Biometric authentication in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a BiometricPrompt instance.

Android Kotlin

val biometricPrompt = BiometricPrompt(this, ContextCompat.getMainExecutor(this), [1])

Drag options to blanks, or click blank then click option'

AauthenticationCallback

BpromptInfo

Cexecutor

DbiometricManager

Attempts:

3 left

💡 Hint

Common Mistakes

Using the executor or promptInfo instead of the callback.

Passing biometricManager which is unrelated here.

The BiometricPrompt constructor requires an AuthenticationCallback to handle authentication events.

2fill in blank

medium

Complete the code to build the BiometricPrompt.PromptInfo.

Android Kotlin

val promptInfo = BiometricPrompt.PromptInfo.Builder()
  .setTitle("Login")
  .setSubtitle("Use your fingerprint")
  .setNegativeButtonText([1])
  .build()

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A"Retry"

B"Cancel"

C"OK"

D"Confirm"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'OK' or 'Confirm' which confuse the cancel action.

Leaving the negative button text empty.

The negative button text should be a clear cancel action, usually labeled "Cancel".

3fill in blank

hard

Fix the error in the authentication callback method name.

Android Kotlin

val authenticationCallback = object : BiometricPrompt.AuthenticationCallback() {
  override fun onAuthentication[1](result: BiometricPrompt.AuthenticationResult) {
    super.onAuthenticationSucceeded(result)
    // Handle success
  }
}

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ASuccessed

BSuccess

CSucceededed

DSucceeded

Attempts:

3 left

💡 Hint

Common Mistakes

Misspelling the method name causes it not to override properly.

Using 'Success' instead of 'Succeeded'.

The correct method name is onAuthenticationSucceeded with 'Succeeded' at the end.

4fill in blank

hard

Fill both blanks to check if biometric authentication is available and strong.

Android Kotlin

val biometricManager = BiometricManager.from(this)
if (biometricManager.canAuthenticate([1]) == [2]) {
  // Biometric authentication is available
}

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ABiometricManager.Authenticators.BIOMETRIC_STRONG

BBiometricManager.Authenticators.DEVICE_CREDENTIAL

CBiometricManager.BIOMETRIC_SUCCESS

DBiometricManager.BIOMETRIC_ERROR_NO_HARDWARE

Attempts:

3 left

💡 Hint

Common Mistakes

Using DEVICE_CREDENTIAL instead of BIOMETRIC_STRONG.

Checking for BIOMETRIC_ERROR_NO_HARDWARE instead of BIOMETRIC_SUCCESS.

Use BIOMETRIC_STRONG to specify strong biometrics and check for BIOMETRIC_SUCCESS to confirm availability.

5fill in blank

hard

Fill all three blanks to start biometric authentication with the prompt info.

Android Kotlin

biometricPrompt.[1](
  [2],
  [3]
)

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Aauthenticate

BpromptInfo

CCancellationSignal()

Dcancel

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'cancel' instead of 'authenticate'.

Passing wrong arguments or missing cancellation signal.

Call authenticate with the prompt info and a new cancellation signal to start authentication.