ValueAnimator

open class ValueAnimator : Animator, AnimationFrameCallback
kotlin.Any
   ↳ androidx.core.animation.Animator
   ↳ androidx.core.animation.ValueAnimator

This class provides a simple timing engine for running animations which calculate animated values and set them on target objects.

There is a single timing pulse that all animations use. It runs in a custom handler to ensure that property changes happen on the UI thread.

By default, ValueAnimator uses non-linear time interpolation, via the AccelerateDecelerateInterpolator class, which accelerates into and decelerates out of an animation. This behavior can be changed by calling ValueAnimator#setInterpolator(Interpolator).

Animators can be created from either code or resource files. Here is an example of a ValueAnimator resource file:

ValueAnimator also supports the use of a combination of PropertyValuesHolder and Keyframe resource tags to create a multi-step animation. Note that you can specify explicit fractional values (from 0 to 1) for each keyframe to determine when, in the overall duration, the animation should arrive at that value. Alternatively, you can leave the fractions off and the keyframes will be equally distributed within the total duration:

Summary

Constants
static Int

This value used used with the setRepeatCount(int) property to repeat the animation indefinitely.

static Int

When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation restarts from the beginning.

static Int

When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation reverses direction on every iteration.

Inherited constants
Public constructors

Creates a new ValueAnimator object.

Public methods
open static Boolean

Returns whether animators are currently enabled, system-wide.

open Unit

open ValueAnimator

open Unit
end()

open Float

Returns the current animation fraction, which is the elapsed/interpolated fraction used in the most recent frame update on the animation.

open Any

The most recent value calculated by this ValueAnimator when there is just one property being animated.

open Any?
getAnimatedValue(@NonNull propertyName: String)

The most recent value calculated by this ValueAnimator for propertyName.

open Long

Gets the current position of the animation in time, which is equal to the current time minus the time that the animation started.

open Long

Gets the length of the animation.

open static Long

The amount of time, in milliseconds, between each frame of the animation.

open Interpolator?

Returns the timing interpolator that this ValueAnimator uses.

open String

Returns the name of this animator for debugging purposes.

open Int

Defines how many times the animation should repeat.

open Int

Defines what this animation should do when it reaches the end.

open Long

The amount of time, in milliseconds, to delay starting the animation after start() is called.

open Long

open Array<PropertyValuesHolder!>

Returns the values that this ValueAnimator animates between.

open Boolean

open Boolean

open static ValueAnimator
ofArgb(@NonNull vararg values: Int)

Constructs and returns a ValueAnimator that animates between color values.

open static ValueAnimator
ofFloat(@NonNull vararg values: Float)

Constructs and returns a ValueAnimator that animates between float values.

open static ValueAnimator
ofInt(@NonNull vararg values: Int)

Constructs and returns a ValueAnimator that animates between int values.

open static ValueAnimator
ofObject(@NonNull evaluator: TypeEvaluator<Any!>, @NonNull vararg values: Any!)

Constructs and returns a ValueAnimator that animates between Object values.

open static ValueAnimator
ofPropertyValuesHolder(@NonNull vararg values: PropertyValuesHolder!)

Constructs and returns a ValueAnimator that animates between the values specified in the PropertyValuesHolder objects.

open Unit

open Unit

open Unit

Plays the ValueAnimator in reverse.

open Unit

Sets the position of the animation to the specified fraction.

open Unit

Sets the position of the animation to the specified point in time.

open ValueAnimator
setDuration(duration: Long)

Sets the length of the animation.

open Unit
setEvaluator(@NonNull value: TypeEvaluator<Any!>)

The type evaluator to be used when calculating the animated values of this animation.

open Unit
setFloatValues(@NonNull vararg values: Float)

Sets float values that will be animated between.

open static Unit
setFrameDelay(frameDelay: Long)

The amount of time, in milliseconds, between each frame of the animation.

open Unit
setIntValues(@NonNull vararg values: Int)

Sets int values that will be animated between.

open Unit
setInterpolator(@Nullable value: Interpolator?)

The interpolator used in calculating the elapsed fraction of this animation.

open Unit
setNameForTrace(@NonNull animationName: String)

Sets a name for the animation to show up in the systrace.

open Unit
setObjectValues(@NonNull vararg values: Any!)

Sets the values to animate between for this animation.

open Unit

Sets how many times the animation should be repeated.

open Unit

Defines what this animation should do when it reaches the end.

open Unit
setStartDelay(startDelay: Long)

The amount of time, in milliseconds, to delay starting the animation after start() is called.

open Unit
setValues(@NonNull vararg values: PropertyValuesHolder!)

Sets the values, per property, being animated between.

open Unit

open String

Inherited functions

Constants

INFINITE

static val INFINITE: Int

This value used used with the setRepeatCount(int) property to repeat the animation indefinitely.

Value: -1

RESTART

static val RESTART: Int

When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation restarts from the beginning.

Value: 1

REVERSE

static val REVERSE: Int

When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation reverses direction on every iteration.

Value: 2

Public constructors

<init>

ValueAnimator()

Creates a new ValueAnimator object. This default constructor is primarily for use internally; the factory methods which take parameters are more generally useful.

Public methods

areAnimatorsEnabled

open static fun areAnimatorsEnabled(): Boolean

Returns whether animators are currently enabled, system-wide. By default, all animators are enabled. This can change if either the user sets a Developer Option to set the animator duration scale to 0 or by Battery Savery mode being enabled (which disables all animations).

Developers should not typically need to call this method, but should an app wish to show a different experience when animators are disabled, this return value can be used as a decider of which experience to offer.

Return
Boolean boolean Whether animators are currently enabled. The default value is true.

cancel

open fun cancel(): Unit

clone

@NonNull open fun clone(): ValueAnimator

end

open fun end(): Unit

getAnimatedFraction

open fun getAnimatedFraction(): Float

Returns the current animation fraction, which is the elapsed/interpolated fraction used in the most recent frame update on the animation.

Return
Float Elapsed/interpolated fraction of the animation.

getAnimatedValue

@NonNull open fun getAnimatedValue(): Any

The most recent value calculated by this ValueAnimator when there is just one property being animated. This value is only sensible while the animation is running. The main purpose for this read-only property is to retrieve the value from the ValueAnimator during a call to androidx.core.animation.Animator.AnimatorUpdateListener#onAnimationUpdate(Animator), which is called during each animation frame, immediately after the value is calculated.

Return
Any animatedValue The value most recently calculated by this ValueAnimator for the single property being animated. If there are several properties being animated (specified by several PropertyValuesHolder objects in the constructor), this function returns the animated value for the first of those objects.

getAnimatedValue

@Nullable open fun getAnimatedValue(@NonNull propertyName: String): Any?

The most recent value calculated by this ValueAnimator for propertyName. The main purpose for this read-only property is to retrieve the value from the ValueAnimator during a call to androidx.core.animation.Animator.AnimatorUpdateListener#onAnimationUpdate(Animator), which is called during each animation frame, immediately after the value is calculated.

Return
Any? animatedValue The value most recently calculated for the named property by this ValueAnimator.

getCurrentPlayTime

open fun getCurrentPlayTime(): Long

Gets the current position of the animation in time, which is equal to the current time minus the time that the animation started. An animation that is not yet started will return a value of zero, unless the animation has has its play time set via setCurrentPlayTime(long) or setCurrentFraction(float), in which case it will return the time that was set.

Return
Long The current position in time of the animation.

getDuration

open fun getDuration(): Long

Gets the length of the animation. The default duration is 300 milliseconds.

Return
Long The length of the animation, in milliseconds.

getFrameDelay

open static fun getFrameDelay(): Long

The amount of time, in milliseconds, between each frame of the animation. This is a requested time that the animation will attempt to honor, but the actual delay between frames may be different, depending on system load and capabilities. This is a static function because the same delay will be applied to all animations, since they are all run off of a single timing loop. The frame delay may be ignored when the animation system uses an external timing source, such as the display refresh rate (vsync), to govern animations. Note that this method should be called from the same thread that start() is called in order to check the frame delay for that animation. A runtime exception will be thrown if the calling thread does not have a Looper.

Return
Long the requested time between frames, in milliseconds

getInterpolator

@Nullable open fun getInterpolator(): Interpolator?

Returns the timing interpolator that this ValueAnimator uses.

Return
Interpolator? The timing interpolator for this ValueAnimator.

getNameForTrace

@NonNull open fun getNameForTrace(): String

Returns the name of this animator for debugging purposes.

getRepeatCount

open fun getRepeatCount(): Int

Defines how many times the animation should repeat. The default value is 0.

Return
Int the number of times the animation should repeat, or INFINITE

getRepeatMode

open fun getRepeatMode(): Int

Defines what this animation should do when it reaches the end.

Return
Int either one of REVERSE or RESTART

getStartDelay

open fun getStartDelay(): Long

The amount of time, in milliseconds, to delay starting the animation after start() is called.

Return
Long the number of milliseconds to delay running the animation

getTotalDuration

open fun getTotalDuration(): Long

getValues

@NonNull open fun getValues(): Array<PropertyValuesHolder!>

Returns the values that this ValueAnimator animates between. These values are stored in PropertyValuesHolder objects, even if the ValueAnimator was created with a simple list of value objects instead.

Return
Array<PropertyValuesHolder!> PropertyValuesHolder[] An array of PropertyValuesHolder objects which hold the values, per property, that define the animation.

isRunning

open fun isRunning(): Boolean

isStarted

open fun isStarted(): Boolean

ofArgb

@NonNull open static fun ofArgb(@NonNull vararg values: Int): ValueAnimator

Constructs and returns a ValueAnimator that animates between color values. A single value implies that that value is the one being animated to. However, this is not typically useful in a ValueAnimator object because there is no way for the object to determine the starting value for the animation (unlike ObjectAnimator, which can derive that value from the target object and property being animated). Therefore, there should typically be two or more values.

Parameters
values Int: A set of values that the animation will animate between over time.
Return
ValueAnimator A ValueAnimator object that is set up to animate between the given values.

ofFloat

@NonNull open static fun ofFloat(@NonNull vararg values: Float): ValueAnimator

Constructs and returns a ValueAnimator that animates between float values. A single value implies that that value is the one being animated to. However, this is not typically useful in a ValueAnimator object because there is no way for the object to determine the starting value for the animation (unlike ObjectAnimator, which can derive that value from the target object and property being animated). Therefore, there should typically be two or more values.

Parameters
values Float: A set of values that the animation will animate between over time.
Return
ValueAnimator A ValueAnimator object that is set up to animate between the given values.

ofInt

@NonNull open static fun ofInt(@NonNull vararg values: Int): ValueAnimator

Constructs and returns a ValueAnimator that animates between int values. A single value implies that that value is the one being animated to. However, this is not typically useful in a ValueAnimator object because there is no way for the object to determine the starting value for the animation (unlike ObjectAnimator, which can derive that value from the target object and property being animated). Therefore, there should typically be two or more values.

Parameters
values Int: A set of values that the animation will animate between over time.
Return
ValueAnimator A ValueAnimator object that is set up to animate between the given values.

ofObject

@NonNull open static fun ofObject(
    @NonNull evaluator: TypeEvaluator<Any!>,
    @NonNull vararg values: Any!
): ValueAnimator

Constructs and returns a ValueAnimator that animates between Object values. A single value implies that that value is the one being animated to. However, this is not typically useful in a ValueAnimator object because there is no way for the object to determine the starting value for the animation (unlike ObjectAnimator, which can derive that value from the target object and property being animated). Therefore, there should typically be two or more values.

Note: The Object values are stored as references to the original objects, which means that changes to those objects after this method is called will affect the values on the animator. If the objects will be mutated externally after this method is called, callers should pass a copy of those objects instead.

Since ValueAnimator does not know how to animate between arbitrary Objects, this factory method also takes a TypeEvaluator object that the ValueAnimator will use to perform that interpolation.

Parameters
evaluator TypeEvaluator<Any!>: A TypeEvaluator that will be called on each animation frame to provide the necessary interpolation between the Object values to derive the animated value.
values Any!: A set of values that the animation will animate between over time.
Return
ValueAnimator A ValueAnimator object that is set up to animate between the given values.

ofPropertyValuesHolder

@NonNull open static fun ofPropertyValuesHolder(@NonNull vararg values: PropertyValuesHolder!): ValueAnimator

Constructs and returns a ValueAnimator that animates between the values specified in the PropertyValuesHolder objects.

Parameters
values PropertyValuesHolder!: A set of PropertyValuesHolder objects whose values will be animated between over time.
Return
ValueAnimator A ValueAnimator object that is set up to animate between the given values.

pause

open fun pause(): Unit

resume

open fun resume(): Unit

reverse

open fun reverse(): Unit

Plays the ValueAnimator in reverse. If the animation is already running, it will stop itself and play backwards from the point reached when reverse was called. If the animation is not currently running, then it will start from the end and play backwards. This behavior is only set for the current animation; future playing of the animation will use the default behavior of playing forward.

setCurrentFraction

open fun setCurrentFraction(fraction: Float): Unit

Sets the position of the animation to the specified fraction. This fraction should be between 0 and the total fraction of the animation, including any repetition. That is, a fraction of 0 will position the animation at the beginning, a value of 1 at the end, and a value of 2 at the end of a reversing animator that repeats once. If the animation has not yet been started, then it will not advance forward after it is set to this fraction; it will simply set the fraction to this value and perform any appropriate actions based on that fraction. If the animation is already running, then setCurrentFraction() will set the current fraction to this value and continue playing from that point. androidx.core.animation.Animator.AnimatorListener events are not called due to changing the fraction; those events are only processed while the animation is running.

Parameters
fraction Float: The fraction to which the animation is advanced or rewound. Values outside the range of 0 to the maximum fraction for the animator will be clamped to the correct range.

setCurrentPlayTime

open fun setCurrentPlayTime(playTime: Long): Unit

Sets the position of the animation to the specified point in time. This time should be between 0 and the total duration of the animation, including any repetition. If the animation has not yet been started, then it will not advance forward after it is set to this time; it will simply set the time to this value and perform any appropriate actions based on that time. If the animation is already running, then setCurrentPlayTime() will set the current playing time to this value and continue playing from that point.

Parameters
playTime Long: The time, in milliseconds, to which the animation is advanced or rewound.

setDuration

@NonNull open fun setDuration(duration: Long): ValueAnimator

Sets the length of the animation. The default duration is 300 milliseconds.

Parameters
duration Long: The length of the animation, in milliseconds. This value cannot be negative.
Return
ValueAnimator ValueAnimator The object called with setDuration(). This return value makes it easier to compose statements together that construct and then set the duration, as in ValueAnimator.ofInt(0, 10).setDuration(500).start().

setEvaluator

open fun setEvaluator(@NonNull value: TypeEvaluator<Any!>): Unit

The type evaluator to be used when calculating the animated values of this animation. The system will automatically assign a float or int evaluator based on the type of startValue and endValue in the constructor. But if these values are not one of these primitive types, or if different evaluation is desired (such as is necessary with int values that represent colors), a custom evaluator needs to be assigned. For example, when running an animation on color values, the ArgbEvaluator should be used to get correct RGB color interpolation.

If this ValueAnimator has only one set of values being animated between, this evaluator will be used for that set. If there are several sets of values being animated, which is the case if PropertyValuesHolder objects were set on the ValueAnimator, then the evaluator is assigned just to the first PropertyValuesHolder object.

Parameters
value TypeEvaluator<Any!>: the evaluator to be used this animation

setFloatValues

open fun setFloatValues(@NonNull vararg values: Float): Unit

Sets float values that will be animated between. A single value implies that that value is the one being animated to. However, this is not typically useful in a ValueAnimator object because there is no way for the object to determine the starting value for the animation (unlike ObjectAnimator, which can derive that value from the target object and property being animated). Therefore, there should typically be two or more values.

If there are already multiple sets of values defined for this ValueAnimator via more than one PropertyValuesHolder object, this method will set the values for the first of those objects.

Parameters
values Float: A set of values that the animation will animate between over time.

setFrameDelay

open static fun setFrameDelay(frameDelay: Long): Unit

The amount of time, in milliseconds, between each frame of the animation. This is a requested time that the animation will attempt to honor, but the actual delay between frames may be different, depending on system load and capabilities. This is a static function because the same delay will be applied to all animations, since they are all run off of a single timing loop. The frame delay may be ignored when the animation system uses an external timing source, such as the display refresh rate (vsync), to govern animations. Note that this method should be called from the same thread that start() is called in order to have the new frame delay take effect on that animation. A runtime exception will be thrown if the calling thread does not have a Looper.

Parameters
frameDelay Long: the requested time between frames, in milliseconds

setIntValues

open fun setIntValues(@NonNull vararg values: Int): Unit

Sets int values that will be animated between. A single value implies that that value is the one being animated to. However, this is not typically useful in a ValueAnimator object because there is no way for the object to determine the starting value for the animation (unlike ObjectAnimator, which can derive that value from the target object and property being animated). Therefore, there should typically be two or more values.

If there are already multiple sets of values defined for this ValueAnimator via more than one PropertyValuesHolder object, this method will set the values for the first of those objects.

Parameters
values Int: A set of values that the animation will animate between over time.

setInterpolator

open fun setInterpolator(@Nullable value: Interpolator?): Unit

The interpolator used in calculating the elapsed fraction of this animation. The interpolator determines whether the animation runs with linear or non-linear motion, such as acceleration and deceleration. The default value is AccelerateDecelerateInterpolator

Parameters
value Interpolator?: the interpolator to be used by this animation. A value of null will result in linear interpolation.

setNameForTrace

open fun setNameForTrace(@NonNull animationName: String): Unit

Sets a name for the animation to show up in the systrace. This makes a particular animation identifiable in the systrace.

Parameters
animationName String: A name for the animation to make the instance identifiable in systrace

setObjectValues

open fun setObjectValues(@NonNull vararg values: Any!): Unit

Sets the values to animate between for this animation. A single value implies that that value is the one being animated to. However, this is not typically useful in a ValueAnimator object because there is no way for the object to determine the starting value for the animation (unlike ObjectAnimator, which can derive that value from the target object and property being animated). Therefore, there should typically be two or more values.

Note: The Object values are stored as references to the original objects, which means that changes to those objects after this method is called will affect the values on the animator. If the objects will be mutated externally after this method is called, callers should pass a copy of those objects instead.

If there are already multiple sets of values defined for this ValueAnimator via more than one PropertyValuesHolder object, this method will set the values for the first of those objects.

There should be a TypeEvaluator set on the ValueAnimator that knows how to interpolate between these value objects. ValueAnimator only knows how to interpolate between the primitive types specified in the other setValues() methods.

Parameters
values Any!: The set of values to animate between.

setRepeatCount

open fun setRepeatCount(value: Int): Unit

Sets how many times the animation should be repeated. If the repeat count is 0, the animation is never repeated. If the repeat count is greater than 0 or INFINITE, the repeat mode will be taken into account. The repeat count is 0 by default.

Parameters
value Int: the number of times the animation should be repeated

setRepeatMode

open fun setRepeatMode(value: Int): Unit

Defines what this animation should do when it reaches the end. This setting is applied only when the repeat count is either greater than 0 or INFINITE. Defaults to RESTART.

Parameters
value Int: RESTART or REVERSE

setStartDelay

open fun setStartDelay(startDelay: Long): Unit

The amount of time, in milliseconds, to delay starting the animation after start() is called. Note that the start delay should always be non-negative. Any negative start delay will be clamped to 0 on N and above.

Parameters
startDelay Long: The amount of the delay, in milliseconds

setValues

open fun setValues(@NonNull vararg values: PropertyValuesHolder!): Unit

Sets the values, per property, being animated between. This function is called internally by the constructors of ValueAnimator that take a list of values. But a ValueAnimator can be constructed without values and this method can be called to set the values manually instead.

Parameters
values PropertyValuesHolder!: The set of values, per property, being animated between.

start

open fun start(): Unit

toString

@NonNull open fun toString(): String