I’ve been trying for a few days to make a nfc tag reader and writer in Android Studio, I’ve asked in another time but I don’t see the question so I repeat with some changes. I’ve been following a tutorial for this new code, but I can’t get it to work, neither in Fragments of my app nor in a normal MainActivity. The strange thing is that neither reads nor writes to the card as it should, but if I leave the app and read the NFC tag when I get the android prompt to read the tag it opens my app with the text of the nfc tag. it should show me ‘write(“PlainText|” + edit_message.getText().toString(), myTag);’ but it shows me ‘ nfc_contents.setText (“NFC card content: ” + text);
‘ now I show you all the code. Also, it shows me this error in the logcat every time I read a nfc card 2024-05-04 20:09:41.404 2573-2702 ActivityStarterImpl system_server E Error: Activity class {com.alfonso.nfcplay/com.alfonso.nfcplay.ui.read.ReadFragment} does not exist, as if it was looking for a package inside the same package.
But well, the code:

”’

`package com.alfonso.nfcplay.ui.read;

import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.NfcManager;
import android.nfc.Tag;
import android.nfc.tech.Ndef;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProvider;

import com.alfonso.nfcplay.R;
import com.alfonso.nfcplay.databinding.FragmentReadBinding;

import java.io.UnsupportedEncodingException;
import java.nio.charset.StandardCharsets;
import java.util.Objects;


public class ReadFragment extends Fragment {

    public static final String ErrorDetected="No NFC Tag Detected";
    public static final String WriteSuccess="Text Written Succesfully";
    public static final String WriteError="Error during writing, Try again!";
    PendingIntent pendingIntent;
    IntentFilter[] writingTagFilters;
    boolean writeMode;
    Tag myTag;
    TextView edit_message;
    TextView nfc_contents;
    Button ActivateButton;
    NfcAdapter nfcAdapter;
    FragmentReadBinding binding;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        binding = FragmentReadBinding.inflate(inflater, container, false);
        View root = binding.getRoot();
        edit_message= root.findViewById(R.id.edit_message);
        nfc_contents= root.findViewById(R.id.nfc_contents);
        ActivateButton = root.findViewById(R.id.ActivateButton);


        ActivateButton.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                try {
                    readFromIntent(requireActivity().getIntent());
                    if(myTag == null){
                        Toast.makeText(requireContext(),ErrorDetected,Toast.LENGTH_SHORT).show();
                    } else {
                        write("PlainText|" + edit_message.getText().toString(), myTag);
                        Toast.makeText(requireContext(), WriteSuccess, Toast.LENGTH_SHORT).show();
                    }
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }

            }
        });

        NfcManager nfcManager = (NfcManager) requireContext().getSystemService(Context.NFC_SERVICE);
        nfcAdapter = nfcManager.getDefaultAdapter();
        if (nfcAdapter != null) {
            // Check NFC enabled
            if (!nfcAdapter.isEnabled()) {
                Toast.makeText(requireContext(), "Por favor, activa el NFC para leer tarjetas", Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(requireContext(), "Este dispositivo no soporta NFC", Toast.LENGTH_SHORT).show();
        }

        readFromIntent(requireActivity().getIntent());
        pendingIntent = PendingIntent.getActivity(requireContext(),0, new Intent(getActivity(), getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), PendingIntent.FLAG_IMMUTABLE);
        IntentFilter tagDetected = new IntentFilter(NfcAdapter.ACTION_TAG_DISCOVERED);
        tagDetected.addCategory(Intent.CATEGORY_DEFAULT);
        writingTagFilters = new IntentFilter[]{tagDetected};

        ReadViewModel readViewModel = new ViewModelProvider(this).get(ReadViewModel.class);

        final TextView textView = binding.Read;
        readViewModel.getText().observe(getViewLifecycleOwner(), textView::setText);

        return root;
    }

    public void readFromIntent(Intent intent){
        String action = intent.getAction();
        if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(action) || NfcAdapter.ACTION_NDEF_DISCOVERED.equals(action) || NfcAdapter.ACTION_TECH_DISCOVERED.equals(action)){
            Parcelable[] rawMsgs = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
            NdefMessage[] msgs = null;
            if (rawMsgs!= null){
                msgs = new NdefMessage[rawMsgs.length];
                for (int i=0; i<rawMsgs.length;i++){
                    msgs[i] = (NdefMessage) rawMsgs[i];
                }
            }
            buildTagViews(msgs);
        }
    }



    public void buildTagViews(NdefMessage[] msgs){
        if(msgs == null || msgs.length == 0) return;

        String text = "";

        byte[] payload = msgs[0].getRecords()[0].getPayload();
        String textEncoding = ((payload[0] & 128) == 0) ? "UTF-8" : "UTF-16";
        int  languageCodeLength = payload[0] & 51;

        try {
            text = new String(payload, languageCodeLength+1, payload.length - languageCodeLength - 1, textEncoding);
        } catch (UnsupportedEncodingException e) {
            Log.e("UnsupportedEncoding", e.toString());
        }
        nfc_contents.setText ( "Contenido de la tarjeta NFC: " + text);
    }
    private void write(String text, Tag tag){
        try {
            NdefRecord[] records = { createRecord(text) };
            NdefMessage message = new NdefMessage(records);
            Ndef ndef = Ndef.get(tag);
            if (ndef != null) {
                ndef.connect();
                ndef.writeNdefMessage(message);
                ndef.close();
                Toast.makeText(requireContext(), WriteSuccess, Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(requireContext(), "NFC no soportado", Toast.LENGTH_SHORT).show();
            }
        } catch (Exception e) {
            Toast.makeText(requireContext(), WriteError, Toast.LENGTH_SHORT).show();
            Log.e("WriteError", Objects.requireNonNull(e.getMessage()));
        }
    }
    private NdefRecord createRecord(String text){
        String lang = "en";
        byte[] textBytes = text.getBytes();
        byte[] langBytes = text.getBytes(StandardCharsets.US_ASCII);
        int langLength = langBytes.length;
        int textLength = textBytes.length;
        byte[] payload = new byte[1 + langLength + textLength];

        payload[0] = (byte) langLength;

        System.arraycopy(langBytes, 0, payload, 1, langLength);
        System.arraycopy(textBytes,0, payload,1 + langLength, textLength);

        NdefRecord recordNFC = new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_TEXT, new byte[0], payload);
        return  recordNFC;
    }

    public void onNewIntent(Intent intent) {
        readFromIntent(intent);
        if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(intent.getAction())) {
            myTag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        WriteModeOff();
    }
    @Override
    public void onResume() {
        super.onResume();
        WriteModeOn();
    }

    private void WriteModeOn(){
        writeMode = true;
        nfcAdapter.enableForegroundDispatch(requireActivity(), pendingIntent, writingTagFilters, null);
    }
    private void WriteModeOff(){
        writeMode = false;
        nfcAdapter.disableForegroundDispatch(requireActivity());
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        binding = null;
    }

}
`

I want it to read the cards for me, all the options and results that have come up so far I have put them in the question