Kotlin Biometrics Or Fingerprint Example

Kotlin Biometrics or Fingerprint Example

Step 1:

Open build.gradle(:app) and add following dependency and rebuild the project.

implementation 'androidx.biometric:biometric:1.2.0-alpha04'

build.gradle(:app)

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
}

android {
    compileSdk 32

    defaultConfig {
        applicationId "com.kotlinkattademo.app"
        minSdk 21
        targetSdk 32
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
    buildFeatures {
        dataBinding true;
        viewBinding true
    }
}

dependencies {

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.4.1'
    implementation 'com.google.android.material:material:1.5.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    implementation 'androidx.biometric:biometric:1.2.0-alpha04'
}

Step 2:

Open AndroidManifest.xml and add following permission.

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

Step 3:

Open layout file activity_main.xml and add following code.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.appcompat.widget.AppCompatButton
        android:background="@color/black"
        android:textColor="@color/white"
        android:textSize="22dp"
        android:id="@+id/biometriclogin"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Biometric login"
        android:textAllCaps="false"
        android:layout_margin="10dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Step 4:

Open Activity class MainActivity.kt and add following code.

package com.kotlinkattademo.app

import android.content.ActivityNotFoundException
import android.content.DialogInterface
import android.content.Intent
import android.os.Build
import android.os.Bundle
import android.provider.Settings
import android.provider.Settings.EXTRA_BIOMETRIC_AUTHENTICATORS_ALLOWED
import android.widget.Toast
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
import androidx.biometric.BiometricPrompt
import androidx.core.content.ContextCompat
import com.kotlinkattademo.app.databinding.ActivityMainBinding
import java.util.concurrent.Executor

class MainActivity : AppCompatActivity() {

    private lateinit var executor: Executor
    private lateinit var biometricPrompt: BiometricPrompt
    private lateinit var promptInfo: BiometricPrompt.PromptInfo

    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        val view = binding.root
        setContentView(view)

        binding.biometriclogin.setOnClickListener {
            biometricPrompt.authenticate(promptInfo)
        }

        promptInfo = BiometricPrompt.PromptInfo.Builder()
            .setTitle("Biometric login for my app")
            .setSubtitle("Log in using your biometric credential")
            .setNegativeButtonText("Use account password")
            .build()

        executor = ContextCompat.getMainExecutor(this)
        biometricPrompt = BiometricPrompt(this, executor,
            object : BiometricPrompt.AuthenticationCallback() {
                override fun onAuthenticationError(
                    errorCode: Int,
                    errString: CharSequence
                ) {
                    super.onAuthenticationError(errorCode, errString)
                    Toast.makeText(
                        applicationContext,
                        "Authentication error: $errString",
                        Toast.LENGTH_SHORT
                    ).show()

                    biomatricAlert()
                }

                override fun onAuthenticationSucceeded(
                    result: BiometricPrompt.AuthenticationResult
                ) {
                    super.onAuthenticationSucceeded(result)
                    Toast.makeText(
                        applicationContext,
                        "Authentication succeeded!",
                        Toast.LENGTH_SHORT
                    ).show()
                }

                override fun onAuthenticationFailed() {
                    super.onAuthenticationFailed()
                    Toast.makeText(applicationContext, "Authentication failed", Toast.LENGTH_SHORT)
                        .show()
                }
            })
    }

    private fun launchIntentToAddBiomatric() {
        val intent: Intent = when {
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.R -> {
                Intent(Settings.ACTION_BIOMETRIC_ENROLL).putExtra(
                    EXTRA_BIOMETRIC_AUTHENTICATORS_ALLOWED,
                    android.hardware.biometrics.BiometricManager.Authenticators.BIOMETRIC_STRONG
                )
            }
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.P -> {
                Intent(Settings.ACTION_FINGERPRINT_ENROLL)
            }
            else -> {
                Intent(Settings.ACTION_SECURITY_SETTINGS)
            }
        }
        try {
            startActivity(intent)
        } catch (error: ActivityNotFoundException) {
            startActivity(Intent(Settings.ACTION_SETTINGS))
        }
    }

    fun biomatricAlert() {
        val builder = AlertDialog.Builder(this)
        with(builder)
        {
            setTitle("Add Biomatric")
            setMessage("would you like to add biomatric?")
            setPositiveButton(
                "Next",
                DialogInterface.OnClickListener(positiveButtonClick)
            )
            setNegativeButton("Close", negativeButtonClick)
            show()
        }
    }

    val positiveButtonClick = { dialog: DialogInterface, which: Int ->
        dialog.dismiss()
        launchIntentToAddBiomatric() // launch Intent to open add Biomatric.
    }
    val negativeButtonClick = { dialog: DialogInterface, which: Int ->
        dialog.dismiss();
    }
}

Output: