Android NFC - ndef.writeNdefMessage() throws IOException and erases tag data
<p>My app uses the foreground dispatch system to allow a user to tap their NFC tag in order to perform a read-then-write operation on the tag.</p>

<p>It works nicely if the user taps their tag properly (i.e., they tap it in the correct place on the phone and leave it connected for long enough), but if they physically remove the tag too early, then <code>ndef.writeNdefMessage(...)</code> throws an IOException.</p>

<p>That means the write operation fails, which is fair enough. But the <em>real problem</em> is that the same failed operation also <strong>deletes</strong> the entire ndef formatting/message from the tag!</p>

<p>My code is built around the snippets from the <a href="http://developer.android.com/guide/topics/connectivity/nfc/advanced-nfc.html" rel="noreferrer">Advanced NFC | Android Developers</a> page (as unfortunately the <a href="http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/nfc/ForegroundDispatch.html" rel="noreferrer">link to the ForegroundDispatch sample</a> appears to be broken and there is no such sample project to import into Android Studio).</p>

<p><strong>Step 1.</strong> Here is the logcat/stacktrace output when the user first taps their NFC tag, but moves it away too soon:</p>

<pre><code>03-28 20:15:18.589 21278-21278/com.example.exampleapp E/NfcTestActivity: Tag error
java.io.IOException
    at android.nfc.tech.Ndef.writeNdefMessage(Ndef.java:320)
    at com.example.exampleapp.NfcTestActivity.onNewIntent(NfcTestActivity.java:170)
    at android.app.Instrumentation.callActivityOnNewIntent(Instrumentation.java:1224)
    at android.app.ActivityThread.deliverNewIntents(ActivityThread.java:2946)
    at android.app.ActivityThread.performNewIntents(ActivityThread.java:2959)
    at android.app.ActivityThread.handleNewIntent(ActivityThread.java:2968)
    at android.app.ActivityThread.access$1700(ActivityThread.java:181)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1554)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:145)
    at android.app.ActivityThread.main(ActivityThread.java:6145)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
03-28 20:15:18.599 1481-17792/? E/SecNfcJni: nfaConnectionCallback: NFA_SELECT_RESULT_EVT error: status = 3
03-28 20:15:18.599 1481-1502/? E/SecNfcJni: reSelect: tag is not active
</code></pre>

<p><strong>Step 2.</strong> Next, the same user taps the same tag again but it appears to no longer contain an ndef message (which I have confirmed by altering the code and checking that <code>ndef.getCachedNdefMessage()</code> returns <code>null</code>):</p>

<pre><code>03-28 20:15:27.499 21278-21278/com.example.exampleapp E/NfcTestActivity: Tag error
java.lang.Exception: Tag was not ndef formatted: android.nfc.action.TECH_DISCOVERED
    at com.example.exampleapp.NfcTestActivity.onNewIntent(NfcTestActivity.java:124)
    at android.app.Instrumentation.callActivityOnNewIntent(Instrumentation.java:1224)
    at android.app.ActivityThread.deliverNewIntents(ActivityThread.java:2946)
    at android.app.ActivityThread.performNewIntents(ActivityThread.java:2959)
    at android.app.ActivityThread.handleNewIntent(ActivityThread.java:2968)
    at android.app.ActivityThread.access$1700(ActivityThread.java:181)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1554)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:145)
    at android.app.ActivityThread.main(ActivityThread.java:6145)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
</code></pre>

<p>I am getting this issue with both devices I have tested with so far - a <em>Samsung Galaxy Core Prime</em> (a lower end phone) running Android 5.1.1 and a <em>Samsung Galaxy A5</em> (a mid range phone) running Android 5.0.2.</p>

<p>The NFC tags used by my app contain important information (i.e., inadvertently deleting the tag data is not an option!), so my questions are...</p>

<ol>
<li>Why is my code (see below) erasing the tag data like this?</li>
<li>How can I fix the underlying problem, or is there an acceptable workaround?</li>
<li>Would it be worth me trying to use NfcA or IsoDep rather than Ndef?</li>
</ol>

<p>Having done a lot of searching, I'm very surprised that this problem has not been discussed elsewhere, so if the problem isn't to do with my code, then could it be to do with the NFC tags I am using?...</p>

<p>The tags I'm using are <em>NXP MIFARE Ultralight (Ultralight C) - NTAG203</em> (Tag type: ISO 14443-3A). Some of these I bought from ebay, and some I bought from Rapid NFC (a reputable company), yet I seem to have this problem with all of them. </p>

<p>Here is my complete code for the activity:</p>

<pre><code>package com.example.exampleapp;

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.nfc.tech.Ndef;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.Toast;

public class NfcTestActivity extends AppCompatActivity {

    private static String LOG_TAG = NfcTestActivity.class.getSimpleName();
    private static int SUCCESS_COUNT = 0;
    private static int FAILURE_COUNT = 0;

    private NfcAdapter nfcAdapter;
    private PendingIntent pendingIntent;
    private IntentFilter[] intentFiltersArray;
    private String[][] techListsArray;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_nfc_test);
        getSupportActionBar().setDisplayShowHomeEnabled(true);

        nfcAdapter = NfcAdapter.getDefaultAdapter(this);
        if (nfcAdapter == null) {

            makeToast("NFC not available!", Toast.LENGTH_LONG);
            finish();

        }
        else {

            //makeToast("NFC available");

            pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);

            IntentFilter ndef = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
            try {
                ndef.addDataType("*/*");    /* Handles all MIME based dispatches.
                                           You should specify only the ones that you need. */
            } catch (IntentFilter.MalformedMimeTypeException e) {
                throw new RuntimeException("fail", e);
            }
            intentFiltersArray = new IntentFilter[]{
                    ndef
            };

            techListsArray = new String[][]{
                    new String[]{
                            Ndef.class.getName()
                    }
            };
        }

    }

    @Override
    public void onPause() {
        super.onPause();

        if (nfcAdapter != null) {
            nfcAdapter.disableForegroundDispatch(this);
        }

    }

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

        if (nfcAdapter != null) {
            nfcAdapter.enableForegroundDispatch(this, pendingIntent, intentFiltersArray, techListsArray);
        }

    }

    public void onNewIntent(Intent intent) {

        Ndef ndef = null;

        try {

            String action = intent.getAction();
            //makeToast("action: " + action);

            if (!NfcAdapter.ACTION_NDEF_DISCOVERED.equals(action)) {

                throw new Exception("Tag was not ndef formatted: " + action); // line #124

            }
            else {

                Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
                //do something with tagFromIntent

                ndef = Ndef.get(tag);
                //makeToast("ndef: " + ndef);

                if (ndef == null) {

                    throw new Exception("ndef == null!");

                }
                else {

                    // Connect
                    ndef.connect();

                    // Get cached message
                    NdefMessage ndefMessageOld = ndef.getCachedNdefMessage();

                    if (ndefMessageOld == null) {

                        throw new Exception("No ndef message on tag!");

                    }
                    else {

                        // Get old records
                        NdefRecord[] ndefRecordsOld = ndefMessageOld.getRecords();
                        int numRecords = (ndefRecordsOld == null) ? 0 : ndefRecordsOld.length;

                        // Create/copy 'new' records

                        NdefRecord[] ndefRecordsNew = new NdefRecord[numRecords];
                        for (int i = 0; i &lt; numRecords; i++) {
                            ndefRecordsNew[i] = ndefRecordsOld[i];
                        }

                        // Create new message
                        NdefMessage ndefMessageNew = new NdefMessage(ndefRecordsNew);

                        // Write new message
                        ndef.writeNdefMessage(ndefMessageNew); // line #170

                        SUCCESS_COUNT++;

                        // Report success
                        String msg = "Read &amp; wrote " + numRecords + " records.";
                        makeToast(msg);
                        Log.d(LOG_TAG, msg);

                    }

                }

            }

        }
        catch(Exception e) {

            FAILURE_COUNT++;

            Log.e(LOG_TAG, "Tag error", e);
            makeToast("Tag error: " + e, Toast.LENGTH_LONG);

        }
        finally {

            try {
                if (ndef != null) {
                    ndef.close();
                }
            }
            catch(Exception e) {
                Log.e(LOG_TAG, "Error closing ndef", e);
                makeToast("Error closing ndef: " + e, Toast.LENGTH_LONG);
            }

            makeToast("Successes: " + SUCCESS_COUNT + ". Failures: " + FAILURE_COUNT);

        }

    }

    private void makeToast(final String msg) {

        makeToast(msg, Toast.LENGTH_SHORT);

    }

    private void makeToast(final String msg, final int duration) {

        new Handler(Looper.getMainLooper()).post(new Runnable() {
            @Override
            public void run() {

                Toast.makeText(NfcTestActivity.this, msg, duration).show();

            }
        });
    }

}
</code></pre>