Package icyllis.modernui.animation

Class ValueAnimator

java.lang.Object
icyllis.modernui.animation.Animator
icyllis.modernui.animation.ValueAnimator
All Implemented Interfaces:
AnimationHandler.FrameCallback, Cloneable
Direct Known Subclasses:
ObjectAnimator
public class ValueAnimator extends Animator implements AnimationHandler.FrameCallback
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 TimeInterpolator.ACCELERATE_DECELERATE, which accelerates into and decelerates out of an animation. This behavior can be changed by calling setInterpolator(TimeInterpolator).

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

Starting from API 23, it is also possible to use 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:

Developer Guides

For more information about animating with ValueAnimator, read the Property Animation developer guide.

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static interface 
    ValueAnimator.AnimatorUpdateListener
    Implementors of this interface can add themselves as update listeners to an ValueAnimator instance to receive callbacks on every animation frame, after the current frame's values have been calculated for that ValueAnimator.
    static @interface 
    ValueAnimator.RepeatMode
     

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    INFINITE
    This value used with the setRepeatCount(int) property to repeat the animation indefinitely.
    static final int
    RESTART
    When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation restarts from the beginning.
    static final int
    REVERSE
    When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation reverses direction on every iteration.
    static float
    sDurationScale
    Internal usage, global config value.

    Fields inherited from class icyllis.modernui.animation.Animator

    DURATION_INFINITE, MARKER

  • Constructor Summary

    Constructors
    Constructor
    Description
    ValueAnimator()
    Creates a new ValueAnimator object.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addUpdateListener(ValueAnimator.AnimatorUpdateListener listener)
    Adds a listener to the set of listeners that are sent update events through the life of an animation.
    void
    cancel()
    Cancels the animation.
    boolean
    canReverse()
     
    ValueAnimator
    clone()
     
    void
    commitAnimationFrame(long frameTime)
    Applies an adjustment to the animation to compensate for jank between when the animation first ran and when the frame was drawn.
    final boolean
    doAnimationFrame(long frameTime)
    Processes a frame of the animation, adjusting the start time if needed.
    void
    end()
    Ends the animation.
    float
    getAnimatedFraction()
    Returns the current animation fraction, which is the elapsed/interpolated fraction used in the most recent frame update on the animation.
    Object
    getAnimatedValue()
    The most recent value calculated by this ValueAnimator when there is just one property being animated.
    long
    getCurrentPlayTime()
    Gets the current position of the animation in time, which is equal to the current time minus the time that the animation started.
    long
    getDuration()
    Gets the length of the animation.
    TimeInterpolator
    getInterpolator()
    Returns the timing interpolator that this animation uses.
    int
    getRepeatCount()
    Defines how many times the animation should repeat.
    int
    getRepeatMode()
    Defines what this animation should do when it reaches the end.
    long
    getStartDelay()
    The amount of time, in milliseconds, to delay starting the animation after start() is called.
    long
    getTotalDuration()
    Gets the total duration of the animation, accounting for animation sequences, start delay, and repeating.
    PropertyValuesHolder[]
    getValues()
    Returns the values that this ValueAnimator animates between.
    boolean
    isRunning()
    Returns whether this Animator is currently running (having been started and gone past any initial startDelay period and not yet ended).
    boolean
    isStarted()
    Returns whether this Animator has been started and not yet ended.
    static ValueAnimator
    ofArgb(int... values)
    Constructs and returns a ValueAnimator that animates between color values.
    static ValueAnimator
    ofFloat(float... values)
    Constructs and returns a ValueAnimator that animates between float values.
    static ValueAnimator
    ofInt(int... values)
    Constructs and returns a ValueAnimator that animates between int values.
    static <V> ValueAnimator
    ofObject(TypeEvaluator<V> evaluator, V... values)
    Constructs and returns a ValueAnimator that animates between Object values.
    void
    pause()
    Pauses a running animation.
    void
    removeAllUpdateListeners()
    Removes all listeners from the set listening to frame updates for this animation.
    void
    removeUpdateListener(ValueAnimator.AnimatorUpdateListener listener)
    Removes a listener from the set listening to frame updates for this animation.
    void
    resume()
    Resumes a paused animation, causing the animator to pick up where it left off when it was paused.
    void
    reverse()
    Plays the ValueAnimator in reverse.
    void
    setCurrentFraction(float fraction)
    Sets the position of the animation to the specified fraction.
    void
    setCurrentPlayTime(long playTime)
    Sets the position of the animation to the specified point in time.
    ValueAnimator
    setDuration(long duration)
    Sets the length of the animation.
    void
    setEvaluator(TypeEvaluator<?> value)
    The type evaluator to be used when calculating the animated values of this animation.
    void
    setInterpolator(TimeInterpolator value)
    The time interpolator used in calculating the elapsed fraction of the animation.
    void
    setRepeatCount(int value)
    Sets how many times the animation should be repeated.
    void
    setRepeatMode(int value)
    Defines what this animation should do when it reaches the end.
    void
    setStartDelay(long startDelay)
    The amount of time, in milliseconds, to delay processing the animation after Animator.start() is called.
    void
    setValues(PropertyValuesHolder... values)
    Sets the values, per property, being animated between.
    void
    start()
    Starts this animation.

    Methods inherited from class icyllis.modernui.animation.Animator

    addListener, getListeners, isPaused, removeAllListeners, removeListener, setTarget, setupEndValues, setupStartValues

    Methods inherited from class java.lang.Object

    equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • sDurationScale

      @Internal public static volatile float sDurationScale
      Internal usage, global config value.

    • RESTART

      public static final int RESTART
      When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation restarts from the beginning.
      See Also:

    • REVERSE

      public static final int REVERSE
      When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation reverses direction on every iteration.
      See Also:

    • INFINITE

      public static final int INFINITE
      This value used with the setRepeatCount(int) property to repeat the animation indefinitely.
      See Also:

  • Constructor Details

    • ValueAnimator

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

  • Method Details

    • ofInt

      @Nonnull public static ValueAnimator ofInt(@Nonnull int... values)
      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 - A set of values that the animation will animate between over time.
      Returns:
      A ValueAnimator object that is set up to animate between the given values.

    • ofArgb

      @Nonnull public static ValueAnimator ofArgb(@Nonnull int... values)
      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 - A set of values that the animation will animate between over time.
      Returns:
      A ValueAnimator object that is set up to animate between the given values.

    • ofFloat

      @Nonnull public static ValueAnimator ofFloat(@Nonnull float... values)
      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 - A set of values that the animation will animate between over time.
      Returns:
      A ValueAnimator object that is set up to animate between the given values.

    • ofObject

      @Nonnull @SafeVarargs public static <V> ValueAnimator ofObject(@Nonnull TypeEvaluator<V> evaluator, @Nonnull V... values)
      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 - 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 - A set of values that the animation will animate between over time.
      Returns:
      A ValueAnimator object that is set up to animate between the given values.

    • setValues

      public void setValues(@Nonnull PropertyValuesHolder... values)
      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 - The set of values, per property, being animated between.

    • getValues

      @Nonnull public PropertyValuesHolder[] getValues()
      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.
      Returns:
      The array of PropertyValuesHolder objects which hold the values, per property, that define the animation.

    • setDuration

      public ValueAnimator setDuration(long duration)
      Sets the length of the animation. The default duration is 300 milliseconds.
      Specified by:
      setDuration in class Animator
      Parameters:
      duration - The length of the animation, in milliseconds. This value cannot be negative.
      Returns:
      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().

    • getDuration

      public long getDuration()
      Gets the length of the animation. The default duration is 300 milliseconds.
      Specified by:
      getDuration in class Animator
      Returns:
      The length of the animation, in milliseconds.

    • getTotalDuration

      public long getTotalDuration()
      Gets the total duration of the animation, accounting for animation sequences, start delay, and repeating. Return Animator.DURATION_INFINITE if the duration is infinite.
      Specified by:
      getTotalDuration in class Animator
      Returns:
      Total time an animation takes to finish, starting from the time start() is called. Animator.DURATION_INFINITE will be returned if the animation or any child animation repeats infinite times.

    • setCurrentPlayTime

      public void setCurrentPlayTime(long playTime)
      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 - The time, in milliseconds, to which the animation is advanced or rewound.

    • setCurrentFraction

      public void setCurrentFraction(float fraction)
      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. AnimatorListener events are not called due to changing the fraction; those events are only processed while the animation is running.
      Parameters:
      fraction - 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.

    • getCurrentPlayTime

      public long getCurrentPlayTime()
      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 its play time set via setCurrentPlayTime(long) or setCurrentFraction(float), in which case it will return the time that was set.
      Returns:
      The current position in time of the animation.

    • setStartDelay

      public void setStartDelay(long startDelay)
      Description copied from class: Animator
      The amount of time, in milliseconds, to delay processing the animation after Animator.start() is called.
      Specified by:
      setStartDelay in class Animator
      Parameters:
      startDelay - The amount of the delay, in milliseconds

    • getStartDelay

      public long getStartDelay()
      The amount of time, in milliseconds, to delay starting the animation after start() is called.
      Specified by:
      getStartDelay in class Animator
      Returns:
      the number of milliseconds to delay running the animation

    • getAnimatedValue

      public Object getAnimatedValue()
      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 ValueAnimator.AnimatorUpdateListener.onAnimationUpdate(ValueAnimator), which is called during each animation frame, immediately after the value is calculated.
      Returns:
      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.

    • setRepeatCount

      public void setRepeatCount(int value)
      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 - the number of times the animation should be repeated

    • getRepeatCount

      public int getRepeatCount()
      Defines how many times the animation should repeat. The default value is 0.
      Returns:
      the number of times the animation should repeat, or INFINITE

    • setRepeatMode

      public void setRepeatMode(int value)
      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 - RESTART or REVERSE

    • getRepeatMode

      public int getRepeatMode()
      Defines what this animation should do when it reaches the end.
      Returns:
      either one of REVERSE or RESTART

    • addUpdateListener

      public void addUpdateListener(@Nonnull ValueAnimator.AnimatorUpdateListener listener)
      Adds a listener to the set of listeners that are sent update events through the life of an animation. This method is called on all listeners for every frame of the animation, after the values for the animation have been calculated.
      Parameters:
      listener - the listener to be added to the current set of listeners for this animation.

    • removeAllUpdateListeners

      public void removeAllUpdateListeners()
      Removes all listeners from the set listening to frame updates for this animation.

    • removeUpdateListener

      public void removeUpdateListener(@Nonnull ValueAnimator.AnimatorUpdateListener listener)
      Removes a listener from the set listening to frame updates for this animation.
      Parameters:
      listener - the listener to be removed from the current set of update listeners for this animation.

    • setInterpolator

      public void setInterpolator(@Nullable TimeInterpolator value)
      The time interpolator used in calculating the elapsed fraction of the animation. The interpolator determines whether the animation runs with linear or non-linear motion, such as acceleration and deceleration. The default value is TimeInterpolator.ACCELERATE_DECELERATE.
      Specified by:
      setInterpolator in class Animator
      Parameters:
      value - the interpolator to be used by this animation. A value of null will result in linear interpolation.

    • getInterpolator

      @Nonnull public TimeInterpolator getInterpolator()
      Returns the timing interpolator that this animation uses.
      Specified by:
      getInterpolator in class Animator
      Returns:
      The timing interpolator for this animation.

    • setEvaluator

      public void setEvaluator(TypeEvaluator<?> value)
      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 ColorEvaluator 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 - the evaluator to be used this animation

    • start

      public void start()
      Starts this animation. If the animation has a nonzero startDelay, the animation will start running after that delay elapses. A non-delayed animation will have its initial value(s) set immediately, followed by calls to AnimatorListener.onAnimationStart(Animator, boolean) for any listeners of this animator.
      Specified by:
      start in class Animator

    • cancel

      public void cancel()
      Description copied from class: Animator
      Cancels the animation. Unlike Animator.end(), cancel() causes the animation to stop in its tracks, sending an AnimatorListener.onAnimationCancel(Animator) to its listeners, followed by an AnimatorListener.onAnimationEnd(Animator, boolean) message.

      This method must be called on the thread that is running the animation.

      Specified by:
      cancel in class Animator

    • end

      public void end()
      Description copied from class: Animator
      Ends the animation. This causes the animation to assign the end value of the property being animated, then calling the AnimatorListener.onAnimationEnd(Animator, boolean) method on its listeners.

      This method must be called on the thread that is running the animation.

      Specified by:
      end in class Animator

    • resume

      public void resume()
      Description copied from class: Animator
      Resumes a paused animation, causing the animator to pick up where it left off when it was paused. This method should only be called on the same thread on which the animation was started. Calls to resume() on an animator that is not currently paused will be ignored.
      Overrides:
      resume in class Animator
      See Also:

    • pause

      public void pause()
      Description copied from class: Animator
      Pauses a running animation. This method should only be called on the same thread on which the animation was started. If the animation has not yet been started or has since ended, then the call is ignored. Paused animations can be resumed by calling Animator.resume().
      Overrides:
      pause in class Animator
      See Also:

    • isRunning

      public boolean isRunning()
      Returns whether this Animator is currently running (having been started and gone past any initial startDelay period and not yet ended).
      Specified by:
      isRunning in class Animator
      Returns:
      whether the Animator is running.

    • isStarted

      public boolean isStarted()
      Returns whether this Animator has been started and not yet ended. For reusable Animators (which most Animators are, apart from the one-shot animator), this state is a superset of isRunning(), because an Animator with a nonzero getStartDelay() will return true during the delay phase, whereas isRunning() will return true only after the delay phase is complete. Non-reusable animators will always return true after they have been started, because they cannot return to a non-started state.
      Specified by:
      isStarted in class Animator
      Returns:
      whether the Animator has been started and not yet ended.

    • reverse

      public void reverse()
      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.
      Overrides:
      reverse in class Animator

    • canReverse

      public boolean canReverse()
      Overrides:
      canReverse in class Animator

    • commitAnimationFrame

      public void commitAnimationFrame(long frameTime)
      Applies an adjustment to the animation to compensate for jank between when the animation first ran and when the frame was drawn.

    • doAnimationFrame

      public final boolean doAnimationFrame(long frameTime)
      Processes a frame of the animation, adjusting the start time if needed.
      Specified by:
      doAnimationFrame in interface AnimationHandler.FrameCallback
      Parameters:
      frameTime - The frame time.
      Returns:
      true if the animation has ended.

    • getAnimatedFraction

      public float getAnimatedFraction()
      Returns the current animation fraction, which is the elapsed/interpolated fraction used in the most recent frame update on the animation.
      Returns:
      Elapsed/interpolated fraction of the animation.

    • clone

      public ValueAnimator clone()
      Overrides:
      clone in class Animator