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Description:

local auth

local_auth #

This Flutter plugin provides means to perform local, on-device authentication of
the user.
On supported devices, this includes authentication with biometrics such as
fingerprint or facial recognition.

Android
iOS
macOS
Windows

Support
SDK 16+*
12.0+
10.14+
Windows 10+

Usage #
Device Capabilities #
To check whether there is local authentication available on this device or not,
call canCheckBiometrics (if you need biometrics support) and/or
isDeviceSupported() (if you just need some device-level authentication):

import 'package:local_auth/local_auth.dart';
// ···
final LocalAuthentication auth = LocalAuthentication();
// ···
final bool canAuthenticateWithBiometrics = await auth.canCheckBiometrics;
final bool canAuthenticate =
canAuthenticateWithBiometrics || await auth.isDeviceSupported();
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Currently the following biometric types are implemented:

BiometricType.face
BiometricType.fingerprint
BiometricType.weak
BiometricType.strong

Enrolled Biometrics #
canCheckBiometrics only indicates whether hardware support is available, not
whether the device has any biometrics enrolled. To get a list of enrolled
biometrics, call getAvailableBiometrics().
The types are device-specific and platform-specific, and other types may be
added in the future, so when possible you should not rely on specific biometric
types and only check that some biometric is enrolled:

final List<BiometricType> availableBiometrics =
await auth.getAvailableBiometrics();

if (availableBiometrics.isNotEmpty) {
// Some biometrics are enrolled.
}

if (availableBiometrics.contains(BiometricType.strong) ||
availableBiometrics.contains(BiometricType.face)) {
// Specific types of biometrics are available.
// Use checks like this with caution!
}
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Options #
The authenticate() method uses biometric authentication when possible, but
also allows fallback to pin, pattern, or passcode.

try {
final bool didAuthenticate = await auth.authenticate(
localizedReason: 'Please authenticate to show account balance');
// ···
} on PlatformException {
// ...
}
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To require biometric authentication, pass AuthenticationOptions with
biometricOnly set to true.

final bool didAuthenticate = await auth.authenticate(
localizedReason: 'Please authenticate to show account balance',
options: const AuthenticationOptions(biometricOnly: true));
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Note: biometricOnly is not supported on Windows since the Windows implementation's underlying API (Windows Hello) doesn't support selecting the authentication method.
Dialogs
The plugin provides default dialogs for the following cases:

Passcode/PIN/Pattern Not Set: The user has not yet configured a passcode on
iOS or PIN/pattern on Android.
Biometrics Not Enrolled: The user has not enrolled any biometrics on the
device.

If a user does not have the necessary authentication enrolled when
authenticate is called, they will be given the option to enroll at that point,
or cancel authentication.
If you don't want to use the default dialogs, set the useErrorDialogs option
to false to have authenticate immediately return an error in those cases.

import 'package:local_auth/error_codes.dart' as auth_error;
// ···
try {
final bool didAuthenticate = await auth.authenticate(
localizedReason: 'Please authenticate to show account balance',
options: const AuthenticationOptions(useErrorDialogs: false));
// ···
} on PlatformException catch (e) {
if (e.code == auth_error.notAvailable) {
// Add handling of no hardware here.
} else if (e.code == auth_error.notEnrolled) {
// ...
} else {
// ...
}
}
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If you want to customize the messages in the dialogs, you can pass
AuthMessages for each platform you support. These are platform-specific, so
you will need to import the platform-specific implementation packages. For
instance, to customize Android and iOS:

import 'package:local_auth_android/local_auth_android.dart';
import 'package:local_auth_darwin/local_auth_darwin.dart';
// ···
final bool didAuthenticate = await auth.authenticate(
localizedReason: 'Please authenticate to show account balance',
authMessages: const <AuthMessages>[
AndroidAuthMessages(
signInTitle: 'Oops! Biometric authentication required!',
cancelButton: 'No thanks',
),
IOSAuthMessages(
cancelButton: 'No thanks',
),
]);
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See the platform-specific classes for details about what can be customized on
each platform.
Exceptions #
authenticate throws PlatformExceptions in many error cases. See
error_codes.dart for known error codes that you may want to have specific
handling for. For example:

import 'package:flutter/services.dart';
import 'package:local_auth/error_codes.dart' as auth_error;
import 'package:local_auth/local_auth.dart';
// ···
final LocalAuthentication auth = LocalAuthentication();
// ···
try {
final bool didAuthenticate = await auth.authenticate(
localizedReason: 'Please authenticate to show account balance',
options: const AuthenticationOptions(useErrorDialogs: false));
// ···
} on PlatformException catch (e) {
if (e.code == auth_error.notEnrolled) {
// Add handling of no hardware here.
} else if (e.code == auth_error.lockedOut ||
e.code == auth_error.permanentlyLockedOut) {
// ...
} else {
// ...
}
}
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iOS Integration #
Note that this plugin works with both Touch ID and Face ID. However, to use the latter,
you need to also add:
<key>NSFaceIDUsageDescription</key>
<string>Why is my app authenticating using face id?</string>
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to your Info.plist file. Failure to do so results in a dialog that tells the user your
app has not been updated to use Face ID.
Android Integration #
* The plugin will build and run on SDK 16+, but isDeviceSupported() will
always return false before SDK 23 (Android 6.0).
Activity Changes #
Note that local_auth requires the use of a FragmentActivity instead of an
Activity. To update your application:

If you are using FlutterActivity directly, change it to
FlutterFragmentActivity in your AndroidManifest.xml.

If you are using a custom activity, update your MainActivity.java:
import io.flutter.embedding.android.FlutterFragmentActivity;

public class MainActivity extends FlutterFragmentActivity {
// ...
}
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or MainActivity.kt:
import io.flutter.embedding.android.FlutterFragmentActivity

class MainActivity: FlutterFragmentActivity() {
// ...
}
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to inherit from FlutterFragmentActivity.

Permissions #
Update your project's AndroidManifest.xml file to include the
USE_BIOMETRIC permissions:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.app">
<uses-permission android:name="android.permission.USE_BIOMETRIC"/>
<manifest>
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Compatibility #
On Android, you can check only for existence of fingerprint hardware prior
to API 29 (Android Q). Therefore, if you would like to support other biometrics
types (such as face scanning) and you want to support SDKs lower than Q,
do not call getAvailableBiometrics. Simply call authenticate with biometricOnly: true.
This will return an error if there was no hardware available.
Android theme
Your LaunchTheme's parent must be a valid Theme.AppCompat theme to prevent
crashes on Android 8 and below. For example, use Theme.AppCompat.DayNight to
enable light/dark modes for the biometric dialog. To do that go to
android/app/src/main/res/values/styles.xml and look for the style with name
LaunchTheme. Then change the parent for that style as follows:
...
<resources>
<style name="LaunchTheme" parent="Theme.AppCompat.DayNight">
...
</style>
...
</resources>
...
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If you don't have a styles.xml file for your Android project you can set up
the Android theme directly in android/app/src/main/AndroidManifest.xml:
...
<application
...
<activity
...
android:theme="@style/Theme.AppCompat.DayNight"
...
>
</activity>
</application>
...
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Sticky Auth #
You can set the stickyAuth option on the plugin to true so that plugin does not
return failure if the app is put to background by the system. This might happen
if the user receives a phone call before they get a chance to authenticate. With
stickyAuth set to false, this would result in plugin returning failure result
to the Dart app. If set to true, the plugin will retry authenticating when the
app resumes.