import 'dart:io';
import 'package:flutter/material.dart';
import 'package:qr_code_scanner/qr_code_scanner.dart';

void main() => runApp(QRScanPage());

// リスト 6.9_cf
class QRScanPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _QRScanPageState();
}

class _QRScanPageState extends State<QRScanPage> {
  final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
  String? scannedUrl;
  QRViewController? controller;

  @override
  void reassemble() {
    super.reassemble();
    if (Platform.isAndroid) {
      controller?.pauseCamera();
    } else if (Platform.isIOS) {
      controller?.resumeCamera();
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.white,
        body: Column(
          children: <Widget>[
            Expanded(
              flex: 5,
              child: QRView(
                key: qrKey,
                onQRViewCreated: _onQRViewCreated,
              )
            ),
            Expanded(
              flex: 1,
              child: Center(
                child: scannedUrl ==
                    null ? CircularProgressIndicator() : Text(scannedUrl!)
              )
            )
          ]
        )
      )
    );
  }

  void _onQRViewCreated(QRViewController controller) {
    this.controller = controller;
    controller.scannedDataStream.listen((scanData) {
      setState(() {
        scannedUrl = scanData.code;
      });
    });
  }

  @override
  void dispose() {
    controller?.dispose();
    super.dispose();
  }
}