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 com.android.launcher3.util;
  
  import static com.android.launcher3.anim.Interpolators.SCROLL;
  
  import android.animation.TimeInterpolator;
  import android.content.Context;
  import android.hardware.SensorManager;
  import android.util.Log;
  import android.view.ViewConfiguration;
  import android.view.animation.AnimationUtils;
  import android.view.animation.Interpolator;
  
  import androidx.dynamicanimation.animation.DynamicAnimation;
  import androidx.dynamicanimation.animation.FloatPropertyCompat;
  import androidx.dynamicanimation.animation.SpringAnimation;
  import androidx.dynamicanimation.animation.SpringForce;
  
  /**
   * Based on {@link android.widget.OverScroller} supporting only 1-d scrolling and with more
   * customization options.
   */
  public class OverScroller {
      private int mMode;
  
      private final SplineOverScroller mScroller;
  
      private TimeInterpolator mInterpolator;
  
      private final boolean mFlywheel;
  
      private static final int DEFAULT_DURATION = 250;
      private static final int SCROLL_MODE = 0;
      private static final int FLING_MODE = 1;
  
      /**
       * Creates an OverScroller with a viscous fluid scroll interpolator and flywheel.
       * @param context
       */
      public OverScroller(Context context) {
          this(context, null);
      }
  
      /**
       * Creates an OverScroller with flywheel enabled.
       * @param context The context of this application.
       * @param interpolator The scroll interpolator. If null, a default (viscous) interpolator will
       * be used.
       */
      public OverScroller(Context context, Interpolator interpolator) {
          this(context, interpolator, true);
      }
  
      /**
       * Creates an OverScroller.
       * @param context The context of this application.
       * @param interpolator The scroll interpolator. If null, a default (viscous) interpolator will
       * be used.
       * @param flywheel If true, successive fling motions will keep on increasing scroll speed.
       */
      public OverScroller(Context context, Interpolator interpolator, boolean flywheel) {
          if (interpolator == null) {
              mInterpolator = SCROLL;
          } else {
              mInterpolator = interpolator;
          }
          mFlywheel = flywheel;
          mScroller = new SplineOverScroller(context);
      }
  
      public void setInterpolator(TimeInterpolator interpolator) {
          if (interpolator == null) {
              mInterpolator = SCROLL;
          } else {
              mInterpolator = interpolator;
          }
      }
  
      /**
       * The amount of friction applied to flings. The default value
       * is {@link ViewConfiguration#getScrollFriction}.
       *
       * @param friction A scalar dimension-less value representing the coefficient of
       *         friction.
       */
      public final void setFriction(float friction) {
          mScroller.setFriction(friction);
      }
  
      /**
       *
       * Returns whether the scroller has finished scrolling.
       *
       * @return True if the scroller has finished scrolling, false otherwise.
       */
      public final boolean isFinished() {
          return mScroller.mFinished;
      }
  
      /**
       * Force the finished field to a particular value. Contrary to
       * {@link #abortAnimation()}, forcing the animation to finished
       * does NOT cause the scroller to move to the final x and y
       * position.
       *
       * @param finished The new finished value.
       */
      public final void forceFinished(boolean finished) {
          mScroller.mFinished = finished;
      }
  
      /**
       * Returns the current offset in the scroll.
       *
       * @return The new offset as an absolute distance from the origin.
       */
      public final int getCurrPos() {
          return mScroller.mCurrentPosition;
      }
  
      /**
       * Returns the absolute value of the current velocity.
       *
       * @return The original velocity less the deceleration, norm of the X and Y velocity vector.
       */
      public float getCurrVelocity() {
          return mScroller.mCurrVelocity;
      }
  
      /**
       * Returns the start offset in the scroll.
       *
       * @return The start offset as an absolute distance from the origin.
       */
      public final int getStartPos() {
          return mScroller.mStart;
      }
  
      /**
       * Returns where the scroll will end. Valid only for "fling" scrolls.
       *
       * @return The final offset as an absolute distance from the origin.
       */
      public final int getFinalPos() {
          return mScroller.mFinal;
      }
  
      /**
       * Returns how long the scroll event will take, in milliseconds.
       *
       * @return The duration of the scroll in milliseconds.
       */
      public final int getDuration() {
          return mScroller.mDuration;
      }
  
      /**
       * Extend the scroll animation. This allows a running animation to scroll
       * further and longer, when used with {@link #setFinalPos(int)}.
       *
       * @param extend Additional time to scroll in milliseconds.
       * @see #setFinalPos(int)
       */
      public void extendDuration(int extend) {
          mScroller.extendDuration(extend);
      }
  
      /**
       * Sets the final position for this scroller.
       *
       * @param newPos The new offset as an absolute distance from the origin.
       * @see #extendDuration(int)
       */
      public void setFinalPos(int newPos) {
          mScroller.setFinalPosition(newPos);
      }
  
      /**
       * Call this when you want to know the new location. If it returns true, the
       * animation is not yet finished.
       */
      public boolean computeScrollOffset() {
          if (isFinished()) {
              return false;
          }
  
          switch (mMode) {
              case SCROLL_MODE:
                  if (isSpringing()) {
                      return true;
                  }
                  long time = AnimationUtils.currentAnimationTimeMillis();
                  // Any scroller can be used for time, since they were started
                  // together in scroll mode. We use X here.
                  final long elapsedTime = time - mScroller.mStartTime;
  
                  final int duration = mScroller.mDuration;
                  if (elapsedTime < duration) {
                      final float q = mInterpolator.getInterpolation(elapsedTime / (float) duration);
                      mScroller.updateScroll(q);
                  } else {
                      abortAnimation();
                  }
                  break;
  
              case FLING_MODE:
                  if (!mScroller.mFinished) {
                      if (!mScroller.update()) {
                          if (!mScroller.continueWhenFinished()) {
                              mScroller.finish();
                          }
                      }
                  }
  
                  break;
          }
  
          return true;
      }
  
      /**
       * Start scrolling by providing a starting point and the distance to travel.
       * The scroll will use the default value of 250 milliseconds for the
       * duration.
       *
       * @param start Starting horizontal scroll offset in pixels. Positive
       *        numbers will scroll the content to the left.
       * @param delta Distance to travel. Positive numbers will scroll the
       *        content to the left.
       */
      public void startScroll(int start, int delta) {
          startScroll(start, delta, DEFAULT_DURATION);
      }
  
      /**
       * Start scrolling by providing a starting point and the distance to travel.
       *
       * @param start Starting scroll offset in pixels. Positive
       *        numbers will scroll the content to the left.
       * @param delta Distance to travel. Positive numbers will scroll the
       *        content to the left.
       * @param duration Duration of the scroll in milliseconds.
       */
      public void startScroll(int start, int delta, int duration) {
          mMode = SCROLL_MODE;
          mScroller.startScroll(start, delta, duration);
      }
  
      /**
       * Start scrolling using a spring by providing a starting point and the distance to travel.
       *
       * @param start Starting scroll offset in pixels. Positive
       *        numbers will scroll the content to the left.
       * @param delta Distance to travel. Positive numbers will scroll the
       *        content to the left.
       * @param duration Duration of the scroll in milliseconds.
       * @param velocity The starting velocity for the spring in px per ms.
       */
      public void startScrollSpring(int start, int delta, int duration, float velocity) {
          mMode = SCROLL_MODE;
          mScroller.mState = mScroller.SPRING;
          mScroller.startScroll(start, delta, duration, velocity);
      }
  
      /**
       * Call this when you want to 'spring back' into a valid coordinate range.
       *
       * @param start Starting X coordinate
       * @param min Minimum valid X value
       * @param max Maximum valid X value
       * @return true if a springback was initiated, false if startX and startY were
       *          already within the valid range.
       */
      public boolean springBack(int start, int min, int max) {
          mMode = FLING_MODE;
          return mScroller.springback(start, min, max);
      }
  
      public void fling(int start, int velocity, int min, int max) {
          fling(start, velocity, min, max, 0);
      }
  
      /**
       * Start scrolling based on a fling gesture. The distance traveled will
       * depend on the initial velocity of the fling.
       *  @param start Starting point of the scroll (X)
       * @param velocity Initial velocity of the fling (X) measured in pixels per
       *            second.
       * @param min Minimum X value. The scroller will not scroll past this point
   *            unless overX > 0. If overfling is allowed, it will use minX as
   *            a springback boundary.
       * @param max Maximum X value. The scroller will not scroll past this point
  *            unless overX > 0. If overfling is allowed, it will use maxX as
  *            a springback boundary.
       * @param over Overfling range. If > 0, horizontal overfling in either
  *            direction will be possible.
       */
      public void fling(int start, int velocity, int min, int max, int over) {
          // Continue a scroll or fling in progress
          if (mFlywheel && !isFinished()) {
              float oldVelocityX = mScroller.mCurrVelocity;
              if (Math.signum(velocity) == Math.signum(oldVelocityX)) {
                  velocity += oldVelocityX;
              }
          }
  
          mMode = FLING_MODE;
          mScroller.fling(start, velocity, min, max, over);
      }
  
      /**
       * Notify the scroller that we've reached a horizontal boundary.
       * Normally the information to handle this will already be known
       * when the animation is started, such as in a call to one of the
       * fling functions. However there are cases where this cannot be known
       * in advance. This function will transition the current motion and
       * animate from startX to finalX as appropriate.
       *  @param start Starting/current X position
       * @param finalPos Desired final X position
       * @param over Magnitude of overscroll allowed. This should be the maximum
       */
      public void notifyEdgeReached(int start, int finalPos, int over) {
          mScroller.notifyEdgeReached(start, finalPos, over);
      }
  
      /**
       * Returns whether the current Scroller is currently returning to a valid position.
       * Valid bounds were provided by the
       * {@link #fling(int, int, int, int, int)} method.
       *
       * One should check this value before calling
       * {@link #startScroll(int, int)} as the interpolation currently in progress
       * to restore a valid position will then be stopped. The caller has to take into account
       * the fact that the started scroll will start from an overscrolled position.
       *
       * @return true when the current position is overscrolled and in the process of
       *         interpolating back to a valid value.
       */
      public boolean isOverScrolled() {
          return (!mScroller.mFinished && mScroller.mState != SplineOverScroller.SPLINE);
      }
  
      /**
       * Stops the animation. Contrary to {@link #forceFinished(boolean)},
       * aborting the animating causes the scroller to move to the final x and y
       * positions.
       *
       * @see #forceFinished(boolean)
       */
      public void abortAnimation() {
          mScroller.finish();
      }
  
      /**
       * Returns the time elapsed since the beginning of the scrolling.
       *
       * @return The elapsed time in milliseconds.
       *
       * @hide
       */
      public int timePassed() {
          final long time = AnimationUtils.currentAnimationTimeMillis();
          return (int) (time - mScroller.mStartTime);
      }
  
      public boolean isSpringing() {
          return mScroller.mState == SplineOverScroller.SPRING && !isFinished();
      }
  
      static class SplineOverScroller {
          // Initial position
          private int mStart;
  
          // Current position
          private int mCurrentPosition;
  
          // Final position
          private int mFinal;
  
          // Initial velocity
          private int mVelocity;
  
          // Current velocity
          private float mCurrVelocity;
  
          // Constant current deceleration
          private float mDeceleration;
  
          // Animation starting time, in system milliseconds
          private long mStartTime;
  
          // Animation duration, in milliseconds
          private int mDuration;
  
          // Duration to complete spline component of animation
          private int mSplineDuration;
  
          // Distance to travel along spline animation
          private int mSplineDistance;
  
          // Whether the animation is currently in progress
          private boolean mFinished;
  
          // The allowed overshot distance before boundary is reached.
          private int mOver;
  
          // Fling friction
          private float mFlingFriction = ViewConfiguration.getScrollFriction();
  
          // Current state of the animation.
          private int mState = SPLINE;
  
          private SpringAnimation mSpring;
  
          // Constant gravity value, used in the deceleration phase.
          private static final float GRAVITY = 2000.0f;
  
          // A context-specific coefficient adjusted to physical values.
          private float mPhysicalCoeff;
  
          private static float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));
          private static final float INFLEXION = 0.35f; // Tension lines cross at (INFLEXION, 1)
          private static final float START_TENSION = 0.5f;
          private static final float END_TENSION = 1.0f;
          private static final float P1 = START_TENSION * INFLEXION;
          private static final float P2 = 1.0f - END_TENSION * (1.0f - INFLEXION);
  
          private static final int NB_SAMPLES = 100;
          private static final float[] SPLINE_POSITION = new float[NB_SAMPLES + 1];
          private static final float[] SPLINE_TIME = new float[NB_SAMPLES + 1];
  
          private static final int SPLINE = 0;
          private static final int CUBIC = 1;
          private static final int BALLISTIC = 2;
          private static final int SPRING = 3;
  
          private static final FloatPropertyCompat<SplineOverScroller> SPRING_PROPERTY =
                  new FloatPropertyCompat<SplineOverScroller>("splineOverScrollerSpring") {
                      @Override
                      public float getValue(SplineOverScroller scroller) {
                          return scroller.mCurrentPosition;
                      }
  
                      @Override
                      public void setValue(SplineOverScroller scroller, float value) {
                          scroller.mCurrentPosition = (int) value;
                      }
                  };
  
          static {
              float x_min = 0.0f;
              float y_min = 0.0f;
              for (int i = 0; i < NB_SAMPLES; i++) {
                  final float alpha = (float) i / NB_SAMPLES;
  
                  float x_max = 1.0f;
                  float x, tx, coef;
                  while (true) {
                      x = x_min + (x_max - x_min) / 2.0f;
                      coef = 3.0f * x * (1.0f - x);
                      tx = coef * ((1.0f - x) * P1 + x * P2) + x * x * x;
                      if (Math.abs(tx - alpha) < 1E-5) break;
                      if (tx > alpha) x_max = x;
                      else x_min = x;
                  }
                  SPLINE_POSITION[i] = coef * ((1.0f - x) * START_TENSION + x) + x * x * x;
  
                  float y_max = 1.0f;
                  float y, dy;
                  while (true) {
                      y = y_min + (y_max - y_min) / 2.0f;
                      coef = 3.0f * y * (1.0f - y);
                      dy = coef * ((1.0f - y) * START_TENSION + y) + y * y * y;
                      if (Math.abs(dy - alpha) < 1E-5) break;
                      if (dy > alpha) y_max = y;
                      else y_min = y;
                  }
                  SPLINE_TIME[i] = coef * ((1.0f - y) * P1 + y * P2) + y * y * y;
              }
              SPLINE_POSITION[NB_SAMPLES] = SPLINE_TIME[NB_SAMPLES] = 1.0f;
          }
  
          void setFriction(float friction) {
              mFlingFriction = friction;
          }
  
          SplineOverScroller(Context context) {
              mFinished = true;
              final float ppi = context.getResources().getDisplayMetrics().density * 160.0f;
              mPhysicalCoeff = SensorManager.GRAVITY_EARTH // g (m/s^2)
                      * 39.37f // inch/meter
                      * ppi
                      * 0.84f; // look and feel tuning
          }
  
          void updateScroll(float q) {
              if (mState == SPRING) {
                  return;
              }
              mCurrentPosition = mStart + Math.round(q * (mFinal - mStart));
          }
  
          /*
           * Get a signed deceleration that will reduce the velocity.
           */
          static private float getDeceleration(int velocity) {
              return velocity > 0 ? -GRAVITY : GRAVITY;
          }
  
          /*
           * Modifies mDuration to the duration it takes to get from start to newFinal using the
           * spline interpolation. The previous duration was needed to get to oldFinal.
           */
          private void adjustDuration(int start, int oldFinal, int newFinal) {
              final int oldDistance = oldFinal - start;
              final int newDistance = newFinal - start;
              final float x = Math.abs((float) newDistance / oldDistance);
              final int index = (int) (NB_SAMPLES * x);
              if (index < NB_SAMPLES) {
                  final float x_inf = (float) index / NB_SAMPLES;
                  final float x_sup = (float) (index + 1) / NB_SAMPLES;
                  final float t_inf = SPLINE_TIME[index];
                  final float t_sup = SPLINE_TIME[index + 1];
                  final float timeCoef = t_inf + (x - x_inf) / (x_sup - x_inf) * (t_sup - t_inf);
                  mDuration *= timeCoef;
              }
          }
  
          void startScroll(int start, int distance, int duration) {
              startScroll(start, distance, duration, 0);
          }
  
          void startScroll(int start, int distance, int duration, float velocity) {
              mFinished = false;
  
              mCurrentPosition = mStart = start;
              mFinal = start + distance;
  
              mStartTime = AnimationUtils.currentAnimationTimeMillis();
              mDuration = duration;
  
              if (mState == SPRING) {
                  if (mSpring != null) {
                      mSpring.cancel();
                  }
                  mSpring = new SpringAnimation(this, SPRING_PROPERTY);
  
                  mSpring.setSpring(new SpringForce(mFinal)
                          .setStiffness(SpringForce.STIFFNESS_LOW)
                          .setDampingRatio(SpringForce.DAMPING_RATIO_LOW_BOUNCY));
                  mSpring.setStartVelocity(velocity);
                  mSpring.animateToFinalPosition(mFinal);
                  mSpring.addEndListener((animation, canceled, value, velocity1) -> {
                      finish();
                      mState = SPLINE;
                      mSpring = null;
                  });
              }
              // Unused
              mDeceleration = 0.0f;
              mVelocity = 0;
          }
  
          void finish() {
              if (mSpring != null && mSpring.isRunning()) mSpring.cancel();
  
              mCurrentPosition = mFinal;
              // Not reset since WebView relies on this value for fast fling.
              // TODO: restore when WebView uses the fast fling implemented in this class.
              // mCurrVelocity = 0.0f;
              mFinished = true;
          }
  
          void setFinalPosition(int position) {
              mFinal = position;
              if (mState == SPRING && mSpring != null) {
                  mSpring.animateToFinalPosition(mFinal);
              }
              mSplineDistance = mFinal - mStart;
              mFinished = false;
          }
  
          void extendDuration(int extend) {
              final long time = AnimationUtils.currentAnimationTimeMillis();
              final int elapsedTime = (int) (time - mStartTime);
              mDuration  = mSplineDuration = elapsedTime + extend;
              mFinished = false;
          }
  
          boolean springback(int start, int min, int max) {
              mFinished = true;
  
              mCurrentPosition = mStart = mFinal = start;
              mVelocity = 0;
  
              mStartTime = AnimationUtils.currentAnimationTimeMillis();
              mDuration = 0;
  
              if (start < min) {
                  startSpringback(start, min, 0);
              } else if (start > max) {
                  startSpringback(start, max, 0);
              }
  
              return !mFinished;
          }
  
          private void startSpringback(int start, int end, int velocity) {
              // mStartTime has been set
              mFinished = false;
              mState = CUBIC;
              mCurrentPosition = mStart = start;
              mFinal = end;
              final int delta = start - end;
              mDeceleration = getDeceleration(delta);
              // TODO take velocity into account
              mVelocity = -delta; // only sign is used
              mOver = Math.abs(delta);
              mDuration = (int) (1000.0 * Math.sqrt(-2.0 * delta / mDeceleration));
          }
  
          void fling(int start, int velocity, int min, int max, int over) {
              mOver = over;
              mFinished = false;
              mCurrVelocity = mVelocity = velocity;
              mDuration = mSplineDuration = 0;
              mStartTime = AnimationUtils.currentAnimationTimeMillis();
              mCurrentPosition = mStart = start;
  
              if (start > max || start < min) {
                  startAfterEdge(start, min, max, velocity);
                  return;
              }
  
              mState = SPLINE;
              double totalDistance = 0.0;
  
              if (velocity != 0) {
                  mDuration = mSplineDuration = getSplineFlingDuration(velocity);
                  totalDistance = getSplineFlingDistance(velocity);
              }
  
              mSplineDistance = (int) (totalDistance * Math.signum(velocity));
              mFinal = start + mSplineDistance;
  
              // Clamp to a valid final position
              if (mFinal < min) {
                  adjustDuration(mStart, mFinal, min);
                  mFinal = min;
              }
  
              if (mFinal > max) {
                  adjustDuration(mStart, mFinal, max);
                  mFinal = max;
              }
          }
  
          private double getSplineDeceleration(int velocity) {
              return Math.log(INFLEXION * Math.abs(velocity) / (mFlingFriction * mPhysicalCoeff));
          }
  
          private double getSplineFlingDistance(int velocity) {
              final double l = getSplineDeceleration(velocity);
              final double decelMinusOne = DECELERATION_RATE - 1.0;
              return mFlingFriction * mPhysicalCoeff * Math.exp(DECELERATION_RATE / decelMinusOne * l);
          }
  
          /* Returns the duration, expressed in milliseconds */
          private int getSplineFlingDuration(int velocity) {
              final double l = getSplineDeceleration(velocity);
              final double decelMinusOne = DECELERATION_RATE - 1.0;
              return (int) (1000.0 * Math.exp(l / decelMinusOne));
          }
  
          private void fitOnBounceCurve(int start, int end, int velocity) {
              // Simulate a bounce that started from edge
              final float durationToApex = - velocity / mDeceleration;
              // The float cast below is necessary to avoid integer overflow.
              final float velocitySquared = (float) velocity * velocity;
              final float distanceToApex = velocitySquared / 2.0f / Math.abs(mDeceleration);
              final float distanceToEdge = Math.abs(end - start);
              final float totalDuration = (float) Math.sqrt(
                      2.0 * (distanceToApex + distanceToEdge) / Math.abs(mDeceleration));
              mStartTime -= (int) (1000.0f * (totalDuration - durationToApex));
              mCurrentPosition = mStart = end;
              mVelocity = (int) (- mDeceleration * totalDuration);
          }
  
          private void startBounceAfterEdge(int start, int end, int velocity) {
              mDeceleration = getDeceleration(velocity == 0 ? start - end : velocity);
              fitOnBounceCurve(start, end, velocity);
              onEdgeReached();
          }
  
          private void startAfterEdge(int start, int min, int max, int velocity) {
              if (start > min && start < max) {
                  Log.e("OverScroller", "startAfterEdge called from a valid position");
                  mFinished = true;
                  return;
              }
              final boolean positive = start > max;
              final int edge = positive ? max : min;
              final int overDistance = start - edge;
              boolean keepIncreasing = overDistance * velocity >= 0;
              if (keepIncreasing) {
                  // Will result in a bounce or a to_boundary depending on velocity.
                  startBounceAfterEdge(start, edge, velocity);
              } else {
                  final double totalDistance = getSplineFlingDistance(velocity);
                  if (totalDistance > Math.abs(overDistance)) {
                      fling(start, velocity, positive ? min : start, positive ? start : max, mOver);
                  } else {
                      startSpringback(start, edge, velocity);
                  }
              }
          }
  
          void notifyEdgeReached(int start, int end, int over) {
              // mState is used to detect successive notifications
              if (mState == SPLINE) {
                  mOver = over;
                  mStartTime = AnimationUtils.currentAnimationTimeMillis();
                  // We were in fling/scroll mode before: current velocity is such that distance to
                  // edge is increasing. This ensures that startAfterEdge will not start a new fling.
                  startAfterEdge(start, end, end, (int) mCurrVelocity);
              }
          }
  
          private void onEdgeReached() {
              // mStart, mVelocity and mStartTime were adjusted to their values when edge was reached.
              // The float cast below is necessary to avoid integer overflow.
              final float velocitySquared = (float) mVelocity * mVelocity;
              float distance = velocitySquared / (2.0f * Math.abs(mDeceleration));
              final float sign = Math.signum(mVelocity);
  
              if (distance > mOver) {
                  // Default deceleration is not sufficient to slow us down before boundary
                  mDeceleration = - sign * velocitySquared / (2.0f * mOver);
                  distance = mOver;
              }
  
              mOver = (int) distance;
              mState = BALLISTIC;
              mFinal = mStart + (int) (mVelocity > 0 ? distance : -distance);
              mDuration = - (int) (1000.0f * mVelocity / mDeceleration);
          }
  
          boolean continueWhenFinished() {
              switch (mState) {
                  case SPLINE:
                      // Duration from start to null velocity
                      if (mDuration < mSplineDuration) {
                          // If the animation was clamped, we reached the edge
                          mCurrentPosition = mStart = mFinal;
                          // TODO Better compute speed when edge was reached
                          mVelocity = (int) mCurrVelocity;
                          mDeceleration = getDeceleration(mVelocity);
                          mStartTime += mDuration;
                          onEdgeReached();
                      } else {
                          // Normal stop, no need to continue
                          return false;
                      }
                      break;
                  case BALLISTIC:
                      mStartTime += mDuration;
                      startSpringback(mFinal, mStart, 0);
                      break;
                  case CUBIC:
                      return false;
              }
  
              update();
              return true;
          }
  
          /*
           * Update the current position and velocity for current time. Returns
           * true if update has been done and false if animation duration has been
           * reached.
           */
          boolean update() {
              if (mState == SPRING) {
                  return mFinished;
              }
  
              final long time = AnimationUtils.currentAnimationTimeMillis();
              final long currentTime = time - mStartTime;
  
              if (currentTime == 0) {
                  // Skip work but report that we're still going if we have a nonzero duration.
                  return mDuration > 0;
              }
              if (currentTime > mDuration) {
                  return false;
              }
  
              double distance = 0.0;
              switch (mState) {
                  case SPLINE: {
                      final float t = (float) currentTime / mSplineDuration;
                      final int index = (int) (NB_SAMPLES * t);
                      float distanceCoef = 1.f;
                      float velocityCoef = 0.f;
                      if (index < NB_SAMPLES) {
                          final float t_inf = (float) index / NB_SAMPLES;
                          final float t_sup = (float) (index + 1) / NB_SAMPLES;
                          final float d_inf = SPLINE_POSITION[index];
                          final float d_sup = SPLINE_POSITION[index + 1];
                          velocityCoef = (d_sup - d_inf) / (t_sup - t_inf);
                          distanceCoef = d_inf + (t - t_inf) * velocityCoef;
                      }
  
                      distance = distanceCoef * mSplineDistance;
                      mCurrVelocity = velocityCoef * mSplineDistance / mSplineDuration * 1000.0f;
                      break;
                  }
  
                  case BALLISTIC: {
                      final float t = currentTime / 1000.0f;
                      mCurrVelocity = mVelocity + mDeceleration * t;
                      distance = mVelocity * t + mDeceleration * t * t / 2.0f;
                      break;
                  }
  
                  case CUBIC: {
                      final float t = (float) (currentTime) / mDuration;
                      final float t2 = t * t;
                      final float sign = Math.signum(mVelocity);
                      distance = sign * mOver * (3.0f * t2 - 2.0f * t * t2);
                      mCurrVelocity = sign * mOver * 6.0f * (- t + t2);
                      break;
                  }
              }
  
              mCurrentPosition = mStart + (int) Math.round(distance);
  
              return true;
          }
      }
  }