blog_cryptoobject_businesslogic

class MainActivity : AppCompatActivity() {

   private lateinit var biometricPrompt: BiometricPrompt
   private lateinit var promptInfo: BiometricPrompt.PromptInfo
   private var readyToEncrypt: Boolean = false
   ...
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)
       ...
       biometricPrompt = createBiometricPrompt()
       promptInfo = createPromptInfo()
       // e.g. secretKeyName = "biometric_sample_encryption_key"
       secretKeyName = getString(R.string.secret_key_name)
       ...
       findViewById<Button>(R.id.encrypt_button).setOnClickListener { authenticateToEncrypt() }
       findViewById<Button>(R.id.decrypt_button).setOnClickListener { authenticateToDecrypt() }
   }

   ...

private fun authenticateToEncrypt() {
   readyToEncrypt = true
   if (BiometricManager.from(applicationContext).canAuthenticate() == BiometricManager
                   .BIOMETRIC_SUCCESS) {
       val cipher = cryptographyManager.getInitializedCipherForEncryption(secretKeyName)
       biometricPrompt.authenticate(promptInfo, BiometricPrompt.CryptoObject(cipher))
   }
}

private fun authenticateToDecrypt() {
   readyToEncrypt = false
   if (BiometricManager.from(applicationContext).canAuthenticate() == BiometricManager
                   .BIOMETRIC_SUCCESS) {
       val cipher = cryptographyManager.getInitializedCipherForDecryption(secretKeyName,initializationVector)
       biometricPrompt.authenticate(promptInfo, BiometricPrompt.CryptoObject(cipher))
   }
 }
}