相关疑难解决方法(0)

我想获得Mifare Ultralight NFC标签的UID.在Java中我有这个代码:

TerminalFactory factory = TerminalFactory.getDefault();
List<CardTerminal> terminals = factory.terminals().list();
System.out.println("Terminals: " + terminals);

CardTerminal terminal = terminals.get(0);

Card card = terminal.connect("*");
System.out.println("card: " + card);
CardChannel channel = card.getBasicChannel();

ResponseAPDU answer = channel.transmit(new CommandAPDU(0xFF, 0xCA, 0x00, 0x00, 0x00));
byte[] uid = answer.getBytes();

问题是我收到两个字节而不是UID.有什么问题？APDU是否正确？