理解---Android(安卓)向右滑动销毁（finish）Activity, 随着手势的滑动而滑动的效果(大神博客)

项目中用到了大神写的Android 带你从源码的角度解析Scroller的滚动实现原理，记录一下，加强记忆

网址：http://blog.csdn.net/xiaanming/article/details/20934541

滑动：

1.基本

scrollTo，滚动的是控件的内容

/**     * Set the scrolled position of your view. This will cause a call to     * {@link #onScrollChanged(int, int, int, int)} and the view will be     * invalidated.     * @param x the x position to scroll to     * @param y the y position to scroll to     */    public void scrollTo(int x, int y) {        if (mScrollX != x || mScrollY != y) {            int oldX = mScrollX;            int oldY = mScrollY;            mScrollX = x;            mScrollY = y;            invalidateParentCaches();            onScrollChanged(mScrollX, mScrollY, oldX, oldY);            if (!awakenScrollBars()) {                postInvalidateOnAnimation();            }        }    } /**     * The offset, in pixels, by which the content of this view is scrolled     * horizontally.     * {@hide}     */    @ViewDebug.ExportedProperty(category = "scrolling")    protected int mScrollX;

2.Scroller

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;    }

startScroll设置一些初始参数

public boolean computeScrollOffset() {        if (mFinished) {            return false;        }        int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);            if (timePassed < mDuration) {            switch (mMode) {            case SCROLL_MODE:                final float x = mInterpolator.getInterpolation(timePassed * mDurationReciprocal);                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 * (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;    }

每次调用时，计算此时离滑动开始的时间，计算这段时间里应该滑动的距离，赋值给mCurrX和MCurrY，若时间到了，就赋值mFinished为true，下次再调用时，直接返回false.

3.View中方法，此方法在每次绘制view的时候调用，所以可以这边调用invalidate()，一直循环

</pre><pre name="code" class="java"> @Override    public void computeScroll() {        if (scroller.computeScrollOffset()) {            mParentView.scrollTo(scroller.getCurrX(), 0);            invalidate();                    }         super.computeScroll();    }

Touch滑动：

onTouch和onTouchEvent

dispatchTouchEvent中调用onTouch，

onTouch返回true,将不执行onTouchEvent

 MotionEvent cancelEvent = MotionEvent.obtain(event);                        cancelEvent                                .setAction(MotionEvent.ACTION_CANCEL                                        | (event.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT));                        v.onTouchEvent(cancelEvent);

可以结束接下来的一系列动作，解决点击事件和滑动的冲突，在滑动的时候屏蔽点击事件

view跟随手势滑动，在move事件中先判断是否符合符合滑动，符合的设置标志位为ture,接下来的一系列滑动都根据手指滑动距离，来让view滑动，知道up事件发生，重置标志位为false。

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