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Diffstat (limited to 'gallerycommon/src/com/android/gallery3d/common/Scroller.java')
| -rw-r--r-- | gallerycommon/src/com/android/gallery3d/common/Scroller.java | 507 |
1 files changed, 507 insertions, 0 deletions
diff --git a/gallerycommon/src/com/android/gallery3d/common/Scroller.java b/gallerycommon/src/com/android/gallery3d/common/Scroller.java new file mode 100644 index 000000000..6cefd6fb0 --- /dev/null +++ b/gallerycommon/src/com/android/gallery3d/common/Scroller.java @@ -0,0 +1,507 @@ +/* + * Copyright (C) 2006 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package com.android.gallery3d.common; + +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; + + +/** + * This class encapsulates scrolling. The duration of the scroll + * can be passed in the constructor and specifies the maximum time that + * the scrolling animation should take. Past this time, the scrolling is + * automatically moved to its final stage and computeScrollOffset() + * will always return false to indicate that scrolling is over. + */ +public class Scroller { + private int mMode; + + private int mStartX; + private int mStartY; + 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 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(0.75) / Math.log(0.9)); + private static float ALPHA = 800; // pixels / seconds + private static float START_TENSION = 0.4f; // Tension at start: (0.4 * total T, 1.0 * Distance) + private static float END_TENSION = 1.0f - START_TENSION; + private static final int NB_SAMPLES = 100; + private static final float[] SPLINE = new float[NB_SAMPLES + 1]; + + private float mDeceleration; + private final float mPpi; + + static { + float x_min = 0.0f; + for (int i = 0; i <= NB_SAMPLES; i++) { + final float t = (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) * START_TENSION + x * END_TENSION) + x * x * x; + if (Math.abs(tx - t) < 1E-5) break; + if (tx > t) x_max = x; + else x_min = x; + } + final float d = coef + x * x * x; + SPLINE[i] = d; + } + SPLINE[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 Scroller(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 Scroller(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 Scroller(Context context, Interpolator interpolator, boolean flywheel) { + mFinished = true; + mInterpolator = interpolator; + mPpi = context.getResources().getDisplayMetrics().density * 160.0f; + mDeceleration = computeDeceleration(ViewConfiguration.getScrollFriction()); + mFlywheel = 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) { + mDeceleration = computeDeceleration(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 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 getFinalX() { + return mFinalX; + } + + /** + * 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 mFinalY; + } + + /** + * 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); + final float t_inf = (float) index / NB_SAMPLES; + final float t_sup = (float) (index + 1) / NB_SAMPLES; + final float d_inf = SPLINE[index]; + final float d_sup = SPLINE[index + 1]; + final float distanceCoef = d_inf + (t - t_inf) / (t_sup - t_inf) * (d_sup - d_inf); + + mCurrX = mStartX + Math.round(distanceCoef * (mFinalX - mStartX)); + // Pin to mMinX <= mCurrX <= mMaxX + mCurrX = Math.min(mCurrX, mMaxX); + mCurrX = Math.max(mCurrX, mMinX); + + mCurrY = mStartY + Math.round(distanceCoef * (mFinalY - mStartY)); + // Pin to mMinY <= mCurrY <= mMaxY + mCurrY = Math.min(mCurrY, mMaxY); + mCurrY = Math.max(mCurrY, mMinY); + + if (mCurrX == mFinalX && mCurrY == mFinalY) { + 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) { + mMode = SCROLL_MODE; + mFinished = false; + mDuration = duration; + mStartTime = AnimationUtils.currentAnimationTimeMillis(); + mStartX = startX; + mStartY = startY; + mFinalX = startX + dx; + mFinalY = startY + dy; + mDeltaX = dx; + mDeltaY = dy; + mDurationReciprocal = 1.0f / mDuration; + } + + /** + * 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 = mFinalX - mStartX; + float dy = mFinalY - 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; + final double l = Math.log(START_TENSION * velocity / ALPHA); + mDuration = (int) (1000.0 * Math.exp(l / (DECELERATION_RATE - 1.0))); + mStartTime = AnimationUtils.currentAnimationTimeMillis(); + mStartX = startX; + mStartY = startY; + + float coeffX = velocity == 0 ? 1.0f : velocityX / velocity; + float coeffY = velocity == 0 ? 1.0f : velocityY / velocity; + + int totalDistance = + (int) (ALPHA * Math.exp(DECELERATION_RATE / (DECELERATION_RATE - 1.0) * l)); + + mMinX = minX; + mMaxX = maxX; + mMinY = minY; + mMaxY = maxY; + + mFinalX = startX + Math.round(totalDistance * coeffX); + // Pin to mMinX <= mFinalX <= mMaxX + mFinalX = Math.min(mFinalX, mMaxX); + mFinalX = Math.max(mFinalX, mMinX); + + mFinalY = startY + Math.round(totalDistance * coeffY); + // Pin to mMinY <= mFinalY <= mMaxY + mFinalY = Math.min(mFinalY, mMaxY); + mFinalY = Math.max(mFinalY, mMinY); + } + + 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 #setFinalX(int)} or {@link #setFinalY(int)}. + * + * @param extend Additional time to scroll in milliseconds. + * @see #setFinalX(int) + * @see #setFinalY(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 #setFinalY(int) + */ + public void setFinalX(int newX) { + mFinalX = newX; + mDeltaX = mFinalX - 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 #setFinalX(int) + */ + public void setFinalY(int newY) { + mFinalY = newY; + mDeltaY = mFinalY - mStartY; + mFinished = false; + } + + /** + * @hide + */ + public boolean isScrollingInDirection(float xvel, float yvel) { + return !mFinished && Math.signum(xvel) == Math.signum(mFinalX - mStartX) && + Math.signum(yvel) == Math.signum(mFinalY - mStartY); + } +} |