How to Pause and Resume the qr_code_scanner using the NavigationBar - flutter

Question

I have a NavigationBar with 3 Destinations and I want to pause or resume the qr_code_scanner depending on what destination is focused, to do this i use a if to evaluate the index and pause or resume the scanner, but i dont now how pass the controller between classes.
My NavigationBar
bottomNavigationBar: NavigationBar(
elevation: 2,
labelBehavior: NavigationDestinationLabelBehavior.onlyShowSelected,
selectedIndex: index,
onDestinationSelected: (index) {
setState(() => this.index = index);
if (index == 1) {
widget.controller!.resumeCamera();
} else {
widget.controller!.pauseCamera();
}
},
destinations: const [
NavigationDestination(
icon: Icon(Icons.store_outlined),
selectedIcon: Icon(Icons.store),
label: 'Tienda',
),
NavigationDestination(
icon: Icon(Icons.qr_code_scanner_outlined),
selectedIcon: Icon(Icons.qr_code_scanner),
label: 'Escaner',
),
NavigationDestination(
icon: Icon(Icons.shopping_cart_outlined),
selectedIcon: Icon(Icons.shopping_cart),
label: 'Carrito',
),
],
),
The Home class
class Home extends StatefulWidget {
final QRViewController? controller;
const Home({Key? key, this.controller}) : super(key: key);
#override
State<Home> createState() => _HomeState();
}
My QrScan Class
class QRScanner extends StatefulWidget {
const QRScanner({Key? key}) : super(key: key);
#override
State<StatefulWidget> createState() => QRScannerState();
}
class QRScannerState extends State<QRScanner> {
Barcode? result;
QRViewController? controller;
final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
#override
void reassemble() {
super.reassemble();
if (Platform.isAndroid) {
controller!.pauseCamera();
}
controller!.resumeCamera();
}
#override
Widget build(BuildContext context) {
void home() {
Home(
controller: controller,
);
}
home();
return Scaffold(
body: Column(
children: <Widget>[
Expanded(child: buildQrView(context)),
Align(
alignment: Alignment.bottomCenter,
child: Container(
alignment: Alignment.center,
height: 100,
color: Colors.black,
child: Row(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Container(
margin: const EdgeInsets.all(8),
child: ElevatedButton(
onPressed: () async {
await controller?.toggleFlash();
setState(() {});
},
child: FutureBuilder(
future: controller?.getFlashStatus(),
builder: (context, snapshot) {
if (snapshot.data == true) {
return const Icon(Icons.flash_on);
} else {
return const Icon(Icons.flash_off);
}
// Text('Flash: ${snapshot.data}');
},
)),
),
const Padding(padding: EdgeInsets.fromLTRB(37, 0, 0, 0)),
if (result != null)
Text('ID:${result!.code}')
else
const Text('Escanee el QR del producto'),
],
),
),
)
],
),
);
}
Widget buildQrView(BuildContext context) {
// For this example we check how width or tall the device is and change the scanArea and overlay accordingly.
var scanArea = (MediaQuery.of(context).size.width < 400 ||
MediaQuery.of(context).size.height < 400)
? 150.0
: 300.0;
// To ensure the Scanner view is properly sizes after rotation
// we need to listen for Flutter SizeChanged notification and update controller
return QRView(
key: qrKey,
onQRViewCreated: onQRViewCreated,
overlay: QrScannerOverlayShape(
borderColor: Colors.white,
borderRadius: 10,
borderLength: 30,
borderWidth: 10,
cutOutSize: scanArea),
onPermissionSet: (ctrl, p) => onPermissionSet(context, ctrl, p),
);
}
void onQRViewCreated(QRViewController controller) {
setState(() {
this.controller = controller;
});
controller.scannedDataStream.listen((scanData) {
setState(() {
result = scanData;
});
controller.pauseCamera();
Stream<List<Products>> readProducts() => FirebaseFirestore.instance
.collection('products')
.where('id', isEqualTo: '${result!.code}')
.snapshots()
.map((snapshot) => snapshot.docs
.map((doc) => Products.fromJson(doc.data()))
.toList());
Future<bool> onWillPop() async {
return false;
}
showDialog(
barrierDismissible: false,
context: context,
builder: (BuildContext context) => WillPopScope(
onWillPop: () async => false,
child: WillPopScope(
onWillPop: onWillPop,
child: Dialog(
insetPadding: const EdgeInsets.all(8),
child: StreamBuilder<List<Products>>(
stream: readProducts(),
builder: (context, snapshot) {
if (snapshot.hasError) {
return Text('Algo ha ocurrido! ${snapshot.error}');
} else if (snapshot.hasData) {
final products = snapshot.data!;
return Container(
margin: const EdgeInsets.all(8),
child: Column(
mainAxisSize: MainAxisSize.min,
children: products
.map((p) => BuildProducts(
products: p, controller: controller))
.toList()),
);
} else {
return const Center(child: CircularProgressIndicator());
}
}),
),
),
),
);
});
}
void onPermissionSet(BuildContext context, QRViewController ctrl, bool p) {
log('${DateTime.now().toIso8601String()}_onPermissionSet $p');
if (!p) {
ScaffoldMessenger.of(context).showSnackBar(
const SnackBar(content: Text('no Permission')),
);
}
}
#override
void dispose() {
controller?.dispose();
super.dispose();
}
}