BiometricPrompt

public class BiometricPrompt
extends Object

java.lang.Object
   ↳ androidx.biometric.BiometricPrompt

A class that manages a system-provided biometric prompt. On devices running P and above, this will show a system-provided authentication prompt, using a device's supported biometric (fingerprint, iris, face, etc). On devices before P, this will show a dialog prompting for fingerprint authentication. The prompt will persist across configuration changes unless explicitly canceled by the client. For security reasons, the prompt will automatically dismiss when the application is no longer in the foreground. To persist authentication across configuration changes, developers should (re)create the BiometricPrompt every time the activity/fragment is created. Instantiating the library with a new callback early in the fragment/activity lifecycle (e.g. onCreate) allows the ongoing authenticate session's callbacks to be received by the new fragment/activity. Note that cancelAuthentication() should not be called, and authenticate(PromptInfo) or authenticate(PromptInfo, CryptoObject) does not need to be invoked after the new activity/fragment is created, since we are keeping/continuing the same session.

Summary

Nested classes

class BiometricPrompt.AuthenticationCallback

Callback structure provided to BiometricPrompt. 

class BiometricPrompt.AuthenticationResult

Container for callback data from BiometricPrompt.authenticate(PromptInfo) and BiometricPrompt.authenticate(PromptInfo, CryptoObject). 

class BiometricPrompt.CryptoObject

A wrapper class for the crypto objects supported by BiometricPrompt. 

class BiometricPrompt.PromptInfo

A class that contains a builder which returns the BiometricPrompt.PromptInfo to be used in BiometricPrompt.authenticate(PromptInfo, CryptoObject) and BiometricPrompt.authenticate(PromptInfo). 

Constants

int ERROR_CANCELED

The operation was canceled because the biometric sensor is unavailable.

int ERROR_HW_NOT_PRESENT

The device does not have a biometric sensor.

int ERROR_HW_UNAVAILABLE

The hardware is unavailable.

int ERROR_LOCKOUT

The operation was canceled because the API is locked out due to too many attempts.

int ERROR_LOCKOUT_PERMANENT

The operation was canceled because ERROR_LOCKOUT occurred too many times.

int ERROR_NEGATIVE_BUTTON

The user pressed the negative button.

int ERROR_NO_BIOMETRICS

The user does not have any biometrics enrolled.

int ERROR_NO_DEVICE_CREDENTIAL

The device does not have pin, pattern, or password set up.

int ERROR_NO_SPACE

Error state returned for operations like enrollment; the operation cannot be completed because there's not enough storage remaining to complete the operation.

int ERROR_TIMEOUT

Error state returned when the current request has been running too long.

int ERROR_UNABLE_TO_PROCESS

Error state returned when the sensor was unable to process the current image.

int ERROR_USER_CANCELED

The user canceled the operation.

int ERROR_VENDOR

Hardware vendors may extend this list if there are conditions that do not fall under one of the above categories.

Public constructors

BiometricPrompt(FragmentActivity fragmentActivity, Executor executor, BiometricPrompt.AuthenticationCallback callback)

Constructs a BiometricPrompt which can be used to prompt the user for authentication.

BiometricPrompt(Fragment fragment, Executor executor, BiometricPrompt.AuthenticationCallback callback)

Constructs a BiometricPrompt which can be used to prompt the user for authentication.

Public methods

void authenticate(BiometricPrompt.PromptInfo info, BiometricPrompt.CryptoObject crypto)

Shows the biometric prompt.

void authenticate(BiometricPrompt.PromptInfo info)

Shows the biometric prompt.

void cancelAuthentication()

Cancels the biometric authentication, and dismisses the dialog upon confirmation from the biometric service.

Inherited methods

Constants

ERROR_CANCELED

public static final int ERROR_CANCELED

The operation was canceled because the biometric sensor is unavailable. For example, this may happen when the user is switched, the device is locked or another pending operation prevents or disables it.

Constant Value: 5 (0x00000005)

ERROR_HW_NOT_PRESENT

public static final int ERROR_HW_NOT_PRESENT

The device does not have a biometric sensor.

Constant Value: 12 (0x0000000c)

ERROR_HW_UNAVAILABLE

public static final int ERROR_HW_UNAVAILABLE

The hardware is unavailable. Try again later.

Constant Value: 1 (0x00000001)

ERROR_LOCKOUT

public static final int ERROR_LOCKOUT

The operation was canceled because the API is locked out due to too many attempts. This occurs after 5 failed attempts, and lasts for 30 seconds.

Constant Value: 7 (0x00000007)

ERROR_LOCKOUT_PERMANENT

public static final int ERROR_LOCKOUT_PERMANENT

The operation was canceled because ERROR_LOCKOUT occurred too many times. Biometric authentication is disabled until the user unlocks with strong authentication (PIN/Pattern/Password)

Constant Value: 9 (0x00000009)

ERROR_NEGATIVE_BUTTON

public static final int ERROR_NEGATIVE_BUTTON

The user pressed the negative button.

Constant Value: 13 (0x0000000d)

ERROR_NO_BIOMETRICS

public static final int ERROR_NO_BIOMETRICS

The user does not have any biometrics enrolled.

Constant Value: 11 (0x0000000b)

ERROR_NO_DEVICE_CREDENTIAL

public static final int ERROR_NO_DEVICE_CREDENTIAL

The device does not have pin, pattern, or password set up.

Constant Value: 14 (0x0000000e)

ERROR_NO_SPACE

public static final int ERROR_NO_SPACE

Error state returned for operations like enrollment; the operation cannot be completed because there's not enough storage remaining to complete the operation.

Constant Value: 4 (0x00000004)

ERROR_TIMEOUT

public static final int ERROR_TIMEOUT

Error state returned when the current request has been running too long. This is intended to prevent programs from waiting for the biometric sensor indefinitely. The timeout is platform and sensor-specific, but is generally on the order of 30 seconds.

Constant Value: 3 (0x00000003)

ERROR_UNABLE_TO_PROCESS

public static final int ERROR_UNABLE_TO_PROCESS

Error state returned when the sensor was unable to process the current image.

Constant Value: 2 (0x00000002)

ERROR_USER_CANCELED

public static final int ERROR_USER_CANCELED

The user canceled the operation. Upon receiving this, applications should use alternate authentication (e.g. a password). The application should also provide the means to return to biometric authentication, such as a "use " button.

Constant Value: 10 (0x0000000a)

ERROR_VENDOR

public static final int ERROR_VENDOR

Hardware vendors may extend this list if there are conditions that do not fall under one of the above categories. Vendors are responsible for providing error strings for these errors. These messages are typically reserved for internal operations such as enrollment, but may be used to express vendor errors not otherwise covered. Applications are expected to show the error message string if they happen, but are advised not to rely on the message id since they will be device and vendor-specific

Constant Value: 8 (0x00000008)

Public constructors

BiometricPrompt

public BiometricPrompt (FragmentActivity fragmentActivity, 
                Executor executor, 
                BiometricPrompt.AuthenticationCallback callback)

Constructs a BiometricPrompt which can be used to prompt the user for authentication. The authentication prompt created by authenticate(PromptInfo, CryptoObject) and authenticate(PromptInfo) will persist across device configuration changes by default. If authentication is in progress, re-creating the BiometricPrompt can be used to update the Executor and BiometricPrompt.AuthenticationCallback. This should be used to update the BiometricPrompt.AuthenticationCallback after configuration changes. such as FragmentActivity.onCreate(Bundle).

Parameters
fragmentActivity FragmentActivity: A reference to the client's activity.
executor Executor: An executor to handle callback events.
callback BiometricPrompt.AuthenticationCallback: An object to receive authentication events.

BiometricPrompt

public BiometricPrompt (Fragment fragment, 
                Executor executor, 
                BiometricPrompt.AuthenticationCallback callback)

Constructs a BiometricPrompt which can be used to prompt the user for authentication. The authentication prompt created by authenticate(PromptInfo, CryptoObject) and authenticate(PromptInfo) will persist across device configuration changes by default. If authentication is in progress, re-creating the BiometricPrompt can be used to update the Executor and BiometricPrompt.AuthenticationCallback. This should be used to update the BiometricPrompt.AuthenticationCallback after configuration changes. such as Fragment.onCreate(Bundle).

Parameters
fragment Fragment: A reference to the client's fragment.
executor Executor: An executor to handle callback events.
callback BiometricPrompt.AuthenticationCallback: An object to receive authentication events.

Public methods

authenticate

public void authenticate (BiometricPrompt.PromptInfo info, 
                BiometricPrompt.CryptoObject crypto)

Shows the biometric prompt. The prompt survives lifecycle changes by default. To cancel the authentication, use cancelAuthentication().

Parameters
info BiometricPrompt.PromptInfo: The information that will be displayed on the prompt. Create this object using BiometricPrompt.PromptInfo.Builder.
crypto BiometricPrompt.CryptoObject: The crypto object associated with the authentication.

authenticate

public void authenticate (BiometricPrompt.PromptInfo info)

Shows the biometric prompt. The prompt survives lifecycle changes by default. To cancel the authentication, use cancelAuthentication().

Parameters
info BiometricPrompt.PromptInfo: The information that will be displayed on the prompt. Create this object using BiometricPrompt.PromptInfo.Builder.

cancelAuthentication

public void cancelAuthentication ()

Cancels the biometric authentication, and dismisses the dialog upon confirmation from the biometric service.

On P or below, calling this method when the device credential prompt is shown will NOT work as expected. See BiometricPrompt.PromptInfo.Builder.setDeviceCredentialAllowed(boolean) for more details.