android_frameworks_base/docs/html/preview/tv/ui/browse.jd

page.title=BrowseFragment

@jd:body

<div id="qv-wrapper">
<div id="qv">
  <h2>In this document</h2>
  <ol>
    <li><a href="#layout">Media Browse Layout</a></li>
    <li><a href="#lists">Displaying Media Lists</a></li>
    <li><a href="#background">Updating the Background</a></li>
  </ol>

</div>
</div>

<p>The <a href="{@docRoot}preview/tv/start/index.html#tv-libraries">Leanback support library</a>
  provides several APIs for displaying and browsing media catalogs
  on the TV devices. This guide discusses how to use the classes provided by this library to
  implement a user interface for browsing music or videos from your app's media catalog.</p>


<h2 id="layout">Media Browse Layout</h2>

<p>The {@code BrowseFragment} class in the Leanback support library allows you to create a primary
  layout for browsing categories and rows of media items with a minimum of code. The following
  example shows how to create a layout that contains a {@code BrowseFragment}:</p>

<pre>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width=&quot;match_parent&quot;
  android:layout_height=&quot;match_parent&quot;
  android:orientation=&quot;vertical&quot;
  &gt;

  &lt;fragment
      <strong>android:name="android.support.v17.leanback.app.BrowseFragment"</strong>
      android:id=&quot;@+id/browse_fragment&quot;
      android:layout_width=&quot;match_parent&quot;
      android:layout_height=&quot;match_parent&quot;
      /&gt;
&lt;/LinearLayout&gt;
</pre>

<p>In order to work with this layout in an activity, retrieve the {@code BrowseFragment} element
  from the layout. Use the methods in {@code BrowseFragment} to set display parameters such as the
  icon, title and whether category headers are enabled. The following code sample demonstrates how
  to set the layout parameters for a {@code BrowseFragment} in a layout:</p>

<pre>
public class BrowseMediaActivity extends Activity {

    public static final String TAG ="BrowseActivity";

    protected BrowseFragment mBrowseFragment;

    &#64;Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.browse_fragment);

        final FragmentManager fragmentManager = getFragmentManager();
        <strong>mBrowseFragment = (BrowseFragment) fragmentManager.findFragmentById(
                R.id.browse_fragment);</strong>

        // Set display parameters for the BrowseFragment
        mBrowseFragment.setHeadersState(BrowseFragment.HEADERS_ENABLED);
        mBrowseFragment.setTitle(getString(R.string.app_name));
        mBrowseFragment.setBadgeDrawable(getResources().getDrawable(R.drawable.ic_launcher));
        mBrowseFragment.setBrowseParams(params);

    }
}
</pre>


<h2 id="lists">Displaying Media Lists</h2>

<p>The {@code BrowseFragment} allows you to define and display browsable media content categories and
  media items from a media catalog using adapters and presenters. Adapters enable you to connect to
  local or online data sources that contain your media catalog information. Presenter classes hold
  data about media items and provide layout information for displaying an item on screen.</p>

<p>The following example code shows an implementation of a presenter for displaying string
  data:</p>

<pre>
public class StringPresenter extends Presenter {
    private static final String TAG = "StringPresenter";

    public ViewHolder onCreateViewHolder(ViewGroup parent) {
        TextView textView = new TextView(parent.getContext());
        textView.setFocusable(true);
        textView.setFocusableInTouchMode(true);
        textView.setBackground(
                parent.getContext().getResources().getDrawable(R.drawable.text_bg));
        return new ViewHolder(textView);
    }

    public void onBindViewHolder(ViewHolder viewHolder, Object item) {
        ((TextView) viewHolder.view).setText(item.toString());
    }

    public void onUnbindViewHolder(ViewHolder viewHolder) {
        // no op
    }
}
</pre>

<p>Once you have constructed a presenter class for your media items, you can build and attach an
  adapter to the {@code BrowseFragment} to display those items on screen for browsing by the user. The
  following example code demonstrates how to construct an adapter to display categories and items
  in those categories using the StringPresenter class shown in the previous code example:</p>

<pre>
private ArrayObjectAdapter mRowsAdapter;
private static final int NUM_ROWS = 4;

&#64;Override
protected void onCreate(Bundle savedInstanceState) {
    ...

    buildRowsAdapter();
}

private void buildRowsAdapter() {
    mRowsAdapter = new ArrayObjectAdapter(new ListRowPresenter());

    for (int i = 0; i &lt; NUM_ROWS; ++i) {
        ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(
                new StringPresenter());
        listRowAdapter.add("Media Item 1");
        listRowAdapter.add("Media Item 2");
        listRowAdapter.add("Media Item 3");
        HeaderItem header = new HeaderItem(i, "Category " + i, null);
        mRowsAdapter.add(new ListRow(header, listRowAdapter));
    }

    mBrowseFragment.setAdapter(mRowsAdapter);
}
</pre>

<p>This example shows a static implementation of the adapters. A typical media browsing
  application uses data from an online database or web service. For an example of a browsing
  application that uses data retrieved from the web, see the
  <a href="http://github.com/googlesamples/androidtv-leanback">Android TV</a> sample app.</p>


<h2 id="background">Updating the Background</h2>

<p>In order to add visual interest to a media-browsing app on TV, you can update the background
  image as users browse through content. This technique can make interaction with your app feel more
  cinematic and enjoyable for users.</p>

<p>The Leanback support library provides a {@code BackgroundManager} class for changing the
  background of your TV app activity. The following example shows how to create a simple method
  for updating the background within your TV app activity:</p>

<pre>
protected void updateBackground(Drawable drawable) {
    BackgroundManager.getInstance(this).setDrawable(drawable);
}
</pre>

<p>Many of the existing media-browse apps automatically update the background as the user
  navigates through media listings. In order to do this, you can set up a selection listener to
  automatically update the background based on the user's current selection. The following example
  shows you how to set up an {@code OnItemSelectedListener}
  class to catch selection events and update the background:</p>

<pre>
protected void clearBackground() {
    BackgroundManager.getInstance(this).setDrawable(mDefaultBackground);
}

protected OnItemSelectedListener getDefaultItemSelectedListener() {
    return new OnItemSelectedListener() {
        &#64;Override
        public void onItemSelected(Object item, Row row) {
            if (item instanceof Movie ) {
                URI uri = ((Movie)item).getBackdropURI();
                updateBackground(uri);
            } else {
                clearBackground();
            }
        }
    };
}
</pre>

<p class="note">
  <strong>Note:</strong> The implementation above is a simple example shown for purposes of
  illustration. When creating this function in your own app, you should consider running the
  background update action in a separate thread for better performance. In addition, if you are
  planning on updating the background in response to users scrolling through items, consider adding
  a time to delay a background image update until the user settles on an item. This technique avoids
  excessive background image updates.
</p>