scan_view.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart' as widgets;
import 'package:permission_handler/permission_handler.dart';
import 'package:flutter_integration_sample/scan_bloc.dart';

class ScanView extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _ScanViewState();
}

class _ScanViewState extends State<ScanView> with WidgetsBindingObserver {
  final ScanBloc _bloc = ScanBloc();

  bool _isPermissionGranted = false;

  @override
  void initState() {
    super.initState();

    _ambiguate(WidgetsBinding.instance)?.addObserver(this);

    // カメラのアクセス権限を確認
    _checkPermission();

    _bloc.singleScanResult.listen((scannedData) {
      // 以下を任意のビジネスロジックに変更して下さい
      // _bloc.enableBarcodeCapture()を呼び出す事でスキャンが再開されます
      showDialog<void>(
        context: context,
        barrierDismissible: false,
        builder: (BuildContext context) {
          return AlertDialog(
            title: const Text('Scan Result'),
            content: SingleChildScrollView(
              child: Text(scannedData),
            ),
            actions: <Widget>[
              TextButton(
                child: const Text('OK'),
                onPressed: () {
                  Navigator.of(context).pop();
                  _bloc.enableBarcodeCapture();
                },
              ),
            ],
          );
        },
      );
    });
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
      _checkPermission();
    } else if (state == AppLifecycleState.paused) {
      _bloc.switchCameraOff();
    }
  }

  @override
  void dispose() {
    _bloc.dispose();
    _ambiguate(WidgetsBinding.instance)?.removeObserver(this);
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    Widget child;
    if (!_isPermissionGranted) {
      child = Text('No permission to access the camera!',
          style: TextStyle(fontSize: 14, fontWeight: FontWeight.bold, color: Colors.black));
    } else {
      child = _bloc.captureView;
    }
    return WillPopScope(
        child: SizedBox.fromSize(
          child: child,
          size: widgets.Size(MediaQuery.of(context).size.width, MediaQuery.of(context).size.height * 1),
          ),
        onWillPop: () {
          dispose();
          return Future.value(true);
        });
  }

  void _checkPermission() async {
    Permission.camera.request().isGranted.then((value) => setState(() {
      _isPermissionGranted = value;
      _bloc.switchCameraOn();
      _bloc.enableBarcodeCapture();
    }));
  }

  T? _ambiguate<T>(T? value) => value;
}