DOC CHANGE: Android Beam training class (2e1c7b74) · Commits · e / os / android_frameworks_base

docs/html/training/beam-files/index.jd

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		page.title=Sharing Files with NFC

		trainingnavtop=true
		startpage=true


		@jd:body

		<div id="tb-wrapper">
		<div id="tb">

		<h2>Dependencies and prerequisites</h2>
		<ul>
		<li>Android 4.1 (API Level 16) or higher</li>
		<li>At least two NFC-enabled Android devices (NFC is not supported in the emulator)</li>
		</ul>

		<h2>You should also read</h2>
		<ul>
		<li>
		<a href="{@docRoot}guide/topics/data/data-storage.html#filesExternal"
		>Using the External Storage</a>
		</li>
		</ul>

		</div>
		</div>

		<p>
		Android allows you to transfer large files between devices using the Android Beam file transfer
		feature. This feature has a simple API and allows users to start the transfer process by simply
		touching devices. In response, Android Beam file transfer automatically copies files from one
		device to the other and notifies the user when it's finished.
		</p>
		<p>
		While the Android Beam file transfer API handles large amounts of data, the Android Beam NDEF
		transfer API introduced in Android 4.0 (API level 14) handles small amounts of data such as
		URIs or other small messages. In addition, Android Beam is only one of the features available
		in the Android NFC framework, which allows you to read NDEF messages from NFC tags. To learn
		more about Android Beam, see the topic
		<a href="{@docRoot}guide/topics/connectivity/nfc/nfc.html#p2p"
		>Beaming NDEF Messages to Other Devices</a>. To learn more about the NFC framework, see the
		<a href="{@docRoot}guide/topics/connectivity/nfc/index.html"
		>Near Field Communication</a> API guide.
		</p>
		<h2>Lessons</h2>
		<dl>
		<dt>
		<b><a href="send-files.html">Sending Files to Another Device</a></b>
		</dt>
		<dd>Learn how to set up your app to send files to another device.</dd>

		<dt>
		<b><a href="receive-files.html">Receiving Files from Another Device</a></b>
		</dt>
		<dd>
		Learn how to set up your app to receive files sent by another device.
		</dd>
		</dl>

docs/html/training/beam-files/receive-files.jd

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		page.title=Receiving Files from Another Device

		trainingnavtop=true
		@jd:body

		<div id="tb-wrapper">
		<div id="tb">

		<h2>This lesson teaches you to</h2>
		<ol>
		<li><a href="#IntentFilter">Respond to a Request to Display Data</a></li>
		<li><a href="#RequestPermissions">Request File Permissions</a></li>
		<li><a href="#GetFilePath">Get the Directory for Copied Files</a></li>
		</ol>
		<h2>You should also read</h2>
		<ul>
		<li>
		<a href="{@docRoot}guide/topics/providers/content-provider-basics.html#ContentURIs"
		>Content URIs</a>
		</li>
		<li>
		<a href="{@docRoot}guide/components/intents-filters.html">Intents and Intent Filters</a>
		</li>
		<li>
		<a href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Notifications</a>
		</li>
		<li>
		<a href="{@docRoot}guide/topics/data/data-storage.html#filesExternal"
		>Using the External Storage</a>
		</li>
		</ul>

		</div>
		</div>

		<p>
		Android Beam file transfer copies files to a special directory on the receiving device. It also
		scans the copied files using the Android Media Scanner and adds entries for media files to
		the {@link android.provider.MediaStore} provider. This lesson shows you how to respond when the
		file copy is complete, and how to locate the copied files on the receiving device.
		</p>
		<h2 id="IntentFilter">Respond to a Request to Display Data</h2>
		<p>
		When Android Beam file transfer finishes copying files to the receiving device, it posts a
		notification containing an {@link android.content.Intent} with the action
		{@link android.content.Intent#ACTION_VIEW ACTION_VIEW}, the MIME type of the first file that
		was transferred, and a URI that points to the first file. When the user clicks the notification,
		this intent is sent out to the system. To have your app respond to this intent, add an
		<code><a href="{@docRoot}guide/topics/manifest/intent-filter-element.html"
		><intent-filter></a></code> element for the
		<code><a href="{@docRoot}guide/topics/manifest/activity-element.html"
		><activity></a></code> element of the {@link android.app.Activity} that should respond.
		In the <code><a href="{@docRoot}guide/topics/manifest/intent-filter-element.html"
		><intent-filter></a></code> element, add the following child elements:
		</p>
		<dl>
		<dt>
		<code><a href="{@docRoot}guide/topics/manifest/action-element.html"
		><action android:name="android.intent.action.VIEW" /></a></code>
		</dt>
		<dd>
		Matches the {@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent sent from the
		notification.
		</dd>
		<dt>
		<code><a href="{@docRoot}guide/topics/manifest/category-element.html"
		><category android:name="android.intent.category.CATEGORY_DEFAULT" /></a></code>
		</dt>
		<dd>
		Matches an {@link android.content.Intent} that doesn't have an explicit category.
		</dd>
		<dt>
		<code><a href="{@docRoot}guide/topics/manifest/data-element.html"
		><data android:mimeType="<i>mime-type</i>" /></a></code>
		</dt>
		<dd>
		Matches a MIME type. Specify only those MIME types that your app can handle.
		</dd>
		</dl>
		<p>
		For example, the following snippet shows you how to add an intent filter that
		triggers the activity <code>com.example.android.nfctransfer.ViewActivity</code>:
		</p>
		<pre>
		<activity
		android:name="com.example.android.nfctransfer.ViewActivity"
		android:label="Android Beam Viewer" >
		...
		<intent-filter>
		<action android:name="android.intent.action.VIEW"/>
		<category android:name="android.intent.category.DEFAULT"/>
		...
		</intent-filter>
		</activity>
		</pre>
		<p class="note">
		<strong>Note:</strong> Android Beam file transfer is not the only source of an
		{@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent. Other apps on the receiving
		device can also send an {@link android.content.Intent} with this action.
		Handling this situation is discussed in the section <a href="#GetDirectory"
		>Get the directory from a content URI</a>.
		</p>
		<h2 id="RequestPermissions">Request File Permissions</h2>
		<p>
		To read files that Android Beam file transfer copies to the device, request the permission
		{@link android.Manifest.permission#READ_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE}. For example:
		</p>
		<pre>
		<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /></pre>
		<p>
		If you want to copy transferred files to your app's own storage area, request the permission
		{@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE WRITE_EXTERNAL_STORAGE} instead.
		{@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE WRITE_EXTERNAL_STORAGE} includes
		{@link android.Manifest.permission#READ_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE}.
		</p>
		<p class="note">
		<strong>Note:</strong> As of Android 4.2.2 (API level 17), the permission
		{@link android.Manifest.permission#READ_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE} is
		only enforced if the user chooses to do so. Future versions of the platform may require this
		permission in all cases. To ensure forward compatibility, request the permission now, before it
		becomes required.
		</p>
		<p>
		Since your app has control over its internal storage area, you don't need to request
		write permission to copy a transferred file to your internal storage area.
		</p>
		<h2 id="GetFilePath">Get the Directory for Copied Files</h2>
		<p>
		Android Beam file transfer copies all the files in a single transfer to one directory
		on the receiving device. The URI in the content {@link android.content.Intent} sent by the
		Android Beam file transfer notification points to the first transferred file. However, your
		app may also receive an {@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent from a
		source other than Android Beam file transfer. To determine how you should handle the incoming
		{@link android.content.Intent}, you need to examine its scheme and authority.
		</p>
		<p>
		To get the scheme for the URI, call {@link android.net.Uri#getScheme() Uri.getScheme()}. The
		following code snippet shows you how to determine the scheme and handle the URI accordingly:
		</p>
		<pre>
		public class MainActivity extends Activity {
		...
		// A File object containing the path to the transferred files
		private File mParentPath;
		// Incoming Intent
		private Intent mIntent;
		...
		/*
		* Called from onNewIntent() for a SINGLE_TOP Activity
		* or onCreate() for a new Activity. For onNewIntent(),
		* remember to call setIntent() to store the most
		* current Intent
		*
		*/
		private void handleViewIntent() {
		...
		// Get the Intent action
		mIntent = getIntent();
		String action = mIntent.getAction();
		/*
		* For ACTION_VIEW, the Activity is being asked to display data.
		* Get the URI.
		*/
		if (TextUtils.equals(action, Intent.ACTION_VIEW)) {
		// Get the URI from the Intent
		Uri beamUri = mIntent.getData();
		/*
		* Test for the type of URI, by getting its scheme value
		*/
		if (TextUtils.equals(beamUri.getScheme(), "file")) {
		mParentPath = handleFileUri(beamUri);
		} else if (TextUtils.equals(
		beamUri.getScheme(), "content")) {
		mParentPath = handleContentUri(beamUri);
		}
		}
		...
		}
		...
		}
		</pre>
		<h3>Get the directory from a file URI</h3>
		<p>
		If the incoming {@link android.content.Intent} contains a file URI, the URI contains the
		absolute file name of a file, including the full directory path and file name. For Android Beam
		file transfer, the directory path points to the location of the other transferred files, if
		any. To get the directory path, get the path part of the URI, which contains all of the URI
		except the <code>file:</code> prefix. Create a {@link java.io.File} from the path part, then
		get the parent path of the {@link java.io.File}:
		</p>
		<pre>
		...
		public String handleFileUri(Uri beamUri) {
		// Get the path part of the URI
		String fileName = beamUri.getPath();
		// Create a File object for this filename
		File copiedFile = new File(fileName);
		// Get a string containing the file's parent directory
		return copiedFile.getParent();
		}
		...
		</pre>

		<h3 id="GetDirectory">Get the directory from a content URI</h3>
		<p>
		If the incoming {@link android.content.Intent} contains a content URI, the URI may point to a
		directory and file name stored in the {@link android.provider.MediaStore} content provider. You
		can detect a content URI for {@link android.provider.MediaStore} by testing the URI's
		authority value. A content URI for {@link android.provider.MediaStore} may come from
		Android Beam file transfer or from another app, but in both cases you can retrieve a directory
		and file name for the content URI.
		</p>
		<p>
		You can also receive an incoming {@link android.content.Intent#ACTION_VIEW ACTION_VIEW}
		intent containing a content URI for a content provider other than
		{@link android.provider.MediaStore}. In this case, the content URI doesn't contain the
		{@link android.provider.MediaStore} authority value, and the content URI usually doesn't point
		to a directory.
		</p>
		<p class="note">
		<strong>Note:</strong> For Android Beam file transfer, you receive a content URI in the
		{@link android.content.Intent#ACTION_VIEW ACTION_VIEW} intent if the first incoming file
		has a MIME type of "audio/", "image/", or "video/*", indicating that the file is media-
		related. Android Beam file transfer indexes the media files it transfers by running Media
		Scanner on the directory where it stores transferred files. Media Scanner writes its results
		to the {@link android.provider.MediaStore} content provider, then it passes a content URI
		for the first file back to Android Beam file transfer. This content URI is the one you
		receive in the notification {@link android.content.Intent}. To get the directory
		of the first file, you retrieve it from {@link android.provider.MediaStore} using the content
		URI.
		</p>
		<h3>Determine the content provider</h3>
		<p>
		To determine if you can retrieve a file directory from the content URI, determine the
		the content provider associated with the URI by calling
		{@link android.net.Uri#getAuthority Uri.getAuthority()} to get the URI's authority. The
		result has two possible values:
		</p>
		<dl>
		<dt>
		{@link android.provider.MediaStore#AUTHORITY MediaStore.AUTHORITY}
		</dt>
		<dd>
		The URI is for a file or files tracked by {@link android.provider.MediaStore}. Retrieve the
		full file name from {@link android.provider.MediaStore}, and get directory from the file
		name.
		</dd>
		<dt>
		Any other authority value
		</dt>
		<dd>
		A content URI from another content provider. Display the data associated with the content
		URI, but don't get the file directory.
		</dd>
		</dl>
		<p>
		To get the directory for a {@link android.provider.MediaStore} content URI,
		run a query that specifies the incoming content URI for the {@link android.net.Uri} argument and
		the column {@link android.provider.MediaStore.MediaColumns#DATA MediaColumns.DATA} for the
		projection. The returned {@link android.database.Cursor} contains the full path and name for
		the file represented by the URI. This path also contains all the other files that Android Beam
		file transfer just copied to the device.
		</p>
		<p>
		The following snippet shows you how to test the authority of the content URI and retrieve the
		the path and file name for the transferred file:
		</p>
		<pre>
		...
		public String handleContentUri(Uri beamUri) {
		// Position of the filename in the query Cursor
		int filenameIndex;
		// File object for the filename
		File copiedFile;
		// The filename stored in MediaStore
		String fileName;
		// Test the authority of the URI
		if (!TextUtils.equals(beamUri.getAuthority(), MediaStore.AUTHORITY)) {
		/*
		* Handle content URIs for other content providers
		*/
		// For a MediaStore content URI
		} else {
		// Get the column that contains the file name
		String[] projection = { MediaStore.MediaColumns.DATA };
		Cursor pathCursor =
		getContentResolver().query(beamUri, projection,
		null, null, null);
		// Check for a valid cursor
		if (pathCursor != null &&
		pathCursor.moveToFirst()) {
		// Get the column index in the Cursor
		filenameIndex = pathCursor.getColumnIndex(
		MediaStore.MediaColumns.DATA);
		// Get the full file name including path
		fileName = pathCursor.getString(filenameIndex);
		// Create a File object for the filename
		copiedFile = new File(fileName);
		// Return the parent directory of the file
		return new File(copiedFile.getParent());
		} else {
		// The query didn't work; return null
		return null;
		}
		}
		}
		...
		</pre>
		<p>
		To learn more about retrieving data from a content provider, see the section
		<a href="{@docRoot}guide/topics/providers/content-provider-basics.html#SimpleQuery"
		>Retrieving Data from the Provider</a>.
		</p>

docs/html/training/beam-files/send-files.jd

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docs/html/training/training_toc.cs

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		@@ -423,7 +423,22 @@ include the action bar on devices running Android 2.1 or higher."
		</li>
		</ul>
		</li>

		<li class="nav-section">
		<div class="nav-section-header">
		<a href="<?cs var:toroot ?>training/beam-files/index.html"
		description=
		"How to transfer files between devices using the NFC Android Beam feature."
		>Sharing Files with NFC</a>
		</div>
		<ul>
		<li>
		<a href="<?cs var:toroot ?>training/beam-files/send-files.html"
		>Sending Files to Another Device</a>
		</li>
		<li><a href="<?cs var:toroot ?>training/beam-files/receive-files.html"
		>Receiving Files from Another Device</a></li>
		</ul>
		</li>
		<li class="nav-section">
		<div class="nav-section-header">
		<a href="<?cs var:toroot ?>training/basics/network-ops/index.html"
		@@ -1181,7 +1196,6 @@ include the action bar on devices running Android 2.1 or higher."
		</a>
		</div>
		<ul>

		<li>
		<a href="<?cs var:toroot ?>training/articles/security-tips.html"
		description=