Android NDEF message with two activities and wrong intent content

Question

I'm new to NFC with Android and I'm trying to make a kind of messaging app with NFC.

I have a first activity that sends the content of an EditText view to the other phone when beaming and displays the incoming message on a TextView on the other phone. This works fine.

I have another activity which is used to add a contact to the contacts register, it should work as the following:

• A wants to add B as a contact,
• A goes to the AddContactActivity, enters the name of the contact in the EditText view,
• then B touches A's phone (on the same activity) and sends their identifier (public key, for further encryption).

My problem is that even though the code concerning the sending via NFC is basically the same between the two activities, when I beam on the second activity (AddContactActivity), the action of the intent sent is ACTION_MAIN instead of ACTION_NDEF_DISCOVERED , which has the effect of opening the first activity and thus not going through the right treatment.

Here is the code of the MainActivity:

public class MainActivity extends Activity {

    private TextView mTextView;
    private EditText mEdit;

    NfcAdapter nfcAdapter;

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

        Intent intent = getIntent();

        mTextView = (TextView)findViewById(R.id.retour);
        mEdit = (EditText)findViewById(R.id.editText);

        nfcAdapter = NfcAdapter.getDefaultAdapter(getApplicationContext());

        nfcAdapter.setNdefPushMessageCallback(new NfcAdapter.CreateNdefMessageCallback() {
            @Override public NdefMessage createNdefMessage(NfcEvent event) {

                String stringOut = mEdit.getText().toString();

                byte[] bytesOut = stringOut.getBytes();

                NdefRecord ndefRecordOut = new NdefRecord(
                        NdefRecord.TNF_MIME_MEDIA,
                        "text/plain".getBytes(),
                        new byte[] {},
                        bytesOut);

                NdefMessage ndefMessageout = new NdefMessage(ndefRecordOut);

                return ndefMessageout;
            }
        }, this);

        checkAndProcessBeamIntent(intent);

    }

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

        Intent intent = getIntent();

        PendingIntent 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("text/plain");
        } catch (IntentFilter.MalformedMimeTypeException e) {
            e.printStackTrace();
        }

        IntentFilter[] intentFiltersArray = new IntentFilter[] {ndef, };
        nfcAdapter.enableForegroundDispatch(this, pendingIntent, intentFiltersArray, null);
    }


    private void checkAndProcessBeamIntent(Intent intent) {
        String action = intent.getAction();

        if(action.equals(NfcAdapter.ACTION_NDEF_DISCOVERED)){
            Parcelable[] parcelables =
                    intent.getParcelableArrayExtra(
                            NfcAdapter.EXTRA_NDEF_MESSAGES);

            NdefMessage inNdefMessage = (NdefMessage)parcelables[0];
            NdefRecord[] inNdefRecords = inNdefMessage.getRecords();
            NdefRecord NdefRecord_0 = inNdefRecords[0];

            String inMsg = new String(NdefRecord_0.getPayload());

            mTextView.setText(inMsg);

        }
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        Toast.makeText(MainActivity.this,
                intent.getAction().toString(),
                Toast.LENGTH_LONG).show();
        checkAndProcessBeamIntent(intent);
    }

    @Override
    public void onPause() {
        super.onPause();
        nfcAdapter.disableForegroundDispatch(this);
    }


    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
    public void generateKeys(){
        Calendar cal = Calendar.getInstance();
        Date now = cal.getTime();
        cal.add(Calendar.YEAR, 1);
        Date end = cal.getTime();

        KeyPairGenerator kpg = null;
        try {
            kpg = KeyPairGenerator.getInstance("RSA", "AndroidKeyStore");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
        }
        try {
            kpg.initialize(new KeyPairGeneratorSpec.Builder(getApplicationContext())
                    .setAlias("Keys")
                    .setStartDate(now)
                    .setEndDate(end)
                    .setSerialNumber(BigInteger.valueOf(1))
                    .setSubject(new X500Principal("CN=test1"))
                    .build());
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        }

        kpg.generateKeyPair();
    }

    public void goToAddContact(View view) {
        Intent intent = new Intent(this, AddContactActivity.class);
        intent.setAction("NewActivity");
        intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
        startActivity(intent);

    }
}

Here is the code of the AddContactActivity:

public class AddContactActivity extends Activity{

    NfcAdapter nfcAdapter;
    EditText editText;

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

        editText = (EditText)findViewById(R.id.editText);

        nfcAdapter = NfcAdapter.getDefaultAdapter(getApplicationContext());

        Intent intent = getIntent();

        nfcAdapter.setNdefPushMessageCallback(new NfcAdapter.CreateNdefMessageCallback() {
            @Override public NdefMessage createNdefMessage(NfcEvent event) {

                String stringOut = getMyPublicKey();

                byte[] bytesOut = stringOut.getBytes();

                NdefRecord ndefRecordOut = new NdefRecord(
                        NdefRecord.TNF_MIME_MEDIA,
                        "text/plain".getBytes(),
                        new byte[] {},
                        bytesOut);

                NdefMessage ndefMessageout = new NdefMessage(ndefRecordOut);

                return ndefMessageout;
            }
        }, this);

        checkAndProcessBeamIntent(intent);

    }

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

        Intent intent = getIntent();

        Toast.makeText(AddContactActivity.this,
                "onResume : "+intent.getAction().toString(),
                Toast.LENGTH_LONG).show();

        PendingIntent 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("text/plain");
        } catch (IntentFilter.MalformedMimeTypeException e) {
            e.printStackTrace();
        }

        IntentFilter[] intentFiltersArray = new IntentFilter[] {ndef, };
        nfcAdapter.enableForegroundDispatch(this, pendingIntent, intentFiltersArray, null);
    }

    public void addContactDataBase(String publicKey){

        SQLiteHelper sqLiteHelper = new SQLiteHelper(this);
        sqLiteHelper.addUser(new User(editText.getText().toString(), publicKey));
    }

    public void checkUserInDataBase(String publicKey){
        SQLiteHelper sqLiteHelper = new SQLiteHelper(this);
        User u = sqLiteHelper.getUser(publicKey);
        Toast.makeText(AddContactActivity.this,
                ""+u.getName(),
                Toast.LENGTH_LONG).show();
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        Toast.makeText(AddContactActivity.this,
                "OnNewIntent : "+intent.getAction().toString(),
                Toast.LENGTH_LONG).show();
        checkAndProcessBeamIntent(intent);
    }

    @Override
    public void onPause() {
        super.onPause();
        nfcAdapter.disableForegroundDispatch(this);
    }

    private void checkAndProcessBeamIntent(Intent intent) {
        String action = intent.getAction();

        if(action.equals(NfcAdapter.ACTION_NDEF_DISCOVERED)){
            Toast.makeText(AddContactActivity.this,
                    "COUCOU",
                    Toast.LENGTH_LONG).show();
            Parcelable[] parcelables =
                    intent.getParcelableArrayExtra(
                            NfcAdapter.EXTRA_NDEF_MESSAGES);

            NdefMessage inNdefMessage = (NdefMessage)parcelables[0];
            NdefRecord[] inNdefRecords = inNdefMessage.getRecords();
            NdefRecord NdefRecord_0 = inNdefRecords[0];

            String inMsg = new String(NdefRecord_0.getPayload());

            addContactDataBase(inMsg);
            checkUserInDataBase(inMsg);

        }
    }

    public String getMyPublicKey(){
        KeyStore ks = null;
        RSAPublicKey publicKey = null;
        try {
            ks = KeyStore.getInstance("AndroidKeyStore");
            ks.load(null);


            KeyStore.PrivateKeyEntry keyEntry = (KeyStore.PrivateKeyEntry)ks.getEntry("Keys", null);
            publicKey = (RSAPublicKey) keyEntry.getCertificate().getPublicKey();

        } catch (KeyStoreException e) {
            e.printStackTrace();
        } catch (CertificateException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (UnrecoverableEntryException e) {
            e.printStackTrace();
        }
        return publicKey.toString();
    }
}

And here is the manifest:

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

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.nfc.action.NDEF_DISCOVERED" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:mimeType="text/plain" />
            </intent-filter>

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

        </activity>
        <activity
            android:name=".AddContactActivity"
            android:label="@string/title_activity_add_contact"
            android:launchMode="singleTop">

            <intent-filter>
                <action android:name="android.nfc.action.NDEF_DISCOVERED" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:mimeType="text/plain" />
            </intent-filter>

        </activity>
    </application>

</manifest>

Answer 1

Check your appCompat libraries. Corruptness of appCompat libraries may cause wrong intent exceptions. Especially when you move your project from another PC or workspace (and/or IDE).

Answer 2

Getting an intent with ACTION_MAIN instead of ACTION_NDEF_DISCOVERED upon receiving an NFC event is a typical indication that an NDEF message containing an Android Application Record (AAR) was received and that the datatype of the first record of the NDEF message was not matched by any intent filter.

Your CreateNdefMessageCallback.createNdefMessage() method clearly does not add an AAR to the NDEF message. Consequently, the only reason why you would still receive an NDEF message containing an AAR would be that the createNdefMessage() raises an unhandled exception . In that case, the NFC stack will automatically generate an NDEF message containing a Play Store link and an AAR.

The most likely place that could cause createNdefmessage() to raise an unhandled exception is getMyPublicKey() (as that's the only part that differs between MainActivity and AddContactActivity ).

So we can track the problem down to this part of your code:

ks = KeyStore.getInstance("AndroidKeyStore");
ks.load(null);
KeyStore.PrivateKeyEntry keyEntry = (KeyStore.PrivateKeyEntry)ks.getEntry("Keys", null);
publicKey = (RSAPublicKey) keyEntry.getCertificate().getPublicKey();

This code either

• raises an unhandled runtime exception (eg if ks , keyEntry , or keyEntry.getCertificate() is null, or if ks.getEntry("Keys", null) cannot be cast to a KeyStore.PrivateKeyEntry ), or
• raises any of the handled exceptions, which causes publicKey to be null which results in an unhandled NullPointerException upon trying to invoke the toString() (in return publicKey.toString(); ).