Android SDK Sample(一) CardReader

导语

本Sample主要是介绍NFC三种模式之一读卡器(Reader)模式的使用，学习本Sample需要对ISO 7816-4报文协议有一定了解。运行本Sample也需要一张智能卡，例如：羊城通。(NFC读取羊城通卡信息)

效果图

Mainifest.xml

minSdk >=19

本Sample要求的最Sdk必须是19，因为在API 19之后，Google提供NFC的API有所改变，本Sample是根据API 19之后的API所写，不兼容API 19以下的机型

所需要的权限

<!-- NFC Reader Mode was added in API 19. --><!-- Min/target SDK versions (<uses-sdk>) managed by build.gradle --><uses-permission android:name="android.permission.NFC" /><uses-feature android:name="android.hardware.nfc" android:required="true" />

首先要求手机或者设备需要有NFC功能，其次需要NFC权限

工程目录

核心类

CardReaderFragment

注册NFC

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);    }}

1.获取NfcAdapter，一般直接使用DefaultAdapter；
2.调用enableReaderMode(Activity activity, ReaderCallback callback, int flags, Bundle extras)函数进行注册Nfc，手机发现Nfc标签后会回调ReaderCallBack，第三个参数flags可以进行标签类型过滤。第四个参数可以传入一些配置，例如读卡延迟时间等。

注销NFC

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

没啥好说的，直接调用disableReaderMode(Activity activity)

生命周期的调用

@Overridepublic 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();    }

本类实现的回调接口

public class CardReaderFragment extends Fragment implements LoyaltyCardReader.AccountCallback {@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);            }        });    }}

主要是实现了一个接口：LoyaltyCardReader.AccountCallback,这个接口在读卡成功后会进行回调。

再来关注下LoyaltyCardReader，本类实现了刚刚所说的注册NFC所需要的回调ReaderCallback,具体分析如下：
成员变量:
具体7816-4指令可以查看相关文档，APDU指令执行成功，返回数据的最后两个字节为9000。

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};

接口实现函数:

@Override    public void onTagDiscovered(Tag tag) {        //Nfc标签被检测到后回调这个函数        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.        //使用IsoDep完成后续操作        IsoDep isoDep = IsoDep.get(tag);        if (isoDep != null) {            try {                // Connect to the remote NFC device                //Nfc与卡片进行连接，抛出IO异常，常见为Tag was Lost                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);                //构建APDU指令                byte[] command = BuildSelectApdu(SAMPLE_LOYALTY_CARD_AID);                // Send command to remote device                Log.i(TAG, "Sending: " + ByteArrayToHexString(command));                //nfc执行APDU指令                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.                //判断指令是否执行成功，最后两个字节为9000则是成功，成功后则回调给Fragment更新UI                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);                } else {                    Log.i(TAG, "Received: " + ByteArrayToHexString(statusWord));                    System.out.println(ByteArrayToHexString(statusWord));                }            } catch (IOException e) {                Log.e(TAG, "Error communicating with card: " + e.toString());            }        }    }

工具函数:
构建APDU指令，返回byte[]数组，AID的长度用16进制表示，长度为2个字节

/**     * 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);    }

byte[]数组转16进制字符串

    /**     * 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);    }

16进制字符串转byte[]数组

    /**     * 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;    }

单元测试

本Sample的单元测试继承了ActivityInstrumentationTestCase2,所以需要运行在真机或者模拟器中

@Override    protected void setUp() throws Exception {        super.setUp();        // Starts the activity under test using the default Intent with:        // action = {@link Intent#ACTION_MAIN}        // flags = {@link Intent#FLAG_ACTIVITY_NEW_TASK}        // All other fields are null or empty.        mTestActivity = getActivity();        mTestFragment = (CardReaderFragment)            mTestActivity.getSupportFragmentManager().getFragments().get(1);    }    /**    * Test if the test fixture has been set up correctly.    */    public void testPreconditions() {        //Try to add a message to add context to your assertions. These messages will be shown if        //a tests fails and make it easy to understand why a test failed        assertNotNull("mTestActivity is null", mTestActivity);        assertNotNull("mTestFragment is null", mTestFragment);    }    /**     * Test building SELECT APDU from AID string.     */    public void testBuildSelectApdu() {        final String aid = "1234";        final byte[] expectedResult = {(byte) 0x00, (byte) 0xA4, 04, (byte) 0x00, (byte) 0x02,                (byte) 0x12, (byte) 0x34};        final byte[] result = LoyaltyCardReader.BuildSelectApdu(aid);        assertEquals(expectedResult.length, result.length);        for (int i = 0; i < expectedResult.length; i++) {            assertEquals(expectedResult[i], result[i]);        }    }    /**     * Test converting from a hex string to binary.     */    public void testHexToBinary() {        final byte[] testData = {(byte) 0xc0, (byte) 0xff, (byte) 0xee};        final byte[] output = LoyaltyCardReader.HexStringToByteArray("C0FFEE");        for (int i = 0; i < testData.length; i++) {            assertEquals(testData[i], output[i]);        }    }    /**     * Test converting from binary to a hex string     */    public void testBinaryToHex() {        final byte[] input = {(byte) 0xc0, (byte) 0xff, (byte) 0xee};        final String output = LoyaltyCardReader.ByteArrayToHexString(input);        assertEquals("C0FFEE", output);    }

单元测试执行结果