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      Latest reply on Mar 16, 2020 10:43 AM by evertee
      evertee Level 1 Level 1 (0 points)

        I have an app that I want to extend with some CoreNFC tag reading.

        I initiate a tagReaderSession with this code, which brings up a system dialoge telling the phone is currently in read mode:

        _readerSession = [[NFCTagReaderSession alloc] initWithPollingOption:NFCPollingISO14443 delegate:self  queue:nil] ;
        _readerSession.alertMessage = @"Bip the top of the phone towards a NFC tag.";
        [_readerSession beginSession];


        This method is called when a tag has been read:

        - (void)tagReaderSession:(NFCTagReaderSession *) session
                  didDetectTags:(NSArray<__kindofid> *)tags


        My intended design:

        - I use NFC tags as sports timing chips and the phone as a reader station.

        - I would like to read many tags before invalidating the tag reader. Not just one tag and then closing down the session.

        => This I can do

        - Between each tag read I would like to pop up a dialogue quickly, 2 seconds, with a message about the tag just scanned and a calculated time, position etc, in the race.

        => Here I get a problem with threads.


        - It is hard to move or customize the standard tag reading message from the system.

        - it is hard to display something else at the same time. Everything else is gray appart from the system dialogue until the readerSession dialoge have been nvalidated.

        - Even first doing readerSession.invalidate and then calling UI methods does not work (bringing up an AlertController). I then get this error below:


        tagString = [tag.asNFCMiFareTag.identifier hexadecimalString];
        [__viewController addResults:tagString];
        [_readerSession invalidateSession];
         UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Result added" message:.......
        2020-03-13 17:48:29.410911+0100 Sportimes[3249:1471500] *** Assertion failure in -[FBSSerialQueue assertOnQueue], /BuildRoot/Library/Caches/com.apple.xbs/Sources/FrontBoardServices/FrontBoard-626.4.1/FrontBoardServices/FBSSerialQueue.m:98
        2020-03-13 17:48:29.411179+0100 Sportimes[3249:1471500] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'threading violation: expected the main thread'


        I guess I need to go into threads.

        Any advice?