user3126480 user3126480 - 4 months ago 69
Java Question

How to use fingerprint scanner to authenticate users

I have been developing my personal android app to store my passwords. (Since lastpass is paid for mobile). I currently use

simple password authentication
, but i would love to be able to take advantage of my
fingerprint
scanner
.

AndroidManifest.xml:

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

MainActivity.java:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
//Fingerprint API only available on from Android 6.0 (M)
FingerprintManager fingerprintManager = (FingerprintManager) context.getSystemService(Context.FINGERPRINT_SERVICE);
if (!fingerprintManager.isHardwareDetected()) {
// Device doesn't support fingerprint authentication
} else if (!fingerprintManager.hasEnrolledFingerprints()) {
// User hasn't enrolled any fingerprints to authenticate with
} else {
// Everything is ready for fingerprint authentication
}
}


but how do i actually
authenticate
phone owner using his
fingerprints
?

UPDATE:

I used Lubomir Babev's answer and its perfect. You fill the two methods that you implement onAuthSucceded, onAuthFailed to handle if authorizartion was successful and i also had to add some permission checks, because Android studio made me do it

public void startListening() {
if (isFingerScannerAvailableAndSet()) {
try {
if (ActivityCompat.checkSelfPermission(mContext.getApplicationContext(), Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
}
mFingerprintManager.authenticate(null, mCancellationSignal, 0 /* flags */, mAuthenticationCallback, null);
} catch (Exception e) {
e.printStackTrace();
}
}
}


and

public void startListening() {
if (isFingerScannerAvailableAndSet()) {
try {
if (ActivityCompat.checkSelfPermission(mContext.getApplicationContext(), Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
}
mFingerprintManager.authenticate(null, mCancellationSignal, 0 /* flags */, mAuthenticationCallback, null);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Answer

I create a custom handler class for fingerprint event :

import android.content.Context;
import android.hardware.fingerprint.FingerprintManager;
import android.os.Build;
import android.os.CancellationSignal;

public class FingerprintHandler {
    private Context                                     mContext;
    private FingerprintManager                          mFingerprintManager = null;
    private CancellationSignal                          mCancellationSignal;
    private FingerprintManager.AuthenticationCallback   mAuthenticationCallback;
    private OnAuthenticationSucceededListener           mSucceedListener;
    private OnAuthenticationErrorListener               mFailedListener;

    public interface OnAuthenticationSucceededListener {
        void onAuthSucceeded();
    }

    public interface OnAuthenticationErrorListener {
        void onAuthFailed();
    }

    public void setOnAuthenticationSucceededListener (OnAuthenticationSucceededListener listener){
        mSucceedListener = listener;
    }

    public void setOnAuthenticationFailedListener(OnAuthenticationErrorListener listener) {
        mFailedListener = listener;
    }

    public FingerprintHandler(Context context){
        mContext = context;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            mFingerprintManager = context.getSystemService(FingerprintManager.class);
            mCancellationSignal = new CancellationSignal();

            mAuthenticationCallback = new FingerprintManager.AuthenticationCallback() {
                @Override
                public void onAuthenticationError(int errorCode, CharSequence errString) {
                    super.onAuthenticationError(errorCode, errString);
                }

                @Override
                public void onAuthenticationHelp(int helpCode, CharSequence helpString) {
                    super.onAuthenticationHelp(helpCode, helpString);
                }

                @Override
                public void onAuthenticationSucceeded(FingerprintManager.AuthenticationResult result) {
                    super.onAuthenticationSucceeded(result);
                    if( mSucceedListener != null )
                        mSucceedListener.onAuthSucceeded();
                }

                @Override
                public void onAuthenticationFailed() {
                    super.onAuthenticationFailed();
                    if (mFailedListener != null)
                        mFailedListener.onAuthFailed();
                }
            };
        }
    }

    public void startListening(){
        if (isFingerScannerAvailableAndSet() ) {
            try{
                mFingerprintManager.authenticate(null, mCancellationSignal, 0 /* flags */, mAuthenticationCallback, null);
            } catch (Exception e){
                e.printStackTrace();
            }
        }
    }

    public void stopListening(){
        if ( isFingerScannerAvailableAndSet() ) {
            try {
                mCancellationSignal.cancel();
                mCancellationSignal = null;
            } catch (Exception e){
                e.printStackTrace();
            }
        }
    }

    public boolean isFingerScannerAvailableAndSet(){
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M)
            return false;
        if( mFingerprintManager == null )
            return false;
        if( !mFingerprintManager.isHardwareDetected() )
            return false;
        if( !mFingerprintManager.hasEnrolledFingerprints())
            return false;

        return true;
    }
}

Then in your activity implement

FingerprintHandler.OnAuthenticationSucceededListener, FingerprintHandler.OnAuthenticationErrorListener

Create fingerprint parameter :

private FingerprintHandler mFingerprintHandler;

After that init this fingerprint handler in onCreate method :

mFingerprintHandler = new FingerprintHandler(this);
mFingerprintHandler.setOnAuthenticationSucceededListener(this);
mFingerprintHandler.setOnAuthenticationFailedListener(this);

You can check if fingerprint is avaivable and set in your activity with this :

    if( mFingerprintHandler.isFingerScannerAvailableAndSet() ){
        // show image or text or do something 
    }

You can handle your fingerprint response in implemented methods :

@Override
public void onAuthSucceeded() {
     //fingerprint auth succeded go to next activity (or do something)
}


@Override
public void onAuthFailed() {
    //fingerpring auth failed, show error toast (or do something)
}

And you are ready ! :) Don't forget to stop and start listening the fingerprint in onPause and onResume methods :

@Override
public void onResume() {
    super.onResume();
    mFingerprintHandler.startListening();
}

@Override
public void onPause() {
    super.onPause();
    mFingerprintHandler.stopListening();
}

Happy codding :)))

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