The issue is reproduced only on old NFC devices like iPhone 8 which don't have a background NFC reading, but everything good on iPhone 12, 11, X. After clicking cancel (invalidate session) - it is impossible to start the NFC session again. Only after force close app it can be started again. Here is the code of openning session (button scan)
session = NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: true)
session?.alertMessage = "Hold your iPhone near the item to scan tag."
session?.begin()
Code of delegate methods NFCNDEFReaderSessionDelegate
func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {
guard let ndefMessage = messages.first,
let record = ndefMessage.records.first,
record.typeNameFormat == .absoluteURI || record.typeNameFormat == .nfcWellKnown,
let payloadText = String(data: record.payload, encoding: .utf8) else {
return
}
print("scanned NFC info: \(payloadText)")
self.session = nil
}
func readerSession(_ session: NFCNDEFReaderSession, didInvalidateWithError error: Error) {
if let readerError = error as? NFCReaderError {
if (readerError.code != .readerSessionInvalidationErrorFirstNDEFTagRead)
&& (readerError.code != .readerSessionInvalidationErrorUserCanceled) {
let alertController = UIAlertController(
title: "Session is expired.",
message: "Please, try again.",//error.localizedDescription,
preferredStyle: .alert
)
alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
DispatchQueue.main.async {
self.present(alertController, animated: true, completion: nil)
}
}
}
self.session = nil
}
You will have to re-start the session again.
@IBAction func beingScanning(){
guard !session?.isReady else {
return
}
// invalidateAfterFirstRead = false
session = NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: false)
session?.alertMessage = "Hold your iPhone near the item to scan tag."
session?.begin()
}
Also use invalidateAfterFirstRead
false instead of true.
Once you are done with successful reading, you can invalidate it.