(getApplicationContext(), R.color.colorPrimary));
        notificationChannel.enableLights(false);
        notificationChannel.enableVibration(false);
        notificationMgr.createNotificationChannel(notificationChannel);
    }
    return notificationMgr;

}

Answer 3

You can try this below code. First of all you need to add properties of Service in Manifest file

  <service
        android:name=".service.Service"
        android:enabled="true"
        android:icon="@drawable/ic_launcher"
        android:isolatedProcess="true">

  </service>

And also add START_STICKY in your service.

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    return START_STICKY;
}