iOS 11 Core NFC - any sample code?

问题:

I just installed the first iOS 11 beta to an iPhone 7 and am interested in trying the NFC. There's nothing about it in settings. I am wondering if there's any sample code out there showing how to read a tag. Can anyone show how to use the Core NFC SDK, in a code snippet?

回答1:

In the Apple Developer site, create a new App ID and make sure that NFC Tag Reading is enabled.

Add the following lines to your .plist file:

<key>NFCReaderUsageDescription</key>
<string>NFC Tag!</string>

and these to the entitlements file:

<key>com.apple.developer.nfc.readersession.formats</key>
    <array>
        <string>NDEF</string>
    </array>

It should look something like this in the corresponding files:

Also Core NFC can be enabled via the Capabilities tab in Xcode.

Objective-c

Import CoreNFC

#import <CoreNFC/CoreNFC.h>

and set the delegate:

@interface YourViewController : UIViewController <NFCNDEFReaderSessionDelegate>

In viewDidLoad:

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NFCNDEFReaderSession *session = [[NFCNDEFReaderSession alloc] initWithDelegate:self queue:dispatch_queue_create(NULL, DISPATCH_QUEUE_CONCURRENT) invalidateAfterFirstRead:NO];
    [session beginSession];
}

In the delegate callback:

- (void) readerSession:(nonnull NFCNDEFReaderSession *)session didDetectNDEFs:(nonnull NSArray<NFCNDEFMessage *> *)messages {

    for (NFCNDEFMessage *message in messages) {
        for (NFCNDEFPayload *payload in message.records) {
            NSLog(@"Payload data:%@",payload.payload);
        }
    }        
}

You must also add the didInvalidateWithError delegate callback or you'll not conform with protocol:

- (void)readerSession:(nonnull NFCNDEFReaderSession *)session didInvalidateWithError:(nonnull NSError *)error {

}

You can stop the reader with:

[session invalidateSession];

Swift 3/4

Import CoreNFC

import CoreNFC

and set the delegate:

class YourViewController: UIViewController, NFCNDEFReaderSessionDelegate

In viewDidLoad:

override func viewDidLoad() {
        super.viewDidLoad()

        let session = NFCNDEFReaderSession(delegate: self,
                      queue: DispatchQueue(label: "queueName", attributes: .concurrent), invalidateAfterFirstRead: false)  
        session?.begin()
    }

In the delegate callback:

func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {
  for message in messages {
    for record in message.records {
      print(record.payload)
    }
  }
}

You can stop the reader with:

session.invalidateSession

Usage

After launching the view you should immediately see the iOS NFC reader dialog like so:

Once this dialog appears you have about a second to place the iPhone near the NFC tag you want to read. Otherwise, the field is deactivated (this seems to be a bug on Apple's end). I often needed to cancel and retry to get consistent readings. More details here.

回答2:

For fix this trouble you should add com.apple.developer.nfc.readersession.formats key into your entitlements file. The key should be associated with array of enabled nfs types. As example, you can add this into you entitlements.

<key>com.apple.developer.nfc.readersession.formats</key> <array> <string>NDEF</string> </array>

It worked for me.

回答3:

Updated for second Xcode beta.

Add the NFC capability to your app from the Developer Center. Identifiers -> App IDs -> enable "NFC Tag Reading".

If your project does not have an entitlement file, let Xcode create one for you by just activating and then subsequently deactivating any capability from within Xcode -> Project Targets -> Capabilities. You will find a new [AppName].entitlements file in your project navigator. Right-click on that file and select "Open as -> Source Code". Enter the following entry manually between <dict></dict>:

<key>com.apple.developer.nfc.readersession.formats</key>
<array>
    <string>NDEF</string>
</array>

As soon as Xcode 9 allows enabling NFC Tag Reading from the Capabilities selection this step becomes obsolete because all you have to do is to enable it there. The current (first) Beta version does not support this.

You also need to enter a usage description for the privacy warning iOS will show the user. (At the moment (beta 1) this warning will be displayed when the device is ready to scan and shows a native system dialogue which will include this message. However, this seems to be unploished.) Open your target's Info.plist and start typing "Privacy" and you can scroll down to "Privacy - NFC Usage Description" to select it by hitting return. Enter a meaningful explanation to your user in the right column.

Now you should be able to import CoreNFC, in Swift:

import CoreNFC

Then head over to Apple's documentation.

Important: If the compiler returns an error with No such module 'CoreNFC' check if you have selected an actual iOS 11 device to build for, not a simulator. It also has to be the iPhone 7 or 7 plus. This might change in a future version, but testing NFC will only ever be fully working with actual hardware. (cp. Core Bluetooth where you can run on Simulator but not test the actual capabilities.) Beta 2 doesn't have this issue anymore. However, actual hardware in form of iPhone 7/p is still required for actual testing.

回答4:

Just to enrich previous answers, it's important to bear in mind these considerations specifically of the NFCNDEFReaderSession class:

• Reader session for processing NFC Data Exchange Format (NDEF) tags. This session requires the "com.apple.developer.nfc.readersession.formats" entitlement in your process. In addition your application's Info.plist must contain a non-empty usage description string.
• A NDEF reader session will automatically scan and detect NFC Forum tags that contain a valid NDEF message. NFC Forum Tag type 1 to 5 that is NDEF formatted are supported. A modal system UI will present once -beginSession is called to inform the start of the session; the UI sheet is automatically dismissed when the session is invalidated either by the user or by calling -invalidateSession.
• An opened session has a 60 seconds time limit restriction after -beginSession is called; -readerSession:didInvalidateWithError: will return NFCReaderSessionInvalidationErrorSessionTimeout error when the time limit is reached.
• Only 1 active reader session is allowed in the system; -readerSession:didInvalidateWithError: will return NFCReaderSessionInvalidationErrorSystemIsBusy when a new reader session is initiated by -beginSession when there is an active reader session.
• -readerSession:didInvalidateWithError: will return NFCReaderSessionInvalidationErrorUserCanceled when user clicks on the done button on the UI.
• -readerSession:didInvalidateWithError: will return NFCReaderSessionInvalidationErrorSessionTerminatedUnexpectedly when the client application enters the background state. -readerSession:didInvalidateWithError: will return NFCReaderErrorUnsupportedFeature when
  1. reader mode feature is not available on the hardware
  2. client application does not have the required entitlement.

回答5:

You need to make sure the usage description is in place and also add the capability to the app inside of the Apple Developer Center. I have a tutorial based on my experience (Swift 4-based). It's available here: Core NFC Tutorial

回答6:

I added Core NFC to a project using the resources in these answers. One additional thing that wasn't noted though was that even if you add the capability manually via the entitlements, Xcode doesn't seem to look at the file unless you have a capability turned on. This is probably due to Xcode 9 Beta 1 not having Core NFC as a capability switch for lots of people's sample projects. So just be sure to turn at least one other capability on if you're still seeing issues! I was seeing an unexpected termination error immediately return until I did this.

I would leave this as a comment as it belongs, but don't have enough reputation yet to do so. Figured this was important enough to note.

回答7:

my two cents:

1) under xcode 9.0 (beta 4 9M189t ) if You have already added capabilities, no need to manually add:

<key>com.apple.developer.nfc.readersession.formats</key>
    <array>
        <string>NDEF</string>
    </array>

it is done automatically

2) no crash if not using iPhone 7 OR you are in simulator:

You wil be called in:

func readerSession(_ session: NFCNDEFReaderSession, didInvalidateWithError error: Error) {
        print(error.localizedDescription)
    }

it will show: "Feature not supported"

3) dont miss:

self.nfcSession?.begin() // will trigger callback

so:

    final private func setup(){
    self.nfcSession = NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: true)
    self.nfcSession?.alertMessage = "Put your NFC TAG over iPhone.."
    self.nfcSession?.begin() // will trigger callback

}

4) if user cancels, you will get:

"Session is invalidated by user cancellation"

in didInvalidateWithError callback.