1page.title=Providing a Card View
2page.tags="card"
3
4trainingnavtop=true
5
6@jd:body
7
8<div id="tb-wrapper">
9<div id="tb">
10  <h2>This lesson teaches you to</h2>
11  <ol>
12    <li><a href="#presenter">Create a Card Presenter</a></li>
13    <li><a href="#card-view">Create a Card View</a></li>
14  </ol>
15  <h2>Try it out</h2>
16  <ul>
17    <li><a class="external-link" href="https://github.com/googlesamples/androidtv-Leanback">Android
18    Leanback sample app</a></li>
19  </ul>
20</div>
21</div>
22
23<p>In the previous lesson, you created a catalog browser, implemented in a browse fragment, that
24displays a list of media items. In this lesson, you create the card views for your media items and
25present them in the browse fragment.</p>
26
27<p>The {@link android.support.v17.leanback.widget.BaseCardView} class and subclasses display the meta
28data associated with a media item. The {@link android.support.v17.leanback.widget.ImageCardView}
29class used in this lesson displays an image for the content along with the media item's title.</p>
30
31<p>This lesson describes code from the <a href="https://github.com/googlesamples/androidtv-Leanback">
32Android Leanback sample app</a>, available on GitHub. Use this sample code to start your own
33app.</p>
34
35<img itemprop="image" src="{@docRoot}images/tv/app-browse.png" alt="App main screen"/>
36<p class="img-caption"><b>Figure 1.</b> The <a href="https://github.com/googlesamples/androidtv-Leanback">
37Leanback sample app</a> browse fragment with a card presenter displaying card view objects.</p>
38
39<h2 id="presenter">Create a Card Presenter</h2>
40
41<p>A {@link android.support.v17.leanback.widget.Presenter} generates views and binds objects to them
42on demand. In the browse fragment where your app presents its content to the user, you create a
43{@link android.support.v17.leanback.widget.Presenter} for the content cards and pass it to the adapter
44that adds the content to the screen. In the following code, the <code>CardPresenter</code> is created
45in the {@link android.support.v4.app.LoaderManager.LoaderCallbacks#onLoadFinished(android.support.v4.content.Loader, java.lang.Object) onLoadFinished()}
46callback of the {@link android.support.v4.app.LoaderManager}.</p>
47
48<pre>
49&#64;Override
50public void onLoadFinished(Loader&lt;HashMap&lt;String, List&lt;Movie&gt;&gt;&gt; arg0,
51                           HashMap&lt;String, List&lt;Movie&gt;&gt; data) {
52
53    mRowsAdapter = new ArrayObjectAdapter(new ListRowPresenter());
54    CardPresenter cardPresenter = new CardPresenter();
55
56    int i = 0;
57
58    for (Map.Entry&lt;String, List&lt;Movie&gt;&gt; entry : data.entrySet()) {
59        ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(cardPresenter);
60        List&lt;Movie&gt; list = entry.getValue();
61
62        for (int j = 0; j &lt; list.size(); j++) {
63            listRowAdapter.add(list.get(j));
64        }
65        HeaderItem header = new HeaderItem(i, entry.getKey(), null);
66        i++;
67        mRowsAdapter.add(new ListRow(header, listRowAdapter));
68    }
69
70    HeaderItem gridHeader = new HeaderItem(i, getString(R.string.more_samples),
71            null);
72
73    GridItemPresenter gridPresenter = new GridItemPresenter();
74    ArrayObjectAdapter gridRowAdapter = new ArrayObjectAdapter(gridPresenter);
75    gridRowAdapter.add(getString(R.string.grid_view));
76    gridRowAdapter.add(getString(R.string.error_fragment));
77    gridRowAdapter.add(getString(R.string.personal_settings));
78    mRowsAdapter.add(new ListRow(gridHeader, gridRowAdapter));
79
80    setAdapter(mRowsAdapter);
81
82    updateRecommendations();
83}
84</pre>
85
86<h2 id="card-view">Create a Card View</h2>
87
88<p>In this step, you build the card presenter with a view holder for the card view that describes
89your media content items. Note that each presenter must only create one view type. If you have two
90different card view types then you need two different card presenters.</p>
91
92<p>In the {@link android.support.v17.leanback.widget.Presenter}, implement an
93{@link android.support.v17.leanback.widget.Presenter#onCreateViewHolder(android.view.ViewGroup) onCreateViewHolder()}
94callback that creates a view holder that can be used to display a content item.</p>
95
96<pre>
97&#64;Override
98public class CardPresenter extends Presenter {
99
100    private Context mContext;
101    private static int CARD_WIDTH = 313;
102    private static int CARD_HEIGHT = 176;
103    private Drawable mDefaultCardImage;
104
105    &#64;Override
106    public ViewHolder onCreateViewHolder(ViewGroup parent) {
107        mContext = parent.getContext();
108        mDefaultCardImage = mContext.getResources().getDrawable(R.drawable.movie);
109...
110</pre>
111
112<p>In the {@link android.support.v17.leanback.widget.Presenter#onCreateViewHolder(android.view.ViewGroup)
113onCreateViewHolder()} method, create a card view for content items. The sample below uses an
114{@link android.support.v17.leanback.widget.ImageCardView}.</p>
115
116<p>When a card is selected, the default behavior expands it to a larger size. If you want to designate
117a different color for the selected card, call {@link android.support.v17.leanback.widget.BaseCardView#setSelected(boolean)
118setSelected()}
119as shown here.</p>
120
121<pre>
122...
123    ImageCardView cardView = new ImageCardView(mContext) {
124        &#64;Override
125        public void setSelected(boolean selected) {
126            int selected_background = mContext.getResources().getColor(R.color.detail_background);
127            int default_background = mContext.getResources().getColor(R.color.default_background);
128            int color = selected ? selected_background : default_background;
129            findViewById(R.id.info_field).setBackgroundColor(color);
130            super.setSelected(selected);
131        }
132    };
133...
134</pre>
135
136<p>When the user opens your app, the {@link android.support.v17.leanback.widget.Presenter.ViewHolder}
137displays the <code>CardView</code> objects for your content items. You need to set these to receive
138focus from the D-pad controller by calling {@link android.view.View#setFocusable(boolean) setFocusable(true)}
139and {@link android.view.View#setFocusableInTouchMode(boolean) setFocusableInTouchMode(true)}.</p>
140
141<pre>
142...
143    cardView.setFocusable(true);
144    cardView.setFocusableInTouchMode(true);
145    return new ViewHolder(cardView);
146}
147</pre>
148
149<p>When the user selects the {@link android.support.v17.leanback.widget.ImageCardView}, it expands
150to reveal its text area with the background color you specify, as shown in figure 2.</p>
151
152<img itemprop="image" src="{@docRoot}images/tv/card-view.png" alt="App card view"/>
153<p class="img-caption"><b>Figure 2.</b> The <a href="https://github.com/googlesamples/androidtv-Leanback">
154Leanback sample app</a> image card view when selected.</p>
155
156
157