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Commit 48872ee0 authored by Joe Malin's avatar Joe Malin Committed by Android (Google) Code Review
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Merge "DOC CHANGE: Android Beam training class" into jb-mr2-docs

parents 6a831b7d 2e1c7b74

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"

    >&lt;intent-filter&gt;</a></code> element for the

    <code><a href="{@docRoot}guide/topics/manifest/activity-element.html"

    >&lt;activity&gt;</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"

    >&lt;intent-filter&gt;</a></code> element, add the following child elements:

</p>

<dl>

    <dt>

        <code><a href="{@docRoot}guide/topics/manifest/action-element.html"

        >&lt;action android:name="android.intent.action.VIEW" /&gt;</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"

        >&lt;category android:name="android.intent.category.CATEGORY_DEFAULT" /&gt;</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"

        >&lt;data android:mimeType="<i>mime-type</i>" /&gt;</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>

    &lt;activity

        android:name="com.example.android.nfctransfer.ViewActivity"

        android:label="Android Beam Viewer" &gt;

        ...

        &lt;intent-filter&gt;

            &lt;action android:name="android.intent.action.VIEW"/&gt;

            &lt;category android:name="android.intent.category.DEFAULT"/&gt;

            ...

        &lt;/intent-filter&gt;

    &lt;/activity&gt;

</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>

    &lt;uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /&gt;</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 &amp;&amp;

                    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=