Host-based Card Emulation or HCE

Question

I want to write a program that can store a unique ID and then share it as NFC tag. Totally I want write program that could use mobile instead of smart card.

I read about it in many sites and here but I don't understand how could I push an ID to my app and how to share this ID whit NFC reader device

I don't know what the code below do and what's their features

public class MainActivity extends Activity {

  public void onCreate(Bundle savedInstanceState) {
    pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this,
                getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
    filters = new IntentFilter[] { new IntentFilter(
                NfcAdapter.ACTION_TECH_DISCOVERED) };
    techLists = new String[][] { { "android.nfc.tech.IsoPcdA" } };
  }

  public void onResume() {
    super.onResume();
    if (adapter != null) {
      adapter.enableForegroundDispatch(this, pendingIntent, filters,
                    techLists);
    }
  }

  public void onPause() {
    super.onPause();
    if (adapter != null) {
      adapter.disableForegroundDispatch(this);
    }
  }

}

Answer 1

I would advice to read something more about NFC in general and Android's ForegroundDispatcher . To make a start i will describe in baseline what this code is doing.

public class MainActivity extends Activity {

  public void onCreate(Bundle savedInstanceState) {

    //Here you define an intent that will be raised when a tag is received.
    pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this,
                getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);

    //These are the tag conditions to throw the intent of above.
    //ACTION_TECH_DISCOVERED means the tag need to be of the type defined in the techlist.      
    filters = new IntentFilter[] { new IntentFilter(
                NfcAdapter.ACTION_TECH_DISCOVERED) };

    //As the name already says, this is your techlist
    techLists = new String[][] { { "android.nfc.tech.IsoPcdA" } };


  }

  public void onResume() {
    super.onResume();
    if (adapter != null) {

      //This enabled the foreground dispatching
      //It means that when a tag is detected of the type `IsoPcdA`. The `pendingIntent` will be given to the current activity
      adapter.enableForegroundDispatch(this, pendingIntent, filters,
                    techLists);
    }
  }

  public void onPause() {
    super.onPause();
    if (adapter != null) {

      //This is to disable the foreground dispatching. You don't want to send this intents to this activity when it isn't active
      adapter.disableForegroundDispatch(this);
    }
  }

}

Since this ForegroundDispatching throws a new intent you need to override the onNewIntent method. Here you can read (and write) the tag.

@Override
public void onNewIntent(Intent intent)
{
    // Get the tag from the given intent
    Tag t = (Tag)intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);   
}       

Good luck!

BTW: This isn't HCE! The code above is an example of reader/writer mode where you can read (or write) tags.