qr-example/lib/main.dart

import 'dart:async';
import 'dart:math';

import 'package:camera/camera.dart';
import 'package:camera_aurora/camera_aurora.dart';
import 'package:camera_aurora/camera_viewfinder.dart';
import 'package:flutter/material.dart';
import 'package:qraurora/qr_code.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  late Future<CameraController> _controller;
  StreamSubscription<String?>? _cameraSearchQrSubscription;
  String? code;

  Future<CameraController> _createController() async {
    final cameras = await availableCameras();
    if (cameras.isEmpty) {
      throw CameraException("not found", null);
    }

    final camera = cameras.where((element) {
      return element.lensDirection == CameraLensDirection.back;
    }).first;

    final controller = CameraController(
      camera,
      ResolutionPreset.medium,
      imageFormatGroup: ImageFormatGroup.jpeg,
    );

    _cameraSearchQrSubscription = cameraSearchQr?.listen((text) {
      if (text.isNotEmpty) {
        setState(() {
          code = text;
          _cameraSearchQrSubscription?.cancel();
        });
      }
    });

    await controller.initialize();
    return controller;
  }

  @override
  void initState() {
    super.initState();
    _controller = _createController();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            FutureBuilder(
              future: _controller,
              builder: (context, snapshot) {
                if (snapshot.hasData) {
                  if (code != null) {
                    Navigator.push(
                        context,
                        MaterialPageRoute(
                            builder: (context) => QrCode(text: code!)));
                  }
                  return Expanded(
                      child: LayoutBuilder(builder: ((context, constraints) {
                    return AspectRatio(
                        aspectRatio: max(
                                constraints.maxHeight, constraints.maxWidth) /
                            min(constraints.maxHeight, constraints.maxWidth),
                        child: snapshot.data!.buildPreview());
                  })));
                }

                return const CircularProgressIndicator();
              },
            )
          ],
        ),
      ),
    );
  }
}