Android NFC framework introduction and develop guide(17)

Android system NFC framework introduction and develop guide

level 13 (Android 3.2). com.android.npp and SNEP are both required on API level 14 (Android 4.0) and later.

Note: If your activity enables Android Beam and is in the foreground, the standard dispatching.

To enable Android Beam:

1. Create an NdefMessage that contains the NdefRecords that you want to push onto the

other device.

2. Call setNdefPushMessage() with a NdefMessage or call setNdefPushMessageCallback passing in a NfcAdapter.CreateNdefMessageCallback object in the onCreate() method of your activity. These methods require at least one activity that you want to enable with

Android Beam, along with an optional list of other activities to activate.

In general, you normally use setNdefPushMessage() if your Activity only needs to push the same NDEF message at all times, when two devices are in range to communicate. You use setNdefPushMessageCallback when your application cares about the current context of the application and wants to push an NDEF message depending on what the user is doing in your application.

The following sample shows how a simple activity calls NfcAdapter.CreateNdefMessageCallback in the onCreate() method of an activity (see for the complete sample). This example also has methods to help you create a MIME record:

Android system NFC framework introduction and develop guide

public class Beam extends Activity implements CreateNdefMessageCallback { NfcAdapter mNfcAdapter; TextView textView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceSt ate); setContentView(yout.main); TextView textView = (TextView) findViewById(R.id.textView); // Check for available NFC Adapter mNfcAdapter = NfcAdapter.getDefaultAdapter(this); if (mNfcAdapter == null) { Toast.makeText(this, "NFC is not available", Toast.LENGTH_LONG).show(); finish(); return; } // Register callback mNfcAdapter.setNdefPushMessage Callback(this, this); } @Override public NdefMessage createNdefMessage(NfcEvent event) { String text = ("Beam me up, Android!\n\n" + "Beam Time: " + System.currentTimeMillis()); NdefMessage msg = new NdefMessage( new NdefRecord[] { createMimeRecord( "application/c om.example.android.beam", text.getBytes()) /** * The Android Application Record (AAR) is commented out. When a device * receives a push with an AAR in it, the application specified in the AAR * is guaranteed to run. The AAR overrides the tag dispatch system. * You can add it back in to

Android system NFC framework introduction and develop guide

guarantee that this * activity starts when receiving a beamed message. For now, this code * uses the tag dispatch system. */ //,NdefRecord.createApplicat ionRecord("com.example.android.beam") }); return msg; } @Override public void onResume() { super.onResume(); // Check to see that the Activity started due to an Android Beam if (NfcAdapter.ACTION_NDEF_DISCOVERED.equ als(getIntent().getAction())) { processIntent(getIntent()) ; } } @Override public void onNewIntent(Intent intent) { // onResume gets called after this to handle the intent setIntent(intent); } /** * Parses the NDEF Message from the intent and prints to the TextView */ void processIntent(Intent intent) { textView = (TextView) findViewById(R.id.textView); Parcelable[] rawMsgs = intent.getParcelableArrayExtra( NfcAdapter.EXTRA_NDEF_ MESSAGES); // only one message sent during the beam NdefMessage msg = (NdefMessage) rawMsgs[0]; // record 0 contains the MIME type, record 1 is the AAR, if present

Android system NFC framework introduction and develop guide

Note that this code comments out an AAR, which you can remove. If you enable the AAR, the application specified in the AAR always receives the Android Beam message. If the application is not present, the Android Market is started to download the application. Therefore, the following intent filter is not technically necessary for Android 4.0 devices or later if the AAR is used:

With this intent filter, the com.example.android.beam application now can be started when it scans an NFC tag or receives an Android Beam with an AAR of type

com.example.android.beam, or when an NDEF formatted message contains a MIME record of type application/com.example.android.beam.

Even though AARs guarantee an application is started or downloaded, intent filters are

recommended, because they let you start an Activity of your choice in your application instead of always starting the main Activity within the package specified by an AAR. AARs do not have