基于主机卡模拟的IOException异常

Question

我一直在使用HCE，但遇到了IOException问题。

isoDep.connect();

在特定的安卓阅读器设备cr100 simcent上，当我启用以下标志的NFC读取模式时，HCE可以正常工作。

public static int READER_FLAGS =
        NfcAdapter.FLAG_READER_NFC_A | NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK;

但是我无法读取NDEF标签。尽管相同的代码在Nexus 7（2012）平板电脑上运行得非常好。

完整的代码已附上。

CardReaderFragment

public class CardReaderFragment extends Fragment implements LoyaltyCardReader.AccountCallback {

    public static final String TAG = "CardReaderFragment";
    // Recommend NfcAdapter flags for reading from other Android devices. Indicates that this
    // activity is interested in NFC-A devices (including other Android devices), and that the
    // system should not check for the presence of NDEF-formatted data (e.g. Android Beam).
    public static int READER_FLAGS =
            NfcAdapter.FLAG_READER_NFC_A | NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK;
    public LoyaltyCardReader mLoyaltyCardReader;
    private TextView mAccountField;

    /** Called when sample is created. Displays generic UI with welcome text. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.main_fragment, container, false);
        if (v != null) {
            mAccountField = (TextView) v.findViewById(R.id.card_account_field);
            mAccountField.setText("Waiting...");

            mLoyaltyCardReader = new LoyaltyCardReader(this);

            // Disable Android Beam and register our card reader callback
            enableReaderMode();
        }

        return v;
    }

    @Override
    public void onPause() {
        super.onPause();
        disableReaderMode();
    }

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

    private void enableReaderMode() {
        Log.i(TAG, "Enabling reader mode");
        Activity activity = getActivity();
        NfcAdapter nfc = NfcAdapter.getDefaultAdapter(activity);
        if (nfc != null) {
            nfc.enableReaderMode(activity, mLoyaltyCardReader, READER_FLAGS, null);
        }
    }

    private void disableReaderMode() {
        Log.i(TAG, "Disabling reader mode");
        Activity activity = getActivity();
        NfcAdapter nfc = NfcAdapter.getDefaultAdapter(activity);
        if (nfc != null) {
            nfc.disableReaderMode(activity);
        }
    }

    @Override
    public void onAccountReceived(final String account) {
        // This callback is run on a background thread, but updates to UI elements must be performed
        // on the UI thread.
        getActivity().runOnUiThread(new Runnable() {
            @Override
            public void run() {
                mAccountField.setText(account);
            }
        });
    }
}

LoyaltyCardReader

public class LoyaltyCardReader implements NfcAdapter.ReaderCallback {
    private static final String TAG = "LoyaltyCardReader";
    // AID for our loyalty card service.
    private static final String SAMPLE_LOYALTY_CARD_AID = "F222222222";
    // 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 = {(byte) 0x90, (byte) 0x00};

    // Weak reference to prevent retain loop. mAccountCallback is responsible for exiting
    // foreground mode before it becomes invalid (e.g. during onPause() or onStop()).
    private WeakReference<AccountCallback> mAccountCallback;

    public interface AccountCallback {
        public void onAccountReceived(String account);
    }

    public LoyaltyCardReader(AccountCallback accountCallback) {
        mAccountCallback = new WeakReference<AccountCallback>(accountCallback);
    }

    /**
     * Callback when a new tag is discovered by the system.
     * <p>
     * <p>Communication with the card should take place here.
     *
     * @param tag Discovered tag
     */
    @Override
    public void onTagDiscovered(Tag tag) {
        Log.i(TAG, "New tag discovered");
        // Android's Host-based Card Emulation (HCE) feature implements the ISO-DEP (ISO 14443-4)
        // protocol.
        //
        // In order to communicate with a device using HCE, the discovered tag should be processed
        // using the IsoDep class.
        IsoDep isoDep = IsoDep.get(tag);
        if (isoDep != null) {
            try {
                // Connect to the remote NFC device
                isoDep.connect();
                // Build SELECT AID command for our loyalty card service.
                // This command tells the remote device which service we wish to communicate with.
                Log.i(TAG, "Requesting remote AID: " + SAMPLE_LOYALTY_CARD_AID);
                byte[] command = BuildSelectApdu(SAMPLE_LOYALTY_CARD_AID);
                // Send command to remote device
                Log.i(TAG, "Sending: " + ByteArrayToHexString(command));
                byte[] result = isoDep.transceive(command);
                // If AID is successfully selected, 0x9000 is returned as the status word (last 2
                // bytes of the result) by convention. Everything before the status word is
                // optional payload, which is used here to hold the account number.
                int resultLength = result.length;
                byte[] statusWord = {result[resultLength - 2], result[resultLength - 1]};
                byte[] payload = Arrays.copyOf(result, resultLength - 2);
                if (Arrays.equals(SELECT_OK_SW, statusWord)) {
                    // The remote NFC device will immediately respond with its stored account number
                    String accountNumber = new String(payload, "UTF-8");
                    Log.i(TAG, "Received: " + accountNumber);
                    // Inform CardReaderFragment of received account number
                    mAccountCallback.get().onAccountReceived(accountNumber);
                }
            } catch (IOException e) {
                Log.e(TAG, "Error communicating with card: " + e.toString());
            }
        } else {
            Ndef ndef = Ndef.get(tag);
            if (ndef == null) {
                // NDEF is not supported by this Tag.
                Log.d("NFCCardTagNDEF", "even this is null");
//                return;
            }

            NdefMessage ndefMessage = ndef.getCachedNdefMessage();

            if (ndefMessage == null) {
                Log.d("NFCCardTagNDEF", "ndef message is null");
//                return;
            }

            NdefRecord[] records = ndefMessage.getRecords();
            String text = ndefRecordToString(records[0]);
            Log.d("NFCCardTagNFC", "old" + text);
            mAccountCallback.get().onAccountReceived(text);
        }
    }


    public String ndefRecordToString(NdefRecord record) {
        byte[] payload = record.getPayload();
        return new String(payload);
    }

    /**
     * Build APDU for SELECT AID command. This command indicates which service a reader is
     * interested in communicating with. See ISO 7816-4.
     *
     * @param aid Application ID (AID) to select
     * @return APDU for SELECT AID command
     */
    public static byte[] BuildSelectApdu(String aid) {
        // Format: [CLASS | INSTRUCTION | PARAMETER 1 | PARAMETER 2 | LENGTH | DATA]
        return HexStringToByteArray(SELECT_APDU_HEADER + String.format("%02X", aid.length() / 2) + aid);
    }

    /**
     * Utility class to convert a byte array to a hexadecimal string.
     *
     * @param bytes Bytes to convert
     * @return String, containing hexadecimal representation.
     */
    public static String ByteArrayToHexString(byte[] bytes) {
        final char[] hexArray = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
        char[] hexChars = new char[bytes.length * 2];
        int v;
        for (int j = 0; j < bytes.length; j++) {
            v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }

    /**
     * Utility class to convert a hexadecimal string to a byte string.
     * <p>
     * <p>Behavior with input strings containing non-hexadecimal characters is undefined.
     *
     * @param s String containing hexadecimal characters to convert
     * @return Byte array generated from input
     */
    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;
    }

}

任何帮助都将不胜感激

- chossen-addict

---

你是将CR100用作读卡器还是HCE设备？ - Michael Roland

我正在使用CR100作为读卡器。 - chossen-addict

添加你的Logcat。 - Oussema Aroua

Answer 1

通常情况下，您无法对此错误做太多事情。在IsoDep.connect()时出现IOException（或更具体的TagLostException）表明读取手机无法与HCE设备建立通信。这通常是由于连接问题引起的（例如，天线尺寸不匹配、天线设计不良、设备电池部分覆盖天线而没有适当的天线设计等），或者长时间启动时间引起的（通常仅针对被动卡而不是HCE）。因此，通常情况下，此错误不是由通信协议的逻辑问题引起的（您可能可以通过软件修复），而是由设备的物理特征问题引起的（通常需要硬件修改）。

不幸的是，您对此无能为力。可能的解决方法可能是：

1. Try to better place the two phones together (so that the reader device antenna and the HCE device antenna) align to each other and that metal parts of the device case or the device battery does not cover the other device's antenna. In case of significanly different antenna sizes, try to align the other borders of the antennas to each other so that the smaller one is inside the larger one.

2. On some(!) devices it may help to increase the transceive timeout before calling connect():

   isoDep.setTimeout(10000);
   

   However, it seems that this timeout does not have any effect before connect was called on most devices.

3. There exist antenna "boosters" for NFC which either detune the HF resonance frequency to get better matching, that mitigate coupling issues do to adapting antenna shape around batteries, or that replace the original antenna altogether. I don't have much experience with this and can't quote any source for such boosters.

编辑

重新阅读您的问题后，如果在读卡器设备上设置标志NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK，则cr100和HCE设备之间的通信将正常工作。如果是这种情况，那么IOException确实可能是由逻辑错误引起的。在这种情况下，可能是cr100的NFC发现实现有问题，如果ISO-DEP卡（例如HCE设备）没有实现NDEF标签规范，则会出现故障。虽然我认为这种情况不太可能发生，但您可以通过在HCE应用程序中实现Type 4标签应用程序来轻松测试此功能。请参见我的答案和源代码以获取如何执行此操作的示例。

- Michael Roland