仿鲜果联播的view

近来换了份工作，做了几个UI，需求不是很明确，任由我发挥，有类似view添加删除的功能，很自然地想到了做一个类似鲜果的View，ubuntu下用

byzanz-record -d 60 -x 70 -y 30 -w 1280 -h 720 byzanz-demo.gif   截图的，第一次截。记录下吧。

（这样截出来的gif不知道为什么cdns显示不出来，唉，截张图吧，大致就是这个效果，感谢这篇博文http://blog.csdn.net/xiaanming/article/details/17718579，我主要就添加了数据的保存及删除操作，点击事件的捕获。）

后来看到评论开源项目https://github.com/mrKlar/PagedDragDropGrid这个也不错啊

新工作大老板说得天花乱坠，现在差不多快一个月了，感觉被忽悠了 ，哎，心开始又乱了。。。记录下吧，改了下SystemUI，添加了些基本按钮，为了实现点击显示原launcher显示所有app的view，于是，感谢然后写了个apk模仿了下，PagedView.java这个开源类不错啊，一下就弄好了，我只是加了换页监听。

DVD，原厂蓝牙主要是通过socket向底层发送指令，因为蜂鸟系统底层做了定制，所以我要做的只是显示一个定制的视频类控件，然后发送指令。

截些图纪念下，

这个系统设置的view，美工如此设计，我... 好像不是很实用啊。。。。

指针可以旋转的view，可以参考  http://www.eoeandroid.com/forum.php?mod=viewthread&tid=71484

仿鲜果联播的view代码

package com.isunicom.isunallapp;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityManager;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.DecelerateInterpolator;
import android.view.animation.Interpolator;
import android.widget.Scroller;

import java.util.ArrayList;

public class PagedView extends ViewGroup {
    private static final int SCREEN_SCROLLED_MIN_VERSION = 11;
    private static float TRANSITION_SCALE_FACTOR = 0.74f;
    private AccelerateInterpolator mAlphaInterpolator = new AccelerateInterpolator(
            0.9f);
    private DecelerateInterpolator mLeftScreenAlphaInterpolator = new DecelerateInterpolator(
            4);
    private static final boolean PERFORM_OVERSCROLL_ROTATION = true;
    private static float CAMERA_DISTANCE = 6500;
    private static float TRANSITION_PIVOT = 0.65f;
    private static float TRANSITION_MAX_ROTATION = 22;

    protected static final int INVALID_PAGE = -1;

    // the min drag distance for a fling to register, to prevent random page
    // shifts
    private static final int MIN_LENGTH_FOR_FLING = 25;

    protected static final int PAGE_SNAP_ANIMATION_DURATION = 550;
    protected static final int SLOW_PAGE_SNAP_ANIMATION_DURATION = 950;
    protected static final float NANOTIME_DIV = 1000000000.0f;

    private static final float OVERSCROLL_ACCELERATE_FACTOR = 2;

    private static final float RETURN_TO_ORIGINAL_PAGE_THRESHOLD = 0.33f;
    // The page is moved more than halfway, automatically move to the next page
    // on touch up.
    private static final float SIGNIFICANT_MOVE_THRESHOLD = 0.4f;

    // The following constants need to be scaled based on density. The scaled
    // versions will be
    // assigned to the corresponding member variables below.
    private static final int FLING_THRESHOLD_VELOCITY = 500;
    private static final int MIN_SNAP_VELOCITY = 1500;
    private static final int MIN_FLING_VELOCITY = 250;

    static final int AUTOMATIC_PAGE_SPACING = -1;

    protected int mFlingThresholdVelocity;
    protected int mMinFlingVelocity;
    protected int mMinSnapVelocity;

    protected float mDensity;
    protected float mSmoothingTime;
    protected float mTouchX;

    protected boolean mFirstLayout = true;

    protected int mCurrentPage;
    protected int mNextPage = INVALID_PAGE;
    protected int mMaxScrollX;
    protected Scroller mScroller;
    private VelocityTracker mVelocityTracker;

    private float mDownMotionX;
    protected float mLastMotionX;
    protected float mLastMotionXRemainder;
    protected float mLastMotionY;
    protected float mTotalMotionX;
    private int mLastScreenCenter = -1;
    private int[] mChildOffsets;
    private int[] mChildRelativeOffsets;
    private int[] mChildOffsetsWithLayoutScale;

    protected final static int TOUCH_STATE_REST = 0;
    protected final static int TOUCH_STATE_SCROLLING = 1;
    protected final static int TOUCH_STATE_PREV_PAGE = 2;
    protected final static int TOUCH_STATE_NEXT_PAGE = 3;
    protected final static float ALPHA_QUANTIZE_LEVEL = 0.0001f;

    protected int mTouchState = TOUCH_STATE_REST;
    protected boolean mForceScreenScrolled = false;

    protected int mTouchSlop;
    private int mPagingTouchSlop;
    private int mMaximumVelocity;
    protected int mPageSpacing;
    protected int mPageLayoutPaddingTop;
    protected int mPageLayoutPaddingBottom;
    protected int mPageLayoutPaddingLeft;
    protected int mPageLayoutPaddingRight;
    protected int mPageLayoutWidthGap;
    protected int mPageLayoutHeightGap;
    protected int mCellCountX = 0;
    protected int mCellCountY = 0;
    protected boolean mCenterPagesVertically;
    protected boolean mAllowOverScroll = true;
    protected int mUnboundedScrollX;
    protected int[] mTempVisiblePagesRange = new int[2];
    protected boolean mForceDrawAllChildrenNextFrame;

    // mOverScrollX is equal to getScrollX() when we're within the normal scroll
    // range. Otherwise
    // it is equal to the scaled overscroll position. We use a separate value so
    // as to prevent
    // the screens from continuing to translate beyond the normal bounds.
    protected int mOverScrollX;

    // parameter that adjusts the layout to be optimized for pages with that
    // scale factor
    protected float mLayoutScale = 1.0f;

    protected static final int INVALID_POINTER = -1;

    protected int mActivePointerId = INVALID_POINTER;

    protected ArrayList<Boolean> mDirtyPageContent;

    // If true, syncPages and syncPageItems will be called to refresh pages
    protected boolean mContentIsRefreshable = true;

    // If true, modify alpha of neighboring pages as user scrolls left/right
    protected boolean mFadeInAdjacentScreens = true;

    // It true, use a different slop parameter (pagingTouchSlop = 2 * touchSlop)
    // for deciding
    // to switch to a new page
    protected boolean mUsePagingTouchSlop = true;

    // If true, the subclass should directly update scrollX itself in its
    // computeScroll method
    // (SmoothPagedView does this)
    protected boolean mDeferScrollUpdate = false;

    protected boolean mIsPageMoving = false;

    // All syncs and layout passes are deferred until data is ready.
    protected boolean mIsDataReady = false;

    // If set, will defer loading associated pages until the scrolling settles

    // Begin Immersion changes
    protected boolean mHapticFlingStarted = false;
    protected boolean mHapticCaptureFling = true;
    protected int mLastHapticScreen = 0;
    ZInterpolator mZInterpolator = new ZInterpolator(0.5f);

    // End Immersion changes

    public PagedView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    public PagedView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public PagedView(Context context) {
        this(context, null);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        final int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        if (widthMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException(
                    "Workspace can only be used in EXACTLY mode.");
        }

        // Return early if we aren't given a proper dimension
        if (widthSize <= 0 || heightSize <= 0) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            return;
        }

        /*
         * Allow the height to be set as WRAP_CONTENT. This allows the
         * particular case of the All apps view on XLarge displays to not take
         * up more space then it needs. Width is still not allowed to be set as
         * WRAP_CONTENT since many parts of the code expect each page to have
         * the same width.
         */
        int maxChildHeight = 0;

        final int verticalPadding = getPaddingTop() + getPaddingBottom();
        final int horizontalPadding = getPaddingLeft() + getPaddingRight();

        // The children are given the same width and height as the workspace
        // unless they were set to WRAP_CONTENT
        final int childCount = getChildCount();
        for (int i = 0; i < childCount; i++) {
            // disallowing padding in paged view (just pass 0)
            final View child = getPageAt(i);
            final LayoutParams lp = (LayoutParams) child.getLayoutParams();

            int childWidthMode;
            if (lp.width == LayoutParams.WRAP_CONTENT) {
                childWidthMode = MeasureSpec.AT_MOST;
            } else {
                childWidthMode = MeasureSpec.EXACTLY;
            }

            int childHeightMode;
            if (lp.height == LayoutParams.WRAP_CONTENT) {
                childHeightMode = MeasureSpec.AT_MOST;
            } else {
                childHeightMode = MeasureSpec.EXACTLY;
            }

            final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
                    widthSize - horizontalPadding, childWidthMode);
            final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
                    heightSize - verticalPadding, childHeightMode);

            child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
            maxChildHeight = Math
                    .max(maxChildHeight, child.getMeasuredHeight());
        }

        if (heightMode == MeasureSpec.AT_MOST) {
            heightSize = maxChildHeight + verticalPadding;
        }

        setMeasuredDimension(widthSize, heightSize);

        // We can't call getChildOffset/getRelativeChildOffset until we set the
        // measured dimensions.
        // We also wait until we set the measured dimensions before flushing the
        // cache as well, to
        // ensure that the cache is filled with good values.
        invalidateCachedOffsets();

        if (childCount > 0) {

            // Calculate the variable page spacing if necessary
            if (mPageSpacing == AUTOMATIC_PAGE_SPACING) {
                // The gap between pages in the PagedView should be equal to the
                // gap from the page
                // to the edge of the screen (so it is not visible in the
                // current screen). To
                // account for unequal padding on each side of the paged view,
                // we take the maximum
                // of the left/right gap and use that as the gap between each
                // page.
                int offset = getRelativeChildOffset(0);
                int spacing = Math.max(offset,
                        widthSize - offset - getChildAt(0).getMeasuredWidth());
                setPageSpacing(spacing);
            }
        }

        if (childCount > 0) {
            mMaxScrollX = getChildOffset(childCount - 1)
                    - getRelativeChildOffset(childCount - 1);
        } else {
            mMaxScrollX = 0;
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {

        final int verticalPadding = getPaddingTop() + getPaddingBottom();
        final int childCount = getChildCount();
        int childLeft = getRelativeChildOffset(0);

        for (int i = 0; i < childCount; i++) {
            final View child = getPageAt(i);
            if (child.getVisibility() != View.GONE) {
                final int childWidth = getScaledMeasuredWidth(child);
                final int childHeight = child.getMeasuredHeight();
                int childTop = getPaddingTop();
                if (mCenterPagesVertically) {
                    childTop += ((getMeasuredHeight() - verticalPadding) - childHeight) / 2;
                }

                child.layout(childLeft, childTop,
                        childLeft + child.getMeasuredWidth(), childTop
                                + childHeight);
                childLeft += childWidth + mPageSpacing;
            }
        }

        if (mFirstLayout && mCurrentPage >= 0 && mCurrentPage < getChildCount()) {
            updateCurrentPageScroll();
            mFirstLayout = false;
        }
    }

    View getPageAt(int index) {
        return getChildAt(index);
    }
    
    public int getmCurrentPage() {
        return mCurrentPage;
    }

    protected int getChildWidth(int index) {
        final int measuredWidth = getPageAt(index).getMeasuredWidth();
        return measuredWidth;
    }

    protected int getScaledMeasuredWidth(View child) {
        final int measuredWidth = child.getMeasuredWidth();
        final int minWidth = 0;
        final int maxWidth = (minWidth > measuredWidth) ? minWidth
                : measuredWidth;
        return (int) (maxWidth * mLayoutScale + 0.5f);
    }

    protected void updateCurrentPageScroll() {
        int offset = getChildOffset(mCurrentPage);
        int relOffset = getRelativeChildOffset(mCurrentPage);
        int newX = offset - relOffset;
        scrollTo(newX, 0);
        mScroller.setFinalX(newX);
        mScroller.forceFinished(true);
    }

    protected int getChildOffset(int index) {
        int[] childOffsets = Float.compare(mLayoutScale, 1f) == 0 ? mChildOffsets
                : mChildOffsetsWithLayoutScale;

        if (childOffsets != null && childOffsets[index] != -1) {
            return childOffsets[index];
        } else {
            if (getChildCount() == 0)
                return 0;

            int offset = getRelativeChildOffset(0);
            for (int i = 0; i < index; ++i) {
                offset += getScaledMeasuredWidth(getPageAt(i)) + mPageSpacing;
            }
            if (childOffsets != null) {
                childOffsets[index] = offset;
            }
            return offset;
        }
    }

    protected int getRelativeChildOffset(int index) {
        if (mChildRelativeOffsets != null && mChildRelativeOffsets[index] != -1) {
            return mChildRelativeOffsets[index];
        } else {
            final int padding = getPaddingLeft() + getPaddingRight();
            final int offset = getPaddingLeft()
                    + (getMeasuredWidth() - padding - getChildWidth(index)) / 2;
            if (mChildRelativeOffsets != null) {
                mChildRelativeOffsets[index] = offset;
            }
            return offset;
        }
    }

    public void setPageSpacing(int pageSpacing) {
        mPageSpacing = pageSpacing;
        invalidateCachedOffsets();
    }

    protected void invalidateCachedOffsets() {
        int count = getChildCount();
        if (count == 0) {
            mChildOffsets = null;
            mChildRelativeOffsets = null;
            mChildOffsetsWithLayoutScale = null;
            return;
        }

        mChildOffsets = new int[count];
        mChildRelativeOffsets = new int[count];
        mChildOffsetsWithLayoutScale = new int[count];
        for (int i = 0; i < count; i++) {
            mChildOffsets[i] = -1;
            mChildRelativeOffsets[i] = -1;
            mChildOffsetsWithLayoutScale[i] = -1;
        }
    }

    protected void init() {
        mDirtyPageContent = new ArrayList<Boolean>();
        mDirtyPageContent.ensureCapacity(32);
        mScroller = new Scroller(getContext(), new ScrollInterpolator());
        mCurrentPage = 0;
        mCenterPagesVertically = true;

        final ViewConfiguration configuration = ViewConfiguration
                .get(getContext());
        mTouchSlop = configuration.getScaledTouchSlop();
        mPagingTouchSlop = configuration.getScaledPagingTouchSlop();
        mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
        mDensity = getResources().getDisplayMetrics().density;

        mFlingThresholdVelocity = (int) (FLING_THRESHOLD_VELOCITY * mDensity);
        mMinFlingVelocity = (int) (MIN_FLING_VELOCITY * mDensity);
        mMinSnapVelocity = (int) (MIN_SNAP_VELOCITY * mDensity);
    }

    private static class ScrollInterpolator implements Interpolator {
        public ScrollInterpolator() {
        }

        public float getInterpolation(float t) {
            t -= 1.0f;
            return t * t * t * t * t + 1;
        }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        /*
         * This method JUST determines whether we want to intercept the motion.
         * If we return true, onTouchEvent will be called and we do the actual
         * scrolling there.
         */
        acquireVelocityTrackerAndAddMovement(ev);

        // Skip touch handling if there are no pages to swipe
        if (getChildCount() <= 0)
            return super.onInterceptTouchEvent(ev);

        /*
         * Shortcut the most recurring case: the user is in the dragging state
         * and he is moving his finger. We want to intercept this motion.
         */
        final int action = ev.getAction();
        if ((action == MotionEvent.ACTION_MOVE)
                && (mTouchState == TOUCH_STATE_SCROLLING)) {
            return true;
        }

        switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_MOVE: {
            /*
             * mIsBeingDragged == false, otherwise the shortcut would have
             * caught it. Check whether the user has moved far enough from his
             * original down touch.
             */
            if (mActivePointerId != INVALID_POINTER) {
                determineScrollingStart(ev);
                break;
            }
            // if mActivePointerId is INVALID_POINTER, then we must have missed
            // an ACTION_DOWN
            // event. in that case, treat the first occurence of a move event as
            // a ACTION_DOWN
            // i.e. fall through to the next case (don't break)
            // (We sometimes miss ACTION_DOWN events in Workspace because it
            // ignores all events
            // while it's small- this was causing a crash before we checked for
            // INVALID_POINTER)
        }

        case MotionEvent.ACTION_DOWN: {
            final float x = ev.getX();
            final float y = ev.getY();
            // Remember location of down touch
            mDownMotionX = x;
            mLastMotionX = x;
            mLastMotionY = y;
            mLastMotionXRemainder = 0;
            mTotalMotionX = 0;
            mActivePointerId = ev.getPointerId(0);

            /*
             * If being flinged and user touches the screen, initiate drag;
             * otherwise don't. mScroller.isFinished should be false when being
             * flinged.
             */
            final int xDist = Math.abs(mScroller.getFinalX()
                    - mScroller.getCurrX());
            final boolean finishedScrolling = (mScroller.isFinished() || xDist < mTouchSlop);
            if (finishedScrolling) {
                mTouchState = TOUCH_STATE_REST;
                mScroller.abortAnimation();
            } else {
                mTouchState = TOUCH_STATE_SCROLLING;
            }

            // check if this can be the beginning of a tap on the side of the
            // pages
            // to scroll the current page
            if (mTouchState != TOUCH_STATE_PREV_PAGE
                    && mTouchState != TOUCH_STATE_NEXT_PAGE) {
                if (getChildCount() > 0) {
                    if (hitsPreviousPage(x, y)) {
                        mTouchState = TOUCH_STATE_PREV_PAGE;
                    } else if (hitsNextPage(x, y)) {
                        mTouchState = TOUCH_STATE_NEXT_PAGE;
                    }
                }
            }
            break;
        }

        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            mTouchState = TOUCH_STATE_REST;
            mActivePointerId = INVALID_POINTER;
            releaseVelocityTracker();
            break;

        case MotionEvent.ACTION_POINTER_UP:
            onSecondaryPointerUp(ev);
            releaseVelocityTracker();
            break;
        }

        /*
         * The only time we want to intercept motion events is if we are in the
         * drag mode.
         */
        return mTouchState != TOUCH_STATE_REST;
    }

    protected boolean hitsPreviousPage(float x, float y) {
        return (x < getRelativeChildOffset(mCurrentPage) - mPageSpacing);
    }

    protected boolean hitsNextPage(float x, float y) {
        return (x > (getMeasuredWidth() - getRelativeChildOffset(mCurrentPage) + mPageSpacing));
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {

        if (getChildCount() <= 0)
            return super.onTouchEvent(ev);

        acquireVelocityTrackerAndAddMovement(ev);

        final int action = ev.getAction();

        switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            /*
             * If being flinged and user touches, stop the fling. isFinished
             * will be false if being flinged.
             */
            if (!mScroller.isFinished()) {
                mScroller.abortAnimation();
            }

            // Remember where the motion event started
            mDownMotionX = mLastMotionX = ev.getX();
            mLastMotionXRemainder = 0;
            mTotalMotionX = 0;
            mActivePointerId = ev.getPointerId(0);
            if (mTouchState == TOUCH_STATE_SCROLLING) {
                pageBeginMoving();
            }
            break;

        case MotionEvent.ACTION_MOVE:
            if (mTouchState == TOUCH_STATE_SCROLLING) {
                // Scroll to follow the motion event
                final int pointerIndex = ev.findPointerIndex(mActivePointerId);
                final float x = ev.getX(pointerIndex);
                final float deltaX = mLastMotionX + mLastMotionXRemainder - x;

                mTotalMotionX += Math.abs(deltaX);

                // Only scroll and update mLastMotionX if we have moved some
                // discrete amount. We
                // keep the remainder because we are actually testing if we've
                // moved from the last
                // scrolled position (which is discrete).
                if (Math.abs(deltaX) >= 1.0f) {
                    mTouchX += deltaX;
                    mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
                    if (!mDeferScrollUpdate) {
                        scrollBy((int) deltaX, 0);
                    } else {
                        invalidate();
                    }
                    mLastMotionX = x;
                    mLastMotionXRemainder = deltaX - (int) deltaX;
                } else {
                    awakenScrollBars();
                }
            } else {
                determineScrollingStart(ev);
            }
            break;

        case MotionEvent.ACTION_UP:
            if (mTouchState == TOUCH_STATE_SCROLLING) {
                final int activePointerId = mActivePointerId;
                final int pointerIndex = ev.findPointerIndex(activePointerId);
                final float x = ev.getX(pointerIndex);
                final VelocityTracker velocityTracker = mVelocityTracker;
                velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
                int velocityX = (int) velocityTracker
                        .getXVelocity(activePointerId);
                final int deltaX = (int) (x - mDownMotionX);
                final int pageWidth = getScaledMeasuredWidth(getPageAt(mCurrentPage));
                boolean isSignificantMove = Math.abs(deltaX) > pageWidth
                        * SIGNIFICANT_MOVE_THRESHOLD;

                mTotalMotionX += Math.abs(mLastMotionX + mLastMotionXRemainder
                        - x);

                boolean isFling = mTotalMotionX > MIN_LENGTH_FOR_FLING
                        && Math.abs(velocityX) > mFlingThresholdVelocity;

                // In the case that the page is moved far to one direction and
                // then is flung
                // in the opposite direction, we use a threshold to determine
                // whether we should
                // just return to the starting page, or if we should skip one
                // further.
                boolean returnToOriginalPage = false;
                if (Math.abs(deltaX) > pageWidth
                        * RETURN_TO_ORIGINAL_PAGE_THRESHOLD
                        && Math.signum(velocityX) != Math.signum(deltaX)
                        && isFling) {
                    returnToOriginalPage = true;
                }

                int finalPage = 0;
                // We give flings precedence over large moves, which is why we
                // short-circuit our
                // test for a large move if a fling has been registered. That
                // is, a large
                // move to the left and fling to the right will register as a
                // fling to the right.
                if (((isSignificantMove && deltaX > 0 && !isFling) || (isFling && velocityX > 0))
                        && mCurrentPage > 0) {
                    finalPage = returnToOriginalPage ? mCurrentPage
                            : mCurrentPage - 1;
                    snapToPageWithVelocity(finalPage, velocityX);
                } else if (((isSignificantMove && deltaX < 0 && !isFling) || (isFling && velocityX < 0))
                        && mCurrentPage < getChildCount() - 1) {
                    finalPage = returnToOriginalPage ? mCurrentPage
                            : mCurrentPage + 1;
                    snapToPageWithVelocity(finalPage, velocityX);
                } else {
                    snapToDestination();
                }

            } else if (mTouchState == TOUCH_STATE_PREV_PAGE) {
                // at this point we have not moved beyond the touch slop
                // (otherwise mTouchState would be TOUCH_STATE_SCROLLING), so
                // we can just page
                int nextPage = Math.max(0, mCurrentPage - 1);
                if (nextPage != mCurrentPage) {
                 
                    snapToPage(nextPage);
                } else {
                    snapToDestination();
                }
            } else if (mTouchState == TOUCH_STATE_NEXT_PAGE) {
                // at this point we have not moved beyond the touch slop
                // (otherwise mTouchState would be TOUCH_STATE_SCROLLING), so
                // we can just page
                int nextPage = Math.min(getChildCount() - 1, mCurrentPage + 1);
                if (nextPage != mCurrentPage) {
               
                    snapToPage(nextPage);
                } else {
                    snapToDestination();
                }
            }
            mTouchState = TOUCH_STATE_REST;
            mActivePointerId = INVALID_POINTER;
            releaseVelocityTracker();
            break;

        case MotionEvent.ACTION_CANCEL:
            if (mTouchState == TOUCH_STATE_SCROLLING) {
                snapToDestination();
            }
            mTouchState = TOUCH_STATE_REST;
            mActivePointerId = INVALID_POINTER;
            releaseVelocityTracker();
            break;

        case MotionEvent.ACTION_POINTER_UP:
            onSecondaryPointerUp(ev);
            break;
        }

        return true;
    }

    @Override
    public boolean onGenericMotionEvent(MotionEvent event) {
        // TODO 
        if (event.getSource()!= 0) {
            switch (event.getAction()) {
            case MotionEvent.ACTION_SCROLL: {
                // Handle mouse (or ext. device) by shifting the page depending
                // on the scroll
                final float vscroll;
                final float hscroll;
                if ((event.getMetaState() & KeyEvent.META_SHIFT_ON) != 0) {
                    vscroll = 0;
                    hscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL);
                } else {
                    vscroll = -event.getAxisValue(MotionEvent.AXIS_VSCROLL);
                    hscroll = event.getAxisValue(MotionEvent.AXIS_HSCROLL);
                }
                if (hscroll != 0 || vscroll != 0) {
                    if (hscroll > 0 || vscroll > 0) {
                        scrollRight();
                    } else {
                        scrollLeft();
                    }
                    return true;
                }
            }
            }
        }
        return super.onGenericMotionEvent(event);
    }

    private void acquireVelocityTrackerAndAddMovement(MotionEvent ev) {
        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(ev);
    }

    private void releaseVelocityTracker() {
        if (mVelocityTracker != null) {
            mVelocityTracker.recycle();
            mVelocityTracker = null;
        }
    }

    protected void pageBeginMoving() {
        if (!mIsPageMoving) {
            mIsPageMoving = true;
            onPageBeginMoving();
        }
    }

    protected void pageEndMoving() {
        if (mIsPageMoving) {
            mIsPageMoving = false;
            onPageEndMoving();
        }
    }

    protected boolean isPageMoving() {
        return mIsPageMoving;
    }

    // a method that subclasses can override to add behavior
    protected void onPageBeginMoving() {

        // Begin Immersion changes
        if (mHapticCaptureFling && mNextPage != mCurrentPage) {
            if (!mHapticFlingStarted) {
                mHapticFlingStarted = true;
                mLastHapticScreen = mCurrentPage;
            } else {
                if ((mNextPage != INVALID_PAGE)
                        && (mLastHapticScreen != mNextPage)) {
                }
                mHapticFlingStarted = false;
            }
        }
        // End Immersion changes
    }

    // a method that subclasses can override to add behavior
    protected void onPageEndMoving() {
        // Reset the Flags
        mHapticCaptureFling = true;
        mHapticFlingStarted = false;
        // End Immersion changes
        mForceDrawAllChildrenNextFrame = true;

    }

    protected void determineScrollingStart(MotionEvent ev) {
        determineScrollingStart(ev, 1.0f);
    }

    /*
     * Determines if we should change the touch state to start scrolling after
     * the user moves their touch point too far.
     */
    protected void determineScrollingStart(MotionEvent ev, float touchSlopScale) {
        /*
         * Locally do absolute value. mLastMotionX is set to the y value of the
         * down event.
         */
        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
        if (pointerIndex == -1) {
            return;
        }
        final float x = ev.getX(pointerIndex);
        final float y = ev.getY(pointerIndex);
        final int xDiff = (int) Math.abs(x - mLastMotionX);
        final int yDiff = (int) Math.abs(y - mLastMotionY);

        final int touchSlop = Math.round(touchSlopScale * mTouchSlop);
        boolean xPaged = xDiff > mPagingTouchSlop;
        boolean xMoved = xDiff > touchSlop;
        boolean yMoved = yDiff > touchSlop;

        if (xMoved || xPaged || yMoved) {
            if (mUsePagingTouchSlop ? xPaged : xMoved) {
                // Scroll if the user moved far enough along the X axis
                mTouchState = TOUCH_STATE_SCROLLING;
                mTotalMotionX += Math.abs(mLastMotionX - x);
                mLastMotionX = x;
                mLastMotionXRemainder = 0;
                mTouchX = getScrollX();
                mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
                pageBeginMoving();
            }
        }

    }

    protected void snapToPageWithVelocity(int whichPage, int velocity) {
        whichPage = Math.max(0, Math.min(whichPage, getChildCount() - 1));
        int halfScreenSize = getMeasuredWidth() / 2;

        final int newX = getChildOffset(whichPage)
                - getRelativeChildOffset(whichPage);
        int delta = newX - mUnboundedScrollX;
        int duration = 0;

        if (Math.abs(velocity) < mMinFlingVelocity) {
            // If the velocity is low enough, then treat this more as an
            // automatic page advance
            // as opposed to an apparent physical response to flinging
            snapToPage(whichPage, PAGE_SNAP_ANIMATION_DURATION);
            return;
        }

        // Here we compute a "distance" that will be used in the computation of
        // the overall
        // snap duration. This is a function of the actual distance that needs
        // to be traveled;
        // we keep this value close to half screen size in order to reduce the
        // variance in snap
        // duration as a function of the distance the page needs to travel.
        float distanceRatio = Math.min(1f, 1.0f * Math.abs(delta)
                / (2 * halfScreenSize));
        float distance = halfScreenSize + halfScreenSize
                * distanceInfluenceForSnapDuration(distanceRatio);

        velocity = Math.abs(velocity);
        velocity = Math.max(mMinSnapVelocity, velocity);

        // we want the page's snap velocity to approximately match the velocity
        // at which the
        // user flings, so we scale the duration by a value near to the
        // derivative of the scroll
        // interpolator at zero, ie. 5. We use 4 to make it a little slower.
        duration = 4 * Math.round(1000 * Math.abs(distance / velocity));

        snapToPage(whichPage, delta, duration);
    }

    protected void snapToPage(int whichPage) {
        snapToPage(whichPage, PAGE_SNAP_ANIMATION_DURATION);
    }

    protected void snapToPage(int whichPage, int duration) {
        whichPage = Math.max(0, Math.min(whichPage, getPageCount() - 1));
        int newX = getChildOffset(whichPage)
                - getRelativeChildOffset(whichPage);
        final int sX = mUnboundedScrollX;
        final int delta = newX - sX;
        snapToPage(whichPage, delta, duration);
    }

    protected void snapToPage(int whichPage, int delta, int duration) {
        mNextPage = whichPage;
        //wufen
        onScreenChangeListener.onScreenChange(mNextPage);
        
        View focusedChild = getFocusedChild();
        if (focusedChild != null && whichPage != mCurrentPage
                && focusedChild == getPageAt(mCurrentPage)) {
            focusedChild.clearFocus();
        }

        pageBeginMoving();
        awakenScrollBars(duration);
        if (duration == 0) {
            duration = Math.abs(delta);
        }

        if (!mScroller.isFinished())
            mScroller.abortAnimation();
        mScroller.startScroll(mUnboundedScrollX, 0, delta, 0, duration);
        // Load associated pages immediately if someone else is handling the
        // scroll, otherwise defer
        // loading associated pages until the scroll settles
        invalidate();
    }

    public void scrollLeft() {
        if (mScroller.isFinished()) {
            if (mCurrentPage > 0)
                snapToPage(mCurrentPage - 1);
        } else {
            if (mNextPage > 0)
                snapToPage(mNextPage - 1);
        }
        
    }

    public void scrollRight() {
        if (mScroller.isFinished()) {
            if (mCurrentPage < getChildCount() - 1)
                snapToPage(mCurrentPage + 1);
        } else {
            if (mNextPage < getChildCount() - 1)
                snapToPage(mNextPage + 1);
        }
    }

    protected void snapToDestination() {
        snapToPage(getPageNearestToCenterOfScreen(),
                PAGE_SNAP_ANIMATION_DURATION);
    }

    private void onSecondaryPointerUp(MotionEvent ev) {
        final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
        final int pointerId = ev.getPointerId(pointerIndex);
        if (pointerId == mActivePointerId) {
            // This was our active pointer going up. Choose a new
            // active pointer and adjust accordingly.
            // TODO: Make this decision more intelligent.
            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
            mLastMotionX = mDownMotionX = ev.getX(newPointerIndex);
            mLastMotionY = ev.getY(newPointerIndex);
            mLastMotionXRemainder = 0;
            mActivePointerId = ev.getPointerId(newPointerIndex);
            if (mVelocityTracker != null) {
                mVelocityTracker.clear();
            }
        }
    }

    float distanceInfluenceForSnapDuration(float f) {
        f -= 0.5f; // center the values about 0.
        f *= 0.3f * Math.PI / 2.0f;
        return (float) Math.sin(f);
    }

    protected int getPageCount() {
        return getChildCount();
    }

    protected int getPageNearestToCenterOfScreen() {
        int minDistanceFromScreenCenter = Integer.MAX_VALUE;
        int minDistanceFromScreenCenterIndex = -1;
        int screenCenter = getScrollX() + (getMeasuredWidth() / 2);
        final int childCount = getChildCount();
        for (int i = 0; i < childCount; ++i) {
            View layout = (View) getPageAt(i);
            int childWidth = getScaledMeasuredWidth(layout);
            int halfChildWidth = (childWidth / 2);
            int childCenter = getChildOffset(i) + halfChildWidth;
            int distanceFromScreenCenter = Math.abs(childCenter - screenCenter);
            if (distanceFromScreenCenter < minDistanceFromScreenCenter) {
                minDistanceFromScreenCenter = distanceFromScreenCenter;
                minDistanceFromScreenCenterIndex = i;
            }
        }
        return minDistanceFromScreenCenterIndex;
    }

    protected void dispatchDraw(Canvas canvas) {
        int halfScreenSize = getMeasuredWidth() / 2;
        // mOverScrollX is equal to getScrollX() when we're within the normal
        // scroll range.
        // Otherwise it is equal to the scaled overscroll position.
        int screenCenter = mOverScrollX + halfScreenSize;

        if (screenCenter != mLastScreenCenter || mForceScreenScrolled) {
            // set mForceScreenScrolled before calling screenScrolled so that
            // screenScrolled can
            // set it for the next frame
            mForceScreenScrolled = false;
            screenScrolled(screenCenter);
            mLastScreenCenter = screenCenter;
        }

        // Find out which screens are visible; as an optimization we only call
        // draw on them
        final int pageCount = getChildCount();
        if (pageCount > 0) {
            getVisiblePages(mTempVisiblePagesRange);
            final int leftScreen = mTempVisiblePagesRange[0];
            final int rightScreen = mTempVisiblePagesRange[1];
            if (leftScreen != -1 && rightScreen != -1) {
                final long drawingTime = getDrawingTime();
                // Clip to the bounds
                canvas.save();
                canvas.clipRect(getScrollX(), getScrollY(), getScrollX()
                        + getRight() - getLeft(), getScrollY() + getBottom()
                        - getTop());

                // On certain graphics drivers, if you draw to a off-screen
                // buffer that's not
                // used, it can lead to poor performance. We were running into
                // this when
                // setChildrenLayersEnabled was called on a CellLayout; that
                // triggered a re-draw
                // of that CellLayout's hardware layer, even if that CellLayout
                // wasn't visible.
                // As a fix, below we set pages that aren't going to be rendered
                // are to be
                // View.INVISIBLE, preventing re-drawing of their hardware layer
                for (int i = getChildCount() - 1; i >= 0; i--) {
                    final View v = getPageAt(i);
                    if (mForceDrawAllChildrenNextFrame
                            || (leftScreen <= i && i <= rightScreen && shouldDrawChild(v))) {
                        v.setVisibility(VISIBLE);
                        drawChild(canvas, v, drawingTime);
                    } else {
                        v.setVisibility(INVISIBLE);
                    }
                }
                mForceDrawAllChildrenNextFrame = false;
                canvas.restore();
            }
        }
    }

    protected void screenScrolled(int screenCenter) {

        for (int i = 0; i < getChildCount(); i++) {
            View v = getPageAt(i);
            if (v != null) {
                float scrollProgress = getScrollProgress(screenCenter, v, i);

                float interpolatedProgress = mZInterpolator
                        .getInterpolation(Math.abs(Math.min(scrollProgress, 0)));
                float scale = (1 - interpolatedProgress) + interpolatedProgress
                        * TRANSITION_SCALE_FACTOR;
                float translationX = Math.min(0, scrollProgress)
                        * v.getMeasuredWidth();

                float alpha;

                if (scrollProgress < 0) {
                    alpha = scrollProgress < 0 ? mAlphaInterpolator
                            .getInterpolation(1 - Math.abs(scrollProgress))
                            : 1.0f;
                            if (i == 0) {
                                setOverScrollAmount(v, Math.abs(scrollProgress));
                            }
                } else {
                    // On large screens we need to fade the page as it nears its
                    // leftmost position
                    alpha = mLeftScreenAlphaInterpolator
                            .getInterpolation(1 - scrollProgress);
                    if (i == getChildCount() - 1) {
                        setOverScrollAmount(v, Math.abs(scrollProgress));
                    }
                }
                int pageWidth = v.getMeasuredWidth();
                int pageHeight = v.getMeasuredHeight();
                if (getVersion() >= SCREEN_SCROLLED_MIN_VERSION) {
                    v.setCameraDistance(mDensity * CAMERA_DISTANCE);
                    if (PERFORM_OVERSCROLL_ROTATION) {
                        if (i == 0 && scrollProgress < 0) {
                            // Overscroll to the left
                            v.setPivotX(TRANSITION_PIVOT * pageWidth);
                            v.setRotationY(-TRANSITION_MAX_ROTATION
                                    * scrollProgress);
                            scale = 1.0f;
                            alpha = 1.0f;
                            // On the first page, we don't want the page to have
                            // any
                            // lateral motion
                            translationX = 0;
                        } else if (i == getChildCount() - 1
                                && scrollProgress > 0) {
                            // Overscroll to the right
                            v.setPivotX((1 - TRANSITION_PIVOT) * pageWidth);
                            v.setRotationY(-TRANSITION_MAX_ROTATION
                                    * scrollProgress);
                            scale = 1.0f;
                            alpha = 1.0f;
                            // On the last page, we don't want the page to have
                            // any
                            // lateral motion.
                            translationX = 0;
                        } else {
                            v.setPivotY(pageHeight / 2.0f);
                            v.setPivotX(pageWidth / 2.0f);
                            v.setRotationY(0f);
                        }
                    }

                    v.setTranslationX(translationX);
                    v.setScaleX(scale);
                    v.setScaleY(scale);
//                    v.setAlpha(alpha * 0.5f);
                    v.setAlpha(alpha);   // if * 0.5f  it will to dark
                }

                // If the view has 0 alpha, we set it to be invisible so as to
                // prevent
                // it from accepting touches
                if (alpha == 0) {
                    v.setVisibility(INVISIBLE);
                } else if (v.getVisibility() != VISIBLE) {
                    v.setVisibility(VISIBLE);
                }
                Log.d("Nevin","VERSION:"+getVersion());
            }
        }
        
       /* for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            if (child != null) {
                float scrollProgress = getScrollProgress(screenCenter, child, i);
                float alpha = 1 - Math.abs(scrollProgress);
                child.setAlpha(alpha);
            }
        }
        invalidate();*/

    }
    
    public int getVersion() {
        try {
            int currentapiVersion=android.os.Build.VERSION.SDK_INT;
            return  currentapiVersion;
        } catch (Exception e) {
            e.printStackTrace();
            return 0;
        }
    }

    protected void setOverScrollAmount(View v, float r) {
        int alpha = (int) Math.round((r * 255));
        if (alpha != 0) {
            v.setBackgroundColor((int) Color.BLACK * ( - alpha));
        }
        v.invalidate();
    }

    protected void getVisiblePages(int[] range) {
        final int pageCount = getChildCount();

        if (pageCount > 0) {
            final int screenWidth = getMeasuredWidth();
            int leftScreen = 0;
            int rightScreen = 0;
            View currPage = getPageAt(leftScreen);
            while (leftScreen < pageCount - 1
                    && currPage.getLeft() + currPage.getWidth()
                            - currPage.getPaddingRight() < getScrollX()) {
                leftScreen++;
                currPage = getPageAt(leftScreen);
            }
            rightScreen = leftScreen;
            currPage = getPageAt(rightScreen + 1);
            while (rightScreen < pageCount - 1
                    && currPage.getLeft() - currPage.getPaddingLeft() < getScrollX()
                            + screenWidth) {
                rightScreen++;
                currPage = getPageAt(rightScreen + 1);
            }
            range[0] = leftScreen;
            range[1] = rightScreen;
        } else {
            range[0] = -1;
            range[1] = -1;
        }
    }

    protected boolean shouldDrawChild(View child) {
        if (getVersion() >= SCREEN_SCROLLED_MIN_VERSION) {
            return child.getAlpha() > 0;
        }
        return true;
    }

    protected float getScrollProgress(int screenCenter, View v, int page) {
        final int halfScreenSize = getMeasuredWidth() / 2;

        int totalDistance = getScaledMeasuredWidth(v) + mPageSpacing;
        int delta = screenCenter
                - (getChildOffset(page) - getRelativeChildOffset(page) + halfScreenSize);

        float scrollProgress = delta / (totalDistance * 1.0f);
        scrollProgress = Math.min(scrollProgress, 1.0f);
        scrollProgress = Math.max(scrollProgress, -1.0f);
        return scrollProgress;
    }

    static class ZInterpolator implements TimeInterpolator {
        private float focalLength;

        public ZInterpolator(float foc) {
            focalLength = foc;
        }

        public float getInterpolation(float input) {
            return (1.0f - focalLength / (focalLength + input))
                    / (1.0f - focalLength / (focalLength + 1.0f));
        }
    }
    
    public interface TimeInterpolator {
        float getInterpolation(float input);
    }

    @Override
    public void scrollBy(int x, int y) {
        scrollTo(mUnboundedScrollX + x, getScrollY() + y);
    }

    @Override
    public void scrollTo(int x, int y) {
        mUnboundedScrollX = x;

        if (x < 0) {
            super.scrollTo(0, y);
            if (mAllowOverScroll) {
                overScroll(x);
            }
        } else if (x > mMaxScrollX) {
            super.scrollTo(mMaxScrollX, y);
            if (mAllowOverScroll) {
                overScroll(x - mMaxScrollX);
            }
        } else {
            mOverScrollX = x;
            super.scrollTo(x, y);
        }

        mTouchX = x;
        mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
    }

    protected void overScroll(float amount) {
        acceleratedOverScroll(amount);
    }

    protected void acceleratedOverScroll(float amount) {
        int screenSize = getMeasuredWidth();

        // We want to reach the max over scroll effect when the user has
        // over scrolled half the size of the screen
        float f = OVERSCROLL_ACCELERATE_FACTOR * (amount / screenSize);

        if (f == 0)
            return;

        // Clamp this factor, f, to -1 < f < 1
        if (Math.abs(f) >= 1) {
            f /= Math.abs(f);
        }

        int overScrollAmount = (int) Math.round(f * screenSize);
        if (amount < 0) {
            mOverScrollX = overScrollAmount;
            super.scrollTo(0, getScrollY());
        } else {
            mOverScrollX = mMaxScrollX + overScrollAmount;
            super.scrollTo(mMaxScrollX, getScrollY());
        }
        invalidate();

    }

    protected boolean computeScrollHelper() {
        if (mScroller.computeScrollOffset()) {
            // Don't bother scrolling if the page does not need to be moved
            if (getScrollX() != mScroller.getCurrX()
                    || getScrollY() != mScroller.getCurrY()
                    || mOverScrollX != mScroller.getCurrX()) {
                scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            }
            invalidate();
            return true;
        } else if (mNextPage != INVALID_PAGE) {
            mCurrentPage = Math.max(0, Math.min(mNextPage, getPageCount() - 1));
            mNextPage = INVALID_PAGE;

            // Load the associated pages if necessary

            // We don't want to trigger a page end moving unless the page has
            // settled
            // and the user has stopped scrolling
            if (mTouchState == TOUCH_STATE_REST) {
                pageEndMoving();
            }

            // Notify the user when the page changes
            AccessibilityManager accessibilityManager = (AccessibilityManager) getContext()
                    .getSystemService(Context.ACCESSIBILITY_SERVICE);
            if (accessibilityManager.isEnabled()) {
                AccessibilityEvent ev = AccessibilityEvent
                        .obtain(AccessibilityEvent.TYPE_VIEW_SCROLLED);
                sendAccessibilityEventUnchecked(ev);
            }
            return true;
        }
        return false;
    }
    

    @Override
    public void computeScroll() {
        computeScrollHelper();
    }
    
    
    //add wufen-------
    //分页监听
    public interface OnScreenChangeListener {
        void onScreenChange(int currentIndex);
    }

    private OnScreenChangeListener onScreenChangeListener;

    public void setOnScreenChangeListener(
            OnScreenChangeListener onScreenChangeListener) {
        this.onScreenChangeListener = onScreenChangeListener;
    }

    // 动态数据监听
    public interface OnScreenChangeListenerDataLoad {
        void onScreenChange(int currentIndex);
    }

    private OnScreenChangeListenerDataLoad onScreenChangeListenerDataLoad;

    public void setOnScreenChangeListenerDataLoad(
            OnScreenChangeListenerDataLoad onScreenChangeListenerDataLoad) {
        this.onScreenChangeListenerDataLoad = onScreenChangeListenerDataLoad;
    }
    //-------
}