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script-astra/Android/Sdk/sources/android-35/android/widget/OverScroller.java

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/*
* 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.widget;
import android.compat.annotation.UnsupportedAppUsage;
import android.content.Context;
import android.hardware.SensorManager;
import android.os.Build;
import android.util.Log;
import android.view.ViewConfiguration;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;
/**
* This class encapsulates scrolling with the ability to overshoot the bounds
* of a scrolling operation. This class is a drop-in replacement for
* {@link android.widget.Scroller} in most cases.
*/
public class OverScroller {
private int mMode;
private final SplineOverScroller mScrollerX;
@UnsupportedAppUsage
private final SplineOverScroller mScrollerY;
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
private Interpolator 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.
* @hide
*/
@UnsupportedAppUsage
public OverScroller(Context context, Interpolator interpolator, boolean flywheel) {
if (interpolator == null) {
mInterpolator = new Scroller.ViscousFluidInterpolator();
} else {
mInterpolator = interpolator;
}
mFlywheel = flywheel;
mScrollerX = new SplineOverScroller(context);
mScrollerY = new SplineOverScroller(context);
}
/**
* 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.
* @param bounceCoefficientX A value between 0 and 1 that will determine the proportion of the
* velocity which is preserved in the bounce when the horizontal edge is reached. A null value
* means no bounce. This behavior is no longer supported and this coefficient has no effect.
* @param bounceCoefficientY Same as bounceCoefficientX but for the vertical direction. This
* behavior is no longer supported and this coefficient has no effect.
* @deprecated Use {@link #OverScroller(Context, Interpolator)} instead.
*/
@Deprecated
public OverScroller(Context context, Interpolator interpolator,
float bounceCoefficientX, float bounceCoefficientY) {
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 bounceCoefficientX A value between 0 and 1 that will determine the proportion of the
* velocity which is preserved in the bounce when the horizontal edge is reached. A null value
* means no bounce. This behavior is no longer supported and this coefficient has no effect.
* @param bounceCoefficientY Same as bounceCoefficientX but for the vertical direction. This
* behavior is no longer supported and this coefficient has no effect.
* @param flywheel If true, successive fling motions will keep on increasing scroll speed.
* @deprecated Use {@link #OverScroller(Context, Interpolator)} instead.
*/
@Deprecated
public OverScroller(Context context, Interpolator interpolator,
float bounceCoefficientX, float bounceCoefficientY, boolean flywheel) {
this(context, interpolator, flywheel);
}
@UnsupportedAppUsage
void setInterpolator(Interpolator interpolator) {
if (interpolator == null) {
mInterpolator = new Scroller.ViscousFluidInterpolator();
} 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) {
mScrollerX.setFriction(friction);
mScrollerY.setFriction(friction);
}
/**
*
* Returns whether the scroller has finished scrolling.
*
* @return True if the scroller has finished scrolling, false otherwise.
*/
public final boolean isFinished() {
return mScrollerX.mFinished && mScrollerY.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) {
mScrollerX.mFinished = mScrollerY.mFinished = finished;
}
/**
* Returns the current X offset in the scroll.
*
* @return The new X offset as an absolute distance from the origin.
*/
public final int getCurrX() {
return mScrollerX.mCurrentPosition;
}
/**
* Returns the current Y offset in the scroll.
*
* @return The new Y offset as an absolute distance from the origin.
*/
public final int getCurrY() {
return mScrollerY.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 (float) Math.hypot(mScrollerX.mCurrVelocity, mScrollerY.mCurrVelocity);
}
/**
* Returns the start X offset in the scroll.
*
* @return The start X offset as an absolute distance from the origin.
*/
public final int getStartX() {
return mScrollerX.mStart;
}
/**
* Returns the start Y offset in the scroll.
*
* @return The start Y offset as an absolute distance from the origin.
*/
public final int getStartY() {
return mScrollerY.mStart;
}
/**
* Returns where the scroll will end. Valid only for "fling" scrolls.
*
* @return The final X offset as an absolute distance from the origin.
*/
public final int getFinalX() {
return mScrollerX.mFinal;
}
/**
* Returns where the scroll will end. Valid only for "fling" scrolls.
*
* @return The final Y offset as an absolute distance from the origin.
*/
public final int getFinalY() {
return mScrollerY.mFinal;
}
/**
* Returns how long the scroll event will take, in milliseconds.
*
* @return The duration of the scroll in milliseconds.
*
* @hide
*/
public final int getDuration() {
return Math.max(mScrollerX.mDuration, mScrollerY.mDuration);
}
/**
* Extend the scroll animation. This allows a running animation to scroll
* further and longer, when used with {@link #setFinalX(int)} or {@link #setFinalY(int)}.
*
* @param extend Additional time to scroll in milliseconds.
* @see #setFinalX(int)
* @see #setFinalY(int)
*
* @hide
*/
@UnsupportedAppUsage
public void extendDuration(int extend) {
mScrollerX.extendDuration(extend);
mScrollerY.extendDuration(extend);
}
/**
* Sets the final position (X) for this scroller.
*
* @param newX The new X offset as an absolute distance from the origin.
* @see #extendDuration(int)
* @see #setFinalY(int)
*
* @hide
*/
public void setFinalX(int newX) {
mScrollerX.setFinalPosition(newX);
}
/**
* Sets the final position (Y) for this scroller.
*
* @param newY The new Y offset as an absolute distance from the origin.
* @see #extendDuration(int)
* @see #setFinalX(int)
*
* @hide
*/
public void setFinalY(int newY) {
mScrollerY.setFinalPosition(newY);
}
/**
* 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:
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 - mScrollerX.mStartTime;
final int duration = mScrollerX.mDuration;
if (elapsedTime < duration) {
final float q = mInterpolator.getInterpolation(elapsedTime / (float) duration);
final float q2 =
mInterpolator.getInterpolation((elapsedTime - 1) / (float) duration);
mScrollerX.updateScroll(q, q2);
mScrollerY.updateScroll(q, q2);
} else {
abortAnimation();
}
break;
case FLING_MODE:
if (!mScrollerX.mFinished) {
if (!mScrollerX.update()) {
if (!mScrollerX.continueWhenFinished()) {
mScrollerX.finish();
}
}
}
if (!mScrollerY.mFinished) {
if (!mScrollerY.update()) {
if (!mScrollerY.continueWhenFinished()) {
mScrollerY.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 startX Starting horizontal scroll offset in pixels. Positive
* numbers will scroll the content to the left.
* @param startY Starting vertical scroll offset in pixels. Positive numbers
* will scroll the content up.
* @param dx Horizontal distance to travel. Positive numbers will scroll the
* content to the left.
* @param dy Vertical distance to travel. Positive numbers will scroll the
* content up.
*/
public void startScroll(int startX, int startY, int dx, int dy) {
startScroll(startX, startY, dx, dy, DEFAULT_DURATION);
}
/**
* Start scrolling by providing a starting point and the distance to travel.
*
* @param startX Starting horizontal scroll offset in pixels. Positive
* numbers will scroll the content to the left.
* @param startY Starting vertical scroll offset in pixels. Positive numbers
* will scroll the content up.
* @param dx Horizontal distance to travel. Positive numbers will scroll the
* content to the left.
* @param dy Vertical distance to travel. Positive numbers will scroll the
* content up.
* @param duration Duration of the scroll in milliseconds.
*/
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
mMode = SCROLL_MODE;
mScrollerX.startScroll(startX, dx, duration);
mScrollerY.startScroll(startY, dy, duration);
}
/**
* Call this when you want to 'spring back' into a valid coordinate range.
*
* @param startX Starting X coordinate
* @param startY Starting Y coordinate
* @param minX Minimum valid X value
* @param maxX Maximum valid X value
* @param minY Minimum valid Y value
* @param maxY Minimum valid Y value
* @return true if a springback was initiated, false if startX and startY were
* already within the valid range.
*/
public boolean springBack(int startX, int startY, int minX, int maxX, int minY, int maxY) {
mMode = FLING_MODE;
// Make sure both methods are called.
final boolean spingbackX = mScrollerX.springback(startX, minX, maxX);
final boolean spingbackY = mScrollerY.springback(startY, minY, maxY);
return spingbackX || spingbackY;
}
public void fling(int startX, int startY, int velocityX, int velocityY,
int minX, int maxX, int minY, int maxY) {
fling(startX, startY, velocityX, velocityY, minX, maxX, minY, maxY, 0, 0);
}
/**
* Start scrolling based on a fling gesture. The distance traveled will
* depend on the initial velocity of the fling.
*
* @param startX Starting point of the scroll (X)
* @param startY Starting point of the scroll (Y)
* @param velocityX Initial velocity of the fling (X) measured in pixels per
* second.
* @param velocityY Initial velocity of the fling (Y) measured in pixels per
* second
* @param minX 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 maxX 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 minY Minimum Y value. The scroller will not scroll past this point
* unless overY > 0. If overfling is allowed, it will use minY as
* a springback boundary.
* @param maxY Maximum Y value. The scroller will not scroll past this point
* unless overY > 0. If overfling is allowed, it will use maxY as
* a springback boundary.
* @param overX Overfling range. If > 0, horizontal overfling in either
* direction will be possible.
* @param overY Overfling range. If > 0, vertical overfling in either
* direction will be possible.
*/
public void fling(int startX, int startY, int velocityX, int velocityY,
int minX, int maxX, int minY, int maxY, int overX, int overY) {
// Continue a scroll or fling in progress
if (mFlywheel && !isFinished()) {
float oldVelocityX = mScrollerX.mCurrVelocity;
float oldVelocityY = mScrollerY.mCurrVelocity;
if (Math.signum(velocityX) == Math.signum(oldVelocityX) &&
Math.signum(velocityY) == Math.signum(oldVelocityY)) {
velocityX += oldVelocityX;
velocityY += oldVelocityY;
}
}
mMode = FLING_MODE;
mScrollerX.fling(startX, velocityX, minX, maxX, overX);
mScrollerY.fling(startY, velocityY, minY, maxY, overY);
}
/**
* 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 startX Starting/current X position
* @param finalX Desired final X position
* @param overX Magnitude of overscroll allowed. This should be the maximum
* desired distance from finalX. Absolute value - must be positive.
*/
public void notifyHorizontalEdgeReached(int startX, int finalX, int overX) {
mScrollerX.notifyEdgeReached(startX, finalX, overX);
}
/**
* Notify the scroller that we've reached a vertical 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 animate a parabolic motion from
* startY to finalY.
*
* @param startY Starting/current Y position
* @param finalY Desired final Y position
* @param overY Magnitude of overscroll allowed. This should be the maximum
* desired distance from finalY. Absolute value - must be positive.
*/
public void notifyVerticalEdgeReached(int startY, int finalY, int overY) {
mScrollerY.notifyEdgeReached(startY, finalY, overY);
}
/**
* 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, int, int, int, int, int)} method.
*
* One should check this value before calling
* {@link #startScroll(int, int, 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 ((!mScrollerX.mFinished &&
mScrollerX.mState != SplineOverScroller.SPLINE) ||
(!mScrollerY.mFinished &&
mScrollerY.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() {
mScrollerX.finish();
mScrollerY.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();
final long startTime = Math.min(mScrollerX.mStartTime, mScrollerY.mStartTime);
return (int) (time - startTime);
}
/**
* @hide
*/
@UnsupportedAppUsage
public boolean isScrollingInDirection(float xvel, float yvel) {
final int dx = mScrollerX.mFinal - mScrollerX.mStart;
final int dy = mScrollerY.mFinal - mScrollerY.mStart;
return !isFinished() && Math.signum(xvel) == Math.signum(dx) &&
Math.signum(yvel) == Math.signum(dy);
}
double getSplineFlingDistance(int velocity) {
return mScrollerY.getSplineFlingDistance(velocity);
}
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
@UnsupportedAppUsage
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;
// 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;
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, float q2) {
int distance = mFinal - mStart;
mCurrentPosition = mStart + Math.round(q * distance);
// q2 is 1ms before q1
mCurrVelocity = 1000f * (q - q2) * distance;
}
/*
* 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) {
mFinished = false;
mCurrentPosition = mStart = start;
mFinal = start + distance;
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mDuration = duration;
// Unused
mDeceleration = 0.0f;
mVelocity = 0;
}
void finish() {
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;
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() {
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;
}
}
}
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