Learn FingerPrintAPI using this step by step example.

Here is the demo screenshot:

Kotlin Android FingerprintAPI Example

Step 1: Create Project

Start by creating an empty Android Studio project.

Step 2: Dependencies

No special dependency is needed to use FingerPrintAPI. We will use classes from android.hardware.fingerprint which is available in the standard android sdk.

Step : Create FingerPrint Handler

FingerprintHandler.kt

import android.Manifest
import android.app.Activity
import android.content.Context
import android.content.pm.PackageManager
import android.hardware.fingerprint.FingerprintManager
import android.os.Build
import android.os.CancellationSignal
import androidx.annotation.RequiresApi
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import android.view.View
import android.widget.TextView

@RequiresApi(Build.VERSION_CODES.M)
class FingerprintHandler// Constructor
(private val context: Context) : FingerprintManager.AuthenticationCallback() {

    fun startAuth(manager: FingerprintManager, cryptoObject: FingerprintManager.CryptoObject) {
        val cancellationSignal = CancellationSignal()
        if (ActivityCompat.checkSelfPermission(context, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
            return
        }
        manager.authenticate(cryptoObject, cancellationSignal, 0, this, null)
    }

    override fun onAuthenticationError(errMsgId: Int, errString: CharSequence) {
        this.update("Fingerprint Authentication errorn$errString", false)
    }

    override fun onAuthenticationHelp(helpMsgId: Int, helpString: CharSequence) {
        this.update("Fingerprint Authentication helpn$helpString", false)
    }

    override fun onAuthenticationFailed() {
        this.update("Fingerprint Authentication failed.", false)
    }

    override fun onAuthenticationSucceeded(result: FingerprintManager.AuthenticationResult) {
        this.update("Fingerprint Authentication succeeded.", true)
    }

    private fun update(e: String, success: Boolean?) {
        val textView = (context as Activity).findViewById<View>(R.id.errorText) as TextView
        textView.text = e
        if (success!!) {
            textView.setTextColor(ContextCompat.getColor(context, R.color.colorPrimaryDark))
        }
    }
}

Step : Write MainActivity code

MainActivity.kt

import android.Manifest
import android.annotation.TargetApi
import android.app.KeyguardManager
import android.content.Context
import android.content.pm.PackageManager
import android.hardware.fingerprint.FingerprintManager
import android.os.Build
import android.os.Bundle
import android.security.keystore.KeyGenParameterSpec
import android.security.keystore.KeyPermanentlyInvalidatedException
import android.security.keystore.KeyProperties
import androidx.annotation.RequiresApi
import androidx.core.app.ActivityCompat
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.widget.Toolbar
import android.widget.TextView
import java.io.IOException
import java.security.*
import java.security.cert.CertificateException
import javax.crypto.Cipher
import javax.crypto.KeyGenerator
import javax.crypto.NoSuchPaddingException
import javax.crypto.SecretKey

class MainActivity : AppCompatActivity() {

    private var keyStore: KeyStore? = null
    // Variable used for storing the key in the Android Keystore container
    private val KEY_NAME = "AndroidExamples"
    private var cipher: Cipher? = null
    private var textView: TextView? = null

    @RequiresApi(Build.VERSION_CODES.M)
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val toolbar = findViewById<Toolbar>(R.id.toolbar)
        setSupportActionBar(toolbar)

        // Initializing both Android Keyguard Manager and Fingerprint Manager
        val keyguardManager = getSystemService(Context.KEYGUARD_SERVICE) as KeyguardManager
        val fingerprintManager = getSystemService(Context.FINGERPRINT_SERVICE) as FingerprintManager

        textView = findViewById<TextView>(R.id.errorText)

        // Check whether the device has a Fingerprint sensor.
        if (!fingerprintManager.isHardwareDetected) {
            /**
             * An error message will be displayed if the device does not contain the fingerprint hardware.
             * However if you plan to implement a default authentication method,
             * you can redirect the user to a default authentication activity from here.
             * Example:
             * Intent intent = new Intent(this, DefaultAuthenticationActivity.class);
             * startActivity(intent);
             */
            textView!!.text = "Your Device does not have a Fingerprint Sensor"
        } else {
            // Checks whether fingerprint permission is set on manifest
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
                textView!!.text = "Fingerprint authentication permission not enabled"
            } else {
                // Check whether at least one fingerprint is registered
                if (!fingerprintManager.hasEnrolledFingerprints()) {
                    textView!!.text = "Register at least one fingerprint in Settings"
                } else {
                    // Checks whether lock screen security is enabled or not
                    if (!keyguardManager.isKeyguardSecure) {
                        textView!!.text = "Lock screen security not enabled in Settings"
                    } else {
                        generateKey()

                        if (cipherInit()) {
                            val cryptoObject = FingerprintManager.CryptoObject(cipher!!)
                            val helper = FingerprintHandler(this)
                            helper.startAuth(fingerprintManager, cryptoObject)
                        }
                    }
                }
            }
        }
    }

    @TargetApi(Build.VERSION_CODES.M)
    protected fun generateKey() {
        try {
            keyStore = KeyStore.getInstance("AndroidKeyStore")
        } catch (e: Exception) {
            e.printStackTrace()
        }

        val keyGenerator: KeyGenerator
        try {
            keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore")
        } catch (e: NoSuchAlgorithmException) {
            throw RuntimeException("Failed to get KeyGenerator instance", e)
        } catch (e: NoSuchProviderException) {
            throw RuntimeException("Failed to get KeyGenerator instance", e)
        }

        try {
            keyStore!!.load(null)
            keyGenerator.init(KeyGenParameterSpec.Builder(KEY_NAME,
                    KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT).setBlockModes(
                    KeyProperties.BLOCK_MODE_CBC)
                    .setUserAuthenticationRequired(true)
                    .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_PKCS7)
                    .build())
            keyGenerator.generateKey()
        } catch (e: NoSuchAlgorithmException) {
            throw RuntimeException(e)
        } catch (e: InvalidAlgorithmParameterException) {
            throw RuntimeException(e)
        } catch (e: CertificateException) {
            throw RuntimeException(e)
        } catch (e: IOException) {
            throw RuntimeException(e)
        }

    }

    @TargetApi(Build.VERSION_CODES.M)
    fun cipherInit(): Boolean {
        try {
            cipher = Cipher.getInstance(KeyProperties.KEY_ALGORITHM_AES
                    + "/"
                    + KeyProperties.BLOCK_MODE_CBC
                    + "/"
                    + KeyProperties.ENCRYPTION_PADDING_PKCS7)
        } catch (e: NoSuchAlgorithmException) {
            throw RuntimeException("Failed to get Cipher", e)
        } catch (e: NoSuchPaddingException) {
            throw RuntimeException("Failed to get Cipher", e)
        }

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

    }
}

Run

Copy the code or download it in the link below, build and run.

Reference

Here are the reference links:

Number Link
1. Download Example
2. Follow code author
3. Code: Apache 2.0 License