New Example - Biometrics (#119)

biometrics/lib/biometrics_verifier.dart

@@ -0,0 +1,34 @@
+import 'package:flutter/services.dart';
+import 'package:local_auth/local_auth.dart';
+
+class BiometricsVerifier {
+  late LocalAuthentication auth;
+
+  BiometricsVerifier() {
+    auth = LocalAuthentication();
+  }
+
+  Future<void> _ableToAuthenticate() async {
+    bool supported = await auth.canCheckBiometrics;
+    bool entryExists = await auth.isDeviceSupported();
+    if (!supported) throw "Device doesn't support Biometrics.";
+    if (!entryExists) throw "Biometric entry not found in phone.";
+  }
+
+  Future<void> verifyBiometrics(String? prompt) async {
+    await _ableToAuthenticate();
+    late bool didAuthenticate;
+    try {
+      didAuthenticate = await auth.authenticate(
+        localizedReason: prompt ?? 'Please authenticate with biometrics',
+        options: const AuthenticationOptions(
+          stickyAuth: true,
+          biometricOnly: true,
+        ),
+      );
+    } on PlatformException {
+      throw "Platform Exception : Biometrics Failed !";
+    }
+    if (!didAuthenticate) throw "Biometrics Failed";
+  }
+}