smooth-app/packages/smooth_app/lib/pages/scan/continuous_scan_page.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:qr_code_scanner/qr_code_scanner.dart';
import 'package:smooth_app/data_models/continuous_scan_model.dart';
import 'package:smooth_app/pages/scan/scan_page_helper.dart';
import 'package:smooth_ui_library/smooth_ui_library.dart';
import 'package:visibility_detector/visibility_detector.dart';

class ContinuousScanPage extends StatefulWidget {
  const ContinuousScanPage();

  @override
  State<ContinuousScanPage> createState() => _ContinuousScanPageState();
}

class _ContinuousScanPageState extends State<ContinuousScanPage> {
  final GlobalKey _scannerViewKey = GlobalKey(debugLabel: 'qr Barcode Scanner');
  late ContinuousScanModel _model;
  QRViewController? _controller;

  @override
  Widget build(BuildContext context) {
    _model = context.watch<ContinuousScanModel>();
    return VisibilityDetector(
      key: const Key('VisibilityDetector qr_code_scanner'),
      onVisibilityChanged: (VisibilityInfo visibilityInfo) {
        if (visibilityInfo.visibleFraction == 0.0) {
          _stopLiveFeed();
        } else {
          _resumeLiveFeed();
        }
      },
      child: LayoutBuilder(
        builder: (BuildContext context, BoxConstraints constraints) {
          final double carouselHeight = constraints.maxHeight /
              1.81; // roughly 55% of the available height
          final double viewFinderBottomOffset = carouselHeight / 2.0;

          final List<Widget> children = getScannerWidgets(
            context,
            constraints,
            _model,
          );

          //Insert scanner at the right position
          children.insert(
            1,
            SmoothRevealAnimation(
              delay: 400,
              startOffset: Offset.zero,
              animationCurve: Curves.easeInOutBack,
              child: QRView(
                overlay: QrScannerOverlayShape(
                  // We use [SmoothViewFinder] instead of the overlay.
                  overlayColor: Colors.transparent,
                  // This offset adjusts the scanning area on iOS.
                  cutOutBottomOffset: viewFinderBottomOffset,
                ),
                key: _scannerViewKey,
                onQRViewCreated: setupScanner,
              ),
            ),
          );

          return Scaffold(
            appBar: AppBar(toolbarHeight: 0.0),
            body: Stack(
              children: children,
            ),
          );
        },
      ),
    );
  }

  void setupScanner(QRViewController controller) {
    _controller = controller;
    _controller?.scannedDataStream
        .listen((Barcode barcode) => _model.onScan(barcode.code));
  }

  //Used when navigating away from the QRView itself
  void _stopLiveFeed() => _controller?.stopCamera();

  //Used when navigating back to the QRView
  void _resumeLiveFeed() => _controller?.resumeCamera();
}