| /* |
| * 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; |
| } |
| } |
| } |
