docs/html/training/material/lists-cards.jd

page.title=Creating Lists and Cards

@jd:body

<div id="tb-wrapper">
<div id="tb">
<h2>This lesson teaches you to</h2>
<ol>
  <li><a href="#RecyclerView">Create Lists</a></li>
  <li><a href="#CardView">Create Cards</a></li>
  <li><a href="#Dependencies">Add Dependencies</a></li>
</ol>
<h2>You should also read</h2>
<ul>
  <li><a href="http://www.google.com/design/spec">Material design specification</a></li>
  <li><a href="{@docRoot}design/material/index.html">Material design on Android</a></li>
</ul>
</div>
</div>


<p>To create complex lists and cards with material design styles in your apps, you can use the
{@link android.support.v7.widget.RecyclerView} and {@link android.support.v7.widget.CardView}
widgets.</p>


<h2 id="RecyclerView">Create Lists</h2>

<p>The {@link android.support.v7.widget.RecyclerView} widget is a more advanced and flexible
version of {@link android.widget.ListView}. This widget is a container for displaying large data
sets that can be scrolled very efficiently by maintaining a limited number of views. Use the
{@link android.support.v7.widget.RecyclerView} widget when you have data collections whose elements
change at runtime based on user action or network events.</p>

<p>The {@link android.support.v7.widget.RecyclerView} class simplifies the display and handling of
large data sets by providing:</p>

<ul>
  <li>Layout managers for positioning items</li>
  <li>Default animations for common item operations, such as removal or addition of items</li>
</ul>

<p>You also have the flexibility to define custom layout managers and animations for {@link
android.support.v7.widget.RecyclerView} widgets.</p>

<img src="{@docRoot}training/material/images/RecyclerView.png" alt="" width="550" height="106"/>
<p class="img-caption">
<strong>Figure 1</strong>. The <code>RecyclerView</code> widget.
</p>

<p>To use the {@link android.support.v7.widget.RecyclerView} widget, you have to specify an
adapter and a layout manager. To create an adapter, extend the {@link
android.support.v7.widget.RecyclerView.Adapter RecyclerView.Adapter} class. The details
of the implementation depend on the specifics of your dataset and the type of views. For more
information, see the <a href="#RVExamples">examples</a> below.</p>

<div style="float:right">
<img src="{@docRoot}design/material/images/list_mail.png" alt="" width="250" height="426"/>
<p class="img-caption" style="margin-left:8px">
<strong>Figure 2</strong> - Lists with <code>RecyclerView</code>.
</p>
</div>

<p>A <strong>layout manager</strong> positions item views inside a {@link
android.support.v7.widget.RecyclerView} and determines when to reuse item views that are no
longer visible to the user. To reuse (or <em>recycle</em>) a view, a layout manager may ask the
adapter to replace the contents of the view with a different element from the dataset. Recycling
views in this manner improves performance by avoiding the creation of unnecessary views or
performing expensive {@link android.app.Activity#findViewById findViewById()} lookups.</p>

<p>{@link android.support.v7.widget.RecyclerView} provides these built-in layout managers:</p>

<ul>
<li>{@link android.support.v7.widget.LinearLayoutManager} shows items in a vertical or horizontal
scrolling list.</li>
<li>{@link android.support.v7.widget.GridLayoutManager} shows items in a grid.</li>
<li>{@link android.support.v7.widget.StaggeredGridLayoutManager} shows items in a staggered grid.</li>
</ul>

<p>To create a custom layout manager, extend the {@link
android.support.v7.widget.RecyclerView.LayoutManager RecyclerView.LayoutManager} class.</p>

<h3>Animations</h3>

<p>Animations for adding and removing items are enabled by default in {@link
android.support.v7.widget.RecyclerView}. To customize these animations, extend the
{@link android.support.v7.widget.RecyclerView.ItemAnimator RecyclerView.ItemAnimator} class and use
the {@link android.support.v7.widget.RecyclerView#setItemAnimator RecyclerView.setItemAnimator()}
method.</p>

<h3 id="RVExamples">Examples</h3>

<p>The following code example demonstrates how to add the
{@link android.support.v7.widget.RecyclerView} to a layout:</p>

<pre>
&lt;!-- A RecyclerView with some commonly used attributes -->
&lt;android.support.v7.widget.RecyclerView
    android:id="@+id/my_recycler_view"
    android:scrollbars="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>
</pre>

<p>Once you have added a {@link android.support.v7.widget.RecyclerView} widget to your layout,
obtain a handle to the object, connect it to a layout manager, and attach an adapter for the data
to be displayed:</p>

<pre>
public class MyActivity extends Activity {
    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;

    &#64;Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_activity);
        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        mRecyclerView.setHasFixedSize(true);

        // use a linear layout manager
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);

        // specify an adapter (see also next example)
        mAdapter = new MyAdapter(myDataset);
        mRecyclerView.setAdapter(mAdapter);
    }
    ...
}
</pre>

<p>The adapter provides access to the items in your data set, creates views for items, and
replaces the content of some of the views with new data items when the original item is no longer
visible. The following code example shows a simple implementation for a data set that consists
of an array of strings displayed using {@link android.widget.TextView} widgets:</p>

<pre>
public class MyAdapter extends RecyclerView.Adapter&lt;MyAdapter.ViewHolder> {
    private String[] mDataset;

    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    public static class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        public TextView mTextView;
        public ViewHolder(TextView v) {
            super(v);
            mTextView = v;
        }
    }

    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(String[] myDataset) {
        mDataset = myDataset;
    }

    // Create new views (invoked by the layout manager)
    &#64;Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                   int viewType) {
        // create a new view
        View v = LayoutInflater.from(parent.getContext())
                               .inflate(R.layout.my_text_view, parent, false);
        // set the view's size, margins, paddings and layout parameters
        ...
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager)
    &#64;Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element
        holder.mTextView.setText(mDataset[position]);

    }

    // Return the size of your dataset (invoked by the layout manager)
    &#64;Override
    public int getItemCount() {
        return mDataset.length;
    }
}
</pre>


<div style="float:right;margin-top:15px;margin-left:30px">
<img src="{@docRoot}design/material/images/card_travel.png" alt="" width="225" height="383">
<p class="img-caption" style="margin-left:12px">
<strong>Figure 3</strong>. Card examples.
</p>
</div>

<h2 id="CardView">Create Cards</h2>

<p>{@link android.support.v7.widget.CardView} extends the {@link android.widget.FrameLayout} class
and lets you show information inside cards that have a consistent look across the platform. {@link
android.support.v7.widget.CardView} widgets can have shadows and rounded corners.</p>

<p>To create a card with a shadow, use the <code>card_view:cardElevation</code> attribute.
{@link android.support.v7.widget.CardView} uses real elevation and dynamic shadows on Android 5.0
(API level 21) and above and falls back to a programmatic shadow implementation on earlier versions.
For more information, see <a href="{@docRoot}training/material/compatibility.html">Maintaining
Compatibility</a>.</p>

<p>Use these properties to customize the appearance of the
{@link android.support.v7.widget.CardView} widget:</p>

<ul>
  <li>To set the corner radius in your layouts, use the <code>card_view:cardCornerRadius</code>
  attribute.</li>
  <li>To set the corner radius in your code, use the <code>CardView.setRadius</code> method.</li>
  <li>To set the background color of a card, use the <code>card_view:cardBackgroundColor</code>
attribute.</li>
</ul>

<p>The following code example shows you how to include a {@link android.support.v7.widget.CardView}
widget in your layout:</p>

<pre>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    ... >
    &lt;!-- A CardView that contains a TextView -->
    &lt;android.support.v7.widget.CardView
        xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:id="@+id/card_view"
        android:layout_gravity="center"
        android:layout_width="200dp"
        android:layout_height="200dp"
        card_view:cardCornerRadius="4dp">

        &lt;TextView
            android:id="@+id/info_text"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    &lt;/android.support.v7.widget.CardView>
&lt;/LinearLayout>
</pre>

<p>For more information, see the API reference for {@link android.support.v7.widget.CardView}.</p>


<h2 id="Dependencies">Add Dependencies</h2>

<p>The {@link android.support.v7.widget.RecyclerView} and {@link android.support.v7.widget.CardView}
widgets are part of the <a href="{@docRoot}tools/support-library/features.html#v7">v7 Support
Libraries</a>. To use these widgets in your project, add these
<a href="{@docRoot}sdk/installing/studio-build.html#dependencies">Gradle dependencies</a> to your
app's module:</p>

<pre>
dependencies {
    ...
    compile 'com.android.support:cardview-v7:21.0.+'
    compile 'com.android.support:recyclerview-v7:21.0.+'
}
</pre>