Plugin.NFC

A Cross-Platform NFC (Near Field Communication) plugin to easily read and write NFC tags in your Xamarin Forms or .NET MAUI applications.

This plugin uses NDEF (NFC Data Exchange Format) for maximum compatibilty between NFC devices, tag types, and operating systems.

Status

Package	Build	NuGet	MyGet
Plugin.NFC

CI Feed : https://www.myget.org/F/plugin-nfc/api/v3/index.json

Supported Platforms

Windows, Mac and Linux are currently not supported. Pull Requests are welcomed!

Setup

Android Specific

• Add NFC Permission android.permission.NFC and NFC feature android.hardware.nfc in your AndroidManifest.xml

  <uses-permission android:name="android.permission.NFC" />
  <uses-feature android:name="android.hardware.nfc" android:required="false" />

• Add the line CrossNFC.Init(this) in your OnCreate()

  protected override void OnCreate(Bundle savedInstanceState)
  {
  // Plugin NFC: Initialization before base.OnCreate(...) (Important on .NET MAUI)
  CrossNFC.Init(this);
  
  base.OnCreate(savedInstanceState);
  [...]
  }

• Add the line CrossNFC.OnResume() in your OnResume()

  protected override void OnResume()
  {
  base.OnResume();
  
  // Plugin NFC: Restart NFC listening on resume (needed for Android 10+) 
  CrossNFC.OnResume();
  }

• Add the line CrossNFC.OnNewIntent(intent) in your OnNewIntent()

  protected override void OnNewIntent(Intent intent)
  {
  base.OnNewIntent(intent);
  
  // Plugin NFC: Tag Discovery Interception
  CrossNFC.OnNewIntent(intent);
  }

iOS Specific

iOS 13+ is required for writing tags.

An iPhone 7+ and iOS 11+ are required in order to use NFC with iOS devices.

• Add Near Field Communication Tag Reading capabilty in your Entitlements.plist

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

• Add a NFC feature description in your Info.plist

  <key>NFCReaderUsageDescription</key>
  <string>NFC tag to read NDEF messages into the application</string>

• Add these lines in your Info.plist if you want to interact with ISO 7816 compatible tags

  <key>com.apple.developer.nfc.readersession.iso7816.select-identifiers</key>
  <string>com.apple.developer.nfc.readersession.iso7816.select-identifiers</string>

• Add these lines in your Info.plist if you want to interact with Mifare Desfire EV3 compatible tags

  <key>com.apple.developer.nfc.readersession.iso7816.select-identifiers</key>
  <array>
  <string>com.apple.developer.nfc.readersession.iso7816.select-identifiers</string>
  <string>D2760000850100</string>
  </array>

iOS Considerations

If you are having issues reading Mifare Classic 1K cards - the chances are the issue is not with this library, but with Apple's API.

On iOS 11, apple released the ability to READ NFC NDEF data only using the NfcNdefReaderSession API (https://developer.apple.com/documentation/corenfc/nfcndefreadersession)

A Mifare Classic 1K card will scan if there is a valid NDEF record on it. A blank card will not scan.

In iOS 11, it was not possible to obtain the CSN (serial number/identity) from NFC tags/card.

With iOS 13, along came the ability to write NDEF data AND read serial numbers. However, rather then adapting the NfcNdefReaderSession API, Apple created a NEW API called NfcTagReaderSession (https://developer.apple.com/documentation/corenfc/nfctagreadersession) and left the old NfcNdefReaderSession API untouched.

The new NfcTagReaderSession API in iOS 13 no longer supports Mifare Classic 1K cards period. No idea why - but if you look at Apple's Dev Forums multiple people have spotted the same thing.

So even if you have a Mifare Classic 1K card which reads fine with the old iOS 11 NfcNdefReaderSession API, that same card will not even scan with iOS 13's NfcTagReaderSession API.

If you need to read NDEF data off of a Mifare Classic 1K card, then you can:

• use version 0.1.11 of this library as it was written with the NfcNdefReaderSession API.
• use CrossNFC.Legacy from 0.1.20+ which allow you to switch between NfcTagReaderSession and NfcNdefReaderSession on-the-fly.

Unfortunately, even with iOS 13, it seems there is no way to read the serial number / CSN off of a Mifare Classic 1K card.

API Usage

Before to use the plugin, please check if NFC feature is supported by the platform using CrossNFC.IsSupported.

To get the current platform implementation of the plugin, please call CrossNFC.Current:

• Check CrossNFC.Current.IsAvailable to verify if NFC is available.
• Check CrossNFC.Current.IsEnabled to verify if NFC is enabled.
• Register events:

  
  // Event raised when a ndef message is received.
  CrossNFC.Current.OnMessageReceived += Current_OnMessageReceived;
  // Event raised when a ndef message has been published.
  CrossNFC.Current.OnMessagePublished += Current_OnMessagePublished;
  // Event raised when a tag is discovered. Used for publishing.
  CrossNFC.Current.OnTagDiscovered += Current_OnTagDiscovered;
  // Event raised when NFC listener status changed
  CrossNFC.Current.OnTagListeningStatusChanged += Current_OnTagListeningStatusChanged;

// Android Only: // Event raised when NFC state has changed. CrossNFC.Current.OnNfcStatusChanged += Current_OnNfcStatusChanged;

// iOS Only: // Event raised when a user cancelled NFC session. CrossNFC.Current.OniOSReadingSessionCancelled += Current_OniOSReadingSessionCancelled;

### Launch app when a compatible tag is detected on Android

In Android, you can use `IntentFilter` attribute on your `MainActivity` to initialize tag listening.
```csharp
[IntentFilter(new[] { NfcAdapter.ActionNdefDiscovered }, Categories = new[] { Intent.CategoryDefault }, DataMimeType = "application/com.companyname.yourapp")]
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity 
{
    ...
}

To launch/open an app with a tag, TypeFormat of the record must be set to NFCNdefTypeFormat.Mime and MimeType should be setted to the same value of IntentFilter.DataMimeType (e.g. application/com.companyname.yourapp):

var record = new NFCNdefRecord {
    TypeFormat = NFCNdefTypeFormat.Mime,
    MimeType = "application/com.companyname.yourapp",
    Payload = NFCUtils.EncodeToByteArray(_writePayload)
};

Read a tag

• Start listening with CrossNFC.Current.StartListening().
• When a NDEF message is received, the event OnMessageReceived is raised.

Write a tag

• To write a tag, call CrossNFC.Current.StartPublishing()
• Then CrossNFC.Current.PublishMessage(ITagInfo) when OnTagDiscovered event is raised.
• Do not forget to call CrossNFC.Current.StopPublishing() once the tag has been written.

Clear a tag

• To clear a tag, call CrossNFC.Current.StartPublishing(clearMessage: true)
• Then CrossNFC.Current.PublishMessage(ITagInfo) when OnTagDiscovered event is raised.
• Do not forget to call CrossNFC.Current.StopPublishing() once the tag has been cleared.

For more examples, see sample application in the repository.

Customizing UI messages

• Set a new NfcConfiguration object to CrossNFC.Current with SetConfiguration(NfcConfiguration cfg) method like below

// Custom NFC configuration (ex. UI messages in French)
CrossNFC.Current.SetConfiguration(new NfcConfiguration
{
    Messages = new UserDefinedMessages
    {
        NFCSessionInvalidated = "Session invalidée",
        NFCSessionInvalidatedButton = "OK",
        NFCWritingNotSupported = "L'écriture des TAGs NFC n'est pas supporté sur cet appareil",
        NFCDialogAlertMessage = "Approchez votre appareil du tag NFC",
        NFCErrorRead = "Erreur de lecture. Veuillez rééssayer",
        NFCErrorEmptyTag = "Ce tag est vide",
        NFCErrorReadOnlyTag = "Ce tag n'est pas accessible en écriture",
        NFCErrorCapacityTag = "La capacité de ce TAG est trop basse",
        NFCErrorMissingTag = "Aucun tag trouvé",
        NFCErrorMissingTagInfo = "Aucune information à écrire sur le tag",
        NFCErrorNotSupportedTag = "Ce tag n'est pas supporté",
        NFCErrorNotCompliantTag = "Ce tag n'est pas compatible NDEF",
        NFCErrorWrite = "Aucune information à écrire sur le tag",
        NFCSuccessRead = "Lecture réussie",
        NFCSuccessWrite = "Ecriture réussie",
        NFCSuccessClear = "Effaçage réussi"
    }
});

Tutorials

Thanks to Saamer Mansoor (@saamerm) who wrote this excellent article on Medium about Plugin.NFC and how to use it, check it out!

He also made this video:

Contributing

Feel free to contribute. PRs are accepted and welcomed.

Credits

Inspired by the great work of many developers. Many thanks to:

• James Montemagno (@jamesmontemagno).
• Matthew Leibowitz (@mattleibow) for Xamarin.Essentials PR #131.
• Alessandro Pozone (@poz1) for NFCForms.
• Ultz (@ultz) for XNFC.
• Sven-Michael Stübe (@smstuebe) for xamarin-nfc.