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Merge "More documentation updates for NFC." into gingerbread

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This commit is contained in:
Jeff Hamilton
2011-02-09 00:34:22 -08:00
committed by Android (Google) Code Review
parent a3f53afd13 28319c0cec
commit 58c9d4726e
3 changed files with 115 additions and 45 deletions
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90
core/java/android/nfc/NfcAdapter.java
View File

@@ -26,8 +26,11 @@ import android.content.Context;
import android.content.IntentFilter;
import android.content.pm.IPackageManager;
import android.content.pm.PackageManager;
import android.nfc.tech.MifareClassic;
import android.nfc.tech.Ndef;
import android.nfc.tech.NfcA;
import android.nfc.tech.NfcF;
import android.os.IBinder;
import android.os.Parcel;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.util.Log;
@@ -43,30 +46,85 @@ public final class NfcAdapter {
/**
* Intent to start an activity when a tag with NDEF payload is discovered.
* If the tag has and NDEF payload this intent is started before
* {@link #ACTION_TECH_DISCOVERED}.
*
* If any activities respond to this intent neither
* <p>The system inspects the first {@link NdefRecord} in the first {@link NdefMessage} and
* looks for a URI, SmartPoster, or MIME record. If a URI or SmartPoster record is found the
* intent will contain the URI in its data field. If a MIME record is found the intent will
* contain the MIME type in its type field. This allows activities to register
* {@link IntentFilter}s targeting specific content on tags. Activities should register the
* most specific intent filters possible to avoid the activity chooser dialog, which can
* disrupt the interaction with the tag as the user interacts with the screen.
*
* <p>If the tag has an NDEF payload this intent is started before
* {@link #ACTION_TECH_DISCOVERED}. If any activities respond to this intent neither
* {@link #ACTION_TECH_DISCOVERED} or {@link #ACTION_TAG_DISCOVERED} will be started.
*/
@SdkConstant(SdkConstantType.ACTIVITY_INTENT_ACTION)
public static final String ACTION_NDEF_DISCOVERED = "android.nfc.action.NDEF_DISCOVERED";
/**
* Intent to started when a tag is discovered. The data URI is formated as
* {@code vnd.android.nfc://tag/} with the path having a directory entry for each technology
* in the {@link Tag#getTechList()} is sorted ascending order.
* Intent to start an activity when a tag is discovered and activities are registered for the
* specific technologies on the tag.
*
* This intent is started after {@link #ACTION_NDEF_DISCOVERED} and before
* {@link #ACTION_TAG_DISCOVERED}
* <p>To receive this intent an activity must include an intent filter
* for this action and specify the desired tech types in a
* manifest <code>meta-data</code> entry. Here is an example manfiest entry:
* <pre>
* &lt;activity android:name=".nfc.TechFilter" android:label="NFC/TechFilter"&gt;
* &lt;!-- Add a technology filter --&gt;
* &lt;intent-filter&gt;
* &lt;action android:name="android.nfc.action.TECH_DISCOVERED" /&gt;
* &lt;/intent-filter&gt;
*
* If any activities respond to this intent {@link #ACTION_TAG_DISCOVERED} will not be started.
* &lt;meta-data android:name="android.nfc.action.TECH_DISCOVERED"
* android:resource="@xml/filter_nfc"
* /&gt;
* &lt;/activity&gt;
* </pre>
*
* <p>The meta-data XML file should contain one or more <code>tech-list</code> entries
* each consisting or one or more <code>tech</code> entries. The <code>tech</code> entries refer
* to the qualified class name implementing the technology, for example "android.nfc.tech.NfcA".
*
* <p>A tag matches if any of the
* <code>tech-list</code> sets is a subset of {@link Tag#getTechList() Tag.getTechList()}. Each
* of the <code>tech-list</code>s is considered independently and the
* activity is considered a match is any single <code>tech-list</code> matches the tag that was
* discovered. This provides AND and OR semantics for filtering desired techs. Here is an
* example that will match any tag using {@link NfcF} or any tag using {@link NfcA},
* {@link MifareClassic}, and {@link Ndef}:
*
* <pre>
* &lt;resources xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2"&gt;
* &lt;!-- capture anything using NfcF --&gt;
* &lt;tech-list&gt;
* &lt;tech&gt;android.nfc.tech.NfcF&lt;/tech&gt;
* &lt;/tech-list&gt;
*
* &lt;!-- OR --&gt;
*
* &lt;!-- capture all MIFARE Classics with NDEF payloads --&gt;
* &lt;tech-list&gt;
* &lt;tech&gt;android.nfc.tech.NfcA&lt;/tech&gt;
* &lt;tech&gt;android.nfc.tech.MifareClassic&lt;/tech&gt;
* &lt;tech&gt;android.nfc.tech.Ndef&lt;/tech&gt;
* &lt;/tech-list&gt;
* &lt;/resources&gt;
* </pre>
*
* <p>This intent is started after {@link #ACTION_NDEF_DISCOVERED} and before
* {@link #ACTION_TAG_DISCOVERED}. If any activities respond to {@link #ACTION_NDEF_DISCOVERED}
* this intent will not be started. If any activities respond to this intent
* {@link #ACTION_TAG_DISCOVERED} will not be started.
*/
@SdkConstant(SdkConstantType.ACTIVITY_INTENT_ACTION)
public static final String ACTION_TECH_DISCOVERED = "android.nfc.action.TECH_DISCOVERED";
/**
* Intent to start an activity when a tag is discovered.
*
* <p>This intent will not be started when a tag is discovered if any activities respond to
* {@link #ACTION_NDEF_DISCOVERED} or {@link #ACTION_TECH_DISCOVERED} for the current tag.
*/
@SdkConstant(SdkConstantType.ACTIVITY_INTENT_ACTION)
public static final String ACTION_TAG_DISCOVERED = "android.nfc.action.TAG_DISCOVERED";
@@ -78,17 +136,23 @@ public final class NfcAdapter {
public static final String ACTION_TAG_LEFT_FIELD = "android.nfc.action.TAG_LOST";
/**
* Mandatory Tag extra for the ACTION_TAG intents.
* Mandatory extra containing the {@link Tag} that was discovered for the
* {@link #ACTION_NDEF_DISCOVERED}, {@link #ACTION_TECH_DISCOVERED}, and
* {@link #ACTION_TAG_DISCOVERED} intents.
*/
public static final String EXTRA_TAG = "android.nfc.extra.TAG";
/**
* Optional NdefMessage[] extra for the ACTION_TAG intents.
* Optional extra containing an array of {@link NdefMessage} present on the discovered tag for
* the {@link #ACTION_NDEF_DISCOVERED}, {@link #ACTION_TECH_DISCOVERED}, and
* {@link #ACTION_TAG_DISCOVERED} intents.
*/
public static final String EXTRA_NDEF_MESSAGES = "android.nfc.extra.NDEF_MESSAGES";
/**
* Optional byte[] extra for the tag identifier.
* Optional extra containing a byte array containing the ID of the discovered tag for
* the {@link #ACTION_NDEF_DISCOVERED}, {@link #ACTION_TECH_DISCOVERED}, and
* {@link #ACTION_TAG_DISCOVERED} intents.
*/
public static final String EXTRA_ID = "android.nfc.extra.ID";

69
core/java/android/nfc/Tag.java
View File

@@ -38,9 +38,9 @@ import java.util.Arrays;
* <p>
* {@link Tag} is an immutable object that represents the state of a NFC tag at
* the time of discovery. It can be used as a handle to {@link TagTechnology} classes
* to perform advanced operations, or directly queried for its ID ({@link #getId} and the
* set of technologies it contains ({@link #getTechList}). Arrays passed to and
* returned by this class are *not* cloned, so be careful not to modify them.
* to perform advanced operations, or directly queried for its ID via {@link #getId} and the
* set of technologies it contains via {@link #getTechList}. Arrays passed to and
* returned by this class are <em>not</em> cloned, so be careful not to modify them.
* <p>
* A new tag object is created every time a tag is discovered (comes into range), even
* if it is the same physical tag. If a tag is removed and then returned into range, then
@@ -48,53 +48,60 @@ import java.util.Arrays;
*
* <h3>Tag Dispatch</h3>
* When a tag is discovered, a {@link Tag} object is created and passed to a
* single application via the {@link NfcAdapter#EXTRA_TAG} extra in a
* {@link Context#startActivity} {@link android.content.Intent}. A four stage dispatch is used to select the
* most appropriate application to handle the tag. The Android OS executes each stage in order,
* and completes dispatch as soon as a single matching application is found. If there are multiple
* matching applications found at any one stage then the Android Activity Chooser dialog is shown
* to allow the user to select the application.
* single activity via the {@link NfcAdapter#EXTRA_TAG} extra in an
* {@link android.content.Intent} via {@link Context#startActivity}. A four stage dispatch is used
* to select the
* most appropriate activity to handle the tag. The Android OS executes each stage in order,
* and completes dispatch as soon as a single matching activity is found. If there are multiple
* matching activities found at any one stage then the Android activity chooser dialog is shown
* to allow the user to select the activity to receive the tag.
*
* <p>The Tag dispatch mechanism was designed to give a high probability of dispatching
* a tag to the correct activity without showing the user an activity chooser dialog.
* This is important for NFC interactions because they are very transient -- if a user has to
* move the Android device to choose an application then the connection will likely be broken.
*
* <h4>1. Foreground activity dispatch</h4>
* A foreground activity that has called {@link NfcAdapter#enableForegroundDispatch} is
* given priority. See the documentation on {#link NfcAdapter#enableForegroundDispatch} for
* A foreground activity that has called
* {@link NfcAdapter#enableForegroundDispatch NfcAdapter.enableForegroundDispatch()} is
* given priority. See the documentation on
* {@link NfcAdapter#enableForegroundDispatch NfcAdapter.enableForegroundDispatch()} for
* its usage.
* <h4>2. NDEF data dispatch</h4>
* If the tag contains NDEF data, then {@link Context#startActivity} is called with
* {@link NfcAdapter#ACTION_NDEF_DISCOVERED} and a data URI determined from the
* first NDEF Record in the first NDEF Message in the Tag. This allows NDEF tags to be given
* priority dispatch to applications that can handle the content.
* If the tag contains NDEF data the system inspects the first {@link NdefRecord} in the first
* {@link NdefMessage}. If the record is a URI, SmartPoster, or MIME data
* {@link Context#startActivity} is called with {@link NfcAdapter#ACTION_NDEF_DISCOVERED}. For URI
* and SmartPoster records the URI is put into the intent's data field. For MIME records the MIME
* type is put in the intent's type field. This allows activities to register to be launched only
* when data they know how to handle is present on a tag. This is the preferred method of handling
* data on a tag since NDEF data can be stored on many types of tags and doesn't depend on a
* specific tag technology.
* See {@link NfcAdapter#ACTION_NDEF_DISCOVERED} for more detail. If the tag does not contain
* NDEF data, or if no application is registered
* for {@link NfcAdapter#ACTION_NDEF_DISCOVERED} with a matching data URI then dispatch moves
* to stage 3.
* NDEF data, or if no activity is registered
* for {@link NfcAdapter#ACTION_NDEF_DISCOVERED} with a matching data URI or MIME type then dispatch
* moves to stage 3.
* <h4>3. Tag Technology dispatch</h4>
* {@link Context#startActivity} is called with {@link NfcAdapter#ACTION_TECH_DISCOVERED} to
* dispatch the tag to an application that can handle the technologies present on the tag.
* dispatch the tag to an activity that can handle the technologies present on the tag.
* Technologies are defined as sub-classes of {@link TagTechnology}, see the package
* {@link android.nfc.tech}. The Android OS looks for an application that can handle one or
* more technologies in the tag. See {@link NfcAdapter#ACTION_TECH_DISCOVERED for more detail.
* {@link android.nfc.tech}. The Android OS looks for an activity that can handle one or
* more technologies in the tag. See {@link NfcAdapter#ACTION_TECH_DISCOVERED} for more detail.
* <h4>4. Fall-back dispatch</h4>
* If no application has been matched, then {@link Context#startActivity} is called with
* If no activity has been matched then {@link Context#startActivity} is called with
* {@link NfcAdapter#ACTION_TAG_DISCOVERED}. This is intended as a fall-back mechanism.
* See {@link NfcAdapter#ACTION_TAG_DISCOVERED}.
*
* <p>
* <i>The Tag dispatch mechanism was designed to give a high probability of dispatching
* a tag to the correct application without showing the user an Application Chooser dialog.
* This is important for NFC interactions because they are very transient - if a user has to
* move the Android device to choose an application then the connection is broken.</i>
*
* <h3>NFC Tag Background</h3>
* An NFC tag is a passive NFC device, powered by the NFC field of this Android device while
* it is in range. Tag's can come in many forms, such as stickers, cards, key fob, or
* it is in range. Tag's can come in many forms, such as stickers, cards, key fobs, or
* even embedded in a more sophisticated device.
* <p>
* Tags can have a wide range of capabilities. Simple tags just offer read/write semantics,
* and contain some one time
* programmable areas to make read-only. More complex tags offer math operations
* and per-sector access control and authentication. The most sophisticated tags
* contain operating environments such as Javacard, allowing complex interactions with the
* applets executing on the tag. Use {@link TagTechnology} classes to access a broad
* contain operating environments allowing complex interactions with the
* code executing on the tag. Use {@link TagTechnology} classes to access a broad
* range of capabilities available in NFC tags.
* <p>
*/

1
core/java/android/nfc/tech/Ndef.java
View File

@@ -136,7 +136,6 @@ public final class Ndef extends BasicTagTechnology {
* @param tag an MIFARE Classic compatible tag
* @return MIFARE Classic object
*/
public static Ndef get(Tag tag) {
if (!tag.hasTech(TagTechnology.NDEF)) return null;
try {