content: /*
   * Copyright (C) 2010 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.animation;
  
  import android.annotation.CallSuper;
  import android.annotation.IntDef;
  import android.annotation.TestApi;
  import android.annotation.UnsupportedAppUsage;
  import android.os.Build;
  import android.os.Looper;
  import android.os.Trace;
  import android.util.AndroidRuntimeException;
  import android.util.Log;
  import android.view.animation.AccelerateDecelerateInterpolator;
  import android.view.animation.Animation;
  import android.view.animation.AnimationUtils;
  import android.view.animation.LinearInterpolator;
  
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  import java.util.ArrayList;
  import java.util.HashMap;
  
  /**
   * This class provides a simple timing engine for running animations
   * which calculate animated values and set them on target objects.
   *
   * <p>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.</p>
   *
   * <p>By default, ValueAnimator uses non-linear time interpolation, via the
   * {@link AccelerateDecelerateInterpolator} class, which accelerates into and decelerates
   * out of an animation. This behavior can be changed by calling
   * {@link ValueAnimator#setInterpolator(TimeInterpolator)}.</p>
   *
   * <p>Animators can be created from either code or resource files. Here is an example
   * of a ValueAnimator resource file:</p>
   *
   * {@sample development/samples/ApiDemos/res/anim/animator.xml ValueAnimatorResources}
   *
   * <p>Starting from API 23, it is also possible to use a combination of {@link PropertyValuesHolder}
   * and {@link 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:</p>
   *
   * {@sample development/samples/ApiDemos/res/anim/value_animator_pvh_kf.xml
   * ValueAnimatorKeyframeResources}
   *
   * <div class="special reference">
   * <h3>Developer Guides</h3>
   * <p>For more information about animating with {@code ValueAnimator}, read the
   * <a href="{@docRoot}guide/topics/graphics/prop-animation.html#value-animator">Property
   * Animation</a> developer guide.</p>
   * </div>
   */
  @SuppressWarnings("unchecked")
  public class ValueAnimator extends Animator implements AnimationHandler.AnimationFrameCallback {
      private static final String TAG = "ValueAnimator";
      private static final boolean DEBUG = false;
  
      /**
       * Internal constants
       */
  
      /**
       * System-wide animation scale.
       *
       * <p>To check whether animations are enabled system-wise use {@link #areAnimatorsEnabled()}.
       */
      @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
      private static float sDurationScale = 1.0f;
  
      /**
       * Internal variables
       * NOTE: This object implements the clone() method, making a deep copy of any referenced
       * objects. As other non-trivial fields are added to this class, make sure to add logic
       * to clone() to make deep copies of them.
       */
  
      /**
       * The first time that the animation's animateFrame() method is called. This time is used to
       * determine elapsed time (and therefore the elapsed fraction) in subsequent calls
       * to animateFrame().
       *
       * Whenever mStartTime is set, you must also update mStartTimeCommitted.
       */
      long mStartTime = -1;
  
      /**
       * When true, the start time has been firmly committed as a chosen reference point in
       * time by which the progress of the animation will be evaluated.  When false, the
       * start time may be updated when the first animation frame is committed so as
       * to compensate for jank that may have occurred between when the start time was
       * initialized and when the frame was actually drawn.
       *
       * This flag is generally set to false during the first frame of the animation
       * when the animation playing state transitions from STOPPED to RUNNING or
       * resumes after having been paused.  This flag is set to true when the start time
       * is firmly committed and should not be further compensated for jank.
       */
      boolean mStartTimeCommitted;
  
      /**
       * Set when setCurrentPlayTime() is called. If negative, animation is not currently seeked
       * to a value.
       */
      float mSeekFraction = -1;
  
      /**
       * Set on the next frame after pause() is called, used to calculate a new startTime
       * or delayStartTime which allows the animator to continue from the point at which
       * it was paused. If negative, has not yet been set.
       */
      private long mPauseTime;
  
      /**
       * Set when an animator is resumed. This triggers logic in the next frame which
       * actually resumes the animator.
       */
      private boolean mResumed = false;
  
      // The time interpolator to be used if none is set on the animation
      private static final TimeInterpolator sDefaultInterpolator =
              new AccelerateDecelerateInterpolator();
  
      /**
       * Flag to indicate whether this animator is playing in reverse mode, specifically
       * by being started or interrupted by a call to reverse(). This flag is different than
       * mPlayingBackwards, which indicates merely whether the current iteration of the
       * animator is playing in reverse. It is used in corner cases to determine proper end
       * behavior.
       */
      private boolean mReversing;
  
      /**
       * Tracks the overall fraction of the animation, ranging from 0 to mRepeatCount + 1
       */
      private float mOverallFraction = 0f;
  
      /**
       * Tracks current elapsed/eased fraction, for querying in getAnimatedFraction().
       * This is calculated by interpolating the fraction (range: [0, 1]) in the current iteration.
       */
      private float mCurrentFraction = 0f;
  
      /**
       * Tracks the time (in milliseconds) when the last frame arrived.
       */
      private long mLastFrameTime = -1;
  
      /**
       * Tracks the time (in milliseconds) when the first frame arrived. Note the frame may arrive
       * during the start delay.
       */
      private long mFirstFrameTime = -1;
  
      /**
       * Additional playing state to indicate whether an animator has been start()'d. There is
       * some lag between a call to start() and the first animation frame. We should still note
       * that the animation has been started, even if it's first animation frame has not yet
       * happened, and reflect that state in isRunning().
       * Note that delayed animations are different: they are not started until their first
       * animation frame, which occurs after their delay elapses.
       */
      private boolean mRunning = false;
  
      /**
       * Additional playing state to indicate whether an animator has been start()'d, whether or
       * not there is a nonzero startDelay.
       */
      private boolean mStarted = false;
  
      /**
       * Tracks whether we've notified listeners of the onAnimationStart() event. This can be
       * complex to keep track of since we notify listeners at different times depending on
       * startDelay and whether start() was called before end().
       */
      private boolean mStartListenersCalled = false;
  
      /**
       * Flag that denotes whether the animation is set up and ready to go. Used to
       * set up animation that has not yet been started.
       */
      boolean mInitialized = false;
  
      /**
       * Flag that tracks whether animation has been requested to end.
       */
      private boolean mAnimationEndRequested = false;
  
      //
      // Backing variables
      //
  
      // How long the animation should last in ms
      @UnsupportedAppUsage
      private long mDuration = 300;
  
      // The amount of time in ms to delay starting the animation after start() is called. Note
      // that this start delay is unscaled. When there is a duration scale set on the animator, the
      // scaling factor will be applied to this delay.
      private long mStartDelay = 0;
  
      // The number of times the animation will repeat. The default is 0, which means the animation
      // will play only once
      private int mRepeatCount = 0;
  
      /**
       * The type of repetition that will occur when repeatMode is nonzero. RESTART means the
       * animation will start from the beginning on every new cycle. REVERSE means the animation
       * will reverse directions on each iteration.
       */
      private int mRepeatMode = RESTART;
  
      /**
       * Whether or not the animator should register for its own animation callback to receive
       * animation pulse.
       */
      private boolean mSelfPulse = true;
  
      /**
       * Whether or not the animator has been requested to start without pulsing. This flag gets set
       * in startWithoutPulsing(), and reset in start().
       */
      private boolean mSuppressSelfPulseRequested = false;
  
      /**
       * The time interpolator to be used. The elapsed fraction of the animation will be passed
       * through this interpolator to calculate the interpolated fraction, which is then used to
       * calculate the animated values.
       */
      private TimeInterpolator mInterpolator = sDefaultInterpolator;
  
      /**
       * The set of listeners to be sent events through the life of an animation.
       */
      ArrayList<AnimatorUpdateListener> mUpdateListeners = null;
  
      /**
       * The property/value sets being animated.
       */
      PropertyValuesHolder[] mValues;
  
      /**
       * A hashmap of the PropertyValuesHolder objects. This map is used to lookup animated values
       * by property name during calls to getAnimatedValue(String).
       */
      HashMap<String, PropertyValuesHolder> mValuesMap;
  
      /**
       * If set to non-negative value, this will override {@link #sDurationScale}.
       */
      private float mDurationScale = -1f;
  
      /**
       * Public constants
       */
  
      /** @hide */
      @IntDef({RESTART, REVERSE})
      @Retention(RetentionPolicy.SOURCE)
      public @interface RepeatMode {}
  
      /**
       * When the animation reaches the end and <code>repeatCount</code> is INFINITE
       * or a positive value, the animation restarts from the beginning.
       */
      public static final int RESTART = 1;
      /**
       * When the animation reaches the end and <code>repeatCount</code> is INFINITE
       * or a positive value, the animation reverses direction on every iteration.
       */
      public static final int REVERSE = 2;
      /**
       * This value used used with the {@link #setRepeatCount(int)} property to repeat
       * the animation indefinitely.
       */
      public static final int INFINITE = -1;
  
      /**
       * @hide
       */
      @TestApi
      public static void setDurationScale(float durationScale) {
          sDurationScale = durationScale;
      }
  
      /**
       * @hide
       */
      @TestApi
      public static float getDurationScale() {
          return sDurationScale;
      }
  
      /**
       * 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).
       *
       * <p>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 Whether animators are currently enabled. The default value is
       * <code>true</code>.
       */
      public static boolean areAnimatorsEnabled() {
          return !(sDurationScale == 0);
      }
  
      /**
       * Creates a new ValueAnimator object. This default constructor is primarily for
       * use internally; the factory methods which take parameters are more generally
       * useful.
       */
      public 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.
       *
       * @param values A set of values that the animation will animate between over time.
       * @return A ValueAnimator object that is set up to animate between the given values.
       */
      public static ValueAnimator ofInt(int... values) {
          ValueAnimator anim = new ValueAnimator();
          anim.setIntValues(values);
          return anim;
      }
  
      /**
       * 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.
       *
       * @param values A set of values that the animation will animate between over time.
       * @return A ValueAnimator object that is set up to animate between the given values.
       */
      public static ValueAnimator ofArgb(int... values) {
          ValueAnimator anim = new ValueAnimator();
          anim.setIntValues(values);
          anim.setEvaluator(ArgbEvaluator.getInstance());
          return anim;
      }
  
      /**
       * 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.
       *
       * @param values A set of values that the animation will animate between over time.
       * @return A ValueAnimator object that is set up to animate between the given values.
       */
      public static ValueAnimator ofFloat(float... values) {
          ValueAnimator anim = new ValueAnimator();
          anim.setFloatValues(values);
          return anim;
      }
  
      /**
       * Constructs and returns a ValueAnimator that animates between the values
       * specified in the PropertyValuesHolder objects.
       *
       * @param values A set of PropertyValuesHolder objects whose values will be animated
       * between over time.
       * @return A ValueAnimator object that is set up to animate between the given values.
       */
      public static ValueAnimator ofPropertyValuesHolder(PropertyValuesHolder... values) {
          ValueAnimator anim = new ValueAnimator();
          anim.setValues(values);
          return anim;
      }
      /**
       * 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.
       *
       * <p><strong>Note:</strong> 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.
       *
       * <p>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.
       *
       * @param evaluator A TypeEvaluator that will be called on each animation frame to
       * provide the ncessry interpolation between the Object values to derive the animated
       * value.
       * @param values A set of values that the animation will animate between over time.
       * @return A ValueAnimator object that is set up to animate between the given values.
       */
      public static ValueAnimator ofObject(TypeEvaluator evaluator, Object... values) {
          ValueAnimator anim = new ValueAnimator();
          anim.setObjectValues(values);
          anim.setEvaluator(evaluator);
          return anim;
      }
  
      /**
       * 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.
       *
       * <p>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.</p>
       *
       * @param values A set of values that the animation will animate between over time.
       */
      public void setIntValues(int... values) {
          if (values == null || values.length == 0) {
              return;
          }
          if (mValues == null || mValues.length == 0) {
              setValues(PropertyValuesHolder.ofInt("", values));
          } else {
              PropertyValuesHolder valuesHolder = mValues[0];
              valuesHolder.setIntValues(values);
          }
          // New property/values/target should cause re-initialization prior to starting
          mInitialized = false;
      }
  
      /**
       * 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.
       *
       * <p>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.</p>
       *
       * @param values A set of values that the animation will animate between over time.
       */
      public void setFloatValues(float... values) {
          if (values == null || values.length == 0) {
              return;
          }
          if (mValues == null || mValues.length == 0) {
              setValues(PropertyValuesHolder.ofFloat("", values));
          } else {
              PropertyValuesHolder valuesHolder = mValues[0];
              valuesHolder.setFloatValues(values);
          }
          // New property/values/target should cause re-initialization prior to starting
          mInitialized = false;
      }
  
      /**
       * 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.
       *
       * <p><strong>Note:</strong> 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.
       *
       * <p>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.</p>
       *
       * <p>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.</p>
       *
       * @param values The set of values to animate between.
       */
      public void setObjectValues(Object... values) {
          if (values == null || values.length == 0) {
              return;
          }
          if (mValues == null || mValues.length == 0) {
              setValues(PropertyValuesHolder.ofObject("", null, values));
          } else {
              PropertyValuesHolder valuesHolder = mValues[0];
              valuesHolder.setObjectValues(values);
          }
          // New property/values/target should cause re-initialization prior to starting
          mInitialized = false;
      }
  
      /**
       * 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.
       *
       * @param values The set of values, per property, being animated between.
       */
      public void setValues(PropertyValuesHolder... values) {
          int numValues = values.length;
          mValues = values;
          mValuesMap = new HashMap<String, PropertyValuesHolder>(numValues);
          for (int i = 0; i < numValues; ++i) {
              PropertyValuesHolder valuesHolder = values[i];
              mValuesMap.put(valuesHolder.getPropertyName(), valuesHolder);
          }
          // New property/values/target should cause re-initialization prior to starting
          mInitialized = false;
      }
  
      /**
       * 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 PropertyValuesHolder[] An array of PropertyValuesHolder objects which hold the
       * values, per property, that define the animation.
       */
      public PropertyValuesHolder[] getValues() {
          return mValues;
      }
  
      /**
       * This function is called immediately before processing the first animation
       * frame of an animation. If there is a nonzero <code>startDelay</code>, the
       * function is called after that delay ends.
       * It takes care of the final initialization steps for the
       * animation.
       *
       *  <p>Overrides of this method should call the superclass method to ensure
       *  that internal mechanisms for the animation are set up correctly.</p>
       */
      @CallSuper
      void initAnimation() {
          if (!mInitialized) {
              int numValues = mValues.length;
              for (int i = 0; i < numValues; ++i) {
                  mValues[i].init();
              }
              mInitialized = true;
          }
      }
  
      /**
       * Sets the length of the animation. The default duration is 300 milliseconds.
       *
       * @param duration The length of the animation, in milliseconds. This value cannot
       * be negative.
       * @return 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 <code>ValueAnimator.ofInt(0, 10).setDuration(500).start()</code>.
       */
      @Override
      public ValueAnimator setDuration(long duration) {
          if (duration < 0) {
              throw new IllegalArgumentException("Animators cannot have negative duration: " +
                      duration);
          }
          mDuration = duration;
          return this;
      }
  
      /**
       * Overrides the global duration scale by a custom value.
       *
       * @param durationScale The duration scale to set; or {@code -1f} to use the global duration
       *                      scale.
       * @hide
       */
      public void overrideDurationScale(float durationScale) {
          mDurationScale = durationScale;
      }
  
      private float resolveDurationScale() {
          return mDurationScale >= 0f ? mDurationScale : sDurationScale;
      }
  
      private long getScaledDuration() {
          return (long)(mDuration * resolveDurationScale());
      }
  
      /**
       * Gets the length of the animation. The default duration is 300 milliseconds.
       *
       * @return The length of the animation, in milliseconds.
       */
      @Override
      public long getDuration() {
          return mDuration;
      }
  
      @Override
      public long getTotalDuration() {
          if (mRepeatCount == INFINITE) {
              return DURATION_INFINITE;
          } else {
              return mStartDelay + (mDuration * (mRepeatCount + 1));
          }
      }
  
      /**
       * 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.
       *
       * @param playTime The time, in milliseconds, to which the animation is advanced or rewound.
       */
      public void setCurrentPlayTime(long playTime) {
          float fraction = mDuration > 0 ? (float) playTime / mDuration : 1;
          setCurrentFraction(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. {@link Animator.AnimatorListener} events are not called
       * due to changing the fraction; those events are only processed while the animation
       * is running.
       *
       * @param 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.
       */
      public void setCurrentFraction(float fraction) {
          initAnimation();
          fraction = clampFraction(fraction);
          mStartTimeCommitted = true; // do not allow start time to be compensated for jank
          if (isPulsingInternal()) {
              long seekTime = (long) (getScaledDuration() * fraction);
              long currentTime = AnimationUtils.currentAnimationTimeMillis();
              // Only modify the start time when the animation is running. Seek fraction will ensure
              // non-running animations skip to the correct start time.
              mStartTime = currentTime - seekTime;
          } else {
              // If the animation loop hasn't started, or during start delay, the startTime will be
              // adjusted once the delay has passed based on seek fraction.
              mSeekFraction = fraction;
          }
          mOverallFraction = fraction;
          final float currentIterationFraction = getCurrentIterationFraction(fraction, mReversing);
          animateValue(currentIterationFraction);
      }
  
      /**
       * Calculates current iteration based on the overall fraction. The overall fraction will be
       * in the range of [0, mRepeatCount + 1]. Both current iteration and fraction in the current
       * iteration can be derived from it.
       */
      private int getCurrentIteration(float fraction) {
          fraction = clampFraction(fraction);
          // If the overall fraction is a positive integer, we consider the current iteration to be
          // complete. In other words, the fraction for the current iteration would be 1, and the
          // current iteration would be overall fraction - 1.
          double iteration = Math.floor(fraction);
          if (fraction == iteration && fraction > 0) {
              iteration--;
          }
          return (int) iteration;
      }
  
      /**
       * Calculates the fraction of the current iteration, taking into account whether the animation
       * should be played backwards. E.g. When the animation is played backwards in an iteration,
       * the fraction for that iteration will go from 1f to 0f.
       */
      private float getCurrentIterationFraction(float fraction, boolean inReverse) {
          fraction = clampFraction(fraction);
          int iteration = getCurrentIteration(fraction);
          float currentFraction = fraction - iteration;
          return shouldPlayBackward(iteration, inReverse) ? 1f - currentFraction : currentFraction;
      }
  
      /**
       * Clamps fraction into the correct range: [0, mRepeatCount + 1]. If repeat count is infinite,
       * no upper bound will be set for the fraction.
       *
       * @param fraction fraction to be clamped
       * @return fraction clamped into the range of [0, mRepeatCount + 1]
       */
      private float clampFraction(float fraction) {
          if (fraction < 0) {
              fraction = 0;
          } else if (mRepeatCount != INFINITE) {
              fraction = Math.min(fraction, mRepeatCount + 1);
          }
          return fraction;
      }
  
      /**
       * Calculates the direction of animation playing (i.e. forward or backward), based on 1)
       * whether the entire animation is being reversed, 2) repeat mode applied to the current
       * iteration.
       */
      private boolean shouldPlayBackward(int iteration, boolean inReverse) {
          if (iteration > 0 && mRepeatMode == REVERSE &&
                  (iteration < (mRepeatCount + 1) || mRepeatCount == INFINITE)) {
              // if we were seeked to some other iteration in a reversing animator,
              // figure out the correct direction to start playing based on the iteration
              if (inReverse) {
                  return (iteration % 2) == 0;
              } else {
                  return (iteration % 2) != 0;
              }
          } else {
              return inReverse;
          }
      }
  
      /**
       * 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
       * {@link #setCurrentPlayTime(long)} or {@link #setCurrentFraction(float)}, in which case
       * it will return the time that was set.
       *
       * @return The current position in time of the animation.
       */
      public long getCurrentPlayTime() {
          if (!mInitialized || (!mStarted && mSeekFraction < 0)) {
              return 0;
          }
          if (mSeekFraction >= 0) {
              return (long) (mDuration * mSeekFraction);
          }
          float durationScale = resolveDurationScale();
          if (durationScale == 0f) {
              durationScale = 1f;
          }
          return (long) ((AnimationUtils.currentAnimationTimeMillis() - mStartTime) / durationScale);
      }
  
      /**
       * The amount of time, in milliseconds, to delay starting the animation after
       * {@link #start()} is called.
       *
       * @return the number of milliseconds to delay running the animation
       */
      @Override
      public long getStartDelay() {
          return mStartDelay;
      }
  
      /**
       * The amount of time, in milliseconds, to delay starting the animation after
       * {@link #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.
       *
       * @param startDelay The amount of the delay, in milliseconds
       */
      @Override
      public void setStartDelay(long startDelay) {
          // Clamp start delay to non-negative range.
          if (startDelay < 0) {
              Log.w(TAG, "Start delay should always be non-negative");
              startDelay = 0;
          }
          mStartDelay = startDelay;
      }
  
      /**
       * 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 {@link #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 the requested time between frames, in milliseconds
       */
      public static long getFrameDelay() {
          return AnimationHandler.getInstance().getFrameDelay();
      }
  
      /**
       * 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 {@link #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.
       *
       * @param frameDelay the requested time between frames, in milliseconds
       */
      public static void setFrameDelay(long frameDelay) {
          AnimationHandler.getInstance().setFrameDelay(frameDelay);
      }
  
      /**
       * The most recent value calculated by this <code>ValueAnimator</code> 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 <code>ValueAnimator</code>
       * during a call to {@link AnimatorUpdateListener#onAnimationUpdate(ValueAnimator)}, which
       * is called during each animation frame, immediately after the value is calculated.
       *
       * @return animatedValue The value most recently calculated by this <code>ValueAnimator</code> 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.
       */
      public Object getAnimatedValue() {
          if (mValues != null && mValues.length > 0) {
              return mValues[0].getAnimatedValue();
          }
          // Shouldn't get here; should always have values unless ValueAnimator was set up wrong
          return null;
      }
  
      /**
       * The most recent value calculated by this <code>ValueAnimator</code> for <code>propertyName</code>.
       * The main purpose for this read-only property is to retrieve the value from the
       * <code>ValueAnimator</code> during a call to
       * {@link AnimatorUpdateListener#onAnimationUpdate(ValueAnimator)}, which
       * is called during each animation frame, immediately after the value is calculated.
       *
       * @return animatedValue The value most recently calculated for the named property
       * by this <code>ValueAnimator</code>.
       */
      public Object getAnimatedValue(String propertyName) {
          PropertyValuesHolder valuesHolder = mValuesMap.get(propertyName);
          if (valuesHolder != null) {
              return valuesHolder.getAnimatedValue();
          } else {
              // At least avoid crashing if called with bogus propertyName
              return null;
          }
      }
  
      /**
       * 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 {@link #INFINITE}, the repeat mode will be taken
       * into account. The repeat count is 0 by default.
       *
       * @param value the number of times the animation should be repeated
       */
      public void setRepeatCount(int value) {
          mRepeatCount = value;
      }
      /**
       * Defines how many times the animation should repeat. The default value
       * is 0.
       *
       * @return the number of times the animation should repeat, or {@link #INFINITE}
       */
      public int getRepeatCount() {
          return mRepeatCount;
      }
  
      /**
       * 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 {@link #INFINITE}. Defaults to {@link #RESTART}.
       *
       * @param value {@link #RESTART} or {@link #REVERSE}
       */
      public void setRepeatMode(@RepeatMode int value) {
          mRepeatMode = value;
      }
  
      /**
       * Defines what this animation should do when it reaches the end.
       *
       * @return either one of {@link #REVERSE} or {@link #RESTART}
       */
      @RepeatMode
      public int getRepeatMode() {
          return mRepeatMode;
      }
  
      /**
       * 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.
       *
       * @param listener the listener to be added to the current set of listeners for this animation.
       */
      public void addUpdateListener(AnimatorUpdateListener listener) {
          if (mUpdateListeners == null) {
              mUpdateListeners = new ArrayList<AnimatorUpdateListener>();
          }
          mUpdateListeners.add(listener);
      }
  
      /**
       * Removes all listeners from the set listening to frame updates for this animation.
       */
      public void removeAllUpdateListeners() {
          if (mUpdateListeners == null) {
              return;
          }
          mUpdateListeners.clear();
          mUpdateListeners = null;
      }
  
      /**
       * Removes a listener from the set listening to frame updates for this animation.
       *
       * @param listener the listener to be removed from the current set of update listeners
       * for this animation.
       */
      public void removeUpdateListener(AnimatorUpdateListener listener) {
          if (mUpdateListeners == null) {
              return;
          }
          mUpdateListeners.remove(listener);
          if (mUpdateListeners.size() == 0) {
              mUpdateListeners = null;
          }
      }
  
  
      /**
       * The time 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
       * {@link android.view.animation.AccelerateDecelerateInterpolator}
       *
       * @param value the interpolator to be used by this animation. A value of <code>null</code>
       * will result in linear interpolation.
       */
      @Override
      public void setInterpolator(TimeInterpolator value) {
          if (value != null) {
              mInterpolator = value;
          } else {
              mInterpolator = new LinearInterpolator();
          }
      }
  
      /**
       * Returns the timing interpolator that this ValueAnimator uses.
       *
       * @return The timing interpolator for this ValueAnimator.
       */
      @Override
      public TimeInterpolator getInterpolator() {
          return mInterpolator;
      }
  
      /**
       * 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 <code>startValue</code> and <code>endValue</code> 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 {@link ArgbEvaluator}
       * should be used to get correct RGB color interpolation.
       *
       * <p>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.</p>
       *
       * @param value the evaluator to be used this animation
       */
      public void setEvaluator(TypeEvaluator value) {
          if (value != null && mValues != null && mValues.length > 0) {
              mValues[0].setEvaluator(value);
          }
      }
  
      private void notifyStartListeners() {
          if (mListeners != null && !mStartListenersCalled) {
              ArrayList<AnimatorListener> tmpListeners =
                      (ArrayList<AnimatorListener>) mListeners.clone();
              int numListeners = tmpListeners.size();
              for (int i = 0; i < numListeners; ++i) {
                  tmpListeners.get(i).onAnimationStart(this, mReversing);
              }
          }
          mStartListenersCalled = true;
      }
  
      /**
       * Start the animation playing. This version of start() takes a boolean flag that indicates
       * whether the animation should play in reverse. The flag is usually false, but may be set
       * to true if called from the reverse() method.
       *
       * <p>The animation started by calling this method will be run on the thread that called
       * this method. This thread should have a Looper on it (a runtime exception will be thrown if
       * this is not the case). Also, if the animation will animate
       * properties of objects in the view hierarchy, then the calling thread should be the UI
       * thread for that view hierarchy.</p>
       *
       * @param playBackwards Whether the ValueAnimator should start playing in reverse.
       */
      private void start(boolean playBackwards) {
          if (Looper.myLooper() == null) {
              throw new AndroidRuntimeException("Animators may only be run on Looper threads");
          }
          mReversing = playBackwards;
          mSelfPulse = !mSuppressSelfPulseRequested;
          // Special case: reversing from seek-to-0 should act as if not seeked at all.
          if (playBackwards && mSeekFraction != -1 && mSeekFraction != 0) {
              if (mRepeatCount == INFINITE) {
                  // Calculate the fraction of the current iteration.
                  float fraction = (float) (mSeekFraction - Math.floor(mSeekFraction));
                  mSeekFraction = 1 - fraction;
              } else {
                  mSeekFraction = 1 + mRepeatCount - mSeekFraction;
              }
          }
          mStarted = true;
          mPaused = false;
          mRunning = false;
          mAnimationEndRequested = false;
          // Resets mLastFrameTime when start() is called, so that if the animation was running,
          // calling start() would put the animation in the
          // started-but-not-yet-reached-the-first-frame phase.
          mLastFrameTime = -1;
          mFirstFrameTime = -1;
          mStartTime = -1;
          addAnimationCallback(0);
  
          if (mStartDelay == 0 || mSeekFraction >= 0 || mReversing) {
              // If there's no start delay, init the animation and notify start listeners right away
              // to be consistent with the previous behavior. Otherwise, postpone this until the first
              // frame after the start delay.
              startAnimation();
              if (mSeekFraction == -1) {
                  // No seek, start at play time 0. Note that the reason we are not using fraction 0
                  // is because for animations with 0 duration, we want to be consistent with pre-N
                  // behavior: skip to the final value immediately.
                  setCurrentPlayTime(0);
              } else {
                  setCurrentFraction(mSeekFraction);
              }
          }
      }
  
      void startWithoutPulsing(boolean inReverse) {
          mSuppressSelfPulseRequested = true;
          if (inReverse) {
              reverse();
          } else {
              start();
          }
          mSuppressSelfPulseRequested = false;
      }
  
      @Override
      public void start() {
          start(false);
      }
  
      @Override
      public void cancel() {
          if (Looper.myLooper() == null) {
              throw new AndroidRuntimeException("Animators may only be run on Looper threads");
          }
  
          // If end has already been requested, through a previous end() or cancel() call, no-op
          // until animation starts again.
          if (mAnimationEndRequested) {
              return;
          }
  
          // Only cancel if the animation is actually running or has been started and is about
          // to run
          // Only notify listeners if the animator has actually started
          if ((mStarted || mRunning) && mListeners != null) {
              if (!mRunning) {
                  // If it's not yet running, then start listeners weren't called. Call them now.
                  notifyStartListeners();
              }
              ArrayList<AnimatorListener> tmpListeners =
                      (ArrayList<AnimatorListener>) mListeners.clone();
              for (AnimatorListener listener : tmpListeners) {
                  listener.onAnimationCancel(this);
              }
          }
          endAnimation();
  
      }
  
      @Override
      public void end() {
          if (Looper.myLooper() == null) {
              throw new AndroidRuntimeException("Animators may only be run on Looper threads");
          }
          if (!mRunning) {
              // Special case if the animation has not yet started; get it ready for ending
              startAnimation();
              mStarted = true;
          } else if (!mInitialized) {
              initAnimation();
          }
          animateValue(shouldPlayBackward(mRepeatCount, mReversing) ? 0f : 1f);
          endAnimation();
      }
  
      @Override
      public void resume() {
          if (Looper.myLooper() == null) {
              throw new AndroidRuntimeException("Animators may only be resumed from the same " +
                      "thread that the animator was started on");
          }
          if (mPaused && !mResumed) {
              mResumed = true;
              if (mPauseTime > 0) {
                  addAnimationCallback(0);
              }
          }
          super.resume();
      }
  
      @Override
      public void pause() {
          boolean previouslyPaused = mPaused;
          super.pause();
          if (!previouslyPaused && mPaused) {
              mPauseTime = -1;
              mResumed = false;
          }
      }
  
      @Override
      public boolean isRunning() {
          return mRunning;
      }
  
      @Override
      public boolean isStarted() {
          return mStarted;
      }
  
      /**
       * 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.
       */
      @Override
      public void reverse() {
          if (isPulsingInternal()) {
              long currentTime = AnimationUtils.currentAnimationTimeMillis();
              long currentPlayTime = currentTime - mStartTime;
              long timeLeft = getScaledDuration() - currentPlayTime;
              mStartTime = currentTime - timeLeft;
              mStartTimeCommitted = true; // do not allow start time to be compensated for jank
              mReversing = !mReversing;
          } else if (mStarted) {
              mReversing = !mReversing;
              end();
          } else {
              start(true);
          }
      }
  
      /**
       * @hide
       */
      @Override
      public boolean canReverse() {
          return true;
      }
  
      /**
       * Called internally to end an animation by removing it from the animations list. Must be
       * called on the UI thread.
       */
      private void endAnimation() {
          if (mAnimationEndRequested) {
              return;
          }
          removeAnimationCallback();
  
          mAnimationEndRequested = true;
          mPaused = false;
          boolean notify = (mStarted || mRunning) && mListeners != null;
          if (notify && !mRunning) {
              // If it's not yet running, then start listeners weren't called. Call them now.
              notifyStartListeners();
          }
          mRunning = false;
          mStarted = false;
          mStartListenersCalled = false;
          mLastFrameTime = -1;
          mFirstFrameTime = -1;
          mStartTime = -1;
          if (notify && mListeners != null) {
              ArrayList<AnimatorListener> tmpListeners =
                      (ArrayList<AnimatorListener>) mListeners.clone();
              int numListeners = tmpListeners.size();
              for (int i = 0; i < numListeners; ++i) {
                  tmpListeners.get(i).onAnimationEnd(this, mReversing);
              }
          }
          // mReversing needs to be reset *after* notifying the listeners for the end callbacks.
          mReversing = false;
          if (Trace.isTagEnabled(Trace.TRACE_TAG_VIEW)) {
              Trace.asyncTraceEnd(Trace.TRACE_TAG_VIEW, getNameForTrace(),
                      System.identityHashCode(this));
          }
      }
  
      /**
       * Called internally to start an animation by adding it to the active animations list. Must be
       * called on the UI thread.
       */
      private void startAnimation() {
          if (Trace.isTagEnabled(Trace.TRACE_TAG_VIEW)) {
              Trace.asyncTraceBegin(Trace.TRACE_TAG_VIEW, getNameForTrace(),
                      System.identityHashCode(this));
          }
  
          mAnimationEndRequested = false;
          initAnimation();
          mRunning = true;
          if (mSeekFraction >= 0) {
              mOverallFraction = mSeekFraction;
          } else {
              mOverallFraction = 0f;
          }
          if (mListeners != null) {
              notifyStartListeners();
          }
      }
  
      /**
       * Internal only: This tracks whether the animation has gotten on the animation loop. Note
       * this is different than {@link #isRunning()} in that the latter tracks the time after start()
       * is called (or after start delay if any), which may be before the animation loop starts.
       */
      private boolean isPulsingInternal() {
          return mLastFrameTime >= 0;
      }
  
      /**
       * Returns the name of this animator for debugging purposes.
       */
      String getNameForTrace() {
          return "animator";
      }
  
      /**
       * Applies an adjustment to the animation to compensate for jank between when
       * the animation first ran and when the frame was drawn.
       * @hide
       */
      public void commitAnimationFrame(long frameTime) {
          if (!mStartTimeCommitted) {
              mStartTimeCommitted = true;
              long adjustment = frameTime - mLastFrameTime;
              if (adjustment > 0) {
                  mStartTime += adjustment;
                  if (DEBUG) {
                      Log.d(TAG, "Adjusted start time by " + adjustment + " ms: " + toString());
                  }
              }
          }
      }
  
      /**
       * This internal function processes a single animation frame for a given animation. The
       * currentTime parameter is the timing pulse sent by the handler, used to calculate the
       * elapsed duration, and therefore
       * the elapsed fraction, of the animation. The return value indicates whether the animation
       * should be ended (which happens when the elapsed time of the animation exceeds the
       * animation's duration, including the repeatCount).
       *
       * @param currentTime The current time, as tracked by the static timing handler
       * @return true if the animation's duration, including any repetitions due to
       * <code>repeatCount</code> has been exceeded and the animation should be ended.
       */
      boolean animateBasedOnTime(long currentTime) {
          boolean done = false;
          if (mRunning) {
              final long scaledDuration = getScaledDuration();
              final float fraction = scaledDuration > 0 ?
                      (float)(currentTime - mStartTime) / scaledDuration : 1f;
              final float lastFraction = mOverallFraction;
              final boolean newIteration = (int) fraction > (int) lastFraction;
              final boolean lastIterationFinished = (fraction >= mRepeatCount + 1) &&
                      (mRepeatCount != INFINITE);
              if (scaledDuration == 0) {
                  // 0 duration animator, ignore the repeat count and skip to the end
                  done = true;
              } else if (newIteration && !lastIterationFinished) {
                  // Time to repeat
                  if (mListeners != null) {
                      int numListeners = mListeners.size();
                      for (int i = 0; i < numListeners; ++i) {
                          mListeners.get(i).onAnimationRepeat(this);
                      }
                  }
              } else if (lastIterationFinished) {
                  done = true;
              }
              mOverallFraction = clampFraction(fraction);
              float currentIterationFraction = getCurrentIterationFraction(
                      mOverallFraction, mReversing);
              animateValue(currentIterationFraction);
          }
          return done;
      }
  
      /**
       * Internal use only.
       *
       * This method does not modify any fields of the animation. It should be called when seeking
       * in an AnimatorSet. When the last play time and current play time are of different repeat
       * iterations,
       * {@link android.view.animation.Animation.AnimationListener#onAnimationRepeat(Animation)}
       * will be called.
       */
      @Override
      void animateBasedOnPlayTime(long currentPlayTime, long lastPlayTime, boolean inReverse) {
          if (currentPlayTime < 0 || lastPlayTime < 0) {
              throw new UnsupportedOperationException("Error: Play time should never be negative.");
          }
  
          initAnimation();
          // Check whether repeat callback is needed only when repeat count is non-zero
          if (mRepeatCount > 0) {
              int iteration = (int) (currentPlayTime / mDuration);
              int lastIteration = (int) (lastPlayTime / mDuration);
  
              // Clamp iteration to [0, mRepeatCount]
              iteration = Math.min(iteration, mRepeatCount);
              lastIteration = Math.min(lastIteration, mRepeatCount);
  
              if (iteration != lastIteration) {
                  if (mListeners != null) {
                      int numListeners = mListeners.size();
                      for (int i = 0; i < numListeners; ++i) {
                          mListeners.get(i).onAnimationRepeat(this);
                      }
                  }
              }
          }
  
          if (mRepeatCount != INFINITE && currentPlayTime >= (mRepeatCount + 1) * mDuration) {
              skipToEndValue(inReverse);
          } else {
              // Find the current fraction:
              float fraction = currentPlayTime / (float) mDuration;
              fraction = getCurrentIterationFraction(fraction, inReverse);
              animateValue(fraction);
          }
      }
  
      /**
       * Internal use only.
       * Skips the animation value to end/start, depending on whether the play direction is forward
       * or backward.
       *
       * @param inReverse whether the end value is based on a reverse direction. If yes, this is
       *                  equivalent to skip to start value in a forward playing direction.
       */
      void skipToEndValue(boolean inReverse) {
          initAnimation();
          float endFraction = inReverse ? 0f : 1f;
          if (mRepeatCount % 2 == 1 && mRepeatMode == REVERSE) {
              // This would end on fraction = 0
              endFraction = 0f;
          }
          animateValue(endFraction);
      }
  
      @Override
      boolean isInitialized() {
          return mInitialized;
      }
  
      /**
       * Processes a frame of the animation, adjusting the start time if needed.
       *
       * @param frameTime The frame time.
       * @return true if the animation has ended.
       * @hide
       */
      public final boolean doAnimationFrame(long frameTime) {
          if (mStartTime < 0) {
              // First frame. If there is start delay, start delay count down will happen *after* this
              // frame.
              mStartTime = mReversing
                      ? frameTime
                      : frameTime + (long) (mStartDelay * resolveDurationScale());
          }
  
          // Handle pause/resume
          if (mPaused) {
              mPauseTime = frameTime;
              removeAnimationCallback();
              return false;
          } else if (mResumed) {
              mResumed = false;
              if (mPauseTime > 0) {
                  // Offset by the duration that the animation was paused
                  mStartTime += (frameTime - mPauseTime);
              }
          }
  
          if (!mRunning) {
              // If not running, that means the animation is in the start delay phase of a forward
              // running animation. In the case of reversing, we want to run start delay in the end.
              if (mStartTime > frameTime && mSeekFraction == -1) {
                  // This is when no seek fraction is set during start delay. If developers change the
                  // seek fraction during the delay, animation will start from the seeked position
                  // right away.
                  return false;
              } else {
                  // If mRunning is not set by now, that means non-zero start delay,
                  // no seeking, not reversing. At this point, start delay has passed.
                  mRunning = true;
                  startAnimation();
              }
          }
  
          if (mLastFrameTime < 0) {
              if (mSeekFraction >= 0) {
                  long seekTime = (long) (getScaledDuration() * mSeekFraction);
                  mStartTime = frameTime - seekTime;
                  mSeekFraction = -1;
              }
              mStartTimeCommitted = false; // allow start time to be compensated for jank
          }
          mLastFrameTime = frameTime;
          // The frame time might be before the start time during the first frame of
          // an animation.  The "current time" must always be on or after the start
          // time to avoid animating frames at negative time intervals.  In practice, this
          // is very rare and only happens when seeking backwards.
          final long currentTime = Math.max(frameTime, mStartTime);
          boolean finished = animateBasedOnTime(currentTime);
  
          if (finished) {
              endAnimation();
          }
          return finished;
      }
  
      @Override
      boolean pulseAnimationFrame(long frameTime) {
          if (mSelfPulse) {
              // Pulse animation frame will *always* be after calling start(). If mSelfPulse isn't
              // set to false at this point, that means child animators did not call super's start().
              // This can happen when the Animator is just a non-animating wrapper around a real
              // functional animation. In this case, we can't really pulse a frame into the animation,
              // because the animation cannot necessarily be properly initialized (i.e. no start/end
              // values set).
              return false;
          }
          return doAnimationFrame(frameTime);
      }
  
      private void addOneShotCommitCallback() {
          if (!mSelfPulse) {
              return;
          }
          getAnimationHandler().addOneShotCommitCallback(this);
      }
  
      private void removeAnimationCallback() {
          if (!mSelfPulse) {
              return;
          }
          getAnimationHandler().removeCallback(this);
      }
  
      private void addAnimationCallback(long delay) {
          if (!mSelfPulse) {
              return;
          }
          getAnimationHandler().addAnimationFrameCallback(this, delay);
      }
  
      /**
       * Returns the current animation fraction, which is the elapsed/interpolated fraction used in
       * the most recent frame update on the animation.
       *
       * @return Elapsed/interpolated fraction of the animation.
       */
      public float getAnimatedFraction() {
          return mCurrentFraction;
      }
  
      /**
       * This method is called with the elapsed fraction of the animation during every
       * animation frame. This function turns the elapsed fraction into an interpolated fraction
       * and then into an animated value (from the evaluator. The function is called mostly during
       * animation updates, but it is also called when the <code>end()</code>
       * function is called, to set the final value on the property.
       *
       * <p>Overrides of this method must call the superclass to perform the calculation
       * of the animated value.</p>
       *
       * @param fraction The elapsed fraction of the animation.
       */
      @CallSuper
      @UnsupportedAppUsage
      void animateValue(float fraction) {
          fraction = mInterpolator.getInterpolation(fraction);
          mCurrentFraction = fraction;
          int numValues = mValues.length;
          for (int i = 0; i < numValues; ++i) {
              mValues[i].calculateValue(fraction);
          }
          if (mUpdateListeners != null) {
              int numListeners = mUpdateListeners.size();
              for (int i = 0; i < numListeners; ++i) {
                  mUpdateListeners.get(i).onAnimationUpdate(this);
              }
          }
      }
  
      @Override
      public ValueAnimator clone() {
          final ValueAnimator anim = (ValueAnimator) super.clone();
          if (mUpdateListeners != null) {
              anim.mUpdateListeners = new ArrayList<AnimatorUpdateListener>(mUpdateListeners);
          }
          anim.mSeekFraction = -1;
          anim.mReversing = false;
          anim.mInitialized = false;
          anim.mStarted = false;
          anim.mRunning = false;
          anim.mPaused = false;
          anim.mResumed = false;
          anim.mStartListenersCalled = false;
          anim.mStartTime = -1;
          anim.mStartTimeCommitted = false;
          anim.mAnimationEndRequested = false;
          anim.mPauseTime = -1;
          anim.mLastFrameTime = -1;
          anim.mFirstFrameTime = -1;
          anim.mOverallFraction = 0;
          anim.mCurrentFraction = 0;
          anim.mSelfPulse = true;
          anim.mSuppressSelfPulseRequested = false;
  
          PropertyValuesHolder[] oldValues = mValues;
          if (oldValues != null) {
              int numValues = oldValues.length;
              anim.mValues = new PropertyValuesHolder[numValues];
              anim.mValuesMap = new HashMap<String, PropertyValuesHolder>(numValues);
              for (int i = 0; i < numValues; ++i) {
                  PropertyValuesHolder newValuesHolder = oldValues[i].clone();
                  anim.mValues[i] = newValuesHolder;
                  anim.mValuesMap.put(newValuesHolder.getPropertyName(), newValuesHolder);
              }
          }
          return anim;
      }
  
      /**
       * Implementors of this interface can add themselves as update listeners
       * to an <code>ValueAnimator</code> instance to receive callbacks on every animation
       * frame, after the current frame's values have been calculated for that
       * <code>ValueAnimator</code>.
       */
      public static interface AnimatorUpdateListener {
          /**
           * <p>Notifies the occurrence of another frame of the animation.</p>
           *
           * @param animation The animation which was repeated.
           */
          void onAnimationUpdate(ValueAnimator animation);
  
      }
  
      /**
       * Return the number of animations currently running.
       *
       * Used by StrictMode internally to annotate violations.
       * May be called on arbitrary threads!
       *
       * @hide
       */
      public static int getCurrentAnimationsCount() {
          return AnimationHandler.getAnimationCount();
      }
  
      @Override
      public String toString() {
          String returnVal = "ValueAnimator@" + Integer.toHexString(hashCode());
          if (mValues != null) {
              for (int i = 0; i < mValues.length; ++i) {
                  returnVal += "\n    " + mValues[i].toString();
              }
          }
          return returnVal;
      }
  
      /**
       * <p>Whether or not the ValueAnimator is allowed to run asynchronously off of
       * the UI thread. This is a hint that informs the ValueAnimator that it is
       * OK to run the animation off-thread, however ValueAnimator may decide
       * that it must run the animation on the UI thread anyway. For example if there
       * is an {@link AnimatorUpdateListener} the animation will run on the UI thread,
       * regardless of the value of this hint.</p>
       *
       * <p>Regardless of whether or not the animation runs asynchronously, all
       * listener callbacks will be called on the UI thread.</p>
       *
       * <p>To be able to use this hint the following must be true:</p>
       * <ol>
       * <li>{@link #getAnimatedFraction()} is not needed (it will return undefined values).</li>
       * <li>The animator is immutable while {@link #isStarted()} is true. Requests
       *    to change values, duration, delay, etc... may be ignored.</li>
       * <li>Lifecycle callback events may be asynchronous. Events such as
       *    {@link Animator.AnimatorListener#onAnimationEnd(Animator)} or
       *    {@link Animator.AnimatorListener#onAnimationRepeat(Animator)} may end up delayed
       *    as they must be posted back to the UI thread, and any actions performed
       *    by those callbacks (such as starting new animations) will not happen
       *    in the same frame.</li>
       * <li>State change requests ({@link #cancel()}, {@link #end()}, {@link #reverse()}, etc...)
       *    may be asynchronous. It is guaranteed that all state changes that are
       *    performed on the UI thread in the same frame will be applied as a single
       *    atomic update, however that frame may be the current frame,
       *    the next frame, or some future frame. This will also impact the observed
       *    state of the Animator. For example, {@link #isStarted()} may still return true
       *    after a call to {@link #end()}. Using the lifecycle callbacks is preferred over
       *    queries to {@link #isStarted()}, {@link #isRunning()}, and {@link #isPaused()}
       *    for this reason.</li>
       * </ol>
       * @hide
       */
      @Override
      public void setAllowRunningAsynchronously(boolean mayRunAsync) {
          // It is up to subclasses to support this, if they can.
      }
  
      /**
       * @return The {@link AnimationHandler} that will be used to schedule updates for this animator.
       * @hide
       */
      public AnimationHandler getAnimationHandler() {
          return AnimationHandler.getInstance();
      }
  }
  