Java Question Extends Service Library

Discussion in 'Libraries developers questions' started by walterf25, May 26, 2019.

  1. walterf25

    walterf25 Well-Known Member Licensed User

    Hi All, i am currently working on a NFCEmulator library wrapper, i found a full project online which emulates an NFC card and another project that acts as the reader, i have been able to run both of these projects with Android Studio and they both seem to work as expected.

    Now i am trying to create a wrapper for the NFCEmulator part but i am having some problems wrapping my head around the Extends Service part, I've looked at the example found here, my B4A Project compiles and runs just fine but I just don't get the expected results, below is part of the code for the wrapper.
    public class B4ANFCEmulatorWrapper extends HostApduService{
    private String TAG = "Host Card Emulator";
    private String STATUS_SUCCESS = "9000";
    private String STATUS_FAILED = "6F00";
    private String CLA_NOT_SUPPORTED = "6E00";
    private String INS_NOT_SUPPORTED = "6D00";
    private String AID = "A0000002471001";
    private static final String SAMPLE_LOYALTY_CARD_AID = "F222222222";
    private String SELECT_INS = "A4";
    public String DEFAULT_CLA = "EB";
    private int MIN_APDU_LENGTH = 12;
        // ISO-DEP command HEADER 
    for selecting an AID.
        // Format: [Class | Instruction | Parameter 
    1 | Parameter 2]
    private static final String SELECT_APDU_HEADER = "00A40400";
    "OK" status word sent in response to SELECT AID command (0x9000)
    private static final byte[] SELECT_OK_SW = hexStringToByteArray("9000");
    "UNKNOWN" status word sent in response to invalid APDU command (0x0000)
    private static final byte[] UNKNOWN_CMD_SW = hexStringToByteArray("0000");
    private static final byte[] SELECT_APDU = BuildSelectApdu(SAMPLE_LOYALTY_CARD_AID);
    private NFCEmulator nfc;
    public void onCreate() {
    "inside onCreate of B4ANFCEmulator library");
    "this.getClass: " + this.getClass().toString());
    startService(new Intent(this, this.getClass())); //Important if the service will be boundinstead of started.

        public void onDeactivated(int arg0) {
            // TODO Auto-generated method stub
            BA.Log("onDeactivated: " + arg0);
  , mEventName + "_ondeactivated", new Object[] {arg0});

        public byte[] processCommandApdu(byte[] arg0, Bundle arg1) {
            // TODO Auto-generated method stub
            BA.Log("arg0: " + arg0 + " Bundle: " + arg1.toString());
  , mEventName + "_processcommandapdu", new Object[] {arg0});
            if (arg0 == null) {
                BA.Log("STATUS_FAILED: " + hexStringToByteArray(STATUS_FAILED));
                return hexStringToByteArray(STATUS_FAILED);
    According to the Android Studio Project, i need to add the following to the Manifest File and which I did.
    nfctargeet is the name of the Service which starts just fine, but I don't see the onDeactivated or the processCommandApdu functions being raised at all, the code inside the service is the following:
    #Region  Service Attributes
    #StartAtBoot: False
    #End Region

    #Extends: com.genesis.nfcemulator.B4ANFCEmulatorWrapper

    Sub Process_Globals
    'These global variables will be declared once when the application starts.
        'These variables can be accessed from all modules.
        Private nfc As NFCEmulator
    End Sub

    Sub Service_Create
    End Sub
    Has anyone else successfully created a library wrapper where there is a need to Extend a Service, if so would you maybe give me some tips or hints about what i may be doing wrong, as I mentioned the B4A project compiles and runs fine, I do not receive any error logs in the filtered or Unfiltered logs, i have the NFCEmulator app running on my Samsung Galaxy S10+ and the NFC Card Reader app running on my other Samsung Galaxy S9+ when i place both phones back to back i can see the NFC Card Reader app trying to communicate with the Emulator side but as I also mentioned the processCommandApdu function does not seem to be invoked at all, that function is needed obviously to look at the NFC Card Reader app's requests and send a response accordingly.

    Any help will be greatly appreciated.

  2. Erel

    Erel Administrator Staff Member Licensed User

    This is probably not needed: startService(new Intent(this, this.getClass())); //Important if the service will be boundinstead of started.

    Check the generated AndroidManifest.xml file and see whether it matches the Android Studio manifest file.
    walterf25 likes this.
  3. walterf25

    walterf25 Well-Known Member Licensed User

    Hi @Erel Thanks, i checked the AndroidManifest.xml file while everything looked OK, i did find a line that wasn't where it was supposed to, I moved the line inside the Intent Filter Tag and everything seems good now.

    Erel likes this.
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