I m creating an android app in java using nfc technology to read a nfc tag. I ve wrote a simple text on it thank to another app downloaded from play store, but I cant manage to make my app read that simple text.

1. I inserted in the manifest permission to use NFC to the app
2. I inserted intent filters for both nfc action NDEF and TAG. My tag results being able to use NfcA, MifareUltralight, Ndef according to the external NFC app I used
3. Specified that my tag should contain MIME type text/plain

Here s the manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <uses-permission android:name="android.permission.NFC" />
    <uses-sdk android:minSdkVersion="31"/>


    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.AppCompat.DayNight"
        tools:targetApi="31">
        <activity
            android:name="com.example.nfcreader.MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
            <intent-filter>
                <action android:name="android.nfc.action.NDEF_DISCOVERED" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:mimeType="text/plain" /> <!-- Adatta il MIME type se necessario -->
            </intent-filter>
            <intent-filter>
                <action android:name="android.nfc.action.TAG_DISCOVERED" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>


        </activity>
    </application>

</manifest>

about the java code

1. I created the NfcAdapter in onCreate()
2. Created an IntentFilter[] with both ACTION_NDEF_DISCOVERED, and ACTION_TAG_DISCOVERED in a separated function createNFCIntentFilter() that I call in onResume()
3. Handled Intents at the start of onResume()
4. Applied enableForegroundDispatch() and disableForegroundDispatch() rispectevely in onResume() and onPause() to get the reading work just when the app is active
5. Added Log.d to check the if the onNewIntent triggers, the type of Intent, and if the Intent contains something at all. In order: the onNewIntent triggers, the type is null, and neither NDEF nor TAG action is detected.
   Looks like I m getting something wrong with the filters. Any suggestion?

Here s the java code

package com.example.nfcreader;

import android.app.PendingIntent;
import android.content.Intent;
import android.content.IntentFilter;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;
import android.widget.Toast;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

import java.nio.charset.StandardCharsets;
import java.util.Arrays;

public class MainActivity extends AppCompatActivity {

    private NfcAdapter nfcAdapter;
    private PendingIntent pendingIntent;
    private IntentFilter[] nfcFilters;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });

        // Ottieni l'adattatore NFC
        nfcAdapter = NfcAdapter.getDefaultAdapter(this);


    }

    @Override
    protected void onResume() {
        super.onResume();
        // Configura un PendingIntent per gestire gli intent NFC
        pendingIntent = PendingIntent.getActivity(
                this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), PendingIntent.FLAG_IMMUTABLE);

        // Richiama la funzione per ottenere i filtri NFC
        nfcFilters = createNFCIntentFilter();
        // Registra la modalità foreground dispatch per intercettare gli intent NFC quando l'app è in primo piano
        if (nfcAdapter != null) {
            nfcAdapter.enableForegroundDispatch(this, pendingIntent, nfcFilters, null);
            Log.d("mytag", "Foreground dispatch enabled");
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        // Disabilita il foreground dispatch quando l'app non è in primo piano
        if (nfcAdapter != null) {
            nfcAdapter.disableForegroundDispatch(this);
        }
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        // Gestisci l'intent NFC qui
        String action = intent.getAction();
        Log.d("mytag", "Intent Action: " + action);
        if (action != null) {
            switch (action) {
                case NfcAdapter.ACTION_NDEF_DISCOVERED:
                    Log.d("mytag", "ACTION_NDEF_DISCOVERED detected");
                    break;

                case NfcAdapter.ACTION_TAG_DISCOVERED:
                    Log.d("mytag", "ACTION_TAG_DISCOVERED detected");
                    break;

                default:
                    Log.d("mytag", "Unknown NFC action: " + action);
                    break;
            }
        } else {
            Log.d("mytag", "No NFC action detected");
        }
        /*if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction())) {
            Log.d("mytag", "trovato nuovo intent");
            Parcelable[] rawMessages = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
            if (rawMessages != null) {
                Log.d("mytag", "il messaggio era non nullo");
                NdefMessage[] messages = new NdefMessage[rawMessages.length];
                for (int i = 0; i < rawMessages.length; i++) {
                    messages[i] = (NdefMessage) rawMessages[i];
                }

            // Ora puoi accedere ai record all'interno del messaggio NDEF
                for (NdefMessage message : messages) {
                    NdefRecord[] records = message.getRecords();
                    for (NdefRecord record : records) {
                        // Processa ogni record, ad esempio, leggi un URI o un testo
                        if (record.getTnf() == NdefRecord.TNF_WELL_KNOWN &&
                                Arrays.equals(record.getType(), NdefRecord.RTD_TEXT)) {

                            byte[] payload = record.getPayload();
                            String text = new String(payload, StandardCharsets.UTF_8);
                            // Usa il testo letto dal record NDEF
                            Toast toast=Toast.makeText(getApplicationContext(),text,Toast.LENGTH_SHORT);
                            toast.show();
                        }
                    }
                }

            }

        } else if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(intent.getAction())) {
            Log.d("mytag", "Intent Action ACTION: " + intent.getAction());
        }*/

    }


    private IntentFilter[] createNFCIntentFilter()  {
        IntentFilter ndefFilter = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
        IntentFilter tagFilter = new IntentFilter(NfcAdapter.ACTION_TAG_DISCOVERED);
        try {
            ndefFilter.addDataType("text/plain");
        } catch (IntentFilter.MalformedMimeTypeException e) {
            throw new RuntimeException("Failed to add MIME type.", e);
        }
        return new IntentFilter[]{ndefFilter, tagFilter};
    }


}