Android NFC Demo (2) - Card Emulator

public class MyHostApduService extends HostApduService { 
@Override 
public byte[] processCommandApdu(byte[] apdu, Bundle extras) {
... 
} 
@Override 
public void onDeactivated(int reason) {
... 
} 
}

public class HostCardEmulatorService extends HostApduService {

public static final String TAG = HostCardEmulatorService.class.getName();

// self-defined APDU
public static final String STATUS_SUCCESS = "9000";
public static final String STATUS_FAILED = "6F00";
public static final String CLA_NOT_SUPPORTED = "6E00";
public static final String INS_NOT_SUPPORTED = "6D00";
public static final String AID = "A0000002471001";
public static final String SELECT_INS = "A4";
public static final String DEFAULT_CLA = "00";
public static final int MIN_APDU_LENGTH = 12;

@Override
public byte[] processCommandApdu(byte[] commandApdu, Bundle extras) {

Toast.makeText(this, "processCommandApdu", Toast.LENGTH_LONG).show();

if (commandApdu == null) {
return hexStringToByteArray(STATUS_SUCCESS);
}

final String hexCommandApdu = encodeHexString(commandApdu);
if (hexCommandApdu.length() < MIN_APDU_LENGTH) {
return hexStringToByteArray(STATUS_FAILED);
}

if (!hexCommandApdu.substring(0, 2).equals(DEFAULT_CLA)) {
return hexStringToByteArray(CLA_NOT_SUPPORTED);
}

if (!hexCommandApdu.substring(2, 4).equals(SELECT_INS)) {
return hexStringToByteArray(INS_NOT_SUPPORTED);
}

if (hexCommandApdu.substring(10, 24).equals(AID)){
return hexStringToByteArray(STATUS_SUCCESS);
} else {
return hexStringToByteArray(STATUS_FAILED);
}
}

@Override
public void onDeactivated(int reason) {
Toast.makeText(this, "Deactivated - reason:" + reason, Toast.LENGTH_LONG).show();
}
}

 public static String byteToHex(byte num, boolean upper) {
char[] hexDigits = new char[2];
if (upper) {
hexDigits[0] = Character.toUpperCase(Character.forDigit((num >> 4) & 0xF, 16));
hexDigits[1] = Character.toUpperCase(Character.forDigit((num & 0xF), 16));
} else {
hexDigits[0] = Character.forDigit((num >> 4) & 0xF, 16);
hexDigits[1] = Character.forDigit((num & 0xF), 16);
}

return new String(hexDigits);
}

public static String encodeHexString(byte[] byteArray, boolean upper) {
StringBuilder hexStringBuffer = new StringBuilder();
for (byte aByteArray : byteArray) {
hexStringBuffer.append(byteToHex(aByteArray, upper));
}
return hexStringBuffer.toString();
}

public static byte[] hexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+ Character.digit(s.charAt(i+1), 16));
}
return data;
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="io.github.stevenocean.cardemulatorsample">

<uses-permission android:name="android.permission.NFC" />

<uses-feature android:name="android.hardware.nfc.hce" android:required="true" />

<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

<service
android:name=".HostCardEmulatorService"
android:exported="true"
android:permission="android.permission.BIND_NFC_SERVICE">
<intent-filter>
<action android:name="android.nfc.cardemulation.action.HOST_APDU_SERVICE" />
</intent-filter>
<meta-data
android:name="android.nfc.cardemulation.host_apdu_service"
android:resource="@xml/apduservice" />
</service>
</application>

</manifest>

<?xml version="1.0" encoding="utf-8"?>
<host-apdu-service xmlns:android="http://schemas.android.com/apk/res/android"
android:description="@string/servicedesc"
android:requireDeviceUnlock="false">
<aid-group android:description="@string/aiddescription"
android:category="other">
<aid-filter android:name="A0000002471001"/>
</aid-group>
</host-apdu-service>

@Override
protected void onResume() {
super.onResume();
mNfcAdapter.enableReaderMode(this, this,
NfcAdapter.FLAG_READER_NFC_A | NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK,
null);
}

@Override
protected void onPause() {
super.onPause();
mNfcAdapter.disableReaderMode(this);
}

@Override
public void onTagDiscovered(Tag tag) {

// Card response for IsoDep
final StringBuilder cardResp = new StringBuilder("Card response: \n");

// read card data of CardEmulator
IsoDep isoDep = IsoDep.get(tag);
try {
isoDep.connect();
byte [] resp = isoDep.transceive(hexStringToByteArray(DEFAULT_CLA + SELECT_INS + "0400" + LC + AID));
String respStatus = encodeHexString(resp, true);
if (respStatus.equals(STATUS_SUCCESS)) {
cardResp.append("Success response");
} else {
cardResp.append("Failed response, code:").append(respStatus);
}
runOnUiThread(new Runnable() {
@Override
public void run() {
mNfcInfoText.setText(cardResp.toString());
}
});
} catch (IOException e) {
e.printStackTrace();
}
}