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import android.view.animation.Interpolator;
/**
* Created with IntelliJ IDEA, best IDE in the world. User: castorflex Date: 06/06/13 Time: 22:18
*/
public class CustomBounceInterpolator implements Interpolator {
@Override
public float getInterpolation(float t) {
return -(float) Math.abs(Math.sin((float) Math.PI * (t + 1) * (t + 1)) * (1 - t));
}
}
import android.content.Context;
import android.hardware.SensorManager;
import android.os.Build;
import android.util.FloatMath;
import android.view.ViewConfiguration;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;
/**
* Created with IntelliJ IDEA, best IDE in the world. User: castorflex Date: 08/05/13 Time: 11:33
*/
public class CustomScroller {
private int mMode;
private int mStartX;
private int mStartY;
private int mThresholdX;
private int mThresholdY;
private int mFinalX;
private int mFinalY;
private int mMinX;
private int mMaxX;
private int mMinY;
private int mMaxY;
private int mCurrX;
private int mCurrY;
private long mStartTime;
private int mDuration;
private float mDurationReciprocal;
private float mDeltaX;
private float mDeltaY;
private boolean mFinished;
private Interpolator mInterpolator;
private boolean mFlywheel;
private float mVelocity;
private float mCurrVelocity;
private int mDistance;
private float mFlingFriction = ViewConfiguration.getScrollFriction();
private static final int DEFAULT_DURATION = 250;
private static final int SCROLL_MODE = 0;
private static final int FLING_MODE = 1;
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 float mDeceleration;
private final float mPpi;
// A context-specific coefficient adjusted to physical values.
private float mPhysicalCoeff;
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;
// This controls the viscous fluid effect (how much of it)
sViscousFluidScale = 8.0f;
// must be set to 1.0 (used in viscousFluid())
sViscousFluidNormalize = 1.0f;
sViscousFluidNormalize = 1.0f / viscousFluid(1.0f);
}
private static float sViscousFluidScale;
private static float sViscousFluidNormalize;
/**
* Create a Scroller with the default duration and interpolator.
*/
public CustomScroller(Context context) {
this(context, null);
}
/**
* Create a Scroller with the specified interpolator. If the interpolator is
* null, the default (viscous) interpolator will be used. "Flywheel" behavior will
* be in effect for apps targeting Honeycomb or newer.
*/
public CustomScroller(Context context, Interpolator interpolator) {
this(context, interpolator,
context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB);
}
/**
* Create a Scroller with the specified interpolator. If the interpolator is
* null, the default (viscous) interpolator will be used. Specify whether or
* not to support progressive "flywheel" behavior in flinging.
*/
public CustomScroller(Context context, Interpolator interpolator, boolean flywheel) {
mFinished = true;
mInterpolator = interpolator;
mPpi = context.getResources().getDisplayMetrics().density * 160.0f;
mDeceleration = computeDeceleration(ViewConfiguration.getScrollFriction());
mFlywheel = flywheel;
mPhysicalCoeff = computeDeceleration(0.84f); // look and feel tuning
}
/**
* 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) {
mDeceleration = computeDeceleration(friction);
mFlingFriction = friction;
}
private float computeDeceleration(float friction) {
return SensorManager.GRAVITY_EARTH // g (m/s^2)
* 39.37f // inch/meter
* mPpi // pixels per inch
* friction;
}
/**
*
* Returns whether the scroller has finished scrolling.
*
* @return True if the scroller has finished scrolling, false otherwise.
*/
public final boolean isFinished() {
return mFinished;
}
/**
* Force the finished field to a particular value.
*
* @param finished The new finished value.
*/
public final void forceFinished(boolean finished) {
mFinished = finished;
}
/**
* Returns how long the scroll event will take, in milliseconds.
*
* @return The duration of the scroll in milliseconds.
*/
public final int getDuration() {
return mDuration;
}
/**
* 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 mCurrX;
}
/**
* 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 mCurrY;
}
/**
* Returns the current velocity.
*
* @return The original velocity less the deceleration. Result may be
* negative.
*/
public float getCurrVelocity() {
return mMode == FLING_MODE ?
mCurrVelocity : mVelocity - mDeceleration * timePassed() / 2000.0f;
}
/**
* 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 mStartX;
}
/**
* 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 mStartY;
}
/**
* 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 getThresholdX() {
return mThresholdX;
}
/**
* 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 getThresholdY() {
return mThresholdY;
}
/**
* Call this when you want to know the new location. If it returns true,
* the animation is not yet finished. loc will be altered to provide the
* new location.
*/
public boolean computeScrollOffset() {
if (mFinished) {
return false;
}
int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
if (timePassed < mDuration) {
switch (mMode) {
case SCROLL_MODE:
float x = timePassed * mDurationReciprocal;
if (mInterpolator == null)
x = viscousFluid(x);
else
x = mInterpolator.getInterpolation(x);
mCurrX = mStartX + Math.round(x * mDeltaX);
mCurrY = mStartY + Math.round(x * mDeltaY);
break;
case FLING_MODE:
final float t = (float) timePassed / mDuration;
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;
}
mCurrVelocity = velocityCoef * mDistance / mDuration * 1000.0f;
mCurrX = mStartX + Math.round(distanceCoef * (mThresholdX - mStartX));
// Pin to mMinX <= mCurrX <= mMaxX
mCurrX = Math.min(mCurrX, mMaxX);
mCurrX = Math.max(mCurrX, mMinX);
mCurrY = mStartY + Math.round(distanceCoef * (mThresholdY - mStartY));
// Pin to mMinY <= mCurrY <= mMaxY
mCurrY = Math.min(mCurrY, mMaxY);
mCurrY = Math.max(mCurrY, mMinY);
//As we are waiting for the end of the animation,
//we don't want to stop if we reach the threshold
// if (mCurrX == mThresholdX && mCurrY == mThresholdY) {
// mFinished = true;
// }
break;
}
}
else {
mCurrX = mFinalX;
mCurrY = mFinalY;
mFinished = true;
}
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) {
startScroll(startX, startY, dx, dy, duration, startX + dx, startY + dy);
}
/**
* Start scrolling by providing a starting point and the distance to travel, with a finalPosition.
*
* @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, int finalX, int finalY) {
mMode = SCROLL_MODE;
mFinished = false;
mDuration = duration;
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mStartX = startX;
mStartY = startY;
mThresholdX = startX + dx;
mThresholdY = startY + dy;
mDeltaX = dx;
mDeltaY = dy;
mDurationReciprocal = 1.0f / (float) mDuration;
mFinalX = finalX;
mFinalY = finalY;
}
/**
* Start scrolling based on a fling gesture. The distance travelled 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.
* @param maxX Maximum X value. The scroller will not scroll past this
* point.
* @param minY Minimum Y value. The scroller will not scroll past this
* point.
* @param maxY Maximum Y value. The scroller will not scroll past this
* point.
*/
public void fling(int startX, int startY, int velocityX, int velocityY,
int minX, int maxX, int minY, int maxY) {
// Continue a scroll or fling in progress
if (mFlywheel && !mFinished) {
float oldVel = getCurrVelocity();
float dx = (float) (mThresholdX - mStartX);
float dy = (float) (mThresholdY - mStartY);
float hyp = FloatMath.sqrt(dx * dx + dy * dy);
float ndx = dx / hyp;
float ndy = dy / hyp;
float oldVelocityX = ndx * oldVel;
float oldVelocityY = ndy * oldVel;
if (Math.signum(velocityX) == Math.signum(oldVelocityX) &&
Math.signum(velocityY) == Math.signum(oldVelocityY)) {
velocityX += oldVelocityX;
velocityY += oldVelocityY;
}
}
mMode = FLING_MODE;
mFinished = false;
float velocity = FloatMath.sqrt(velocityX * velocityX + velocityY * velocityY);
mVelocity = velocity;
mDuration = getSplineFlingDuration(velocity);
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mStartX = startX;
mStartY = startY;
float coeffX = velocity == 0 ? 1.0f : velocityX / velocity;
float coeffY = velocity == 0 ? 1.0f : velocityY / velocity;
double totalDistance = getSplineFlingDistance(velocity);
mDistance = (int) (totalDistance * Math.signum(velocity));
mMinX = minX;
mMaxX = maxX;
mMinY = minY;
mMaxY = maxY;
mThresholdX = startX + (int) Math.round(totalDistance * coeffX);
// Pin to mMinX <= mThresholdX <= mMaxX
mThresholdX = Math.min(mThresholdX, mMaxX);
mThresholdX = Math.max(mThresholdX, mMinX);
mThresholdY = startY + (int) Math.round(totalDistance * coeffY);
// Pin to mMinY <= mThresholdY <= mMaxY
mThresholdY = Math.min(mThresholdY, mMaxY);
mThresholdY = Math.max(mThresholdY, mMinY);
}
private double getSplineDeceleration(float velocity) {
return Math.log(INFLEXION * Math.abs(velocity) / (mFlingFriction * mPhysicalCoeff));
}
private int getSplineFlingDuration(float velocity) {
final double l = getSplineDeceleration(velocity);
final double decelMinusOne = DECELERATION_RATE - 1.0;
return (int) (1000.0 * Math.exp(l / decelMinusOne));
}
private double getSplineFlingDistance(float velocity) {
final double l = getSplineDeceleration(velocity);
final double decelMinusOne = DECELERATION_RATE - 1.0;
return mFlingFriction * mPhysicalCoeff * Math.exp(DECELERATION_RATE / decelMinusOne * l);
}
static float viscousFluid(float x)
{
x *= sViscousFluidScale;
if (x < 1.0f) {
x -= (1.0f - (float)Math.exp(-x));
} else {
float start = 0.36787944117f; // 1/e == exp(-1)
x = 1.0f - (float)Math.exp(1.0f - x);
x = start + x * (1.0f - start);
}
x *= sViscousFluidNormalize;
return x;
}
/**
* Stops the animation. Contrary to {@link #forceFinished(boolean)},
* aborting the animating cause the scroller to move to the final x and y
* position
*
* @see #forceFinished(boolean)
*/
public void abortAnimation() {
mCurrX = mFinalX;
mCurrY = mFinalY;
mFinished = true;
}
/**
* Extend the scroll animation. This allows a running animation to scroll
* further and longer, when used with {@link #setThresholdX(int)} or {@link #setThresholdY(int)}.
*
* @param extend Additional time to scroll in milliseconds.
* @see #setThresholdX(int)
* @see #setThresholdY(int)
*/
public void extendDuration(int extend) {
int passed = timePassed();
mDuration = passed + extend;
mDurationReciprocal = 1.0f / mDuration;
mFinished = false;
}
/**
* Returns the time elapsed since the beginning of the scrolling.
*
* @return The elapsed time in milliseconds.
*/
public int timePassed() {
return (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
}
/**
* 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 #setThresholdY(int)
*/
public void setThresholdX(int newX) {
mThresholdX = newX;
mDeltaX = mThresholdX - mStartX;
mFinished = false;
}
/**
* 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 #setThresholdX(int)
*/
public void setThresholdY(int newY) {
mThresholdY = newY;
mDeltaY = mThresholdY - mStartY;
mFinished = false;
}
/**
* @hide
*/
public boolean isScrollingInDirection(float xvel, float yvel) {
return !mFinished && Math.signum(xvel) == Math.signum(mThresholdX - mStartX) &&
Math.signum(yvel) == Math.signum(mThresholdY - mStartY);
}
}
private CustomScroller mBounceScroller;
void initCustomViewAbove() {
//some code...
mBounceScroller = new CustomScroller(context, new CustomBounceInterpolator());
}
public void scrollWithBounceInterpolator() {
int x = mViewBehind.getBehindWidth();
int y = 0;
if (getChildCount() == 0) {
// Nothing to do.
setScrollingCacheEnabled(false);
return;
}
int sx = getScrollX();
int sy = getScrollY();
int dx = x - sx;
int dy = y - sy;
mBounceScroller.startScroll(sx, sy, dx, dy, 1000, 0, 0);
invalidate();
}
@Override
public void computeScroll() {
if (!mBounceScroller.isFinished()) {
if (mBounceScroller.computeScrollOffset()) {
int x = mBounceScroller.getCurrX();
int y = mBounceScroller.getCurrY();
scrollTo(x, y);
// Keep on drawing until the animation has finished.
invalidate();
return;
}
}
if (!mScroller.isFinished()) {
if (mScroller.computeScrollOffset()) {
int oldX = getScrollX();
int oldY = getScrollY();
int x = mScroller.getCurrX();
int y = mScroller.getCurrY();
if (oldX != x || oldY != y) {
scrollTo(x, y);
pageScrolled(x);
}
// Keep on drawing until the animation has finished.
invalidate();
return;
}
}
// Done with scroll, clean up state.
completeScroll();
}
public void scrollWithBounceInterpolator(){
mViewAbove.scrollWithBounceInterpolator();
}
@ferranpons

This comment has been minimized.

ferranpons commented Jun 10, 2013

It would be cool if you could change the frequency and the number of times you can make it bounce with params. Anyway it's cool! Thanks for the code! :)

@castorflex

This comment has been minimized.

Owner

castorflex commented Jun 17, 2013

Absolutely, that could be interesting. Try to play with the maths (in the interpolator) and you will find some fancy things :D

@seshuvinay

This comment has been minimized.

seshuvinay commented Mar 18, 2015

How to make it bounce only once? I could hardly understand Math used by you.

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