How can I send a text string to another device via NFC?

I want to create a mini app just to read an NFC tag and later send to another device on Android. That part is done already and I can read the tag and I can print the string on a EditText. But I also want to send the text that I have read from that tag to another device with NFC. How can I do that?

//I have this code here when a tag is discovered...
@Override
protected void onNewIntent(Intent intent) {
    if (intent.getAction().equals(NfcAdapter.ACTION_TAG_DISCOVERED)) {
        String result = "";
        result = ByteArrayToHexString(intent.getByteArrayExtra(NfcAdapter.EXTRA_ID));
        myTag = result;
        txtTag.setText(myTag);

    }
}

How can I send the text string to another device via NFC?

Solution

What you want to do is simply not possible with Android right no (and probably won't be in future).

You currently read the anti-collision identifier (UID, PUPI, or whatever it is called for that specific tag platform that you read):

result = ByteArrayToHexString(intent.getByteArrayExtra(NfcAdapter.EXTRA_ID));

The anti-collision identifier is part of a very low protocol layer. While Android does support host-based card emulation (see Android HCE), the Android API has no means to control such low-level parameters as the UID. Typically, its also not possible to change that information on NFC tags.

Note that if your tag also contains some high-level data in NDEF format you could obtain that using:

Parcelable[] rawMsgs = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
NdefMessage msg = null;
if ((rawMsgs != null) && (rawMsgs.length > 0)) {
    msg = (NdefMessage)rawMsgs[0];
}
if (msg != null) {
    // do something with the received message
}

Android does support storing these NDEF messages on (writable) NFC tags and it also supports sending NDEF messages to other NFC devices (see Beaming NDEF Messages to Other Devices).

E.g. to store an NDEF message on an NFC tag you could use:

Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
Ndef ndef = Ndef.get(tag);
if (ndef != null) {
    try {
        ndef.connect();
        ndef.writeNdefMessage(msg);
    } finally {
        ndef.close();
    }
} else {
    NdefFormatable ndefFormatable = NdefFormatable.get(tag);
    if (ndefFormatable != null) {
        try {
            ndefFormatable.connect();
            ndefFormatable.format(message);
        } finally {
            ndefFormatable.close();
        }
    }
}

Or in order to send the message to another NFC device through peer-to-peer mode (Android Beam), you could use:
```
 NfcAdapter nfcAdapter = NfcAdapter.getDefaultAdapter(this);
 nfcAdapter.setNdefPushMessage(msg, this);
```