page.title=Animations @jd:body

In this document

Touch Feedback
Reveal Effect
Activity Transitions
Curved Motion
View State Changes
Drawable Tinting

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 the Android L Developer Preview provides additional APIs that let you customize these animations and create new ones:

Touch feedback
Reveal effect
Activity transitions
Curved motion
View state changes

Touch Feedback

In the Android L Developer Preview the default touch feedback animations for buttons use the new RippleDrawable class, which transitions between different states with a ripple effect.

To use this functionality in your custom views, create a RippleDrawable and set it as the background of your view. You can define a RippleDrawable as an XML resource using the ripple element.

Reveal Effect

The View.createRevealAnimator method enables you to animate a clipping circle to reveal or hide a view.

To reveal a previously invisible view using this effect:

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

// get the center for the clipping circle
int cx = (myView.getLeft() + myView.getRight()) / 2;
int cy = (myView.getTop() + myView.getBottom()) / 2;

// get the final radius for the clipping circle
int finalRadius = myView.getWidth();

// create and start the animator for this view
// (the start radius is zero)
ValueAnimator anim = myView.createRevealAnimator(cx, cy, 0, finalRadius);
anim.start();

To hide a previously visible view using this effect:

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

// get the center for the clipping circle
int cx = (myView.getLeft() + myView.getRight()) / 2;
int cy = (myView.getTop() + myView.getBottom()) / 2;

// get the initial radius for the clipping circle
int initialRadius = myView.getWidth();

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

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

// start the animation
anim.start();

Activity Transitions

The Android L Developer Preview enables your app to customize the default animations for activity transitions. You can specify custom animations for enter and exit transitions and for transitions of shared elements between activities.

An enter transition determines how views in an activity enter the scene. For example, in the explode enter transition the views enter the scene from outside and fly in towards the center of the screen.
An exit transition determines how views in an activity exit the scene. For example, in the explode exit transition the views exit the scene away from the center.
A shared elements 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 moveImage shared element transition translates and scales the image smoothly between these activities.

Figure 1 - A scene transition with one shared element.

Specify custom transitions

First, enable window content transitions with the android:windowContentTransitions attribute when you define a style that inherits from the material theme:

<style name="BaseAppTheme" parent="android:Theme.Material">
  <!-- enable window content transitions -->
  <item name="android:windowContentTransitions">true</item>

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

  <!-- specify shared element transitions -->
  <item name="android:windowSharedElementEnterTransition">
    @transition/move_image</item>
  <item name="android:windowSharedElementExitTransition">
    @transition/move_image</item>
</style>

You can also specify enter, exit, and shared element transitions in your style definition. The move_image transition in this example is defined as follows:

<!-- res/transition/move_image.xml -->
<!-- (see also Shared Transitions below) -->
<transitionSet xmlns:android="http://schemas.android.com/apk/res/android">
  <moveImage>
    <targets>
      <!-- shared view in the first activity -->
      <target android:targetId="@id/image_small" />
      <!-- shared view in the second activity -->
      <target android:targetId="@id/image_big" />
    </targets>
  </moveImage>
</transitionSet>

The moveImage element corresponds to the android.transition.MoveImage class. For more information, see the API reference for android.transition.Transition.

To enable window content transitions in your code instead, call the Window.requestFeature method:

// inside your activity
getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);

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

To specify transitions in your code, call these methods with a Transition object:

Window.setEnterTransition
Window.setExitTransition
Window.setSharedElementEnterTransition
Window.setSharedElementExitTransition

Start an activity using transitions

If you enable transitions and set an exit transition for an activity, the transition is activated when you launch another activity with the startActivity method. If you have set an enter transition for the second activity, the transition is also activated when the activity starts.

Shared elements transitions

To make a screne transition animation between two activities that have a shared element:

Enable window content transitions in your style.
Specify a shared elements transition in your style.
Define your transition as an XML resource specifying the IDs of the target views.
Assign a common name to the shared elements in both layouts with the android:viewName attribute.
Use the ActivityOptions.makeSceneTransitionAnimation method.

// 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.android_robot_img);

// define a click listener
imgContainerView.setOnClickListener(new View.OnClickListener() {
    @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:viewName="robot"
        ActivityOptions options = ActivityOptions
            .makeSceneTransitionAnimation(this, androidRobotView, "robot");
        // start the new activity
        startActivity(intent, options.toBundle());
    }
});

For shared dynamic views that you generate in your code, use the View.setViewName method to specify a common element name in both activities.

Multiple shared elements

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 android:viewName attribute (or use the View.setViewName in both activities), and create an ActivityOptions object as follows:

ActivityOptions options = ActivityOptions.makeSceneTransitionAnimation(this,
    new Pair[] {
        Pair.create(view1, "agreedName1"),
        Pair.create(view2, "agreedName2"),
        ...
    }
);

Curved Motion

Animations in material design rely on curves for time interpolation and spatial movement patterns. The Android L Developer Preview provides new APIs that enable you to define custom timing curves and curved motion patterns for animations.

The PathInterpolator class is a new interpolator based on a Bézier curve or a 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 PathInterpolator as an XML resource:

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

The Android L Developer Preview provides XML resources for the three basic curves in the material design specification:

@interpolator/fast_out_linear_in.xml
@interpolator/fast_out_slow_in.xml
@interpolator/linear_out_slow_in.xml

You can pass a PathInterpolator object to the Animation.setInterpolation method.

The 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 Path object to animate the X and Y properties of a view:

ObjectAnimator mAnimator;
mAnimator = ObjectAnimator.ofFloat(view, View.X, View.Y, path);
...
mAnimator.start();

View State Changes

The new StateListAnimator class lets you define animators that run when the state of a view changes. The following example shows how to define an StateListAnimator as an XML resource:

<!-- animate the elevation property of a view when pressed -->
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_pressed="true">
    <set>
      <objectAnimator android:propertyName="elevation"
        android:duration="100"
        android:valueTo="60"
        android:valueType="floatType"/>
        <!-- you could have other objectAnimator elements
             here for "x" and "y", or other properties -->
    </set>
  </item>
  <item android:state_enabled="true"
    android:state_pressed="false"
    android:state_focused="true">
    <set>
      <objectAnimator android:propertyName="elevation"
        android:duration="100"
        android:valueTo="10"
        android:valueType="floatType"/>
    </set>
  </item>
</selector>

The new AnimatedStateListDrawable class lets you create drawables that show animations between state changes of the associated view. Some of the system widgets in the Android L Developer Preview use these animations by default. The following example shows how to define an AnimatedStateListDrawable as an XML resource:

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

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

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

Drawable Tinting

The Android L Developer Preview enables you to define bitmaps as an alpha mask and to tint them using a color resource or a theme attribute that resolves to a color resource. You can create these assets only once and color them automatically to match your theme.

To apply a tint to a bitmap in your code, use the setTint method in these classes:

PaintDrawable
NinePatchDrawable
RippleDrawable

In your layouts, use the android:tint attribute instead.

The setTint method also lets you set the tint blending mode for NinePatchDrawable and RippleDrawable objects in your code. To set the tint mode in your layouts, use the android:tintMode attribute.