How to Write NDEF Records to NFC Tags with Android's enableReaderMode API?

How to Write NDEF Records to NFC Tag Using the enableReaderMode API

Introduction

Writing NDEF records to NFC tags requires a different approach in Android to ensure reliability and avoid failed writes. The older Intent-based system often led to issues due to interrupted reads and silent errors.

Using the enableReaderMode API

The newer enableReaderMode API provides a more robust approach. It disables system notifications, allowing your app to control the timing of sounds and handle the read/write process efficiently. By doing so, you can minimize failed writes and data corruption.

Example Code

The following Java code snippet demonstrates how to use the enableReaderMode API:

public class NFCActivity extends AppCompatActivity implements NfcAdapter.ReaderCallback{

    private NfcAdapter mNfcAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_nfc);

        mNfcAdapter = NfcAdapter.getDefaultAdapter(this);

        // Rest of Activity setup
    }

    @Override
    protected void onResume() {
        super.onResume();

        if(mNfcAdapter!= null) {
            Bundle options = new Bundle();
            options.putInt(NfcAdapter.EXTRA_READER_PRESENCE_CHECK_DELAY, 250);

            mNfcAdapter.enableReaderMode(this,
                    this,
                    NfcAdapter.FLAG_READER_NFC_A |
                            NfcAdapter.FLAG_READER_NFC_B |
                            NfcAdapter.FLAG_READER_NFC_F |
                            NfcAdapter.FLAG_READER_NFC_V |
                            NfcAdapter.FLAG_READER_NFC_BARCODE |
                            NfcAdapter.FLAG_READER_NO_PLATFORM_SOUNDS,
                    options);
        }

    }

    @Override
    protected void onPause() {
        super.onPause();
        if(mNfcAdapter!= null)
            mNfcAdapter.disableReaderMode(this);
    }

    @Override
    public void onTagDiscovered(Tag tag) {
        Ndef mNdef = Ndef.get(tag);

        if (mNdef!= null) {
            NdefRecord mRecord = NdefRecord.createTextRecord("en", "English String");

            NdefMessage mMsg = new NdefMessage(mRecord);

            try {
                mNdef.connect();
                mNdef.writeNdefMessage(mMsg);

                runOnUiThread(() -> {
                    Toast.makeText(getApplicationContext(),
                            "Write to NFC Success",
                            Toast.LENGTH_SHORT).show();
                });

                Uri notification = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
                Ringtone r = RingtoneManager.getRingtone(getApplicationContext(), notification);
                r.play();

            } catch (Exception e) {
                // Handle errors
            } finally {
                try {
                    mNdef.close();
                } catch (IOException e) {
                    // Handle I/O failure or cancelled operation
                }
            }
        }
    }
}

Additional Notes

• You can read the cached NDEF message by using mNdef.getCachedNdefMessage().
• To avoid silent errors, you should handle all exceptions during read/write operations.
• For Android 12L and above, a SecurityException can be thrown if the Tag object becomes stale.

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