NFC 开发

本文来自http://blog.csdn.net/hellogv/ ，引用必须注明出处！

 

       目前常见的智能IC卡运行着JavaCard虚拟机，智能IC卡上可以运行由精简后的Java语言编写的卡应用（简称Applet）。智能IC卡的Applet不能自己启动，必须由外部终端（例如POS机，地铁刷卡终端等）向卡片发送Select命令，由此选中卡片的Applet，Applet才能运行。Appplet侧重于数据的处理，没有花销的I/O功能。Applet的程序有生命周期和指定入口，其中最主要的几个方法如下：

• public static void install(byte[] bArray, short bOffset, byte bLength)

构建了Applet子类的实例，JCRE将会最先调用这个；所有的初始化和分配内存的操作应该在这个里面实现；可以获取卡外实体传进来的一些应用初始化参数。

• public void process(APDU apdu)

类似于正常java class的main，在安装后，APDU的执行将在这里实现。

• protected final void register()

applet用来在JCRE中注册该applet实例

• register(byte[] bArray, short bOffset, byte bLength)

register( )功能一样，增加了可以分配其特定的AID的功能。

• public boolean select()

        JCRE一旦接收到SELECT[by name]命令时，将寻找命令中指示的AID对应的Applet，使之处于活跃状态，接收并处理接下来的APDU命令；在选择新的Applet前，JCRE先调用当前Applet的 deselect 方法；Applet可以拒绝被选择，此时 select 方法返回false；SELECT[by name]命令本身也将传递给applet处理，此时通过 selectingApplet 用以判断当前状态。

        本文的DEMO运行效果如下，包含一个JavaCard的Applet实现和一个Android端的NFC读写程序，实现智能IC卡与Android手机的简单通信。



接下来贴段简单的Applet 源码，下载地址：http://download.csdn.net/detail/hellogv/8090041。

大概的思路是：Applet定义了2个开头标识皆为CMD_CLA的自定义命令CMD_INS_1和CMD_INS_2，当Android手机通过NFC分别发送CMD_INS_1和CMD_INS_2，Applet分别返回strHello和strWorld。

核心源码如下：

<span style="font-family:Microsoft YaHei;">public class mytest extends Applet {

    private static final byte[] strHello= { (byte) 'H', (byte) 'e',
            (byte) 'l', (byte) 'l', (byte) 'o'};

    private static final byte[] strWorld = {(byte) 'W',
        (byte) 'o', (byte) 'r', (byte) 'l', (byte) 'd', };

    private static final byte CMD_CLA = (byte) 0x80;
    private static final byte CMD_INS_1 = (byte) 0x10;
    private static final byte CMD_INS_2 = (byte) 0x20;

    public static void install(byte[] bArray, short bOffset, byte bLength) {
        // GP-compliant JavaCard applet registration
        new mytest().register(bArray, (short) (bOffset + 1), bArray[bOffset]);
    }

    /*
     * 当Java卡Applet被选中时，由JCRE调用。Java卡Applet可以定义select()完成初始化，
     * 否则，JCRE调用父类的select()。
     * @see javacard.framework.Applet#select()
     */
    public boolean select() {
        short debug=100;
        debug++;//用于断点调试，当被select时触发。
        return super.select();
    }

    /*
     * 当Java卡Applet被放弃时，由JCRE调用。Java卡Applet可以定义deselect()完成清除，
     * 否则，JCRE调用父类的deselect()。
     * @see javacard.framework.Applet#deselect()
     */
    public void deselect() {
        short debug=100;
        debug++;//用于断点调试
        super.deselect();
    }

    /*
     * 每次收到APDU命令，都会执行
     * @see javacard.framework.Applet#process(javacard.framework.APDU)
     */
    public void process(APDU apdu) {
        if (selectingApplet()) {
            return;
        }

        //获取外部终端发过来的数据
        byte[] buffer = apdu.getBuffer();
        //获取第一位数据
        byte CLA = (byte) (buffer[ISO7816.OFFSET_CLA] & 0xFF);
        //获取第二位数据
        byte INS = (byte) (buffer[ISO7816.OFFSET_INS] & 0xFF);

        if (CLA != CMD_CLA) {//格式不对
            ISOException.throwIt(ISO7816.SW_CLA_NOT_SUPPORTED);
        }

        switch (INS) {
        case CMD_INS_1:
            sendBytes(apdu,strHello);
            break;
        case CMD_INS_2:
            sendBytes(apdu,strWorld);
            break;
        default:
            ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
        }
    }

    private void sendBytes(APDU apdu,byte[] arrays) {
        byte[] buffer = apdu.getBuffer();
        short length = (short) arrays.length;

        Util.arrayCopyNonAtomic(arrays, (short) 0, buffer, (short) 0,
                (short) length);

        apdu.setOutgoingAndSend((short) 0, length);
    }
}</span>

接下来贴出Android端的核心代码，下载地址：http://download.csdn.net/detail/hellogv/8090053。

大概的思路是：Android端的NFC读写程序定义1个Applet的ID（AID），SELECT命令的报文头（SELECT_APDU_HEADER），2个自定义命令CMD_INS_1和CMD_INS_2。首先使用AID和SELECT_APDU_HEADER生成完整的SELECT命令，transceive（发送）到卡片，用于启动卡片里的AID对应的Applet。启动卡片里的Applet后，NFC读写程序发送SAMPLE_COMMAND里面的2条自定义命令，Applet分别返回"Hello""World"。

核心源码如下：

<span style="font-family:Microsoft YaHei;">public final class CardReader {
    private static final String TAG = "LoyaltyCardReader";
    // AID for our loyalty card service.
    private static final String SAMPLE_CARD_AID = "1122001122";
    // 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};
    //自定义的命令
    private static final String[] SAMPLE_COMMAND={"8010000000",//卡片收到后返回"Hello"
        "8020000000"};//卡片收到后返回"World"

    public static String[][] TECHLISTS;
    public static IntentFilter[] FILTERS;

    static {
        try {
            //the tech lists used to perform matching for dispatching of the ACTION_TECH_DISCOVERED intent
            TECHLISTS = new String[][] { { IsoDep.class.getName() }};

            FILTERS = new IntentFilter[] { new IntentFilter(
                    NfcAdapter.ACTION_TECH_DISCOVERED, "*/*") };
        } catch (Exception e) {
        }
    }

    static public String tagDiscovered(Tag tag) {
        Log.e(TAG, "New tag discovered");

        String strResult="";
        IsoDep isoDep = IsoDep.get(tag);
        if (isoDep != null) {
            try {
                // Connect to the remote NFC device
                isoDep.connect();

                //发送select 命令,卡片会返回SELECT_OK_SW（90 00）
                byte[] cmdSelect = BuildSelectApdu(SAMPLE_CARD_AID);
                Log.e(TAG, "Sending: " + ByteArrayToHexString(cmdSelect));
                byte[] result = isoDep.transceive(cmdSelect);
                Log.e(TAG, "Receive: " + ByteArrayToHexString(result));
                byte[][] response = getResponse(result);
                byte[] statusWord =response[0];

                if (Arrays.equals(SELECT_OK_SW, statusWord) == false)
                    return "";

                //循环发送自定义命令
                for(int i=0;i<SAMPLE_COMMAND.length;i++){
                    String command = SAMPLE_COMMAND[i];
                    result = HexStringToByteArray(command);
                    Log.e(TAG, "Sending: " + command);

                    result = isoDep.transceive(result);
                    Log.e(TAG, "Receive: " + ByteArrayToHexString(result));
                    response = getResponse(result);
                    byte[] body =response[1];

                    strResult=strResult+new String(body)+":"+ByteArrayToHexString(body)+"
";
                }


                return strResult;

            } catch (IOException e) {
                Log.e(TAG, "Error communicating with card: " + e.toString());
            }
        }
        return null;
    }

    /***
     * 分解卡片返回的数据
     * @param b
     * @return [0]表示返回的状态值，[1]表示返回的正文
     */
    private static byte[][] getResponse(byte[] b){
        byte[][] result = new byte[2][];

        int length = b.length;
        byte[] status = { b[length - 2],b[length - 1] };

        byte[] body = Arrays.copyOf(b, length - 2);

        result[0]=status;
        result[1]=body;
        return result;
    }

    public static String load(Parcelable parcelable) {
        // 从Parcelable筛选出各类NFC标准数据
        final Tag tag = (Tag) parcelable;
        return tagDiscovered(tag);
    }


    /**
     * 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>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;
    }
}</span>