NfcA.java revision 39cf3a445e507f219ecc8a476f6038f095d9d520 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.nfc.tech;
18
19import android.nfc.Tag;
20import android.os.Bundle;
21import android.os.RemoteException;
22
23import java.io.IOException;
24
25/**
26 * Provides access to NFC-A (ISO 14443-3A) properties and I/O operations on a {@link Tag}.
27 *
28 * <p>Acquire a {@link NfcA} object using {@link #get}.
29 * <p>The primary NFC-A I/O operation is {@link #transceive}. Applications must
30 * implement their own protocol stack on top of {@link #transceive}.
31 *
32 * <p class="note"><strong>Note:</strong> Methods that perform I/O operations
33 * require the {@link android.Manifest.permission#NFC} permission.
34 */
35public final class NfcA extends BasicTagTechnology {
36    /** @hide */
37    public static final String EXTRA_SAK = "sak";
38    /** @hide */
39    public static final String EXTRA_ATQA = "atqa";
40
41    private short mSak;
42    private byte[] mAtqa;
43
44    /**
45     * Get an instance of {@link NfcA} for the given tag.
46     * <p>Returns null if {@link NfcA} was not enumerated in {@link Tag#getTechList}.
47     * This indicates the tag does not support NFC-A.
48     * <p>Does not cause any RF activity and does not block.
49     *
50     * @param tag an NFC-A compatible tag
51     * @return NFC-A object
52     */
53    public static NfcA get(Tag tag) {
54        if (!tag.hasTech(TagTechnology.NFC_A)) return null;
55        try {
56            return new NfcA(tag);
57        } catch (RemoteException e) {
58            return null;
59        }
60    }
61
62    /** @hide */
63    public NfcA(Tag tag) throws RemoteException {
64        super(tag, TagTechnology.NFC_A);
65        Bundle extras = tag.getTechExtras(TagTechnology.NFC_A);
66        mSak = extras.getShort(EXTRA_SAK);
67        mAtqa = extras.getByteArray(EXTRA_ATQA);
68    }
69
70    /**
71     * Return the ATQA/SENS_RES bytes from tag discovery.
72     *
73     * <p>Does not cause any RF activity and does not block.
74     *
75     * @return ATQA/SENS_RES bytes
76     */
77    public byte[] getAtqa() {
78        return mAtqa;
79    }
80
81    /**
82     * Return the SAK/SEL_RES bytes from tag discovery.
83     *
84     * <p>Does not cause any RF activity and does not block.
85     *
86     * @return SAK bytes
87     */
88    public short getSak() {
89        return mSak;
90    }
91
92    /**
93     * Send raw NFC-A commands to the tag and receive the response.
94     *
95     * <p>Applications must not append the EoD (CRC) to the payload,
96     * it will be automatically calculated.
97     * <p>Applications must only send commands that are complete bytes,
98     * for example a SENS_REQ is not possible (these are used to
99     * manage tag polling and initialization).
100     *
101     * <p>This is an I/O operation and will block until complete. It must
102     * not be called from the main application thread. A blocked call will be canceled with
103     * {@link IOException} if {@link #close} is called from another thread.
104     *
105     * <p class="note">Requires the {@link android.Manifest.permission#NFC} permission.
106     *
107     * @param data bytes to send
108     * @return bytes received in response
109     * @throws TagLostException if the tag leaves the field
110     * @throws IOException if there is an I/O failure, or this operation is canceled
111     */
112    public byte[] transceive(byte[] data) throws IOException {
113        return transceive(data, true);
114    }
115}
116