docs/html/training/material/animations.jd

page.title=Defining Custom Animations

@jd:body

<div id="tb-wrapper">
<div id="tb">
<h2>This lesson teaches you to</h2>
<ol>
  <li><a href="#Touch">Customize Touch Feedback</a></li>
  <li><a href="#Reveal">Use the Reveal Effect</a></li>
  <li><a href="#Transitions">Customize Activity Transitions</a></li>
  <li><a href="#ViewState">Animate View State Changes</a></li>
  <li><a href="#AnimVector">Animate Vector Drawables</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>Animations in material design give users feedback on their actions and provide visual
continuity as users interact with your app. The material theme provides some default animations
for buttons and activity transitions, and Android 5.0 (API level 21) and above lets you customize
these animations and create new ones:</p>

<ul>
<li>Touch feedback</li>
<li>Circular Reveal</li>
<li>Activity transitions</li>
<li>Curved motion</li>
<li>View state changes</li>
</ul>


<h2 id="Touch">Customize Touch Feedback</h2>

<p>Touch feedback in material design provides an instantaneous visual confirmation at the
point of contact when users interact with UI elements. The default touch feedback animations
for buttons use the new {@link android.graphics.drawable.RippleDrawable} class, which transitions
between different states with a ripple effect.</p>

<p>In most cases, you should apply this functionality in your view XML by specifying the view
background as:</p>

<ul>
<li><code>?android:attr/selectableItemBackground</code> for a bounded ripple.</li>
<li><code>?android:attr/selectableItemBackgroundBorderless</code> for a ripple that extends beyond
the view. It will be drawn upon, and bounded by, the nearest parent of the view with a non-null
background.</li>
</ul>

<p class="note"><strong>Note:</strong> <code>selectableItemBackgroundBorderless</code> is a new
attribute introduced in API level 21.</p>


<p>Alternatively, you can define a {@link android.graphics.drawable.RippleDrawable}
as an XML resource using the <code>ripple</code> element.</p>

<p>You can assign a color to {@link android.graphics.drawable.RippleDrawable} objects. To change
the default touch feedback color, use the theme's <code>android:colorControlHighlight</code>
attribute.</p>

<p>For more information, see the API reference for the {@link
android.graphics.drawable.RippleDrawable} class.</p>


<h2 id="Reveal">Use the Reveal Effect</h2>

<p>Reveal animations provide users visual continuity when you show or hide a group of UI
elements. The {@link android.view.ViewAnimationUtils#createCircularReveal
ViewAnimationUtils.createCircularReveal()} method enables you to animate a clipping circle to
reveal or hide a view.</p>

<p>To reveal a previously invisible view using this effect:</p>

<pre>
// previously invisible view
View myView = findViewById(R.id.my_view);

// get the center for the clipping circle
int cx = myView.getWidth() / 2;
int cy = myView.getHeight() / 2;

// get the final radius for the clipping circle
float finalRadius = (float) Math.hypot(cx, cy);

// create the animator for this view (the start radius is zero)
Animator anim =
    ViewAnimationUtils.createCircularReveal(myView, cx, cy, 0, finalRadius);

// make the view visible and start the animation
myView.setVisibility(View.VISIBLE);
anim.start();
</pre>

<p>To hide a previously visible view using this effect:</p>

<pre>
// previously visible view
final View myView = findViewById(R.id.my_view);

// get the center for the clipping circle
int cx = myView.getWidth() / 2;
int cy = myView.getHeight() / 2;

// get the initial radius for the clipping circle
float initialRadius = (float) Math.hypot(cx, cy);

// create the animation (the final radius is zero)
Animator anim =
    ViewAnimationUtils.createCircularReveal(myView, cx, cy, initialRadius, 0);

// make the view invisible when the animation is done
anim.addListener(new AnimatorListenerAdapter() {
    &#64;Override
    public void onAnimationEnd(Animator animation) {
        super.onAnimationEnd(animation);
        myView.setVisibility(View.INVISIBLE);
    }
});

// start the animation
anim.start();
</pre>


<h2 id="Transitions">Customize Activity Transitions</h2>

<!-- shared transition video -->
<div style="width:290px;margin-left:35px;float:right">
  <div class="framed-nexus5-port-span-5">
  <video class="play-on-hover" autoplay="">
    <source src="{@docRoot}design/material/videos/ContactsAnim.mp4">
    <source src="{@docRoot}design/material/videos/ContactsAnim.webm">
    <source src="{@docRoot}design/material/videos/ContactsAnim.ogv">
  </video>
  </div>
  <div style="font-size:10pt;margin-left:20px;margin-bottom:30px">
    <p class="img-caption" style="margin-top:3px;margin-bottom:10px"><strong>Figure 1</strong> - A
    transition with shared elements.</p>
    <em>To replay the movie, click on the device screen</em>
  </div>
</div>

<p>Activity transitions in material design apps provide visual connections between different states
through motion and transformations between common elements. You can specify custom animations for
enter and exit transitions and for transitions of shared elements between activities.</p>

<ul>
<li>An <strong>enter</strong> transition determines how views in an activity enter the scene.
For example, in the <em>explode</em> enter transition, the views enter the scene from the outside
and fly in towards the center of the screen.</li>

<li>An <strong>exit</strong> transition determines how views in an activity exit the scene. For
  example, in the <em>explode</em> exit transition, the views exit the scene away from the
center.</li>

<li>A <strong>shared elements</strong> transition determines how views that are shared between
two activities transition between these activities. For example, if two activities have the same
image in different positions and sizes, the <em>changeImageTransform</em> shared element transition
translates and scales the image smoothly between these activities.</li>
</ul>

<p>Android 5.0 (API level 21) supports these enter and exit transitions:</p>

<ul>
<li><em>explode</em> - Moves views in or out from the center of the scene.</li>
<li><em>slide</em> - Moves views in or out from one of the edges of the scene.</li>
<li><em>fade</em> - Adds or removes a view from the scene by changing its opacity.</li>
</ul>

<p>Any transition that extends the {@link android.transition.Visibility} class is supported
as an enter or exit transition. For more information, see the API reference for the
{@link android.transition.Transition} class.</p>

<p>Android 5.0 (API level 21) also supports these shared elements transitions:</p>

<ul>
<li><em>changeBounds</em> - Animates the changes in layout bounds of target views.</li>
<li><em>changeClipBounds</em> - Animates the changes in clip bounds of target views.</li>
<li><em>changeTransform</em> - Animates the changes in scale and rotation of target views.</li>
<li><em>changeImageTransform</em> - Animates changes in size and scale of target images.</li>
</ul>

<p>When you enable activity transitions in your app, the default cross-fading transition is
activated between the entering and exiting activities.</p>

<img src="{@docRoot}training/material/images/SceneTransition.png" alt="" width="600" height="405"
     style="margin-top:20px"/>
<p class="img-caption">
  <strong>Figure 2</strong> - A scene transition with one shared element.
</p>

<h3 id="custom-trans">Specify custom transitions</h3>

<p>First, enable window content transitions with the <code>android:windowActivityTransitions</code>
attribute when you define a style that inherits from the material theme. You can also specify
enter, exit, and shared element transitions in your style definition:</p>

<pre>
&lt;style name="BaseAppTheme" parent="android:Theme.Material">
  &lt;!-- enable window content transitions -->
  &lt;item name="android:windowActivityTransitions">true&lt;/item>

  &lt;!-- specify enter and exit transitions -->
  &lt;item name="android:windowEnterTransition">@transition/explode&lt;/item>
  &lt;item name="android:windowExitTransition">@transition/explode&lt;/item>

  &lt;!-- specify shared element transitions -->
  &lt;item name="android:windowSharedElementEnterTransition">
    &#64;transition/change_image_transform&lt;/item>
  &lt;item name="android:windowSharedElementExitTransition">
    &#64;transition/change_image_transform&lt;/item>
&lt;/style>
</pre>

<p>The <code>change_image_transform</code> transition in this example is defined as follows:</p>

<pre>
&lt;!-- res/transition/change_image_transform.xml -->
&lt;!-- (see also Shared Transitions below) -->
&lt;transitionSet xmlns:android="http://schemas.android.com/apk/res/android">
  &lt;changeImageTransform/>
&lt;/transitionSet>
</pre>

<p>The <code>changeImageTransform</code> element corresponds to the
{@link android.transition.ChangeImageTransform} class. For more information, see the API
reference for {@link android.transition.Transition}.</p>

<p>To enable window content transitions in your code instead, call the
{@link android.view.Window#requestFeature Window.requestFeature()} method:</p>

<pre>
// inside your activity (if you did not enable transitions in your theme)
getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);

// set an exit transition
getWindow().setExitTransition(new Explode());
</pre>

<p>To specify transitions in your code, call these methods with a {@link
android.transition.Transition} object:</p>

<ul>
  <li>{@link android.view.Window#setEnterTransition Window.setEnterTransition()}</li>
  <li>{@link android.view.Window#setExitTransition Window.setExitTransition()}</li>
  <li>{@link android.view.Window#setSharedElementEnterTransition
      Window.setSharedElementEnterTransition()}</li>
  <li>{@link android.view.Window#setSharedElementExitTransition
      Window.setSharedElementExitTransition()}</li>
</ul>

<p>The {@link android.view.Window#setExitTransition setExitTransition()} and {@link
android.view.Window#setSharedElementExitTransition setSharedElementExitTransition()} methods define
the exit transition for the calling activity. The {@link android.view.Window#setEnterTransition
setEnterTransition()} and {@link android.view.Window#setSharedElementEnterTransition
setSharedElementEnterTransition()} methods define the enter transition for the called activity.</p>

<p>To get the full effect of a transition, you must enable window content transitions on both the
calling and called activities. Otherwise, the calling activity will start the exit transition,
but then you'll see a window transition (like scale or fade).</p>

<p>To start an enter transition as soon as possible, use the
{@link android.view.Window#setAllowEnterTransitionOverlap Window.setAllowEnterTransitionOverlap()}
method on the called activity. This lets you have more dramatic enter transitions.</p>

<h3>Start an activity using transitions</h3>

<p>If you enable transitions and set an exit transition for an activity, the transition is activated
when you launch another activity as follows:</p>

<pre>
startActivity(intent,
              ActivityOptions.makeSceneTransitionAnimation(this).toBundle());
</pre>

<p>If you have set an enter transition for the second activity, the transition is also activated
when the activity starts. To disable transitions when you start another activity, provide
a <code>null</code> options bundle.</p>

<h3>Start an activity with a shared element</h3>

<p>To make a screen transition animation between two activities that have a shared element:</p>

<ol>
<li>Enable window content transitions in your theme.</li>
<li>Specify a shared elements transition in your style.</li>
<li>Define your transition as an XML resource.</li>
<li>Assign a common name to the shared elements in both layouts with the
    <code>android:transitionName</code> attribute.</li>
<li>Use the {@link android.app.ActivityOptions#makeSceneTransitionAnimation
ActivityOptions.makeSceneTransitionAnimation()} method.</li>
</ol>

<pre>
// get the element that receives the click event
final View imgContainerView = findViewById(R.id.img_container);

// get the common element for the transition in this activity
final View androidRobotView = findViewById(R.id.image_small);

// define a click listener
imgContainerView.setOnClickListener(new View.OnClickListener() {
    &#64;Override
    public void onClick(View view) {
        Intent intent = new Intent(this, Activity2.class);
        // create the transition animation - the images in the layouts
        // of both activities are defined with android:transitionName="robot"
        ActivityOptions options = ActivityOptions
            .makeSceneTransitionAnimation(this, androidRobotView, "robot");
        // start the new activity
        startActivity(intent, options.toBundle());
    }
});
</pre>

<p>For shared dynamic views that you generate in your code, use the
{@link android.view.View#setTransitionName View.setTransitionName()} method to specify a common
element name in both activities.</p>

<p>To reverse the scene transition animation when you finish the second activity, call the
{@link android.app.Activity#finishAfterTransition Activity.finishAfterTransition()}
method instead of {@link android.app.Activity#finish Activity.finish()}.</p>

<h3>Start an activity with multiple shared elements</h3>

<p>To make a scene transition animation between two activities that have more than one shared
element, define the shared elements in both layouts with the <code>android:transitionName</code>
attribute (or use the {@link android.view.View#setTransitionName View.setTransitionName()} method
in both activities), and create an {@link android.app.ActivityOptions} object as follows:</p>

<pre>
ActivityOptions options = ActivityOptions.makeSceneTransitionAnimation(this,
        Pair.create(view1, "agreedName1"),
        Pair.create(view2, "agreedName2"));
</pre>


<h2 id="CurvedMotion">Use Curved Motion</h2>

<p>Animations in material design rely on curves for time interpolation and spatial movement
patterns. With Android 5.0 (API level 21) and above, you can define custom timing curves and
curved motion patterns for animations.</p>

<p>The {@link android.view.animation.PathInterpolator} class is a new interpolator based on a
Bézier curve or a {@link android.graphics.Path} object. This interpolator specifies a motion curve
in a 1x1 square, with anchor points at (0,0) and (1,1) and control points as specified using the
constructor arguments. You can also define a path interpolator as an XML resource:</p>

<pre>
&lt;pathInterpolator xmlns:android="http://schemas.android.com/apk/res/android"
    android:controlX1="0.4"
    android:controlY1="0"
    android:controlX2="1"
    android:controlY2="1"/>
</pre>

<p>The system provides XML resources for the three basic curves in the material design
specification:</p>

<ul>
  <li><code>&#64;interpolator/fast_out_linear_in.xml</code></li>
  <li><code>&#64;interpolator/fast_out_slow_in.xml</code></li>
  <li><code>&#64;interpolator/linear_out_slow_in.xml</code></li>
</ul>

<p>You can pass a {@link android.view.animation.PathInterpolator} object to the {@link
android.animation.Animator#setInterpolator Animator.setInterpolator()} method.</p>

<p>The {@link android.animation.ObjectAnimator} class has new constructors that enable you to animate
coordinates along a path using two or more properties at once. For example, the following animator
uses a {@link android.graphics.Path} object to animate the X and Y properties of a view:</p>

<pre>
ObjectAnimator mAnimator;
mAnimator = ObjectAnimator.ofFloat(view, View.X, View.Y, path);
...
mAnimator.start();
</pre>


<h2 id="ViewState">Animate View State Changes</h2>

<p>The {@link android.animation.StateListAnimator} class lets you define animators that run when
the state of a view changes. The following example shows how to define an {@link
android.animation.StateListAnimator}  as an XML resource:</p>

<pre>
&lt;!-- animate the translationZ property of a view when pressed -->
&lt;selector xmlns:android="http://schemas.android.com/apk/res/android">
  &lt;item android:state_pressed="true">
    &lt;set>
      &lt;objectAnimator android:propertyName="translationZ"
        android:duration="@android:integer/config_shortAnimTime"
        android:valueTo="2dp"
        android:valueType="floatType"/>
        &lt;!-- you could have other objectAnimator elements
             here for "x" and "y", or other properties -->
    &lt;/set>
  &lt;/item>
  &lt;item android:state_enabled="true"
    android:state_pressed="false"
    android:state_focused="true">
    &lt;set>
      &lt;objectAnimator android:propertyName="translationZ"
        android:duration="100"
        android:valueTo="0"
        android:valueType="floatType"/>
    &lt;/set>
  &lt;/item>
&lt;/selector>
</pre>

<p>
  To attach custom view state animations to a view, define an animator using
  the <code>selector</code> element in an XML resource file as in this example,
  and assign it to your view with the <code>android:stateListAnimator</code>
  attribute. To assign a state list animator to a view in your code, use the
  {@link android.animation.AnimatorInflater#loadStateListAnimator
  AnimatorInflater.loadStateListAnimator()} method, and assign the animator to
  your view with the {@link android.view.View#setStateListAnimator
  View.setStateListAnimator()} method.
</p>

<p>When your theme extends the material theme, buttons have a Z animation by default. To avoid this
behavior in your buttons, set the <code>android:stateListAnimator</code> attribute to
<code>@null</code>.</p>

<p>The {@link android.graphics.drawable.AnimatedStateListDrawable} class lets you create drawables
that show animations between state changes of the associated view. Some of the system widgets in
Android 5.0 use these animations by default. The following example shows how
to define an {@link android.graphics.drawable.AnimatedStateListDrawable} as an XML resource:</p>

<pre>
&lt;!-- res/drawable/myanimstatedrawable.xml -->
&lt;animated-selector
    xmlns:android="http://schemas.android.com/apk/res/android">

    &lt;!-- provide a different drawable for each state-->
    &lt;item android:id="@+id/pressed" android:drawable="@drawable/drawableP"
        android:state_pressed="true"/>
    &lt;item android:id="@+id/focused" android:drawable="@drawable/drawableF"
        android:state_focused="true"/>
    &lt;item android:id="@id/default"
        android:drawable="@drawable/drawableD"/>

    &lt;!-- specify a transition -->
    &lt;transition android:fromId="@+id/default" android:toId="@+id/pressed">
        &lt;animation-list>
            &lt;item android:duration="15" android:drawable="@drawable/dt1"/>
            &lt;item android:duration="15" android:drawable="@drawable/dt2"/>
            ...
        &lt;/animation-list>
    &lt;/transition>
    ...
&lt;/animated-selector>
</pre>


<h2 id="AnimVector">Animate Vector Drawables</h2>

<p><a href="{@docRoot}training/material/drawables.html#VectorDrawables">Vector Drawables</a> are
scalable without losing definition. The {@link android.graphics.drawable.AnimatedVectorDrawable}
class lets you animate the properties of a vector drawable.</p>

<p>You normally define animated vector drawables in three XML files:</p>

<ul>
<li>A vector drawable with the <code>&lt;vector&gt;</code> element in
<code>res/drawable/</code></li>
<li>An animated vector drawable with the <code>&lt;animated-vector&gt;</code> element in
<code>res/drawable/</code></li>
<li>One or more object animators with the <code>&lt;objectAnimator&gt;</code> element in
<code>res/anim/</code></li>
</ul>

<p>Animated vector drawables can animate the attributes of the <code>&lt;group&gt;</code> and
<code>&lt;path&gt;</code> elements. The <code>&lt;group&gt;</code> elements defines a set of
paths or subgroups, and the <code>&lt;path&gt;</code> element defines paths to be drawn.</p>

<p>When you define a vector drawable that you want to animate, use the <code>android:name</code>
attribute to assign a unique name to groups and paths, so you can refer to them from your animator
definitions. For example:</p>

<pre>
&lt;!-- res/drawable/vectordrawable.xml -->
&lt;vector xmlns:android="http://schemas.android.com/apk/res/android"
    android:height="64dp"
    android:width="64dp"
    android:viewportHeight="600"
    android:viewportWidth="600">
    &lt;group
        <strong>android:name="rotationGroup"</strong>
        android:pivotX="300.0"
        android:pivotY="300.0"
        android:rotation="45.0" >
        &lt;path
            <strong>android:name="v"</strong>
            android:fillColor="#000000"
            android:pathData="M300,70 l 0,-70 70,70 0,0 -70,70z" />
    &lt;/group>
&lt;/vector>
</pre>

<p>The animated vector drawable definition refers to the groups and paths in the vector drawable
by their names:</p>

<pre>
&lt;!-- res/drawable/animvectordrawable.xml -->
&lt;animated-vector xmlns:android="http://schemas.android.com/apk/res/android"
  android:drawable="@drawable/vectordrawable" >
    &lt;target
        android:name="rotationGroup"
        android:animation="@anim/rotation" />
    &lt;target
        android:name="v"
        android:animation="@anim/path_morph" />
&lt;/animated-vector>
</pre>

<p>The animation definitions represent {@link android.animation.ObjectAnimator} or {@link
android.animation.AnimatorSet} objects. The first animator in this example rotates the target
group 360 degrees:</p>

<pre>
&lt;!-- res/anim/rotation.xml -->
&lt;objectAnimator
    android:duration="6000"
    android:propertyName="rotation"
    android:valueFrom="0"
    android:valueTo="360" />
</pre>

<p>The second animator in this example morphs the vector drawable's path from one shape to
another. Both paths must be compatible for morphing: they must have the same number of commands
and the same number of parameters for each command.</p>

<pre>
&lt;!-- res/anim/path_morph.xml -->
&lt;set xmlns:android="http://schemas.android.com/apk/res/android">
    &lt;objectAnimator
        android:duration="3000"
        android:propertyName="pathData"
        android:valueFrom="M300,70 l 0,-70 70,70 0,0   -70,70z"
        android:valueTo="M300,70 l 0,-70 70,0  0,140 -70,0 z"
        android:valueType="pathType" />
&lt;/set>
</pre>

<p>For more information, see the API reference for {@link
android.graphics.drawable.AnimatedVectorDrawable}.</p>