Flutter QR-code scanner rapidly scan issue, how to control the second scan? - flutter

Question

Does anyone know how to adjust the QR code scanner speed? since the second scan is so quick,
source example is down below, you can download it add and run it in your Flutter project to test!
What are the differenceis are in the controller.scannedDataStream.listen() function. I posted down below:
Barcode? result;
var qrText = "";
bool isValid = false;
bool isExpired = false;
QRViewController? controller;
controller.scannedDataStream.listen((scanData) async {
log(scanData.code);
if (!scanData.code.contains('?key=')) {
setState(() {
qrText = "This is not a correct code";
isValid = false;
});
} else {
var key_hash = scanData.code.split('?key=');
log('hash: ' + key_hash[1]);
await decrypt(key_hash[1]).then((String result) async {
if (result == "") {
log('result: ' + result);
await controller.stopCamera();
setState(() {
qrText = result;
isValid = true;
isExpired = true;
});
}
else {
log('result: ' + result);
await controller.pauseCamera();
await controller.stopCamera();
setState(() {
qrText = result;
isValid = true;
isExpired = false;
});
}
});
}
});
https://pub.dev/packages/qr_code_scanner/example