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Question

I am developing an app that will use NFC tags for identification. All examples I find however, are about starting an app when a certain card is read. I tried looking for an example or documentation on how to do it differently, to no avail.

What I want is:

1. user starts my app
2. user scans NFC card
3. app decides next step

I got some code working now, I just don't get the tag data:

In onCreate :

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

tech = new IntentFilter(NfcAdapter.ACTION_TECH_DISCOVERED);
try {
    tech.addDataType("*/*");
} catch (MalformedMimeTypeException e) {
   throw new RuntimeException("fail", e);
}
intentFiltersArray = new IntentFilter[] { tech };

And in onResume :

nfcAdapter.enableForegroundDispatch(this, pendingIntent, intentFiltersArray, techList);

The intent only gets there when the app is active, but the Intent I receive is the PendingIntent I defined myself, not the ACTION_TECH_DISCOVERED intent I want.

Answer 1

I found part of the answer here: NFC broadcastreceiver problem

That solution doesn't provide a complete working example, so I tried a little extra. To help future visitors, I'll post my solution. It is a NfcActivity which subclasses Activity , if you subclass this NfcActivity , all you have to do is implement its NfcRead method, and you're good to go:

public abstract class NfcActivity extends Activity  {
    // NFC handling stuff
    PendingIntent pendingIntent;
    NfcAdapter nfcAdapter;

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

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

         nfcAdapter = NfcAdapter.getDefaultAdapter(this);
         nfcAdapter.enableForegroundDispatch(this, pendingIntent, null, null);
    }

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

    // does nothing, has to be overridden in child classes
    public abstract void NfcRead(Intent intent);

    @Override
    public void onNewIntent(Intent intent) {
        String action = intent.getAction();

        if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(action)) {
            NfcRead(intent);            
        } 
    }
}

Answer 2

If you want that the user first starts your app and only then scans an NFC card, I would recommend using NFC foreground dispatch . In that way, your Activity does not need to have any intent filters in the manifest (and thus will never be called by accident when the user scans another NFC card). With foreground dispatch enabled, your Activity can receive all NFC intents directly (without any app chooser pop-ups) and decide what to do with it (eg pass it on to another Activity).