BiometricUtil.kt

fun initBiometricPrompt(
    activity: AppCompatActivity,
    listener: BiometricAuthListener
): BiometricPrompt {
  // 1
  val executor = ContextCompat.getMainExecutor(activity)

  // 2
  val callback = object : BiometricPrompt.AuthenticationCallback() {
    override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
      super.onAuthenticationError(errorCode, errString)
      listener.onBiometricAuthenticationError(errorCode, errString.toString())
    }

    override fun onAuthenticationFailed() {
      super.onAuthenticationFailed()
      Log.w(this.javaClass.simpleName, "Authentication failed for an unknown reason")
    }

    override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
      super.onAuthenticationSucceeded(result)
      listener.onBiometricAuthenticationSuccess(result)
    }
  }

  // 3
  return BiometricPrompt(activity, executor, callback)
}