android_frameworks_base/docs/html/training/tv/playback/card.jd

page.title=Providing a Card View
page.tags="card"

trainingnavtop=true

@jd:body

<div id="tb-wrapper">
<div id="tb">
  <h2>This lesson teaches you to</h2>
  <ol>
    <li><a href="#presenter">Create a Card Presenter</a></li>
    <li><a href="#card-view">Create a Card View</a></li>
  </ol>
  <h2>Try it out</h2>
  <ul>
    <li><a class="external-link" href="https://github.com/googlesamples/androidtv-Leanback">Android
    Leanback sample app</a></li>
  </ul>
</div>
</div>

<p>In the previous lesson, you created a catalog browser, implemented in a browse fragment, that
displays a list of media items. In this lesson, you create the card views for your media items and
present them in the browse fragment.</p>

<p>The {@link android.support.v17.leanback.widget.BaseCardView} class and subclasses display the meta
data associated with a media item. The {@link android.support.v17.leanback.widget.ImageCardView}
class used in this lesson displays an image for the content along with the media item's title.</p>

<p>This lesson describes code from the <a href="https://github.com/googlesamples/androidtv-Leanback">
Android Leanback sample app</a>, available on GitHub. Use this sample code to start your own
app.</p>

<img itemprop="image" src="{@docRoot}images/tv/app-browse.png" alt="App main screen"/>
<p class="img-caption"><b>Figure 1.</b> The <a href="https://github.com/googlesamples/androidtv-Leanback">
Leanback sample app</a> browse fragment with a card presenter displaying card view objects.</p>

<h2 id="presenter">Create a Card Presenter</h2>

<p>A {@link android.support.v17.leanback.widget.Presenter} generates views and binds objects to them
on demand. In the browse fragment where your app presents its content to the user, you create a
{@link android.support.v17.leanback.widget.Presenter} for the content cards and pass it to the adapter
that adds the content to the screen. In the following code, the <code>CardPresenter</code> is created
in the {@link android.support.v4.app.LoaderManager.LoaderCallbacks#onLoadFinished(android.support.v4.content.Loader, java.lang.Object) onLoadFinished()}
callback of the {@link android.support.v4.app.LoaderManager}.</p>

<pre>
&#64;Override
public void onLoadFinished(Loader&lt;HashMap&lt;String, List&lt;Movie&gt;&gt;&gt; arg0,
                           HashMap&lt;String, List&lt;Movie&gt;&gt; data) {

    mRowsAdapter = new ArrayObjectAdapter(new ListRowPresenter());
    CardPresenter cardPresenter = new CardPresenter();

    int i = 0;

    for (Map.Entry&lt;String, List&lt;Movie&gt;&gt; entry : data.entrySet()) {
        ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(cardPresenter);
        List&lt;Movie&gt; list = entry.getValue();

        for (int j = 0; j &lt; list.size(); j++) {
            listRowAdapter.add(list.get(j));
        }
        HeaderItem header = new HeaderItem(i, entry.getKey(), null);
        i++;
        mRowsAdapter.add(new ListRow(header, listRowAdapter));
    }

    HeaderItem gridHeader = new HeaderItem(i, getString(R.string.more_samples),
            null);

    GridItemPresenter gridPresenter = new GridItemPresenter();
    ArrayObjectAdapter gridRowAdapter = new ArrayObjectAdapter(gridPresenter);
    gridRowAdapter.add(getString(R.string.grid_view));
    gridRowAdapter.add(getString(R.string.error_fragment));
    gridRowAdapter.add(getString(R.string.personal_settings));
    mRowsAdapter.add(new ListRow(gridHeader, gridRowAdapter));

    setAdapter(mRowsAdapter);

    updateRecommendations();
}
</pre>

<h2 id="card-view">Create a Card View</h2>

<p>In this step, you build the card presenter with a view holder for the card view that describes
your media content items. Note that each presenter must only create one view type. If you have two
different card view types then you need two different card presenters.</p>

<p>In the {@link android.support.v17.leanback.widget.Presenter}, implement an
{@link android.support.v17.leanback.widget.Presenter#onCreateViewHolder(android.view.ViewGroup) onCreateViewHolder()}
callback that creates a view holder that can be used to display a content item.</p>

<pre>
&#64;Override
public class CardPresenter extends Presenter {

    private Context mContext;
    private static int CARD_WIDTH = 313;
    private static int CARD_HEIGHT = 176;
    private Drawable mDefaultCardImage;

    &#64;Override
    public ViewHolder onCreateViewHolder(ViewGroup parent) {
        mContext = parent.getContext();
        mDefaultCardImage = mContext.getResources().getDrawable(R.drawable.movie);
...
</pre>

<p>In the {@link android.support.v17.leanback.widget.Presenter#onCreateViewHolder(android.view.ViewGroup)
onCreateViewHolder()} method, create a card view for content items. The sample below uses an
{@link android.support.v17.leanback.widget.ImageCardView}.</p>

<p>When a card is selected, the default behavior expands it to a larger size. If you want to designate
a different color for the selected card, call {@link android.support.v17.leanback.widget.BaseCardView#setSelected(boolean)
setSelected()}
as shown here.</p>

<pre>
...
    ImageCardView cardView = new ImageCardView(mContext) {
        &#64;Override
        public void setSelected(boolean selected) {
            int selected_background = mContext.getResources().getColor(R.color.detail_background);
            int default_background = mContext.getResources().getColor(R.color.default_background);
            int color = selected ? selected_background : default_background;
            findViewById(R.id.info_field).setBackgroundColor(color);
            super.setSelected(selected);
        }
    };
...
</pre>

<p>When the user opens your app, the {@link android.support.v17.leanback.widget.Presenter.ViewHolder}
displays the <code>CardView</code> objects for your content items. You need to set these to receive
focus from the D-pad controller by calling {@link android.view.View#setFocusable(boolean) setFocusable(true)}
and {@link android.view.View#setFocusableInTouchMode(boolean) setFocusableInTouchMode(true)}.</p>

<pre>
...
    cardView.setFocusable(true);
    cardView.setFocusableInTouchMode(true);
    return new ViewHolder(cardView);
}
</pre>

<p>When the user selects the {@link android.support.v17.leanback.widget.ImageCardView}, it expands
to reveal its text area with the background color you specify, as shown in figure 2.</p>

<img itemprop="image" src="{@docRoot}images/tv/card-view.png" alt="App card view"/>
<p class="img-caption"><b>Figure 2.</b> The <a href="https://github.com/googlesamples/androidtv-Leanback">
Leanback sample app</a> image card view when selected.</p>