我一直在使用HCE，一直面临着
isoDep.connect();
在特定的android阅读器设备上。
当我使用下面的标志在nfc中启用reader模式时，hce工作得非常好。
public static int READER_FLAGS =
NfcAdapter.FLAG_READER_NFC_A | NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK;
但这样我就不能读ndef标签了。尽管同样的代码在Nexus7（2012）平板电脑上运行得非常好。
附上完整的代码
读卡器碎片
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);
}
});
}
}
忠诚的读者
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
最佳答案
通常情况下，对于这个错误，您无能为力。IOException上的TagLostException（或更具体的IsoDep.connect()）表示读取电话无法启动与HCE设备的通信。这通常是由于不良耦合（例如天线尺寸不匹配、天线设计不良、天线部分被设备电池覆盖而没有正确的天线设计等）或长时间通电（通常只有无源卡而没有HCE）导致的连接问题。因此，通常这种错误不是由通信协议的逻辑问题（您可以通过软件修复）引起的，而是由设备的物理特性问题（通常需要硬件修改）引起的。
不幸的是，你对此无能为力。可能的解决办法是：
尽量将两部手机放在一起（以便读卡器设备天线和HCE设备天线相互对齐），并且设备外壳或设备电池的金属部分不会覆盖另一个设备的天线。在天线尺寸明显不同的情况下，尝试将天线的其他边界彼此对齐，以便较小的边界位于较大的边界内。
在一些（！）在调用connect()之前增加收发器超时可能会有帮助的设备：
isoDep.setTimeout(10000);
但是，在大多数设备上调用connect之前，此超时似乎没有任何影响。
NFC有天线“助推器”，它可以使高频谐振频率失谐以获得更好的匹配，减轻耦合问题，使电池周围的天线形状适应，或者完全取代原来的天线。我没有太多的经验，不能引用任何来源这样的助推器。
编辑
在重新阅读您的问题后，如果您在读卡器设备上设置了
NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK标志，则CR100和HCE设备之间的通信似乎可以正常工作。如果是这样的话，IOException可能确实是由逻辑错误引起的。在这种情况下，如果iso-dep卡（例如hce设备）没有实现ndef标记规范，则cr100可能具有中断的nfc发现实现。虽然我认为这不太可能，但您可以通过在hce应用程序中实现type 4标记应用程序来轻松测试这一点。有关如何执行此操作的示例，请参见my answer here和source code here。