| /* |
| * 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 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. The duration of the scroll |
| * is either specified along with the distance or depends on the initial fling velocity. |
| * 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 { |
| int mMode; |
| |
| MagneticScroller mScrollerX; |
| MagneticScroller mScrollerY; |
| |
| private final Interpolator mInterpolator; |
| |
| static final int DEFAULT_DURATION = 250; |
| static final int SCROLL_MODE = 0; |
| static final int FLING_MODE = 1; |
| |
| // This controls the viscous fluid effect (how much of it) |
| private final static float VISCOUS_FLUID_SCALE = 8.0f; |
| private static float VISCOUS_FLUID_NORMALIZE; |
| |
| static { |
| // Set a neutral value that will be used in the next call to viscousFluid(). |
| VISCOUS_FLUID_NORMALIZE = 1.0f; |
| VISCOUS_FLUID_NORMALIZE = 1.0f / viscousFluid(1.0f); |
| } |
| |
| /** |
| * Create a Scroller with a viscous fluid scroll 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. |
| */ |
| public Scroller(Context context, Interpolator interpolator) { |
| instantiateScrollers(); |
| MagneticScroller.initializeFromContext(context); |
| |
| mInterpolator = interpolator; |
| } |
| |
| void instantiateScrollers() { |
| mScrollerX = new MagneticScroller(); |
| mScrollerY = new MagneticScroller(); |
| } |
| |
| /** |
| * |
| * 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. |
| * |
| * @param finished The new finished value. |
| */ |
| public final void forceFinished(boolean finished) { |
| mScrollerX.mFinished = mScrollerY.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 Math.max(mScrollerX.mDuration, mScrollerY.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 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; |
| } |
| |
| /** |
| * 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 = 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); |
| } |
| |
| /** |
| * Start scrolling based on a fling gesture. The distance traveled will |
| * depend on the initial velocity of the fling. Velocity is slowed down by a |
| * constant deceleration until it reaches 0 or the limits are reached. |
| * |
| * @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) { |
| mMode = FLING_MODE; |
| mScrollerX.fling(startX, velocityX, minX, maxX); |
| mScrollerY.fling(startY, velocityY, minY, maxY); |
| } |
| |
| private static float viscousFluid(float x) { |
| x *= VISCOUS_FLUID_SCALE; |
| 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 *= VISCOUS_FLUID_NORMALIZE; |
| 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() { |
| mScrollerX.finish(); |
| mScrollerY.finish(); |
| } |
| |
| /** |
| * 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) { |
| mScrollerX.extendDuration(extend); |
| mScrollerY.extendDuration(extend); |
| } |
| |
| /** |
| * Returns the time elapsed since the beginning of the scrolling. |
| * |
| * @return The elapsed time in milliseconds. |
| */ |
| public int timePassed() { |
| final long time = AnimationUtils.currentAnimationTimeMillis(); |
| final long startTime = Math.min(mScrollerX.mStartTime, mScrollerY.mStartTime); |
| return (int) (time - startTime); |
| } |
| |
| /** |
| * 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) { |
| 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) |
| */ |
| public void setFinalY(int newY) { |
| mScrollerY.setFinalPosition(newY); |
| } |
| |
| static class MagneticScroller { |
| // 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(); |
| } |
| |
| MagneticScroller() { |
| mFinished = true; |
| } |
| |
| void updateScroll(float q) { |
| mCurrentPosition = mStart + Math.round(q * (mFinal - mStart)); |
| } |
| |
| /* |
| * 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; |
| } |
| |
| final float t = duration / 1000.0f; |
| mCurrVelocity = mVelocity + mDeceleration * t; |
| final float distance = mVelocity * t + mDeceleration * t * t / 2.0f; |
| mCurrentPosition = mStart + (int) distance; |
| |
| return true; |
| } |
| |
| /* |
| * 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; |
| } |
| |
| boolean continueWhenFinished() { |
| return false; |
| } |
| |
| 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; |
| } |
| } |
| } |