/*
* 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.tencent.widget;
import android.content.Context;
import android.hardware.SensorManager;
import android.util.FloatMath;
import android.view.ViewConfiguration;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;
import com.tencent.util.AnimateUtils;
/**
* 修改了回弹算法
* 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;
private final SplineOverScroller mScrollerY;
private final 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
*/
public OverScroller(Context context, Interpolator interpolator, boolean flywheel)
{
mInterpolator = interpolator;
mFlywheel = flywheel;
mScrollerX = new SplineOverScroller();
mScrollerY = new SplineOverScroller();
SplineOverScroller.initFromContext(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, boolean)} instead.
*/
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, boolean)} instead.
*/
public OverScroller(Context context, Interpolator interpolator, float bounceCoefficientX, float bounceCoefficientY,
boolean flywheel)
{
this(context, interpolator, flywheel);
}
/**
* 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()
{
float squaredNorm = mScrollerX.mCurrVelocity * mScrollerX.mCurrVelocity;
squaredNorm += mScrollerY.mCurrVelocity * mScrollerY.mCurrVelocity;
return FloatMath.sqrt(squaredNorm);
}
/**
* 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 Pending removal once nothing depends on it
* @deprecated OverScrollers don't necessarily have a fixed duration. This function will lie to the best of its
* ability.
*/
@Deprecated
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 Pending removal once nothing depends on it
* @deprecated OverScrollers don't necessarily have a fixed duration. Instead of setting a new final position and
* extending the duration of an existing scroll, use startScroll to begin a new animation.
*/
@Deprecated
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 Pending removal once nothing depends on it
* @deprecated OverScroller's final position may change during an animation. Instead of setting a new final position
* and extending the duration of an existing scroll, use startScroll to begin a new animation.
*/
@Deprecated
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 Pending removal once nothing depends on it
* @deprecated OverScroller's final position may change during an animation. Instead of setting a new final position
* and extending the duration of an existing scroll, use startScroll to begin a new animation.
*/
@Deprecated
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)
{
float q = (float) (elapsedTime) / duration;
if (mInterpolator == null)
{
q = AnimateUtils.viscousFluid(q);
}
else
{
q = mInterpolator.getInterpolation(q);
}
if (!mScrollerX.mFinished)
{
mScrollerX.updateScroll(q);
}
if (!mScrollerY.mFinished)
{
mScrollerY.updateScroll(q);
}
}
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);
}
/**
* 添加起始时间
* 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(long startTime, int startX, int startY, int velocityX, int velocityY, int minX, int maxX, int minY, int maxY,
int overX, int overY)
{
fling(startX, startY, velocityX, velocityY, minX, maxX, minY, maxY, overX, overY);
mScrollerX.mStartTime = startTime;
mScrollerY.mStartTime = startTime;
}
/**
* 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
*/
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);
}
static class SplineOverScroller
{
private static final int BOUNCE_DURANTION = 400;
// 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;
// Constant gravity value, used in the deceleration phase.
private static final float GRAVITY = 2000.0f;
// A device specific coefficient adjusted to physical values.
private static float PHYSICAL_COEF;
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];
/**
* fling减速
*/
private static final int SPLINE = 0;
private static final int CUBIC = 1;
// private static final int BALLISTIC = 2;
/**
* 回弹
*/
private static final int BOUNCE = 3;
private static final int SCROLL = 4;
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;
}
static void initFromContext(Context context)
{
final float ppi = context.getResources().getDisplayMetrics().density * 160.0f;
PHYSICAL_COEF = SensorManager.GRAVITY_EARTH // g (m/s^2)
* 39.37f // inch/meter
* ppi * 0.84f; // look and feel tuning
}
void setFriction(float friction)
{
mFlingFriction = friction;
}
SplineOverScroller()
{
mFinished = true;
}
void updateScroll(float q)
{
mCurrentPosition = mStart + Math.round(q * (mFinal - mStart));
}
/*
* 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;
mStart = start;
mFinal = start + distance;
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mDuration = duration;
// Unused
mDeceleration = 0.0f;
mVelocity = 0;
mState = SCROLL;
}
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;
mFinished = false;
}
void extendDuration(int extend)
{
final long time = AnimationUtils.currentAnimationTimeMillis();
final int elapsedTime = (int) (time - mStartTime);
mDuration = elapsedTime + extend;
mFinished = false;
}
boolean springback(int start, int min, int max)
{
mFinished = true;
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;
}
// 回弹
private void startSpringback(int start, int end, int velocity)
{
// mStartTime has been set
mFinished = false;
mState = CUBIC;
mStart = start;
mFinal = end;
mOver = end - start;
mDuration = BOUNCE_DURANTION;
}
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)
{
// 初始值就已经在边界之外了. 直接进行回弹
startSpringback(start, start > max ? max : min, velocity);
return;
}
mState = SPLINE;
double totalDistance = 0.0;
if (velocity != 0)
{
mDuration = mSplineDuration = getSplineFlingDuration(velocity);
mDeceleration = (float) (getSplineDeceleration(velocity) * 1000);
totalDistance = getSplineFlingDistance(velocity);
}
mSplineDistance = (int) (totalDistance * Math.signum(velocity));
mFinal = start + mSplineDistance;
// Clamp to a valid final position
// 越界了. 调整时长
if (mFinal < min)
{
adjustDuration(mStart, mFinal, min);
mFinal = min;
}
if (mFinal > max)
{
adjustDuration(mStart, mFinal, max);
mFinal = max;
}
mLastVelocity = velocity;
mLastTime = mStartTime;
}
private double getSplineDeceleration(int velocity)
{
return Math.log(INFLEXION * Math.abs(velocity) / (mFlingFriction * PHYSICAL_COEF));
}
private double getSplineFlingDistance(int velocity)
{
final double l = getSplineDeceleration(velocity);
final double decelMinusOne = DECELERATION_RATE - 1.0;
return mFlingFriction * PHYSICAL_COEF * 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 float mTension;
/**
* 开始回滚
* @param edge
* @param range
* @param velocity
* @param duration
*/
void bounce(int edge,int range, int velocity, int duration)
{
// int velocityAbs = Math.abs(velocity);
// 最大速度(px/s)
float maxVelocity = 0.09606f * range / (0.01f * 0.001f * duration);
float tension = velocity > 0 ? 10f : -10f;
// 根据最大速度, 计算弹力系数
if(Math.abs(velocity) < maxVelocity)
{
tension = velocity * 10f / maxVelocity;
}
mStart = edge;
mFinal = edge;
mVelocity = velocity;
mOver = range;
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mDuration = duration;
mTension = tension;
mState = BOUNCE;
// 开始回滚
}
/**
* 通知到达边界. 开始计算回弹
* @param start
* @param end
* @param over
*/
void notifyEdgeReached(int start, int end, int over)
{
// mState is used to detect successive notifications
if (mState == SPLINE)
{
if(start == end)
{
bounce(end, over, mVelocity, BOUNCE_DURANTION);
}
else
{
// 计算过原点的时间
adjustDuration(mStart, mFinal, mCurrentPosition - (start - end));
mOver = over;
mFinal = end;
onEdgeReached();
}
}
// scroll模式
else if(mState == SCROLL)
{
mFinal = mCurrentPosition = 0;
mFinished = true;
}
}
/**
* 到达边界,开始回弹
*/
private void onEdgeReached()
{
final long time = mStartTime + mDuration;
// 计算通过终点时的速度
final float t = (float) mDuration / mSplineDuration;
final int index = (int) (NB_SAMPLES * t);
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);
}
// 通过原点的速度
mCurrVelocity = velocityCoef * mSplineDistance / mSplineDuration * 1000.0f;
mDeceleration = (float) ((mCurrVelocity - mLastVelocity)/ (time - mLastTime) * 1000);
// 计算回弹参数
bounce(mFinal, mOver, (int) mCurrVelocity, BOUNCE_DURANTION);
mStartTime = time;
// 因为越过边界, 重新计算新的位置
update();
}
boolean continueWhenFinished()
{
switch (mState)
{
case SPLINE:
// Duration from start to null velocity
// 有回弹
if (mDuration < mSplineDuration)
{
onEdgeReached();
}
else
{
// Normal stop, no need to continue
return false;
}
break;
case CUBIC:
return false;
case BOUNCE:
return false;
}
update();
return true;
}
// private double mLastDistance = 0;
private double mLastVelocity;
private long mLastTime;
/*
* 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 > 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;
mDeceleration = (float) ((mCurrVelocity - mLastVelocity)/ (time - mLastTime) * 1000);
// Log.d("XListView", "mDeceleration: " + mDeceleration);
break;
}
case CUBIC:
{
final float t = (float) (currentTime) / mDuration;
distance = AnimateUtils.viscousFluid(t) * mOver;
break;
}
case BOUNCE:
{
final float t = (float) (currentTime) / mDuration - 1f;
// t^4*(at+t)
distance = mOver * t * t * t * t * (mTension * t + mTension);
}
}
mCurrentPosition = mStart + (int) Math.round(distance);
return true;
}
}
}