Merge "docs: Added virtual files to preview doc" into mnc-docs

        <li><a href="#scoped_directory_access">Scoped directory access</a></li>

        <li><a href="#launcher_shortcuts">Launcher shortcuts</a></li>

        <li><a href="#print_svc">Print service enhancements</a></li>

        <li><a href="#virtual_files">Virtual Files</a></li>

      </ol>

</div>

</div>

  For more information about these methods, see the downloadable <a href=

  "{@docRoot}preview/setup-sdk.html#docs-dl">API Reference</a>.

</p>

<h2 id="virtual_files">Virtual Files</h2>

<p>

  In previous versions of Android, your app could use the Storage Access

  Framework to allow users to select files from their cloud storage accounts,

  such as Google Drive. However, there was no way to represent files that did

  not have a direct bytecode representation; every file was required to provide

  an input stream.

</p>

<p>

  Android N adds the concept of <em>virtual files</em> to the Storage Access

  Framework. The virtual files feature allows your

  {@link android.provider.DocumentsProvider} to return document URIs that can be

  used with an {@link android.content.Intent#ACTION_VIEW} intent even if they

  don't have a direct bytecode representation. Android N also allows you to

  provide alternate formats for user files, virtual or otherwise.

</p>

<p>

  To get a URI for a virtual document in your app, first you create an

  {@link android.content.Intent} to open the file picker UI. Since an app

  cannot directly open a virtual file by using the

  {@link android.content.ContentResolver#openInputStream(Uri) openInputStream()}

  method, your app does not receive any virtual files if you include the

  {@link android.content.Intent#CATEGORY_OPENABLE} category.

</p>

<p>

  After the user has made a selection, the system calls the

  {@link android.app.Activity#onActivityResult onActivityResult()} method.

  Your app can retrieve the URI of the virtual file and get an input stream, as

  demonstrated in the code snippet below.

</p>

<pre>

  // Other Activity code ...

  final static private int REQUEST_CODE = 64;

  // We listen to the OnActivityResult event to respond to the user's selection.

  @Override

  public void onActivityResult(int requestCode, int resultCode,

    Intent resultData) {

      try {

        if (requestCode == REQUEST_CODE &&

            resultCode == Activity.RESULT_OK) {

            Uri uri = null;

            if (resultData != null) {

                uri = resultData.getData();

                ContentResolver resolver = getContentResolver();

                // Before attempting to coerce a file into a MIME type,

                // check to see what alternative MIME types are available to

                // coerce this file into.

                String[] streamTypes =

                  resolver.getStreamTypes(uri, "*/*");

                AssetFileDescriptor descriptor =

                    resolver.openTypedAssetFileDescriptor(

                        uri,

                        streamTypes[0],

                        null);

                // Retrieve a stream to the virtual file.

                InputStream inputStream = descriptor.createInputStream();

            }

        }

      } catch (Exception ex) {

        Log.e("EXCEPTION", "ERROR: ", ex);

      }

  }

</pre>

<p>

  For more information about accessing user files, see the

  <a href="{@docRoot}guide/topics/providers/document-provider.html">Storage

  Access Frameworks guide</a>.

</p>

 No newline at end of file