Biometric Change Detection

Monitor real-time changes to device biometric settings and enrollments.

subscribeToBiometricChanges()

Subscribes to biometric change events. Returns an event subscription that can be used to unsubscribe later.

const subscribeToBiometricChanges = (
  callback: (event: BiometricChangeEvent) => void
): EventSubscription => {
};

Parameters:

• callback: Function called when biometric changes are detected

Returns: EventSubscription - Subscription object for unsubscribing

Example:

import { subscribeToBiometricChanges } from '@sbaiahmed1/react-native-biometrics';

const subscription = subscribeToBiometricChanges((event) => {
  console.log('Change type:', event.changeType);
  console.log('Available:', event.available);
  console.log('Biometry type:', event.biometryType);
});

unsubscribeFromBiometricChanges()

Unsubscribes from biometric change events to prevent memory leaks.

const unsubscribeFromBiometricChanges = (subscription: EventSubscription): void => {
};

Parameters:

• subscription: The subscription object returned from subscribeToBiometricChanges

Example:

import { unsubscribeFromBiometricChanges } from '@sbaiahmed1/react-native-biometrics';

unsubscribeFromBiometricChanges(subscription);

startBiometricChangeDetection()

Starts monitoring for biometric changes. Must be called explicitly to begin detection after subscribing.

const startBiometricChangeDetection = (): Promise<void> => {
};

Returns: Promise<void> - Resolves when detection has started

Example:

import { startBiometricChangeDetection } from '@sbaiahmed1/react-native-biometrics';

await startBiometricChangeDetection();
console.log('Monitoring biometric changes...');

stopBiometricChangeDetection()

Stops monitoring for biometric changes. Useful for conserving battery and resources.

const stopBiometricChangeDetection = (): Promise<void> => {
};

Returns: Promise<void> - Resolves when detection has stopped

Example:

import { stopBiometricChangeDetection } from '@sbaiahmed1/react-native-biometrics';

await stopBiometricChangeDetection();
console.log('Stopped monitoring');

BiometricChangeEvent

interface BiometricChangeEvent {
  timestamp: number;        // Unix epoch milliseconds when the change occurred
  changeType: string;       // Type of change (see below)
  biometryType: string;     // Current biometry type
  available: boolean;       // Whether biometrics are available
  enrolled: boolean;        // Whether biometrics are enrolled
}

Change Types:

• BIOMETRIC_ENABLED: Biometrics became available
• BIOMETRIC_DISABLED: Biometrics became unavailable
• ENROLLMENT_CHANGED: Biometric enrollments added/removed
• HARDWARE_UNAVAILABLE: Biometric hardware changed
• STATE_CHANGED: General state change

Complete Example:

import React, { useEffect, useState } from 'react';
import {
  subscribeToBiometricChanges,
  unsubscribeFromBiometricChanges,
  startBiometricChangeDetection,
  stopBiometricChangeDetection
} from '@sbaiahmed1/react-native-biometrics';

const MyComponent = () => {
  const [subscription, setSubscription] = useState(null);

  useEffect(() => {
    // Subscribe to changes
    const sub = subscribeToBiometricChanges((event) => {
      console.log('Biometric change:', event.changeType);

      if (event.changeType === 'BIOMETRIC_DISABLED') {
        alert('Biometrics were disabled on this device');
      }
    });
    setSubscription(sub);

    // Start detection
    startBiometricChangeDetection();

    // Cleanup on unmount
    return () => {
      if (sub) {
        unsubscribeFromBiometricChanges(sub);
      }
      stopBiometricChangeDetection();
    };
  }, []);

  return <View>{/* Your UI */}</View>;
};

For comprehensive documentation including platform-specific behavior, implementation details, and best practices, see the Biometric Change Detection Guide.