local_auth

local_auth

This Flutter plugin provides means to perform local, on-device authentication of the user.

This means referring to biometric authentication on iOS (Touch ID or lock code) and the fingerprint APIs on Android (introduced in Android 6.0).

Usage in Dart

Import the relevant file:

import 'package:local_auth/local_auth.dart';

We have default dialogs with an 'OK' button to show authentication error messages for the following 2 cases:

1. Passcode/PIN/Pattern Not Set. The user has not yet configured a passcode on iOS or PIN/pattern on Android.
2. Touch ID/Fingerprint Not Enrolled. The user has not enrolled any fingerprints on the device.

Which means, if there's no fingerprint on the user's device, a dialog with instructions will pop up to let the user set up fingerprint. If the user clicks 'OK' button, it will return 'false'.

Use the exported APIs to trigger local authentication with default dialogs:

var localAuth = new LocalAuthentication();
bool didAuthenticate =
    await localAuth.authenticateWithBiometrics(
    localizedReason: 'Please authenticate to show account balance');

If you don't want to use the default dialogs, call this API with 'useErrorDialogs = false'. In this case, it will throw the error message back and you need to handle them in your dart code:

bool didAuthenticate =
    await localAuth.authenticateWithBiometrics(
        localizedReason: 'Please authenticate to show account balance',
        useErrorDialogs: false);

You can use our default dialog messages, or you can use your own messages by passing in IOSAuthMessages and AndroidAuthMessages:

import 'package:local_auth/auth_strings.dart';

const iosStrings = const IOSAuthMessages(
    cancelButton: 'cancel',
    goToSettingsButton: 'settings',
    goToSettingsDescription: 'Please set up your Touch ID.',
    lockOut: 'Please reenable your Touch ID');
await localAuth.authenticateWithBiometrics(
    localizedReason: 'Please authenticate to show account balance',
    useErrorDialogs: false,
    iOSAuthStrings: iosStrings);

Exceptions

There are 4 types of exceptions: PasscodeNotSet, NotEnrolled, NotAvailable and OtherOperatingSystem. They are wrapped in LocalAuthenticationError class. You can catch the exception and handle them by different types. For example:

import 'package:flutter/services.dart';
import 'package:local_auth/error_codes.dart' as auth_error;

try {
  bool didAuthenticate = await local_auth.authenticateWithBiometrics(
      localizedReason: 'Please authenticate to show account balance');
} on PlatformException catch (e) {
  if (e.code == auth_error.notAvailable) {
    // Handle this exception here.
  }
}

Android integration

Update your project's AndroidManifest.xml file to include the USE_FINGERPRINT permissions:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.example.app">
  <uses-permission android:name="android.permission.USE_FINGERPRINT"/>
<manifest>

Getting Started

For help getting started with Flutter, view our online documentation.

For help on editing plugin code, view the documentation.