Biometric Prompt¶
Non-Visible component| Category | Requires | Version |
|---|---|---|
| Sensors | API 21, Android 5.0 Lollipop | 1 |
Overview¶
A component that provides biometric authentication (fingerprint, face, iris) and device credential authentication (PIN, pattern, password). Requires Android 6 (API 23) or higher for device credentials and Android 9 (API 28) or higher for the unified biometric prompt UI.
Events¶
On Authentication Error¶
Triggered on a non-recoverable authentication error. The prompt is dismissed. Common error codes: 7 = too many attempts (temporary lockout), 9 = permanent lockout, 10 = user canceled, 11 = no biometrics enrolled, 12 = no biometric hardware.
| Params | |
|---|---|
| error Code | Number |
| error Message | Text |
On Authentication Failed¶
Triggered when a biometric is recognized but does not match (e.g., wrong finger). The prompt stays open for retry. May fire multiple times.
On Authentication Succeeded¶
Triggered when biometric or device credential authentication succeeds.
On Negative Button Clicked¶
Triggered when the user taps the negative/cancel button (only in BiometricOnly mode). Use this to handle user-initiated cancellation.
Methods¶
Authenticate¶
Starts authentication. Fires OnAuthenticationSucceeded, OnAuthenticationFailed, OnAuthenticationError, or OnNegativeButtonClicked based on the result.
Cancel Authentication¶
Cancels the current biometric authentication. Safe to call even if no authentication is in progress.
Has Biometric Hardware¶
Returns: Boolean
Returns true if the device has biometric hardware (fingerprint sensor, face sensor, etc.).
Has Enrolled Biometrics¶
Returns: Boolean
Returns true if at least one biometric (fingerprint, face, etc.) is enrolled on the device.
Is Available¶
Returns: Boolean
Returns true if authentication is available right now with the current AuthenticatorType setting. This is the recommended check before calling Authenticate.
Properties¶
Authenticator Type¶
Com.google.appinventor.components.common.authenticatortypeenum Default: BiometricOrDeviceCredential 
Read Write - Designer Blocks
Sets the type of authentication allowed. BiometricOnly = biometrics only, DeviceCredentialOnly = PIN/pattern/password, BiometricOrDeviceCredential = biometrics with PIN fallback.
Description¶
Text Read Write - Designer Blocks
Sets the optional description displayed on the biometric prompt.
Negative Button Text¶
Text Default: Cancel Read Write - Designer Blocks
Sets the text for the negative button on the biometric prompt. Only shown when AuthenticatorType is BiometricOnly. Ignored when device credentials are allowed.
Subtitle¶
Text Read Write - Designer Blocks
Sets the optional subtitle displayed on the biometric prompt.
Title¶
Text Default: Verify your identity Read Write - Designer Blocks
Sets the title displayed on the biometric prompt.