| /* |
| * Copyright (C) 2013 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package com.example.android.cardreader; |
| |
| import android.nfc.NfcAdapter; |
| import android.nfc.Tag; |
| import android.nfc.tech.IsoDep; |
| |
| import com.example.android.common.logger.Log; |
| |
| import java.io.IOException; |
| import java.lang.ref.WeakReference; |
| import java.util.Arrays; |
| |
| /** |
| * Callback class, invoked when an NFC card is scanned while the device is running in reader mode. |
| * |
| * Reader mode can be invoked by calling NfcAdapter |
| */ |
| 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>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()); |
| } |
| } |
| } |
| |
| /** |
| * 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; |
| } |
| |
| } |