M7350/base/core/java/android/widget/OverScroller.java
2024-09-09 08:52:07 +00:00

850 lines
30 KiB
Java

/*
* 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.content.Context;
import android.hardware.SensorManager;
import android.util.FloatMath;
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 MagneticOverScroller mScrollerX;
private MagneticOverScroller mScrollerY;
private final Interpolator mInterpolator;
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.
* @param context
*/
public OverScroller(Context context) {
this(context, null);
}
/**
* Creates an OverScroller with default edge bounce coefficients.
* @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, MagneticOverScroller.DEFAULT_BOUNCE_COEFFICIENT,
MagneticOverScroller.DEFAULT_BOUNCE_COEFFICIENT);
}
/**
* 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.
* @param bounceCoefficientY Same as bounceCoefficientX but for the vertical direction.
*/
public OverScroller(Context context, Interpolator interpolator,
float bounceCoefficientX, float bounceCoefficientY) {
mInterpolator = interpolator;
mScrollerX = new MagneticOverScroller();
mScrollerY = new MagneticOverScroller();
MagneticOverScroller.initializeFromContext(context);
mScrollerX.setBounceCoefficient(bounceCoefficientX);
mScrollerY.setBounceCoefficient(bounceCoefficientY);
}
/**
*
* 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;
}
/**
* @hide
* Returns 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.
*/
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.
*/
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.
*/
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.
*/
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 = Scroller.viscousFluid(q);
else
q = mInterpolator.getInterpolation(q);
mScrollerX.updateScroll(q);
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) {
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.
*/
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 != MagneticOverScroller.TO_EDGE) ||
(!mScrollerY.mFinished &&
mScrollerY.mState != MagneticOverScroller.TO_EDGE));
}
/**
* 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);
}
static class MagneticOverScroller {
// Initial position
int mStart;
// Current position
int mCurrentPosition;
// Final position
int mFinal;
// Initial velocity
int mVelocity;
// Current velocity
float mCurrVelocity;
// Constant current deceleration
float mDeceleration;
// Animation starting time, in system milliseconds
long mStartTime;
// Animation duration, in milliseconds
int mDuration;
// Whether the animation is currently in progress
boolean mFinished;
// Constant gravity value, used to scale deceleration
static float GRAVITY;
static void initializeFromContext(Context context) {
final float ppi = context.getResources().getDisplayMetrics().density * 160.0f;
GRAVITY = SensorManager.GRAVITY_EARTH // g (m/s^2)
* 39.37f // inch/meter
* ppi // pixels per inch
* ViewConfiguration.getScrollFriction();
}
private static final int TO_EDGE = 0;
private static final int TO_BOUNDARY = 1;
private static final int TO_BOUNCE = 2;
private int mState = TO_EDGE;
// The allowed overshot distance before boundary is reached.
private int mOver;
// Duration in milliseconds to go back from edge to edge. Springback is half of it.
private static final int OVERSCROLL_SPRINGBACK_DURATION = 200;
// Oscillation period
private static final float TIME_COEF =
1000.0f * (float) Math.PI / OVERSCROLL_SPRINGBACK_DURATION;
// If the velocity is smaller than this value, no bounce is triggered
// when the edge limits are reached (would result in a zero pixels
// displacement anyway).
private static final float MINIMUM_VELOCITY_FOR_BOUNCE = Float.MAX_VALUE;//140.0f;
// Proportion of the velocity that is preserved when the edge is reached.
private static final float DEFAULT_BOUNCE_COEFFICIENT = 0.16f;
private float mBounceCoefficient = DEFAULT_BOUNCE_COEFFICIENT;
MagneticOverScroller() {
mFinished = true;
}
void updateScroll(float q) {
mCurrentPosition = mStart + Math.round(q * (mFinal - mStart));
}
/*
* Get a signed deceleration that will reduce the velocity.
*/
static float getDeceleration(int velocity) {
return velocity > 0 ? -GRAVITY : GRAVITY;
}
/*
* Returns the time (in milliseconds) it will take to go from start to end.
*/
static int computeDuration(int start, int end, float initialVelocity, float deceleration) {
final int distance = start - end;
final float discriminant = initialVelocity * initialVelocity - 2.0f * deceleration
* distance;
if (discriminant >= 0.0f) {
float delta = (float) Math.sqrt(discriminant);
if (deceleration < 0.0f) {
delta = -delta;
}
return (int) (1000.0f * (-initialVelocity - delta) / deceleration);
}
// End position can not be reached
return 0;
}
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;
}
void fling(int start, int velocity, int min, int max) {
mFinished = false;
mStart = start;
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mVelocity = velocity;
mDeceleration = getDeceleration(velocity);
// A start from an invalid position immediately brings back to a valid position
if (mStart < min) {
mDuration = 0;
mFinal = min;
return;
}
if (mStart > max) {
mDuration = 0;
mFinal = max;
return;
}
// Duration are expressed in milliseconds
mDuration = (int) (-1000.0f * velocity / mDeceleration);
mFinal = start - Math.round((velocity * velocity) / (2.0f * mDeceleration));
// Clamp to a valid final position
if (mFinal < min) {
mFinal = min;
mDuration = computeDuration(mStart, min, mVelocity, mDeceleration);
}
if (mFinal > max) {
mFinal = max;
mDuration = computeDuration(mStart, max, mVelocity, mDeceleration);
}
}
void finish() {
mCurrentPosition = mFinal;
// Not reset since WebView relies on this value for fast fling.
// 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;
}
void setBounceCoefficient(float coefficient) {
mBounceCoefficient = coefficient;
}
boolean springback(int start, int min, int max) {
mFinished = true;
mStart = start;
mVelocity = 0;
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mDuration = 0;
if (start < min) {
startSpringback(start, min, false);
} else if (start > max) {
startSpringback(start, max, true);
}
return !mFinished;
}
private void startSpringback(int start, int end, boolean positive) {
mFinished = false;
mState = TO_BOUNCE;
mStart = mFinal = end;
mDuration = OVERSCROLL_SPRINGBACK_DURATION;
mStartTime -= OVERSCROLL_SPRINGBACK_DURATION / 2;
mVelocity = (int) (Math.abs(end - start) * TIME_COEF * (positive ? 1.0 : -1.0f));
}
void fling(int start, int velocity, int min, int max, int over) {
mState = TO_EDGE;
mOver = over;
mFinished = false;
mStart = start;
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mVelocity = velocity;
mDeceleration = getDeceleration(velocity);
// Duration are expressed in milliseconds
mDuration = (int) (-1000.0f * velocity / mDeceleration);
mFinal = start - Math.round((velocity * velocity) / (2.0f * mDeceleration));
// Clamp to a valid final position
if (mFinal < min) {
mFinal = min;
mDuration = computeDuration(mStart, min, mVelocity, mDeceleration);
}
if (mFinal > max) {
mFinal = max;
mDuration = computeDuration(mStart, max, mVelocity, mDeceleration);
}
if (start > max) {
if (start >= max + over) {
springback(max + over, min, max);
} else {
if (velocity <= 0) {
springback(start, min, max);
} else {
long time = AnimationUtils.currentAnimationTimeMillis();
final double durationSinceEdge =
Math.atan((start-max) * TIME_COEF / velocity) / TIME_COEF;
mStartTime = (int) (time - 1000.0f * durationSinceEdge);
// Simulate a bounce that started from edge
mStart = max;
mVelocity = (int) (velocity / Math.cos(durationSinceEdge * TIME_COEF));
onEdgeReached();
}
}
} else {
if (start < min) {
if (start <= min - over) {
springback(min - over, min, max);
} else {
if (velocity >= 0) {
springback(start, min, max);
} else {
long time = AnimationUtils.currentAnimationTimeMillis();
final double durationSinceEdge =
Math.atan((start-min) * TIME_COEF / velocity) / TIME_COEF;
mStartTime = (int) (time - 1000.0f * durationSinceEdge);
// Simulate a bounce that started from edge
mStart = min;
mVelocity = (int) (velocity / Math.cos(durationSinceEdge * TIME_COEF));
onEdgeReached();
}
}
}
}
}
void notifyEdgeReached(int start, int end, int over) {
mDeceleration = getDeceleration(mVelocity);
// Local time, used to compute edge crossing time.
float timeCurrent = mCurrVelocity / mDeceleration;
final int distance = end - start;
float timeEdge = -(float) Math.sqrt((2.0f * distance / mDeceleration)
+ (timeCurrent * timeCurrent));
mVelocity = (int) (mDeceleration * timeEdge);
// Simulate a symmetric bounce that started from edge
mStart = end;
mOver = over;
long time = AnimationUtils.currentAnimationTimeMillis();
mStartTime = (int) (time - 1000.0f * (timeCurrent - timeEdge));
onEdgeReached();
}
private void onEdgeReached() {
// mStart, mVelocity and mStartTime were adjusted to their values when edge was reached.
final float distance = mVelocity / TIME_COEF;
if (Math.abs(distance) < mOver) {
// Spring force will bring us back to final position
mState = TO_BOUNCE;
mFinal = mStart;
mDuration = OVERSCROLL_SPRINGBACK_DURATION;
} else {
// Velocity is too high, we will hit the boundary limit
mState = TO_BOUNDARY;
int over = mVelocity > 0 ? mOver : -mOver;
mFinal = mStart + over;
mDuration = (int) (1000.0f * Math.asin(over / distance) / TIME_COEF);
}
}
boolean continueWhenFinished() {
switch (mState) {
case TO_EDGE:
// Duration from start to null velocity
int duration = (int) (-1000.0f * mVelocity / mDeceleration);
if (mDuration < duration) {
// If the animation was clamped, we reached the edge
mStart = mFinal;
// Speed when edge was reached
mVelocity = (int) (mVelocity + mDeceleration * mDuration / 1000.0f);
mStartTime += mDuration;
onEdgeReached();
} else {
// Normal stop, no need to continue
return false;
}
break;
case TO_BOUNDARY:
mStartTime += mDuration;
startSpringback(mFinal, mFinal - (mVelocity > 0 ? mOver:-mOver), mVelocity > 0);
break;
case TO_BOUNCE:
//mVelocity = (int) (mVelocity * BOUNCE_COEFFICIENT);
mVelocity = (int) (mVelocity * mBounceCoefficient);
if (Math.abs(mVelocity) < MINIMUM_VELOCITY_FOR_BOUNCE) {
return false;
}
mStartTime += mDuration;
break;
}
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 duration = time - mStartTime;
if (duration > mDuration) {
return false;
}
double distance;
final float t = duration / 1000.0f;
if (mState == TO_EDGE) {
mCurrVelocity = mVelocity + mDeceleration * t;
distance = mVelocity * t + mDeceleration * t * t / 2.0f;
} else {
final float d = t * TIME_COEF;
mCurrVelocity = mVelocity * (float)Math.cos(d);
distance = mVelocity / TIME_COEF * Math.sin(d);
}
mCurrentPosition = mStart + (int) distance;
return true;
}
}
}