onScan callback of ReaderWidget is not called on older Android devices

[kaboc]

I've experienced the issue on Android 5.1, but not on Android 10. I haven't tried on other Android versions.

Environment:

• Android 5.1
• flutter_zxing 0.9.1

Reproducible code:

android/app/src/main/AndroidManifest.xml

<!-- Add AdMob app ID -->
<!-- e.g. ca-app-pub-3940256099942544~3347511713 -->
<meta-data
    android:name="com.google.android.gms.ads.APPLICATION_ID"
    android:value="ca-app-pub-xxxxxxxxxxxxxxxx~yyyyyyyyyy"/>

lib/main.dart

import 'package:flutter/material.dart';

import 'package:flutter_zxing/flutter_zxing.dart';
import 'package:google_mobile_ads/google_mobile_ads.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  MobileAds.instance.initialize();

  runApp(const App());
}

class App extends StatefulWidget {
  const App({super.key});

  @override
  State<App> createState() => _AppState();
}

class _AppState extends State<App> {
  late final _ad = BannerAd(
    adUnitId: 'ca-app-pub-3940256099942544/6300978111', // Demo banner ad unit ID
    size: AdSize.banner,
    request: const AdRequest(),
    listener: const BannerAdListener(),
  )..load();

  @override
  void dispose() {
    _ad.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.black,
        body: Column(
          children: [
            Expanded(
              child: ReaderWidget(
                onScan: (code) {
                  print('text: ${code.text}'); // This is never called.
                },
              ),
            ),
            SizedBox(
              height: 50.0,
              child: AdWidget(ad: _ad),
            ),
          ],
        ),
      ),
    );
  }
}

[kaboc]

I run the code again and found the issue wasn't reproduced. I'm sorry.

It happens on an actual app, so there may be some differences. I'll compare the two and try to make a literally "reproducible" code. If I can't, I will just close this page then.

[kaboc]

I managed to reproduce the issue. It appears to have something to do with google_mobile_ads.

The example app repeatedly outputs the following message:

type 'ArgumentError' is not a subtype of type 'FutureOr<Code>'