| /* |
| * 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.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 float mViscousFluidScale; |
| private float mViscousFluidNormalize; |
| private boolean mFinished; |
| private Interpolator mInterpolator; |
| |
| private float mCoeffX = 0.0f; |
| private float mCoeffY = 1.0f; |
| 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 final float mDeceleration; |
| |
| /** |
| * 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. |
| */ |
| public Scroller(Context context, Interpolator interpolator) { |
| mFinished = true; |
| mInterpolator = interpolator; |
| float ppi = context.getResources().getDisplayMetrics().density * 160.0f; |
| mDeceleration = SensorManager.GRAVITY_EARTH // g (m/s^2) |
| * 39.37f // inch/meter |
| * ppi // pixels per inch |
| * ViewConfiguration.getScrollFriction(); |
| } |
| |
| /** |
| * |
| * 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 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 = (float)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); |
| if ((mCurrX == mFinalX) && (mCurrY == mFinalY)) { |
| mFinished = true; |
| } |
| break; |
| case FLING_MODE: |
| float timePassedSeconds = timePassed / 1000.0f; |
| float distance = (mVelocity * timePassedSeconds) |
| - (mDeceleration * timePassedSeconds * timePassedSeconds / 2.0f); |
| |
| mCurrX = mStartX + Math.round(distance * mCoeffX); |
| // Pin to mMinX <= mCurrX <= mMaxX |
| mCurrX = Math.min(mCurrX, mMaxX); |
| mCurrX = Math.max(mCurrX, mMinX); |
| |
| mCurrY = mStartY + Math.round(distance * mCoeffY); |
| // 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 / (float) mDuration; |
| // This controls the viscous fluid effect (how much of it) |
| mViscousFluidScale = 8.0f; |
| // must be set to 1.0 (used in viscousFluid()) |
| mViscousFluidNormalize = 1.0f; |
| mViscousFluidNormalize = 1.0f / viscousFluid(1.0f); |
| } |
| |
| /** |
| * 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) { |
| mMode = FLING_MODE; |
| mFinished = false; |
| |
| float velocity = (float)Math.hypot(velocityX, velocityY); |
| |
| mVelocity = velocity; |
| mDuration = (int) (1000 * velocity / mDeceleration); // Duration is in |
| // milliseconds |
| mStartTime = AnimationUtils.currentAnimationTimeMillis(); |
| mStartX = startX; |
| mStartY = startY; |
| |
| mCoeffX = velocity == 0 ? 1.0f : velocityX / velocity; |
| mCoeffY = velocity == 0 ? 1.0f : velocityY / velocity; |
| |
| int totalDistance = (int) ((velocity * velocity) / (2 * mDeceleration)); |
| |
| mMinX = minX; |
| mMaxX = maxX; |
| mMinY = minY; |
| mMaxY = maxY; |
| |
| |
| mFinalX = startX + Math.round(totalDistance * mCoeffX); |
| // Pin to mMinX <= mFinalX <= mMaxX |
| mFinalX = Math.min(mFinalX, mMaxX); |
| mFinalX = Math.max(mFinalX, mMinX); |
| |
| mFinalY = startY + Math.round(totalDistance * mCoeffY); |
| // Pin to mMinY <= mFinalY <= mMaxY |
| mFinalY = Math.min(mFinalY, mMaxY); |
| mFinalY = Math.max(mFinalY, mMinY); |
| } |
| |
| |
| |
| private float viscousFluid(float x) |
| { |
| x *= mViscousFluidScale; |
| 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 *= mViscousFluidNormalize; |
| 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 / (float)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; |
| } |
| } |