Android SDK Sample(一) CardReader

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。

<
4000
p>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

@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();
}

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", mTestF
9e32
ragment);
}

/**
* 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