This is a simple app showing how to detect and read some data from an NFC tag tapped to the Android's NFC reader.
As there are a lot of questions on Stackoverflow.com that use an Intent-based NFC detection system I'm showing here how to use the more modern Reader Mode for NFC communication.
This is from an answer by Andrew regarding the two modes:
Also note that using enableForegroundDispatch is actually not the best way to use NFC. Using enableReaderMode is a newer and much better API to use. NFC.enableReaderMode does not use Intent's and gives you more control, it is easy to do NFC operations in a background Thread (which is recommended), for writing to NFC Tag's it is much more reliable and leads to less errors.
This application is described in an tutorial on medium.com: How to use NFC Reader Mode in Android to connect to NFC tags (Java)
There are 4 simples steps to implement the Reader mode:
- in
AndroidManifest.xmladd one line:<uses-permission android:name="android.permission.NFC" /> - in your activity or fragment expand your class definition by
implements NfcAdapter.ReaderCallback - create an
onTagDiscoveredmethod where all the work with the tag is done. - create an
onResumemethod to define the technologies and settings for the Reader Mode:
@Override
protected void onResume() {
super.onResume();
if (myNfcAdapter != null) {
if (!myNfcAdapter.isEnabled())
showWirelessSettings();
Bundle options = new Bundle();
// Work around for some broken Nfc firmware implementations that poll the card too fast
options.putInt(NfcAdapter.EXTRA_READER_PRESENCE_CHECK_DELAY, 250);
// Enable ReaderMode for all types of card and disable platform sounds
// The option NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK is NOT set
// to get the data of the tag after reading
myNfcAdapter.enableReaderMode(this,
this,
NfcAdapter.FLAG_READER_NFC_A |
NfcAdapter.FLAG_READER_NFC_B |
NfcAdapter.FLAG_READER_NFC_F |
NfcAdapter.FLAG_READER_NFC_V |
NfcAdapter.FLAG_READER_NFC_BARCODE |
NfcAdapter.FLAG_READER_NO_PLATFORM_SOUNDS,
options);
}
}
The flags are responsible for defining the NFC classes the NFC reader should detect. If you e.g. delete
the line NfcAdapter.FLAG_READER_NFC_A your app will not detect any NFC tags using the NfcA technology.
The last flag NfcAdapter.FLAG_READER_NO_PLATFORM_SOUNDS is useful for a better user experience. Using
the Intent based mode a system sound will appear when the NFC tag is detected at the beginning.
This causes some uses to move the NFC tag out of the reader field and you receive a "Tag Lost Exception".
When using the Reader Mode the flag prohibits the device to give any feedback to the user. In my app
I'm playing a short beep at the end or the reading process, signalizing that everything is done.
Note: the onTagDetected method is not running on the User Interface (UI) thread, so you are not allowed to write directly to any UI elements like
e.g. TextViews or Toasts - you need to encapsulate them in a run onUiTHread construct. This method is running in an background thread:
runOnUiThread(() -> {
Toast.makeText(getApplicationContext(), message, Toast.LENGTH_SHORT).show();
});
Here are some commands to get the first information's about the tag:
byte[] tagUid = tag.getId();: receive the tag Unique Identifier (the length depending on tag type).
String[] techlist = tag.getTechList();: this is very important as the NFC tag informs us about the NFC technologies
it is been able to communicate with us (e.g. android.nfc.tech.NfcA).
Now it is time to assign the received tag to an NFC technology class, e.g. to the NDEF class. It is important to double check that the ndef variable is not NULL to avoid any errors. If e.g. the ndef-var is not null you can connect to the NFC tag. Always surround the tag operations with a try.. catch clause.
From the tag I'm getting the ATQA and SAK value - they are required to identify an NfcA tag on the first level. The maxTransceiveLength is important when trying to read data from tag - if the data length including some protocol bytes is extending this maximum you will receive an error from your device, as the maximum is the size of your device's NFC reader unit.
The next steps would be to send commands to the tag using the transceive method. I don't show any code for this
within the app as commands are tag specific.
Please don't forget to close the NfcA class after your work is done.
NfcA nfcA = null;
nfcA = NfcA.get(tag);
if (nfcA == null) {
output += "This tag is NOT supporting the NfcA class" + "\n";
output += lineDivider + "\n";
} else {
// I'm trying to get more information's about the tag and connect to the tag
byte[] atqa = nfcA.getAtqa();
byte sak = (byte) nfcA.getSak();
int maxTransceiveLength = nfcA.getMaxTransceiveLength();
output += "-= NfcA Technology =-" + "\n";
output += "ATQA: " + bytesToHex(atqa) + "\n";
output += "SAK: " + byteToHex(sak) + "\n";
output += "maxTransceiveLength: " + maxTransceiveLength + "\n";
output += lineDivider + "\n";
try {
nfcA.connect();
output += "Connected to the tag using NfcA technology" + "\n";
output += lineDivider + "\n";
nfcA.close();
} catch (IOException e) {
output += "NfcA connect to tag IOException: " + e.getMessage() + "\n";
output += lineDivider + "\n";
}
}
This example has a very limited NDEF workflow and just print out the raw NDEF data. Usually you will divide the NDEF Message in separate NDEF records and work with the data depending on the NDEF Record type (not shown in this app).
Please don't forget to close the technology after reading is done.
Ndef ndef = null;
ndef = Ndef.get(tag);
if (ndef == null) {
output += "This tag is NOT supporting the NDEF class" + "\n";
output += lineDivider + "\n";
} else {
try {
ndef.connect();
output += "Connected to the tag using NDEF technology" + "\n";
output += lineDivider + "\n";
NdefMessage ndefMessage = ndef.getNdefMessage();
String ndefMessageString = ndefMessage.toString();
byte[] ndefMessageBytes = ndefMessage.toByteArray();
output += "NDEF message: " + ndefMessageString + "\n";
if (ndefMessageBytes != null) {
output += "NDEF message: " + bytesToHex(ndefMessageBytes) + "\n";
output += "NDEF message: " + new String(ndefMessageBytes, StandardCharsets.UTF_8) + "\n";
}
output += lineDivider + "\n";
ndef.close();
} catch (IOException e) {
output += "NDEF connect to tag IOException: " + e.getMessage() + "\n";
output += lineDivider + "\n";
} catch (FormatException e) {
output += "NDEF connect to tag RunTimeException: " + e.getMessage() + "\n";
output += lineDivider + "\n";
}
}
Below you find outputs for some tags with different technologies involved:
NFC tag detected
Tag UID length: 7 UID: 04be7982355b80
--------------------
The TechList contains 3 entry/ies:
Entry 0: android.nfc.tech.NfcA
Entry 1: android.nfc.tech.MifareUltralight
Entry 2: android.nfc.tech.NdefFormatable
--------------------
TAG: Tech [android.nfc.tech.NfcA, android.nfc.tech.MifareUltralight, android.nfc.tech.NdefFormatable]
--------------------
-= NfcA Technology =-
ATQA: 4400
SAK: 00
maxTransceiveLength: 253
--------------------
Connected to the tag using NfcA technology
--------------------
This tag is NOT supporting the NfcV class
--------------------
This tag is NOT supporting the NDEF class
--------------------
NFC tag detected
Tag UID length: 7 UID: 04be7982355b80
--------------------
The TechList contains 3 entry/ies:
Entry 0: android.nfc.tech.NfcA
Entry 1: android.nfc.tech.MifareUltralight
Entry 2: android.nfc.tech.Ndef
--------------------
TAG: Tech [android.nfc.tech.NfcA, android.nfc.tech.MifareUltralight, android.nfc.tech.Ndef]
--------------------
-= NfcA Technology =-
ATQA: 4400
SAK: 00
maxTransceiveLength: 253
--------------------
Connected to the tag using NfcA technology
--------------------
This tag is NOT supporting the NfcV class
--------------------
Connected to the tag using NDEF technology
--------------------
NDEF message: NdefMessage [NdefRecord tnf=1 type=54 payload=02656E416E64726F696443727970746F]
NDEF message: d101105402656e416e64726f696443727970746f
NDEF message: enAndroidCrypto
NFC tag detected
Tag UID length: 4 UID: 641a35cf
--------------------
The TechList contains 3 entry/ies:
Entry 0: android.nfc.tech.NfcA
Entry 1: android.nfc.tech.MifareClassic
Entry 2: android.nfc.tech.NdefFormatable
--------------------
TAG: Tech [android.nfc.tech.NfcA, android.nfc.tech.MifareClassic, android.nfc.tech.NdefFormatable]
--------------------
-= NfcA Technology =-
ATQA: 0400
SAK: 08
maxTransceiveLength: 253
--------------------
Connected to the tag using NfcA technology
--------------------
This tag is NOT supporting the NfcV class
--------------------
This tag is NOT supporting the NDEF class
--------------------
NFC tag detected
Tag UID length: 4 UID: b58fcc6d
--------------------
The TechList contains 2 entry/ies:
Entry 0: android.nfc.tech.IsoDep
Entry 1: android.nfc.tech.NfcA
--------------------
TAG: Tech [android.nfc.tech.IsoDep, android.nfc.tech.NfcA]
--------------------
-= NfcA Technology =-
ATQA: 0400
SAK: 20
maxTransceiveLength: 253
--------------------
Connected to the tag using NfcA technology
--------------------
This tag is NOT supporting the NfcV class
--------------------
This tag is NOT supporting the NDEF class
--------------------
NFC tag detected
Tag UID length: 8 UID: 18958608530104e0
--------------------
The TechList contains 2 entry/ies:
Entry 0: android.nfc.tech.NfcV
Entry 1: android.nfc.tech.NdefFormatable
--------------------
TAG: Tech [android.nfc.tech.NfcV, android.nfc.tech.NdefFormatable]
--------------------
This tag is NOT supporting the NfcA class
--------------------
-= NfcV Technology =-
DsfId: 00
maxTransceiveLength: 253
--------------------
Connected to the tag using NfcV technology
--------------------
This tag is NOT supporting the NDEF class
--------------------
Android Basic NFC Reader is available under the MIT license. See the LICENSE.md file for more info.