NFC Reader Android application with Python and Kivy

NFC_reader.py

__version__ = '1.0'

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.clock import Clock


# Android NFC-specific imports
from jnius import autoclass, cast
from android import activity

# Accessing Android NFC Java classes
Context = autoclass('android.content.Context')
NfcAdapter = autoclass('android.nfc.NfcAdapter')
NfcAdapterReader = autoclass('android.nfc.NfcAdapter$ReaderCallback')
Ndef = autoclass('android.nfc.tech.Ndef')
NdefMessage = autoclass('android.nfc.NdefMessage')
Intent = autoclass('android.content.Intent')
PendingIntent = autoclass('android.app.PendingIntent')
IntentFilter = autoclass('android.content.IntentFilter')
NfcAdapter = autoclass('android.nfc.NfcAdapter')


class NFCReaderApp(App):
    def build(self):
        self.layout = BoxLayout(orientation='vertical')
        self.label = Label(text="Please scan your NFC card", font_size=42)
        self.layout.add_widget(self.label)

        # Schedule the setup of NFC adapter after the app starts
        Clock.schedule_once(self.setup_nfc, 0)

        return self.layout

    def setup_nfc(self, dt):
        # Get the current Android activity and context
        self.activity = autoclass('org.kivy.android.PythonActivity').mActivity
        self.context = self.activity.getApplicationContext()

        # Get the NFC Adapter
        self.nfc_adapter = NfcAdapter.getDefaultAdapter(self.context)

        if not self.nfc_adapter:
            self.label.text = "NFC not supported on this device."
            return

        # Create a PendingIntent to start your app when an NFC tag is discovered
        intent = Intent(self.context, self.activity.getClass())
        intent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP)
        self.pending_intent = PendingIntent.getActivity(
            self.context, 0, intent, 0)

        # Create an intent filter for detecting NFC tags
        nfc_intent_filter = IntentFilter(NfcAdapter.ACTION_TAG_DISCOVERED)
        self.nfc_intent_filter = [nfc_intent_filter]

        # Enable foreground dispatch to ensure the app catches NFC intents
        self.nfc_adapter.enableForegroundDispatch(
            self.activity, self.pending_intent, self.nfc_intent_filter, None)

        # Bind activity lifecycle events to properly manage NFC (pause/resume)
        activity.bind(on_new_intent=self.on_new_intent)

    def on_pause(self):
        # Disable NFC foreground dispatch when the app goes to background
        # self.disable_nfc_foreground_dispatch()
        return True

    def on_resume(self):
        # Re-enable NFC foreground dispatch when the app is resumed
        self.enable_nfc_foreground_dispatch()

    def enable_nfc_foreground_dispatch(self, *args):
        print("enable nfc")
        if self.nfc_adapter:
            self.nfc_adapter.enableForegroundDispatch(
                self.activity, self.pending_intent, self.nfc_intent_filter, None)

    def disable_nfc_foreground_dispatch(self, *args):
        print("disable nfc")
        if self.nfc_adapter:
            self.nfc_adapter.disableForegroundDispatch(self.activity)

    def on_new_intent(self, intent):
        # This method is called when an NFC intent is received
        action = intent.getAction()
        if action == NfcAdapter.ACTION_TAG_DISCOVERED:
            self.handle_nfc_tag(intent)

    def handle_nfc_tag(self, intent):
        # Get the tag from the intent and cast it to android.nfc.Tag
        tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG)

        if tag is not None:
            # Cast the Parcelable tag to the correct Tag object
            tag = cast('android.nfc.Tag', tag)

            # Get the tag's UID (Unique Identifier)
            tag_id = tag.getId()
            tag_uid = ''.join('{:02X}'.format(byte)
                              for byte in tag_id)  # Convert to hexadecimal format

            # Get the list of technologies supported by the tag
            tech_list = tag.getTechList()

            # Display the UID and technology list in the app
            self.label.text = f"Tag UID: {tag_uid}\nTechnologies: {tech_list}"

        else:
            self.label.text = "No valid NFC tag detected."


if __name__ == "__main__":
    NFCReaderApp().run()