Error: error using biometric auth: PlatformException(no_fragment_activity, local_auth plugin requires activity to be a FragmentActivity., null, null)

Question

I am trying to add fingerprint access in y flutter app but I am not able to as I am getting the following error:

error using biometric auth: PlatformException(no_fragment_activity, local_auth plugin requires activity to be a FragmentActivity., null, null)

Following is my code:

main.dart:

import 'package:flutter/material.dart';
import 'package:local_auth/local_auth.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool isAuth = false;
  void checkBiometric() async {
    final LocalAuthentication auth = LocalAuthentication();
    bool canCheckBiometrics = false;
    try {
      canCheckBiometrics = await auth.canCheckBiometrics;
    } catch (e) {
      print("error biome trics $e");
    }
    print("biometric is available: $canCheckBiometrics");
    List<BiometricType> availableBiometrics;
    try {
      availableBiometrics = await auth.getAvailableBiometrics();
    } catch (e) {
      print("error enumerate biometrics $e");
    }
    print("following biometrics are available");
    if (availableBiometrics.isNotEmpty) {
      availableBiometrics.forEach((ab) {
        print("\ttech: $ab");
      });
    } else {
      print("no biometrics are available");
    }

    bool authenticated = false;

    try {
      authenticated = await auth.authenticateWithBiometrics(
          localizedReason: 'Touch your finger on the sensor to login',
          useErrorDialogs: true,
          stickyAuth: false
        // androidAuthStrings:AndroidAuthMessages(signInTitle: "Login to HomePage")
      );
    } catch (e) {
      print("error using biometric auth: $e");
    }

    setState(() {
      isAuth = authenticated ? true : false;
    });

    print("authenticated: $authenticated");
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        debugShowCheckedModeBanner: false,
        home: new Scaffold(
          appBar: new AppBar(
            title: new Text('BioAuthentication'),
          ),
          body: new Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              Expanded(
                child: Container(),
              ),
              new RaisedButton(
                splashColor: Colors.pinkAccent,
                color: Colors.black,
                child: new Text(
                  "Authentiate",
                  style: new TextStyle(fontSize: 20.0, color: Colors.white),
                ),
                onPressed: checkBiometric,
              ),
              new Expanded(
                child: Container(),
              ),
              isAuth == true
                  ? Text(
                "Authenticated",
                softWrap: true,
                style: new TextStyle(fontSize: 30.0, color: Colors.black),
              )
                  : Text(
                "Not Authenticated",
                softWrap: true,
                style: new TextStyle(fontSize: 30.0, color: Colors.black),
              ),
              new Expanded(
                child: Container(),
              ),
            ],
          ),
        ));
  }
}

MainActivity.kt:

package com.open.flutter_fingerprint_new

import androidx.annotation.NonNull;
import io.flutter.embedding.android.FlutterFragmentActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugins.GeneratedPluginRegistrant

class MainActivity: FlutterFragmentActivity() {
    override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
        GeneratedPluginRegistrant.registerWith(flutterEngine);
    }
}

Can someone help me with this please?

Note: Instead of using a button is there any option so that on the launch of the screen the application prompts the user to enter the fingerprint?

Answer 1

Changing from FlutterActivity causes other plugins that depends on that doesn't work. (If someone knows why that happens, please let me know in the comments).

This fixed that issue for me, change ".MainActivity" in android.name to "io.flutter.embedding.android.FlutterFragmentActivity" . But, doing like the below code makes us unable to customize or edit in MainActivity.

 <application
    ...
    <activity
        android:name="io.flutter.embedding.android.FlutterFragmentActivity" 
        android:launchMode="singleTop"
        android:theme="@style/LaunchTheme"

Answer 2

You should carefully check Android Integration and ios Integration.https://github.com/flutter/plugins/tree/master/packages/local_auth#android-integration

Android Integration

Note that local_auth plugin requires the use of a FragmentActivity as opposed to Activity. This can be easily done by switching to use FlutterFragmentActivity as opposed to FlutterActivity in your manifest (or your own Activity class if you are extending the base class).

import android.os.Bundle;
import io.flutter.app.FlutterFragmentActivity;
import io.flutter.plugins.flutter_plugin_android_lifecycle.FlutterAndroidLifecyclePlugin;
import io.flutter.plugins.localauth.LocalAuthPlugin;

public class MainActivity extends FlutterFragmentActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FlutterAndroidLifecyclePlugin.registerWith(
                registrarFor(
                        "io.flutter.plugins.flutter_plugin_android_lifecycle.FlutterAndroidLifecyclePlugin"));
        LocalAuthPlugin.registerWith(registrarFor("io.flutter.plugins.localauth.LocalAuthPlugin"));
    }
}

OR Update your MainActivity.kt:

import io.flutter.embedding.android.FlutterFragmentActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugins.GeneratedPluginRegistrant

class MainActivity: FlutterFragmentActivity() {
    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        GeneratedPluginRegistrant.registerWith(flutterEngine)
    }
}