monorepo/dialer/lib/widgets/qr_scanner.dart

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

class QRCodeScannerScreen extends StatefulWidget {
  const QRCodeScannerScreen({Key? key}) : super(key: key);

  @override
  _QRCodeScannerScreenState createState() => _QRCodeScannerScreenState();
}

class _QRCodeScannerScreenState extends State<QRCodeScannerScreen> {
  final MobileScannerController cameraController = MobileScannerController();
  bool isScanning = true;

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

  void _showInvalidQRDialog() {
    showDialog(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('Invalid QR Code'),
        content:
        const Text('The scanned QR code does not contain valid vCard data.'),
        actions: [
          TextButton(
            onPressed: () {
              Navigator.of(context).pop(); // Close dialog
              setState(() {
                isScanning = true; // Resume scanning
              });
            },
            child: const Text('Try Again'),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Scan Contact QR Code'),
      ),
      body: MobileScanner(
        controller: cameraController,
        // allowDuplicates: false, // or true, depending on your preference
        onDetect: (capture) {
          if (!isScanning) return;
          isScanning = false; // Stop multiple triggers

          final List<Barcode> barcodes = capture.barcodes;
          for (final barcode in barcodes) {
            final String? code = barcode.rawValue;
            // If the QR code contains 'BEGIN:VCARD', let's assume it's a valid vCard
            if (code != null && code.contains('BEGIN:VCARD')) {
              Navigator.pop(context, code); // pop back with the full vCard text
              return;
            }
          }

          // If no valid vCard was found in any of the barcodes
          _showInvalidQRDialog();
        },
      ),
    );
  }
}