page.title=Views and Shadows

@jd:body

<div id="qv-wrapper">
<div id="qv">
<h2>In this document</h2>
<ol>
  <li><a href="#elevation">View Elevation</a></li>
  <li><a href="#shadows">Shadows and Outlines</a></li>
  <li><a href="#clip">Clipping Views</a></li>
</ol>
</div>
</div>

<p>The elevation of a view determines the size of its shadow:
views with higher Z values cast bigger shadows. Views only cast shadows on the Z=0 plane under an
orthographic projection (the views do not scale for different values of Z).</p>

<p>Elevation is also useful to create animations where widgets temporarily rise above the
view plane when performing some action.</p>


<h2 id="elevation">View Elevation</h2>

<p>The Z value for a view has two components, elevation and translation. The elevation is the
static component, and the translation is used for animations:</p>

<p><code>Z = elevation + translationZ</code></p>

<p>To set the elevation of a view:</p>

<ul>
  <li>In a layout definition, use the <code>android:elevation</code> attribute.</li>
  <li>In the code of an activity, use the <code>View.setElevation</code> method.</li>
</ul>

<p>To set the translation of a view, use the <code>View.setTranslationZ</code> method.</p>

<p>The new <code>ViewPropertyAnimator.z</code> and <code>ViewPropertyAnimator.translationZ</code>
methods enable you to easily animate the elevation of views. For more information, see
the API reference for <code>ViewPropertyAnimator</code> and the <a
href="{@docRoot}guide/topics/graphics/prop-animation.html#object-animator">Property Animation</a>
developer guide.</p>

<p>The Z values are measured in the same units as the X and Y values.</p>


<h2 id="shadows">Shadows and Outlines</h2>

<p>The bounds of a view's background drawable determine the default shape of its shadow.
<strong>Outlines</strong> represent the outer shape of a graphics object and define the ripple
area for touch feedback.</p>

<p>For example, if you define a view with a background drawable:</p>

<pre>
&lt;TextView
    android:id="@+id/myview"
    ...
    android:elevation="2dp"
    android:background="@drawable/myrect" />
</pre>

<p>where the background drawable is defined as a rectangle with rounded corners:</p>

<pre>
&lt;!-- res/drawable/myrect.xml -->
&lt;shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">
    &lt;solid android:color="#42000000" />
    &lt;corners android:radius="5dp" />
&lt;/shape>
</pre>

<p>Then this view and drawable cast the appropriate shadow.</p>

<p>You can also create outlines in your code using the methods in the <code>Outline</code> class,
and you can assign them to views with the <code>View.setOutline</code> method.</p>

<p>To prevent a view from casting a shadow, set its outline to <code>null</code>.</p>


<h2 id="clip">Clipping Views</h2>

<p>Clip a view to its outline area using the
<code>View.setClipToOutline</code> method. Only rectangle, circle, and round rectangle outlines
support clipping, as determined by the <code>Outline.canClip</code> method.</p>

<p>To clip a view to the shape of a drawable, set the drawable as the background of the view
(as shown above) and call the <code>View.setClipToOutline</code> method.</p>

<p>Because clipping views is an expensive operation, don't animate the shape you use to
clip a view. To achieve this effect, use a <a
href="{@docRoot}preview/material/animations.html#reveal">Reveal Effect</a> animation.</p>