mobile scanner

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

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'SN scanner Demo',
      home: MyHomePage(),
    );
  }
}

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

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  ValueNotifier<String> snFound = ValueNotifier('');

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          SnScanner(
            onSnFound: (sn) {
              print('********** SN found: $sn');
              snFound.value = sn;
            },
          ),

          ValueListenableBuilder(
              valueListenable: snFound,
              builder: (_, sn, __) {
                return Align(
                  alignment: Alignment.bottomCenter,
                  child: Text(
                    sn,
                    textScaleFactor: 2,
                    style: const TextStyle(backgroundColor: Colors.white54),
                  ),
                );
              },
          ),
        ],
      ),
    );
  }
}


class SnScanner extends StatelessWidget {
  final Function(String sn)? onSnFound;

  const SnScanner({Key? key, this.onSnFound})
      : super(key: key);

  @override
  Widget build(BuildContext context) {
    MobileScannerController cameraController = MobileScannerController();

    return Scaffold(
        appBar: AppBar(
          title: const Text('Mobile Scanner'),
          actions: [
            IconButton(
              color: Colors.white,
              icon: ValueListenableBuilder(
                valueListenable: cameraController.torchState,
                builder: (context, state, child) {
                  switch (state as TorchState) {
                    case TorchState.off:
                      return const Icon(Icons.flash_off, color: Colors.grey);
                    case TorchState.on:
                      return const Icon(Icons.flash_on, color: Colors.yellow);
                  }
                },
              ),
              iconSize: 32.0,
              onPressed: () => cameraController.toggleTorch(),
            ),
            IconButton(
              color: Colors.white,
              icon: ValueListenableBuilder(
                valueListenable: cameraController.cameraFacingState,
                builder: (context, state, child) {
                  switch (state as CameraFacing) {
                    case CameraFacing.front:
                      return const Icon(Icons.camera_front);
                    case CameraFacing.back:
                      return const Icon(Icons.camera_rear);
                  }
                },
              ),
              iconSize: 32.0,
              onPressed: () => cameraController.switchCamera(),
            ),
          ],
        ),
        body: MobileScanner(
            allowDuplicates: false,
            controller: cameraController,
            onDetect: (barcode, args) {
              if (barcode.rawValue == null) {
              } else {
                final String code = barcode.rawValue!;
                if (onSnFound != null && _validateSn(code)) {
                  onSnFound!(code);
                }
              }
            }));
  }

  bool _validateSn(String sn) {
    return sn.isNotEmpty && sn.startsWith('S') && sn.length == 13;
  }

}