竖直方向的ViewPager的实现方式

  现在的ViewPager主要是横向的滑动实现，现在公司的业务需要实现竖直方向ViewPager，通过大量的寻找资料终于实现了

废话不说 直接上代码：

   一：自定义viewPager

   

package com.example.test;import java.lang.reflect.Method;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import android.content.Context;import android.content.res.Resources;import android.content.res.TypedArray;import android.database.DataSetObserver;import android.graphics.Canvas;import android.graphics.Rect;import android.graphics.drawable.Drawable;import android.os.Build;import android.os.Bundle;import android.os.Parcel;import android.os.Parcelable;import android.os.SystemClock;import android.support.v4.os.ParcelableCompat;import android.support.v4.os.ParcelableCompatCreatorCallbacks;import android.support.v4.view.AccessibilityDelegateCompat;import android.support.v4.view.KeyEventCompat;import android.support.v4.view.MotionEventCompat;import android.support.v4.view.PagerAdapter;import android.support.v4.view.VelocityTrackerCompat;import android.support.v4.view.ViewCompat;import android.support.v4.view.ViewConfigurationCompat;import android.support.v4.view.ViewPager;import android.support.v4.view.accessibility.AccessibilityEventCompat;import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat;import android.support.v4.view.accessibility.AccessibilityRecordCompat;import android.support.v4.widget.EdgeEffectCompat;import android.util.AttributeSet;import android.util.Log;import android.view.FocusFinder;import android.view.Gravity;import android.view.KeyEvent;import android.view.MotionEvent;import android.view.SoundEffectConstants;import android.view.VelocityTracker;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.view.ViewParent;import android.view.accessibility.AccessibilityEvent;import android.view.animation.Interpolator;import android.widget.Scroller;public class VerticalViewPager extends ViewGroup {    private static final String TAG = "ViewPager";    private static final boolean DEBUG = false;    private static final boolean USE_CACHE = false;    private static final int DEFAULT_OFFSCREEN_PAGES = 1;    private static final int MAX_SETTLE_DURATION = 600; // ms    private static final int MIN_DISTANCE_FOR_FLING = 25; // dips    private static final int DEFAULT_GUTTER_SIZE = 16; // dips    private static final int MIN_FLING_VELOCITY = 400; // dips    private static final int[] LAYOUT_ATTRS = new int[] { android.R.attr.layout_gravity };    /**     * Used to track what the expected number of items in the adapter should be.     * If the app changes this when we don't expect it, we'll throw a big     * obnoxious exception.     */    private int mExpectedAdapterCount;    static class ItemInfo {        Object object;        int position;        boolean scrolling;        float heightFactor;        float offset;    }    private static final Comparator<ItemInfo> COMPARATOR = new Comparator<ItemInfo>() {        @Override        public int compare(ItemInfo lhs, ItemInfo rhs) {            return lhs.position - rhs.position;        }    };    private static final Interpolator sInterpolator = new Interpolator() {        public float getInterpolation(float t) {            t -= 1.0f;            return t * t * t * t * t + 1.0f;        }    };    private final ArrayList<ItemInfo> mItems = new ArrayList<ItemInfo>();    private final ItemInfo mTempItem = new ItemInfo();    private final Rect mTempRect = new Rect();    private PagerAdapter mAdapter;    private int mCurItem; // Index of currently displayed page.    private int mRestoredCurItem = -1;    private Parcelable mRestoredAdapterState = null;    private ClassLoader mRestoredClassLoader = null;    private Scroller mScroller;    private PagerObserver mObserver;    private int mPageMargin;    private Drawable mMarginDrawable;    private int mLeftPageBounds;    private int mRightPageBounds;    // Offsets of the first and last items, if known.    // Set during population, used to determine if we are at the beginning    // or end of the pager data set during touch scrolling.    private float mFirstOffset = -Float.MAX_VALUE;    private float mLastOffset = Float.MAX_VALUE;    private int mChildWidthMeasureSpec;    private int mChildHeightMeasureSpec;    private boolean mInLayout;    private boolean mScrollingCacheEnabled;    private boolean mPopulatePending;    private int mOffscreenPageLimit = DEFAULT_OFFSCREEN_PAGES;    private boolean mIsBeingDragged;    private boolean mIsUnableToDrag;    private boolean mIgnoreGutter;    private int mDefaultGutterSize;    private int mGutterSize;    private int mTouchSlop;    /**     * Position of the last motion event.     */    private float mLastMotionX;    private float mLastMotionY;    private float mInitialMotionX;    private float mInitialMotionY;    /**     * ID of the active pointer. This is used to retain consistency during     * drags/flings if multiple pointers are used.     */    private int mActivePointerId = INVALID_POINTER;    /**     * Sentinel value for no current active pointer. Used by     * {@link #mActivePointerId}.     */    private static final int INVALID_POINTER = -1;    /**     * Determines speed during touch scrolling     */    private VelocityTracker mVelocityTracker;    private int mMinimumVelocity;    private int mMaximumVelocity;    private int mFlingDistance;    private int mCloseEnough;    // If the pager is at least this close to its final position, complete the    // scroll    // on touch down and let the user interact with the content inside instead    // of    // "catching" the flinging pager.    private static final int CLOSE_ENOUGH = 2; // dp    private boolean mFakeDragging;    private long mFakeDragBeginTime;    private EdgeEffectCompat mTopEdge;    private EdgeEffectCompat mBottomEdge;    private boolean mFirstLayout = true;    private boolean mNeedCalculatePageOffsets = false;    private boolean mCalledSuper;    private int mDecorChildCount;    private ViewPager.OnPageChangeListener mOnPageChangeListener;    private ViewPager.OnPageChangeListener mInternalPageChangeListener;    private OnAdapterChangeListener mAdapterChangeListener;    private ViewPager.PageTransformer mPageTransformer;    private Method mSetChildrenDrawingOrderEnabled;    private static final int DRAW_ORDER_DEFAULT = 0;    private static final int DRAW_ORDER_FORWARD = 1;    private static final int DRAW_ORDER_REVERSE = 2;    private int mDrawingOrder;    private ArrayList<View> mDrawingOrderedChildren;    private static final ViewPositionComparator sPositionComparator = new ViewPositionComparator();    /**     * Indicates that the pager is in an idle, settled state. The current page     * is fully in view and no animation is in progress.     */    public static final int SCROLL_STATE_IDLE = 0;    /**     * Indicates that the pager is currently being dragged by the user.     */    public static final int SCROLL_STATE_DRAGGING = 1;    /**     * Indicates that the pager is in the process of settling to a final     * position.     */    public static final int SCROLL_STATE_SETTLING = 2;    private final Runnable mEndScrollRunnable = new Runnable() {        public void run() {            setScrollState(SCROLL_STATE_IDLE);            populate();        }    };    private int mScrollState = SCROLL_STATE_IDLE;    /**     * Used internally to monitor when adapters are switched.     */    interface OnAdapterChangeListener {        public void onAdapterChanged(PagerAdapter oldAdapter, PagerAdapter newAdapter);    }    /**     * Used internally to tag special types of child views that should be added     * as pager decorations by default.     */    interface Decor {    }    public VerticalViewPager(Context context) {        super(context);        initViewPager();    }    public VerticalViewPager(Context context, AttributeSet attrs) {        super(context, attrs);        initViewPager();    }    void initViewPager() {        setWillNotDraw(false);        setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);        setFocusable(true);        final Context context = getContext();        mScroller = new Scroller(context, sInterpolator);        final ViewConfiguration configuration = ViewConfiguration.get(context);        final float density = context.getResources().getDisplayMetrics().density;        mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);        mMinimumVelocity = (int) (MIN_FLING_VELOCITY * density);        mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();        mTopEdge = new EdgeEffectCompat(context);        mBottomEdge = new EdgeEffectCompat(context);        mFlingDistance = (int) (MIN_DISTANCE_FOR_FLING * density);        mCloseEnough = (int) (CLOSE_ENOUGH * density);        mDefaultGutterSize = (int) (DEFAULT_GUTTER_SIZE * density);        ViewCompat.setAccessibilityDelegate(this, new MyAccessibilityDelegate());        if (ViewCompat.getImportantForAccessibility(this) == ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {            ViewCompat.setImportantForAccessibility(this, ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_YES);        }    }    @Override    protected void onDetachedFromWindow() {        removeCallbacks(mEndScrollRunnable);        super.onDetachedFromWindow();    }    private void setScrollState(int newState) {        if (mScrollState == newState) {            return;        }        mScrollState = newState;        if (mPageTransformer != null) {            // PageTransformers can do complex things that benefit from hardware            // layers.            enableLayers(newState != SCROLL_STATE_IDLE);        }        if (mOnPageChangeListener != null) {            mOnPageChangeListener.onPageScrollStateChanged(newState);        }    }    /**     * Set a PagerAdapter that will supply views for this pager as needed.     *     * @param adapter     *            Adapter to use     */    public void setAdapter(PagerAdapter adapter) {        if (mAdapter != null) {            mAdapter.unregisterDataSetObserver(mObserver);            mAdapter.startUpdate(this);            for (int i = 0; i < mItems.size(); i++) {                final ItemInfo ii = mItems.get(i);                mAdapter.destroyItem(this, ii.position, ii.object);            }            mAdapter.finishUpdate(this);            mItems.clear();            removeNonDecorViews();            mCurItem = 0;            scrollTo(0, 0);        }        final PagerAdapter oldAdapter = mAdapter;        mAdapter = adapter;        mExpectedAdapterCount = 0;        if (mAdapter != null) {            if (mObserver == null) {                mObserver = new PagerObserver();            }            mAdapter.registerDataSetObserver(mObserver);            mPopulatePending = false;            final boolean wasFirstLayout = mFirstLayout;            mFirstLayout = true;            mExpectedAdapterCount = mAdapter.getCount();            if (mRestoredCurItem >= 0) {                mAdapter.restoreState(mRestoredAdapterState, mRestoredClassLoader);                setCurrentItemInternal(mRestoredCurItem, false, true);                mRestoredCurItem = -1;                mRestoredAdapterState = null;                mRestoredClassLoader = null;            } else if (!wasFirstLayout) {                populate();            } else {                requestLayout();            }        }        if (mAdapterChangeListener != null && oldAdapter != adapter) {            mAdapterChangeListener.onAdapterChanged(oldAdapter, adapter);        }    }    private void removeNonDecorViews() {        for (int i = 0; i < getChildCount(); i++) {            final View child = getChildAt(i);            final LayoutParams lp = (LayoutParams) child.getLayoutParams();            if (!lp.isDecor) {                removeViewAt(i);                i--;            }        }    }    /**     * Retrieve the current adapter supplying pages.     *     * @return The currently registered PagerAdapter     */    public PagerAdapter getAdapter() {        return mAdapter;    }    void setOnAdapterChangeListener(OnAdapterChangeListener listener) {        mAdapterChangeListener = listener;    }    // private int getClientWidth() {    // return getMeasuredWidth() - getPaddingLeft() - getPaddingRight();    // }    private int getClientHeight() {        return getMeasuredHeight() - getPaddingTop() - getPaddingBottom();    }    /**     * Set the currently selected page. If the ViewPager has already been     * through its first layout with its current adapter there will be a smooth     * animated transition between the current item and the specified item.     *     * @param item     *            Item index to select     */    public void setCurrentItem(int item) {        mPopulatePending = false;        setCurrentItemInternal(item, !mFirstLayout, false);    }    /**     * Set the currently selected page.     *     * @param item     *            Item index to select     * @param smoothScroll     *            True to smoothly scroll to the new item, false to transition     *            immediately     */    public void setCurrentItem(int item, boolean smoothScroll) {        mPopulatePending = false;        setCurrentItemInternal(item, smoothScroll, false);    }    public int getCurrentItem() {        return mCurItem;    }    void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {        setCurrentItemInternal(item, smoothScroll, always, 0);    }    void setCurrentItemInternal(int item, boolean smoothScroll, boolean always, int velocity) {        if (mAdapter == null || mAdapter.getCount() <= 0) {            setScrollingCacheEnabled(false);            return;        }        if (!always && mCurItem == item && mItems.size() != 0) {            setScrollingCacheEnabled(false);            return;        }        if (item < 0) {            item = 0;        } else if (item >= mAdapter.getCount()) {            item = mAdapter.getCount() - 1;        }        final int pageLimit = mOffscreenPageLimit;        if (item > (mCurItem + pageLimit) || item < (mCurItem - pageLimit)) {            // We are doing a jump by more than one page. To avoid            // glitches, we want to keep all current pages in the view            // until the scroll ends.            for (int i = 0; i < mItems.size(); i++) {                mItems.get(i).scrolling = true;            }        }        final boolean dispatchSelected = mCurItem != item;        if (mFirstLayout) {            // We don't have any idea how big we are yet and shouldn't have any            // pages either.            // Just set things up and let the pending layout handle things.            mCurItem = item;            if (dispatchSelected && mOnPageChangeListener != null) {                mOnPageChangeListener.onPageSelected(item);            }            if (dispatchSelected && mInternalPageChangeListener != null) {                mInternalPageChangeListener.onPageSelected(item);            }            requestLayout();        } else {            populate(item);            scrollToItem(item, smoothScroll, velocity, dispatchSelected);        }    }    private void scrollToItem(int item, boolean smoothScroll, int velocity, boolean dispatchSelected) {        final ItemInfo curInfo = infoForPosition(item);        int destY = 0;        if (curInfo != null) {            final int height = getClientHeight();            destY = (int) (height * Math.max(mFirstOffset, Math.min(curInfo.offset, mLastOffset)));        }        if (smoothScroll) {            smoothScrollTo(0, destY, velocity);            if (dispatchSelected && mOnPageChangeListener != null) {                mOnPageChangeListener.onPageSelected(item);            }            if (dispatchSelected && mInternalPageChangeListener != null) {                mInternalPageChangeListener.onPageSelected(item);            }        } else {            if (dispatchSelected && mOnPageChangeListener != null) {                mOnPageChangeListener.onPageSelected(item);            }            if (dispatchSelected && mInternalPageChangeListener != null) {                mInternalPageChangeListener.onPageSelected(item);            }            completeScroll(false);            scrollTo(0, destY);            pageScrolled(destY);        }    }    /**     * Set a listener that will be invoked whenever the page changes or is     * incrementally scrolled. See     * {@link android.support.v4.view.ViewPager.OnPageChangeListener}.     *     * @param listener     *            Listener to set     */    public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {        mOnPageChangeListener = listener;    }    /**     * Set a {@link android.support.v4.view.ViewPager.PageTransformer} that will     * be called for each attached page whenever the scroll position is changed.     * This allows the application to apply custom property transformations to     * each page, overriding the default sliding look and feel.     * <p/>     * <p>     * <em>Note:</em> Prior to Android 3.0 the property animation APIs did not     * exist. As a result, setting a PageTransformer prior to Android 3.0 (API     * 11) will have no effect.     * </p>     *     * @param reverseDrawingOrder     *            true if the supplied PageTransformer requires page views to be     *            drawn from last to first instead of first to last.     * @param transformer     *            PageTransformer that will modify each page's animation     *            properties     */    public void setPageTransformer(boolean reverseDrawingOrder, ViewPager.PageTransformer transformer) {        if (Build.VERSION.SDK_INT >= 11) {            final boolean hasTransformer = transformer != null;            final boolean needsPopulate = hasTransformer != (mPageTransformer != null);            mPageTransformer = transformer;            setChildrenDrawingOrderEnabledCompat(hasTransformer);            if (hasTransformer) {                mDrawingOrder = reverseDrawingOrder ? DRAW_ORDER_REVERSE : DRAW_ORDER_FORWARD;            } else {                mDrawingOrder = DRAW_ORDER_DEFAULT;            }            if (needsPopulate)                populate();        }    }    void setChildrenDrawingOrderEnabledCompat(boolean enable) {        if (Build.VERSION.SDK_INT >= 7) {            if (mSetChildrenDrawingOrderEnabled == null) {                try {                    mSetChildrenDrawingOrderEnabled = ViewGroup.class.getDeclaredMethod("setChildrenDrawingOrderEnabled", new Class[] { Boolean.TYPE });                } catch (NoSuchMethodException e) {                    Log.e(TAG, "Can't find setChildrenDrawingOrderEnabled", e);                }            }            try {                mSetChildrenDrawingOrderEnabled.invoke(this, enable);            } catch (Exception e) {                Log.e(TAG, "Error changing children drawing order", e);            }        }    }    @Override    protected int getChildDrawingOrder(int childCount, int i) {        final int index = mDrawingOrder == DRAW_ORDER_REVERSE ? childCount - 1 - i : i;        final int result = ((LayoutParams) mDrawingOrderedChildren.get(index).getLayoutParams()).childIndex;        return result;    }    /**     * Set a separate OnPageChangeListener for internal use by the support     * library.     *     * @param listener     *            Listener to set     * @return The old listener that was set, if any.     */    ViewPager.OnPageChangeListener setInternalPageChangeListener(ViewPager.OnPageChangeListener listener) {        ViewPager.OnPageChangeListener oldListener = mInternalPageChangeListener;        mInternalPageChangeListener = listener;        return oldListener;    }    /**     * Returns the number of pages that will be retained to either side of the     * current page in the view hierarchy in an idle state. Defaults to 1.     *     * @return How many pages will be kept offscreen on either side     * @see #setOffscreenPageLimit(int)     */    public int getOffscreenPageLimit() {        return mOffscreenPageLimit;    }    /**     * Set the number of pages that should be retained to either side of the     * current page in the view hierarchy in an idle state. Pages beyond this     * limit will be recreated from the adapter when needed.     * <p/>     * <p>     * This is offered as an optimization. If you know in advance the number of     * pages you will need to support or have lazy-loading mechanisms in place     * on your pages, tweaking this setting can have benefits in perceived     * smoothness of paging animations and interaction. If you have a small     * number of pages (3-4) that you can keep active all at once, less time     * will be spent in layout for newly created view subtrees as the user pages     * back and forth.     * </p>     * <p/>     * <p>     * You should keep this limit low, especially if your pages have complex     * layouts. This setting defaults to 1.     * </p>     *     * @param limit     *            How many pages will be kept offscreen in an idle state.     */    public void setOffscreenPageLimit(int limit) {        if (limit < DEFAULT_OFFSCREEN_PAGES) {            Log.w(TAG, "Requested offscreen page limit " + limit + " too small; defaulting to " + DEFAULT_OFFSCREEN_PAGES);            limit = DEFAULT_OFFSCREEN_PAGES;        }        if (limit != mOffscreenPageLimit) {            mOffscreenPageLimit = limit;            populate();        }    }    /**     * Set the margin between pages.     *     * @param marginPixels     *            Distance between adjacent pages in pixels     * @see #getPageMargin()     * @see #setPageMarginDrawable(Drawable)     * @see #setPageMarginDrawable(int)     */    public void setPageMargin(int marginPixels) {        final int oldMargin = mPageMargin;        mPageMargin = marginPixels;        final int height = getHeight();        recomputeScrollPosition(height, height, marginPixels, oldMargin);        requestLayout();    }    /**     * Return the margin between pages.     *     * @return The size of the margin in pixels     */    public int getPageMargin() {        return mPageMargin;    }    /**     * Set a drawable that will be used to fill the margin between pages.     *     * @param d     *            Drawable to display between pages     */    public void setPageMarginDrawable(Drawable d) {        mMarginDrawable = d;        if (d != null)            refreshDrawableState();        setWillNotDraw(d == null);        invalidate();    }    /**     * Set a drawable that will be used to fill the margin between pages.     *     * @param resId     *            Resource ID of a drawable to display between pages     */    public void setPageMarginDrawable(int resId) {        setPageMarginDrawable(getContext().getResources().getDrawable(resId));    }    @Override    protected boolean verifyDrawable(Drawable who) {        return super.verifyDrawable(who) || who == mMarginDrawable;    }    @Override    protected void drawableStateChanged() {        super.drawableStateChanged();        final Drawable d = mMarginDrawable;        if (d != null && d.isStateful()) {            d.setState(getDrawableState());        }    }    // We want the duration of the page snap animation to be influenced by the    // distance that    // the screen has to travel, however, we don't want this duration to be    // effected in a    // purely linear fashion. Instead, we use this method to moderate the effect    // that the distance    // of travel has on the overall snap duration.    float distanceInfluenceForSnapDuration(float f) {        f -= 0.5f; // center the values about 0.        f *= 0.3f * Math.PI / 2.0f;        return (float) Math.sin(f);    }    /**     * Like {@link View#scrollBy}, but scroll smoothly instead of immediately.     *     * @param x     *            the number of pixels to scroll by on the X axis     * @param y     *            the number of pixels to scroll by on the Y axis     */    void smoothScrollTo(int x, int y) {        smoothScrollTo(x, y, 0);    }    /**     * Like {@link View#scrollBy}, but scroll smoothly instead of immediately.     *     * @param x     *            the number of pixels to scroll by on the X axis     * @param y     *            the number of pixels to scroll by on the Y axis     * @param velocity     *            the velocity associated with a fling, if applicable. (0     *            otherwise)     */    void smoothScrollTo(int x, int y, int velocity) {        if (getChildCount() == 0) {            // Nothing to do.            setScrollingCacheEnabled(false);            return;        }        int sx = getScrollX();        int sy = getScrollY();        int dx = x - sx;        int dy = y - sy;        if (dx == 0 && dy == 0) {            completeScroll(false);            populate();            setScrollState(SCROLL_STATE_IDLE);            return;        }        setScrollingCacheEnabled(true);        setScrollState(SCROLL_STATE_SETTLING);        final int height = getClientHeight();        final int halfHeight = height / 2;        final float distanceRatio = Math.min(1f, 1.0f * Math.abs(dx) / height);        final float distance = halfHeight + halfHeight * distanceInfluenceForSnapDuration(distanceRatio);        int duration = 0;        velocity = Math.abs(velocity);        if (velocity > 0) {            duration = 4 * Math.round(1000 * Math.abs(distance / velocity));        } else {            final float pageHeight = height * mAdapter.getPageWidth(mCurItem);            final float pageDelta = (float) Math.abs(dx) / (pageHeight + mPageMargin);            duration = (int) ((pageDelta + 1) * 100);        }        duration = Math.min(duration, MAX_SETTLE_DURATION);        mScroller.startScroll(sx, sy, dx, dy, duration);        ViewCompat.postInvalidateOnAnimation(this);    }    ItemInfo addNewItem(int position, int index) {        ItemInfo ii = new ItemInfo();        ii.position = position;        ii.object = mAdapter.instantiateItem(this, position);        ii.heightFactor = mAdapter.getPageWidth(position);        if (index < 0 || index >= mItems.size()) {            mItems.add(ii);        } else {            mItems.add(index, ii);        }        return ii;    }    void dataSetChanged() {        // This method only gets called if our observer is attached, so mAdapter        // is non-null.        final int adapterCount = mAdapter.getCount();        mExpectedAdapterCount = adapterCount;        boolean needPopulate = mItems.size() < mOffscreenPageLimit * 2 + 1 && mItems.size() < adapterCount;        int newCurrItem = mCurItem;        boolean isUpdating = false;        for (int i = 0; i < mItems.size(); i++) {            final ItemInfo ii = mItems.get(i);            final int newPos = mAdapter.getItemPosition(ii.object);            if (newPos == PagerAdapter.POSITION_UNCHANGED) {                continue;            }            if (newPos == PagerAdapter.POSITION_NONE) {                mItems.remove(i);                i--;                if (!isUpdating) {                    mAdapter.startUpdate(this);                    isUpdating = true;                }                mAdapter.destroyItem(this, ii.position, ii.object);                needPopulate = true;                if (mCurItem == ii.position) {                    // Keep the current item in the valid range                    newCurrItem = Math.max(0, Math.min(mCurItem, adapterCount - 1));                    needPopulate = true;                }                continue;            }            if (ii.position != newPos) {                if (ii.position == mCurItem) {                    // Our current item changed position. Follow it.                    newCurrItem = newPos;                }                ii.position = newPos;                needPopulate = true;            }        }        if (isUpdating) {            mAdapter.finishUpdate(this);        }        Collections.sort(mItems, COMPARATOR);        if (needPopulate) {            // Reset our known page widths; populate will recompute them.            final int childCount = getChildCount();            for (int i = 0; i < childCount; i++) {                final View child = getChildAt(i);                final LayoutParams lp = (LayoutParams) child.getLayoutParams();                if (!lp.isDecor) {                    lp.heightFactor = 0.f;                }            }            setCurrentItemInternal(newCurrItem, false, true);            requestLayout();        }    }    void populate() {        populate(mCurItem);    }    void populate(int newCurrentItem) {        ItemInfo oldCurInfo = null;        int focusDirection = View.FOCUS_FORWARD;        if (mCurItem != newCurrentItem) {            focusDirection = mCurItem < newCurrentItem ? View.FOCUS_DOWN : View.FOCUS_UP;            oldCurInfo = infoForPosition(mCurItem);            mCurItem = newCurrentItem;        }        if (mAdapter == null) {            sortChildDrawingOrder();            return;        }        // Bail now if we are waiting to populate. This is to hold off        // on creating views from the time the user releases their finger to        // fling to a new position until we have finished the scroll to        // that position, avoiding glitches from happening at that point.        if (mPopulatePending) {            if (DEBUG)                Log.i(TAG, "populate is pending, skipping for now...");            sortChildDrawingOrder();            return;        }        // Also, don't populate until we are attached to a window. This is to        // avoid trying to populate before we have restored our view hierarchy        // state and conflicting with what is restored.        if (getWindowToken() == null) {            return;        }        mAdapter.startUpdate(this);        final int pageLimit = mOffscreenPageLimit;        final int startPos = Math.max(0, mCurItem - pageLimit);        final int N = mAdapter.getCount();        final int endPos = Math.min(N - 1, mCurItem + pageLimit);        if (N != mExpectedAdapterCount) {            String resName;            try {                resName = getResources().getResourceName(getId());            } catch (Resources.NotFoundException e) {                resName = Integer.toHexString(getId());            }            throw new IllegalStateException("The application's PagerAdapter changed the adapter's" + " contents without calling PagerAdapter#notifyDataSetChanged!" + " Expected adapter item count: " + mExpectedAdapterCount + ", found: " + N + " Pager id: " + resName + " Pager class: " + getClass() + " Problematic adapter: " + mAdapter.getClass());        }        // Locate the currently focused item or add it if needed.        int curIndex = -1;        ItemInfo curItem = null;        for (curIndex = 0; curIndex < mItems.size(); curIndex++) {            final ItemInfo ii = mItems.get(curIndex);            if (ii.position >= mCurItem) {                if (ii.position == mCurItem)                    curItem = ii;                break;            }        }        if (curItem == null && N > 0) {            curItem = addNewItem(mCurItem, curIndex);        }        // Fill 3x the available width or up to the number of offscreen        // pages requested to either side, whichever is larger.        // If we have no current item we have no work to do.        if (curItem != null) {            float extraHeightTop = 0.f;            int itemIndex = curIndex - 1;            ItemInfo ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;            final int clientHeight = getClientHeight();            final float topHeightNeeded = clientHeight <= 0 ? 0 : 2.f - curItem.heightFactor + (float) getPaddingLeft() / (float) clientHeight;            for (int pos = mCurItem - 1; pos >= 0; pos--) {                if (extraHeightTop >= topHeightNeeded && pos < startPos) {                    if (ii == null) {                        break;                    }                    if (pos == ii.position && !ii.scrolling) {                        mItems.remove(itemIndex);                        mAdapter.destroyItem(this, pos, ii.object);                        if (DEBUG) {                            Log.i(TAG, "populate() - destroyItem() with pos: " + pos + " view: " + ((View) ii.object));                        }                        itemIndex--;                        curIndex--;                        ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;                    }                } else if (ii != null && pos == ii.position) {                    extraHeightTop += ii.heightFactor;                    itemIndex--;                    ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;                } else {                    ii = addNewItem(pos, itemIndex + 1);                    extraHeightTop += ii.heightFactor;                    curIndex++;                    ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;                }            }            float extraHeightBottom = curItem.heightFactor;            itemIndex = curIndex + 1;            if (extraHeightBottom < 2.f) {                ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;                final float bottomHeightNeeded = clientHeight <= 0 ? 0 : (float) getPaddingRight() / (float) clientHeight + 2.f;                for (int pos = mCurItem + 1; pos < N; pos++) {                    if (extraHeightBottom >= bottomHeightNeeded && pos > endPos) {                        if (ii == null) {                            break;                        }                        if (pos == ii.position && !ii.scrolling) {                            mItems.remove(itemIndex);                            mAdapter.destroyItem(this, pos, ii.object);                            if (DEBUG) {                                Log.i(TAG, "populate() - destroyItem() with pos: " + pos + " view: " + ((View) ii.object));                            }                            ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;                        }                    } else if (ii != null && pos == ii.position) {                        extraHeightBottom += ii.heightFactor;                        itemIndex++;                        ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;                    } else {                        ii = addNewItem(pos, itemIndex);                        itemIndex++;                        extraHeightBottom += ii.heightFactor;                        ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;                    }                }            }            calculatePageOffsets(curItem, curIndex, oldCurInfo);        }        if (DEBUG) {            Log.i(TAG, "Current page list:");            for (int i = 0; i < mItems.size(); i++) {                Log.i(TAG, "#" + i + ": page " + mItems.get(i).position);            }        }        mAdapter.setPrimaryItem(this, mCurItem, curItem != null ? curItem.object : null);        mAdapter.finishUpdate(this);        // Check width measurement of current pages and drawing sort order.        // Update LayoutParams as needed.        final int childCount = getChildCount();        for (int i = 0; i < childCount; i++) {            final View child = getChildAt(i);            final LayoutParams lp = (LayoutParams) child.getLayoutParams();            lp.childIndex = i;            if (!lp.isDecor && lp.heightFactor == 0.f) {                // 0 means requery the adapter for this, it doesn't have a valid                // width.                final ItemInfo ii = infoForChild(child);                if (ii != null) {                    lp.heightFactor = ii.heightFactor;                    lp.position = ii.position;                }            }        }        sortChildDrawingOrder();        if (hasFocus()) {            View currentFocused = findFocus();            ItemInfo ii = currentFocused != null ? infoForAnyChild(currentFocused) : null;            if (ii == null || ii.position != mCurItem) {                for (int i = 0; i < getChildCount(); i++) {                    View child = getChildAt(i);                    ii = infoForChild(child);                    if (ii != null && ii.position == mCurItem) {                        if (child.requestFocus(focusDirection)) {                            break;                        }                    }                }            }        }    }    private void sortChildDrawingOrder() {        if (mDrawingOrder != DRAW_ORDER_DEFAULT) {            if (mDrawingOrderedChildren == null) {                mDrawingOrderedChildren = new ArrayList<View>();            } else {                mDrawingOrderedChildren.clear();            }            final int childCount = getChildCount();            for (int i = 0; i < childCount; i++) {                final View child = getChildAt(i);                mDrawingOrderedChildren.add(child);            }            Collections.sort(mDrawingOrderedChildren, sPositionComparator);        }    }    private void calculatePageOffsets(ItemInfo curItem, int curIndex, ItemInfo oldCurInfo) {        final int N = mAdapter.getCount();        final int height = getClientHeight();        final float marginOffset = height > 0 ? (float) mPageMargin / height : 0;        // Fix up offsets for later layout.        if (oldCurInfo != null) {            final int oldCurPosition = oldCurInfo.position;            // Base offsets off of oldCurInfo.            if (oldCurPosition < curItem.position) {                int itemIndex = 0;                ItemInfo ii = null;                float offset = oldCurInfo.offset + oldCurInfo.heightFactor + marginOffset;                for (int pos = oldCurPosition + 1; pos <= curItem.position && itemIndex < mItems.size(); pos++) {                    ii = mItems.get(itemIndex);                    while (pos > ii.position && itemIndex < mItems.size() - 1) {                        itemIndex++;                        ii = mItems.get(itemIndex);                    }                    while (pos < ii.position) {                        // We don't have an item populated for this,                        // ask the adapter for an offset.                        offset += mAdapter.getPageWidth(pos) + marginOffset;                        pos++;                    }                    ii.offset = offset;                    offset += ii.heightFactor + marginOffset;                }            } else if (oldCurPosition > curItem.position) {                int itemIndex = mItems.size() - 1;                ItemInfo ii = null;                float offset = oldCurInfo.offset;                for (int pos = oldCurPosition - 1; pos >= curItem.position && itemIndex >= 0; pos--) {                    ii = mItems.get(itemIndex);                    while (pos < ii.position && itemIndex > 0) {                        itemIndex--;                        ii = mItems.get(itemIndex);                    }                    while (pos > ii.position) {                        // We don't have an item populated for this,                        // ask the adapter for an offset.                        offset -= mAdapter.getPageWidth(pos) + marginOffset;                        pos--;                    }                    offset -= ii.heightFactor + marginOffset;                    ii.offset = offset;                }            }        }        // Base all offsets off of curItem.        final int itemCount = mItems.size();        float offset = curItem.offset;        int pos = curItem.position - 1;        mFirstOffset = curItem.position == 0 ? curItem.offset : -Float.MAX_VALUE;        mLastOffset = curItem.position == N - 1 ? curItem.offset + curItem.heightFactor - 1 : Float.MAX_VALUE;        // Previous pages        for (int i = curIndex - 1; i >= 0; i--, pos--) {            final ItemInfo ii = mItems.get(i);            while (pos > ii.position) {                offset -= mAdapter.getPageWidth(pos--) + marginOffset;            }            offset -= ii.heightFactor + marginOffset;            ii.offset = offset;            if (ii.position == 0)                mFirstOffset = offset;        }        offset = curItem.offset + curItem.heightFactor + marginOffset;        pos = curItem.position + 1;        // Next pages        for (int i = curIndex + 1; i < itemCount; i++, pos++) {            final ItemInfo ii = mItems.get(i);            while (pos < ii.position) {                offset += mAdapter.getPageWidth(pos++) + marginOffset;            }            if (ii.position == N - 1) {                mLastOffset = offset + ii.heightFactor - 1;            }            ii.offset = offset;            offset += ii.heightFactor + marginOffset;        }        mNeedCalculatePageOffsets = false;    }    /**     * This is the persistent state that is saved by ViewPager. Only needed if     * you are creating a sublass of ViewPager that must save its own state, in     * which case it should implement a subclass of this which contains that     * state.     */    public static class SavedState extends BaseSavedState {        int position;        Parcelable adapterState;        ClassLoader loader;        public SavedState(Parcelable superState) {            super(superState);        }        @Override        public void writeToParcel(Parcel out, int flags) {            super.writeToParcel(out, flags);            out.writeInt(position);            out.writeParcelable(adapterState, flags);        }        @Override        public String toString() {            return "FragmentPager.SavedState{" + Integer.toHexString(System.identityHashCode(this)) + " position=" + position + "}";        }        public static final Parcelable.Creator<SavedState> CREATOR = ParcelableCompat.newCreator(new ParcelableCompatCreatorCallbacks<SavedState>() {            @Override            public SavedState createFromParcel(Parcel in, ClassLoader loader) {                return new SavedState(in, loader);            }            @Override            public SavedState[] newArray(int size) {                return new SavedState[size];            }        });        SavedState(Parcel in, ClassLoader loader) {            super(in);            if (loader == null) {                loader = getClass().getClassLoader();            }            position = in.readInt();            adapterState = in.readParcelable(loader);            this.loader = loader;        }    }    @Override    public Parcelable onSaveInstanceState() {        Parcelable superState = super.onSaveInstanceState();        SavedState ss = new SavedState(superState);        ss.position = mCurItem;        if (mAdapter != null) {            ss.adapterState = mAdapter.saveState();        }        return ss;    }    @Override    public void onRestoreInstanceState(Parcelable state) {        if (!(state instanceof SavedState)) {            super.onRestoreInstanceState(state);            return;        }        SavedState ss = (SavedState) state;        super.onRestoreInstanceState(ss.getSuperState());        if (mAdapter != null) {            mAdapter.restoreState(ss.adapterState, ss.loader);            setCurrentItemInternal(ss.position, false, true);        } else {            mRestoredCurItem = ss.position;            mRestoredAdapterState = ss.adapterState;            mRestoredClassLoader = ss.loader;        }    }    @Override    public void addView(View child, int index, ViewGroup.LayoutParams params) {        if (!checkLayoutParams(params)) {            params = generateLayoutParams(params);        }        final LayoutParams lp = (LayoutParams) params;        lp.isDecor |= child instanceof Decor;        if (mInLayout) {            if (lp != null && lp.isDecor) {                throw new IllegalStateException("Cannot add pager decor view during layout");            }            lp.needsMeasure = true;            addViewInLayout(child, index, params);        } else {            super.addView(child, index, params);        }        if (USE_CACHE) {            if (child.getVisibility() != GONE) {                child.setDrawingCacheEnabled(mScrollingCacheEnabled);            } else {                child.setDrawingCacheEnabled(false);            }        }    }    @Override    public void removeView(View view) {        if (mInLayout) {            removeViewInLayout(view);        } else {            super.removeView(view);        }    }    ItemInfo infoForChild(View child) {        for (int i = 0; i < mItems.size(); i++) {            ItemInfo ii = mItems.get(i);            if (mAdapter.isViewFromObject(child, ii.object)) {                return ii;            }        }        return null;    }    ItemInfo infoForAnyChild(View child) {        ViewParent parent;        while ((parent = child.getParent()) != this) {            if (parent == null || !(parent instanceof View)) {                return null;            }            child = (View) parent;        }        return infoForChild(child);    }    ItemInfo infoForPosition(int position) {        for (int i = 0; i < mItems.size(); i++) {            ItemInfo ii = mItems.get(i);            if (ii.position == position) {                return ii;            }        }        return null;    }    @Override    protected void onAttachedToWindow() {        super.onAttachedToWindow();        mFirstLayout = true;    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        // For simple implementation, our internal size is always 0.        // We depend on the container to specify the layout size of        // our view. We can't really know what it is since we will be        // adding and removing different arbitrary views and do not        // want the layout to change as this happens.        setMeasuredDimension(getDefaultSize(0, widthMeasureSpec), getDefaultSize(0, heightMeasureSpec));        final int measuredHeight = getMeasuredHeight();        final int maxGutterSize = measuredHeight / 10;        mGutterSize = Math.min(maxGutterSize, mDefaultGutterSize);        // Children are just made to fill our space.        int childWidthSize = getMeasuredWidth() - getPaddingLeft() - getPaddingRight();        int childHeightSize = measuredHeight - getPaddingTop() - getPaddingBottom();        /*         * Make sure all children have been properly measured. Decor views         * first. Right now we cheat and make this less complicated by assuming         * decor views won't intersect. We will pin to edges based on gravity.         */        int size = getChildCount();        for (int i = 0; i < size; ++i) {            final View child = getChildAt(i);            if (child.getVisibility() != GONE) {                final LayoutParams lp = (LayoutParams) child.getLayoutParams();                if (lp != null && lp.isDecor) {                    final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;                    final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;                    int widthMode = MeasureSpec.AT_MOST;                    int heightMode = MeasureSpec.AT_MOST;                    boolean consumeVertical = vgrav == Gravity.TOP || vgrav == Gravity.BOTTOM;                    boolean consumeHorizontal = hgrav == Gravity.LEFT || hgrav == Gravity.RIGHT;                    if (consumeVertical) {                        widthMode = MeasureSpec.EXACTLY;                    } else if (consumeHorizontal) {                        heightMode = MeasureSpec.EXACTLY;                    }                    int widthSize = childWidthSize;                    int heightSize = childHeightSize;                    if (lp.width != LayoutParams.WRAP_CONTENT) {                        widthMode = MeasureSpec.EXACTLY;                        if (lp.width != LayoutParams.FILL_PARENT) {                            widthSize = lp.width;                        }                    }                    if (lp.height != LayoutParams.WRAP_CONTENT) {                        heightMode = MeasureSpec.EXACTLY;                        if (lp.height != LayoutParams.FILL_PARENT) {                            heightSize = lp.height;                        }                    }                    final int widthSpec = MeasureSpec.makeMeasureSpec(widthSize, widthMode);                    final int heightSpec = MeasureSpec.makeMeasureSpec(heightSize, heightMode);                    child.measure(widthSpec, heightSpec);                    if (consumeVertical) {                        childHeightSize -= child.getMeasuredHeight();                    } else if (consumeHorizontal) {                        childWidthSize -= child.getMeasuredWidth();                    }                }            }        }        mChildWidthMeasureSpec = MeasureSpec.makeMeasureSpec(childWidthSize, MeasureSpec.EXACTLY);        mChildHeightMeasureSpec = MeasureSpec.makeMeasureSpec(childHeightSize, MeasureSpec.EXACTLY);        // Make sure we have created all fragments that we need to have shown.        mInLayout = true;        populate();        mInLayout = false;        // Page views next.        size = getChildCount();        for (int i = 0; i < size; ++i) {            final View child = getChildAt(i);            if (child.getVisibility() != GONE) {                if (DEBUG)                    Log.v(TAG, "Measuring #" + i + " " + child + ": " + mChildWidthMeasureSpec);                final LayoutParams lp = (LayoutParams) child.getLayoutParams();                if (lp == null || !lp.isDecor) {                    final int heightSpec = MeasureSpec.makeMeasureSpec((int) (childHeightSize * lp.heightFactor), MeasureSpec.EXACTLY);                    child.measure(mChildWidthMeasureSpec, heightSpec);                }            }        }    }    @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {        super.onSizeChanged(w, h, oldw, oldh);        // Make sure scroll position is set correctly.        if (h != oldh) {            recomputeScrollPosition(h, oldh, mPageMargin, mPageMargin);        }    }    private void recomputeScrollPosition(int height, int oldHeight, int margin, int oldMargin) {        if (oldHeight > 0 && !mItems.isEmpty()) {            final int heightWithMargin = height - getPaddingTop() - getPaddingBottom() + margin;            final int oldHeightWithMargin = oldHeight - getPaddingTop() - getPaddingBottom() + oldMargin;            final int ypos = getScrollY();            final float pageOffset = (float) ypos / oldHeightWithMargin;            final int newOffsetPixels = (int) (pageOffset * heightWithMargin);            scrollTo(getScrollX(), newOffsetPixels);            if (!mScroller.isFinished()) {                // We now return to your regularly scheduled scroll, already in                // progress.                final int newDuration = mScroller.getDuration() - mScroller.timePassed();                ItemInfo targetInfo = infoForPosition(mCurItem);                mScroller.startScroll(0, newOffsetPixels, 0, (int) (targetInfo.offset * height), newDuration);            }        } else {            final ItemInfo ii = infoForPosition(mCurItem);            final float scrollOffset = ii != null ? Math.min(ii.offset, mLastOffset) : 0;            final int scrollPos = (int) (scrollOffset * (height - getPaddingTop() - getPaddingBottom()));            if (scrollPos != getScrollY()) {                completeScroll(false);                scrollTo(getScrollX(), scrollPos);            }        }    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        final int count = getChildCount();        int width = r - l;        int height = b - t;        int paddingLeft = getPaddingLeft();        int paddingTop = getPaddingTop();        int paddingRight = getPaddingRight();        int paddingBottom = getPaddingBottom();        final int scrollY = getScrollY();        int decorCount = 0;        // First pass - decor views. We need to do this in two passes so that        // we have the proper offsets for non-decor views later.        for (int i = 0; i < count; i++) {            final View child = getChildAt(i);            if (child.getVisibility() != GONE) {                final LayoutParams lp = (LayoutParams) child.getLayoutParams();                int childLeft = 0;                int childTop = 0;                if (lp.isDecor) {                    final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;                    final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;                    switch (hgrav) {                    default:                        childLeft = paddingLeft;                        break;                    case Gravity.LEFT:                        childLeft = paddingLeft;                        paddingLeft += child.getMeasuredWidth();                        break;                    case Gravity.CENTER_HORIZONTAL:                        childLeft = Math.max((width - child.getMeasuredWidth()) / 2, paddingLeft);                        break;                    case Gravity.RIGHT:                        childLeft = width - paddingRight - child.getMeasuredWidth();                        paddingRight += child.getMeasuredWidth();                        break;                    }                    switch (vgrav) {                    default:                        childTop = paddingTop;                        break;                    case Gravity.TOP:                        childTop = paddingTop;                        paddingTop += child.getMeasuredHeight();                        break;                    case Gravity.CENTER_VERTICAL:                        childTop = Math.max((height - child.getMeasuredHeight()) / 2, paddingTop);                        break;                    case Gravity.BOTTOM:                        childTop = height - paddingBottom - child.getMeasuredHeight();                        paddingBottom += child.getMeasuredHeight();                        break;                    }                    childTop += scrollY;                    child.layout(childLeft, childTop, childLeft + child.getMeasuredWidth(), childTop + child.getMeasuredHeight());                    decorCount++;                }            }        }        final int childHeight = height - paddingTop - paddingBottom;        // Page views. Do this once we have the right padding offsets from        // above.        for (int i = 0; i < count; i++) {            final View child = getChildAt(i);            if (child.getVisibility() != GONE) {                final LayoutParams lp = (LayoutParams) child.getLayoutParams();                ItemInfo ii;                if (!lp.isDecor && (ii = infoForChild(child)) != null) {                    int toff = (int) (childHeight * ii.offset);                    int childLeft = paddingLeft;                    int childTop = paddingTop + toff;                    if (lp.needsMeasure) {                        // This was added during layout and needs measurement.                        // Do it now that we know what we're working with.                        lp.needsMeasure = false;                        final int widthSpec = MeasureSpec.makeMeasureSpec((int) (width - paddingLeft - paddingRight), MeasureSpec.EXACTLY);                        final int heightSpec = MeasureSpec.makeMeasureSpec((int) (childHeight * lp.heightFactor), MeasureSpec.EXACTLY);                        child.measure(widthSpec, heightSpec);                    }                    if (DEBUG)                        Log.v(TAG, "Positioning #" + i + " " + child + " f=" + ii.object + ":" + childLeft + "," + childTop + " " + child.getMeasuredWidth() + "x" + child.getMeasuredHeight());                    child.layout(childLeft, childTop, childLeft + child.getMeasuredWidth(), childTop + child.getMeasuredHeight());                }            }        }        mLeftPageBounds = paddingLeft;        mRightPageBounds = width - paddingRight;        mDecorChildCount = decorCount;        if (mFirstLayout) {            scrollToItem(mCurItem, false, 0, false);        }        mFirstLayout = false;    }    @Override    public void computeScroll() {        if (!mScroller.isFinished() && mScroller.computeScrollOffset()) {            int oldX = getScrollX();            int oldY = getScrollY();            int x = mScroller.getCurrX();            int y = mScroller.getCurrY();            if (oldX != x || oldY != y) {                scrollTo(x, y);                if (!pageScrolled(y)) {                    mScroller.abortAnimation();                    scrollTo(x, 0);                }            }            // Keep on drawing until the animation has finished.            ViewCompat.postInvalidateOnAnimation(this);            return;        }        // Done with scroll, clean up state.        completeScroll(true);    }    private boolean pageScrolled(int ypos) {        if (mItems.size() == 0) {            mCalledSuper = false;            onPageScrolled(0, 0, 0);            if (!mCalledSuper) {                throw new IllegalStateException("onPageScrolled did not call superclass implementation");            }            return false;        }        final ItemInfo ii = infoForCurrentScrollPosition();        final int height = getClientHeight();        final int heightWithMargin = height + mPageMargin;        final float marginOffset = (float) mPageMargin / height;        final int currentPage = ii.position;        final float pageOffset = (((float) ypos / height) - ii.offset) / (ii.heightFactor + marginOffset);        final int offsetPixels = (int) (pageOffset * heightWithMargin);        mCalledSuper = false;        onPageScrolled(currentPage, pageOffset, offsetPixels);        if (!mCalledSuper) {            throw new IllegalStateException("onPageScrolled did not call superclass implementation");        }        return true;    }    /**     * This method will be invoked when the current page is scrolled, either as     * part of a programmatically initiated smooth scroll or a user initiated     * touch scroll. If you override this method you must call through to the     * superclass implementation (e.g. super.onPageScrolled(position, offset,     * offsetPixels)) before onPageScrolled returns.     *     * @param position     *            Position index of the first page currently being displayed.     *            Page position+1 will be visible if positionOffset is nonzero.     * @param offset     *            Value from [0, 1) indicating the offset from the page at     *            position.     * @param offsetPixels     *            Value in pixels indicating the offset from position.     */    protected void onPageScrolled(int position, float offset, int offsetPixels) {        // Offset any decor views if needed - keep them on-screen at all times.        if (mDecorChildCount > 0) {            final int scrollY = getScrollY();            int paddingTop = getPaddingTop();            int paddingBottom = getPaddingBottom();            final int height = getHeight();            final int childCount = getChildCount();            for (int i = 0; i < childCount; i++) {                final View child = getChildAt(i);                final LayoutParams lp = (LayoutParams) child.getLayoutParams();                if (!lp.isDecor)                    continue;                final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;                int childTop = 0;                switch (vgrav) {                default:                    childTop = paddingTop;                    break;                case Gravity.TOP:                    childTop = paddingTop;                    paddingTop += child.getHeight();                    break;                case Gravity.CENTER_VERTICAL:                    childTop = Math.max((height - child.getMeasuredHeight()) / 2, paddingTop);                    break;                case Gravity.BOTTOM:                    childTop = height - paddingBottom - child.getMeasuredHeight();                    paddingBottom += child.getMeasuredHeight();                    break;                }                childTop += scrollY;                final int childOffset = childTop - child.getTop();                if (childOffset != 0) {                    child.offsetTopAndBottom(childOffset);                }            }        }        if (mOnPageChangeListener != null) {            mOnPageChangeListener.onPageScrolled(position, offset, offsetPixels);        }        if (mInternalPageChangeListener != null) {            mInternalPageChangeListener.onPageScrolled(position, offset, offsetPixels);        }        if (mPageTransformer != null) {            final int scrollY = getScrollY();            final int childCount = getChildCount();            for (int i = 0; i < childCount; i++) {                final View child = getChildAt(i);                final LayoutParams lp = (LayoutParams) child.getLayoutParams();                if (lp.isDecor)                    continue;                final float transformPos = (float) (child.getTop() - scrollY) / getClientHeight();                mPageTransformer.transformPage(child, transformPos);            }        }        mCalledSuper = true;    }    private void completeScroll(boolean postEvents) {        boolean needPopulate = mScrollState == SCROLL_STATE_SETTLING;        if (needPopulate) {            // Done with scroll, no longer want to cache view drawing.            setScrollingCacheEnabled(false);            mScroller.abortAnimation();            int oldX = getScrollX();            int oldY = getScrollY();            int x = mScroller.getCurrX();            int y = mScroller.getCurrY();            if (oldX != x || oldY != y) {                scrollTo(x, y);            }        }        mPopulatePending = false;        for (int i = 0; i < mItems.size(); i++) {            ItemInfo ii = mItems.get(i);            if (ii.scrolling) {                needPopulate = true;                ii.scrolling = false;            }        }        if (needPopulate) {            if (postEvents) {                ViewCompat.postOnAnimation(this, mEndScrollRunnable);            } else {                mEndScrollRunnable.run();            }        }    }    private boolean isGutterDrag(float y, float dy) {        return (y < mGutterSize && dy > 0) || (y > getHeight() - mGutterSize && dy < 0);    }    private void enableLayers(boolean enable) {        final int childCount = getChildCount();        for (int i = 0; i < childCount; i++) {            final int layerType = enable ? ViewCompat.LAYER_TYPE_HARDWARE : ViewCompat.LAYER_TYPE_NONE;            ViewCompat.setLayerType(getChildAt(i), layerType, null);        }    }    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        /*         * This method JUST determines whether we want to intercept the motion.         * If we return true, onMotionEvent will be called and we do the actual         * scrolling there.         */        final int action = ev.getAction() & MotionEventCompat.ACTION_MASK;        // Always take care of the touch gesture being complete.        if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {            // Release the drag.            if (DEBUG)                Log.v(TAG, "Intercept done!");            mIsBeingDragged = false;            mIsUnableToDrag = false;            mActivePointerId = INVALID_POINTER;            if (mVelocityTracker != null) {                mVelocityTracker.recycle();                mVelocityTracker = null;            }            return false;        }        // Nothing more to do here if we have decided whether or not we        // are dragging.        if (action != MotionEvent.ACTION_DOWN) {            if (mIsBeingDragged) {                if (DEBUG)                    Log.v(TAG, "Intercept returning true!");                return true;            }            if (mIsUnableToDrag) {                if (DEBUG)                    Log.v(TAG, "Intercept returning false!");                return false;            }        }        switch (action) {        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.             */            /*             * Locally do absolute value. mLastMotionY is set to the y value of             * the down event.             */            final int activePointerId = mActivePointerId;            if (activePointerId == INVALID_POINTER) {                // If we don't have a valid id, the touch down wasn't on                // content.                break;            }            final int pointerIndex = MotionEventCompat.findPointerIndex(ev, activePointerId);            final float y = MotionEventCompat.getY(ev, pointerIndex);            final float dy = y - mLastMotionY;            final float yDiff = Math.abs(dy);            final float x = MotionEventCompat.getX(ev, pointerIndex);            final float xDiff = Math.abs(x - mInitialMotionX);            if (DEBUG)                Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);            if (dy != 0 && !isGutterDrag(mLastMotionY, dy) && canScroll(this, false, (int) dy, (int) x, (int) y)) {                // Nested view has scrollable area under this point. Let it be                // handled there.                mLastMotionX = x;                mLastMotionY = y;                mIsUnableToDrag = true;                return false;            }            if (yDiff > mTouchSlop && yDiff * 0.5f > xDiff) {                if (DEBUG)                    Log.v(TAG, "Starting drag!");                mIsBeingDragged = true;                requestParentDisallowInterceptTouchEvent(true);                setScrollState(SCROLL_STATE_DRAGGING);                mLastMotionY = dy > 0 ? mInitialMotionY + mTouchSlop : mInitialMotionY - mTouchSlop;                mLastMotionX = x;                setScrollingCacheEnabled(true);            } else if (xDiff > mTouchSlop) {                // The finger has moved enough in the vertical                // direction to be counted as a drag... abort                // any attempt to drag horizontally, to work correctly                // with children that have scrolling containers.                if (DEBUG)                    Log.v(TAG, "Starting unable to drag!");                mIsUnableToDrag = true;            }            if (mIsBeingDragged) {                // Scroll to follow the motion event                if (performDrag(y)) {                    ViewCompat.postInvalidateOnAnimation(this);                }            }            break;        }        case MotionEvent.ACTION_DOWN: {            /*             * Remember location of down touch. ACTION_DOWN always refers to             * pointer index 0.             */            mLastMotionX = mInitialMotionX = ev.getX();            mLastMotionY = mInitialMotionY = ev.getY();            mActivePointerId = MotionEventCompat.getPointerId(ev, 0);            mIsUnableToDrag = false;            mScroller.computeScrollOffset();            if (mScrollState == SCROLL_STATE_SETTLING && Math.abs(mScroller.getFinalY() - mScroller.getCurrY()) > mCloseEnough) {                // Let the user 'catch' the pager as it animates.                mScroller.abortAnimation();                mPopulatePending = false;                populate();                mIsBeingDragged = true;                requestParentDisallowInterceptTouchEvent(true);                setScrollState(SCROLL_STATE_DRAGGING);            } else {                completeScroll(false);                mIsBeingDragged = false;            }            if (DEBUG)                Log.v(TAG, "Down at " + mLastMotionX + "," + mLastMotionY + " mIsBeingDragged=" + mIsBeingDragged + "mIsUnableToDrag=" + mIsUnableToDrag);            break;        }        case MotionEventCompat.ACTION_POINTER_UP:            onSecondaryPointerUp(ev);            break;        }        if (mVelocityTracker == null) {            mVelocityTracker = VelocityTracker.obtain();        }        mVelocityTracker.addMovement(ev);        /*         * The only time we want to intercept motion events is if we are in the         * drag mode.         */        return mIsBeingDragged;    }    @Override    public boolean onTouchEvent(MotionEvent ev) {        if (mFakeDragging) {            // A fake drag is in progress already, ignore this real one            // but still eat the touch events.            // (It is likely that the user is multi-touching the screen.)            return true;        }        if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {            // Don't handle edge touches immediately -- they may actually belong            // to one of our            // descendants.            return false;        }        if (mAdapter == null || mAdapter.getCount() == 0) {            // Nothing to present or scroll; nothing to touch.            return false;        }        if (mVelocityTracker == null) {            mVelocityTracker = VelocityTracker.obtain();        }        mVelocityTracker.addMovement(ev);        final int action = ev.getAction();        boolean needsInvalidate = false;        switch (action & MotionEventCompat.ACTION_MASK) {        case MotionEvent.ACTION_DOWN: {            mScroller.abortAnimation();            mPopulatePending = false;            populate();            // Remember where the motion event started            mLastMotionX = mInitialMotionX = ev.getX();            mLastMotionY = mInitialMotionY = ev.getY();            mActivePointerId = MotionEventCompat.getPointerId(ev, 0);            break;        }        case MotionEvent.ACTION_MOVE:            if (!mIsBeingDragged) {                final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);                final float y = MotionEventCompat.getY(ev, pointerIndex);                final float yDiff = Math.abs(y - mLastMotionY);                final float x = MotionEventCompat.getX(ev, pointerIndex);                final float xDiff = Math.abs(x - mLastMotionX);                if (DEBUG)                    Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);                if (yDiff > mTouchSlop && yDiff > xDiff) {                    if (DEBUG)                        Log.v(TAG, "Starting drag!");                    mIsBeingDragged = true;                    requestParentDisallowInterceptTouchEvent(true);                    mLastMotionY = y - mInitialMotionY > 0 ? mInitialMotionY + mTouchSlop : mInitialMotionY - mTouchSlop;                    mLastMotionX = x;                    setScrollState(SCROLL_STATE_DRAGGING);                    setScrollingCacheEnabled(true);                    // Disallow Parent Intercept, just in case                    ViewParent parent = getParent();                    if (parent != null) {                        parent.requestDisallowInterceptTouchEvent(true);                    }                }            }            // Not else! Note that mIsBeingDragged can be set above.            if (mIsBeingDragged) {                // Scroll to follow the motion event                final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);                final float y = MotionEventCompat.getY(ev, activePointerIndex);                needsInvalidate |= performDrag(y);            }            break;        case MotionEvent.ACTION_UP:            if (mIsBeingDragged) {                final VelocityTracker velocityTracker = mVelocityTracker;                velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);                int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker, mActivePointerId);                mPopulatePending = true;                final int height = getClientHeight();                final int scrollY = getScrollY();                final ItemInfo ii = infoForCurrentScrollPosition();                final int currentPage = ii.position;                final float pageOffset = (((float) scrollY / height) - ii.offset) / ii.heightFactor;                final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);                final float y = MotionEventCompat.getY(ev, activePointerIndex);                final int totalDelta = (int) (y - mInitialMotionY);                int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity, totalDelta);                setCurrentItemInternal(nextPage, true, true, initialVelocity);                mActivePointerId = INVALID_POINTER;                endDrag();                needsInvalidate = mTopEdge.onRelease() | mBottomEdge.onRelease();            }            break;        case MotionEvent.ACTION_CANCEL:            if (mIsBeingDragged) {                scrollToItem(mCurItem, true, 0, false);                mActivePointerId = INVALID_POINTER;                endDrag();                needsInvalidate = mTopEdge.onRelease() | mBottomEdge.onRelease();            }            break;        case MotionEventCompat.ACTION_POINTER_DOWN: {            final int index = MotionEventCompat.getActionIndex(ev);            final float y = MotionEventCompat.getY(ev, index);            mLastMotionY = y;            mActivePointerId = MotionEventCompat.getPointerId(ev, index);            break;        }        case MotionEventCompat.ACTION_POINTER_UP:            onSecondaryPointerUp(ev);            mLastMotionY = MotionEventCompat.getY(ev, MotionEventCompat.findPointerIndex(ev, mActivePointerId));            break;        }        if (needsInvalidate) {            ViewCompat.postInvalidateOnAnimation(this);        }        return true;    }    private void requestParentDisallowInterceptTouchEvent(boolean disallowIntercept) {        final ViewParent parent = getParent();        if (parent != null) {            parent.requestDisallowInterceptTouchEvent(disallowIntercept);        }    }    private boolean performDrag(float y) {        boolean needsInvalidate = false;        final float deltaY = mLastMotionY - y;        mLastMotionY = y;        float oldScrollY = getScrollY();        float scrollY = oldScrollY + deltaY;        final int height = getClientHeight();        float topBound = height * mFirstOffset;        float bottomBound = height * mLastOffset;        boolean topAbsolute = true;        boolean bottomAbsolute = true;        final ItemInfo firstItem = mItems.get(0);        final ItemInfo lastItem = mItems.get(mItems.size() - 1);        if (firstItem.position != 0) {            topAbsolute = false;            topBound = firstItem.offset * height;        }        if (lastItem.position != mAdapter.getCount() - 1) {            bottomAbsolute = false;            bottomBound = lastItem.offset * height;        }        if (scrollY < topBound) {            if (topAbsolute) {                float over = topBound - scrollY;                needsInvalidate = mTopEdge.onPull(Math.abs(over) / height);            }            scrollY = topBound;        } else if (scrollY > bottomBound) {            if (bottomAbsolute) {                float over = scrollY - bottomBound;                needsInvalidate = mBottomEdge.onPull(Math.abs(over) / height);            }            scrollY = bottomBound;        }        // Don't lose the rounded component        mLastMotionX += scrollY - (int) scrollY;        scrollTo(getScrollX(), (int) scrollY);        pageScrolled((int) scrollY);        return needsInvalidate;    }    /**     * @return Info about the page at the current scroll position. This can be     *         synthetic for a missing middle page; the 'object' field can be     *         null.     */    private ItemInfo infoForCurrentScrollPosition() {        final int height = getClientHeight();        final float scrollOffset = height > 0 ? (float) getScrollY() / height : 0;        final float marginOffset = height > 0 ? (float) mPageMargin / height : 0;        int lastPos = -1;        float lastOffset = 0.f;        float lastHeight = 0.f;        boolean first = true;        ItemInfo lastItem = null;        for (int i = 0; i < mItems.size(); i++) {            ItemInfo ii = mItems.get(i);            float offset;            if (!first && ii.position != lastPos + 1) {                // Create a synthetic item for a missing page.                ii = mTempItem;                ii.offset = lastOffset + lastHeight + marginOffset;                ii.position = lastPos + 1;                ii.heightFactor = mAdapter.getPageWidth(ii.position);                i--;            }            offset = ii.offset;            final float topBound = offset;            final float bottomBound = offset + ii.heightFactor + marginOffset;            if (first || scrollOffset >= topBound) {                if (scrollOffset < bottomBound || i == mItems.size() - 1) {                    return ii;                }            } else {                return lastItem;            }            first = false;            lastPos = ii.position;            lastOffset = offset;            lastHeight = ii.heightFactor;            lastItem = ii;        }        return lastItem;    }    private int determineTargetPage(int currentPage, float pageOffset, int velocity, int deltaY) {        int targetPage;        if (Math.abs(deltaY) > mFlingDistance && Math.abs(velocity) > mMinimumVelocity) {            targetPage = velocity > 0 ? currentPage : currentPage + 1;        } else {            final float truncator = currentPage >= mCurItem ? 0.4f : 0.6f;            targetPage = (int) (currentPage + pageOffset + truncator);        }        if (mItems.size() > 0) {            final ItemInfo firstItem = mItems.get(0);            final ItemInfo lastItem = mItems.get(mItems.size() - 1);            // Only let the user target pages we have items for            targetPage = Math.max(firstItem.position, Math.min(targetPage, lastItem.position));        }        return targetPage;    }    @Override    public void draw(Canvas canvas) {        super.draw(canvas);        boolean needsInvalidate = false;        final int overScrollMode = ViewCompat.getOverScrollMode(this);        if (overScrollMode == ViewCompat.OVER_SCROLL_ALWAYS || (overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS && mAdapter != null && mAdapter.getCount() > 1)) {            if (!mTopEdge.isFinished()) {                final int restoreCount = canvas.save();                final int height = getHeight();                final int width = getWidth() - getPaddingLeft() - getPaddingRight();                canvas.translate(getPaddingLeft(), mFirstOffset * height);                mTopEdge.setSize(width, height);                needsInvalidate |= mTopEdge.draw(canvas);                canvas.restoreToCount(restoreCount);            }            if (!mBottomEdge.isFinished()) {                final int restoreCount = canvas.save();                final int height = getHeight();                final int width = getWidth() - getPaddingLeft() - getPaddingRight();                canvas.rotate(180);                canvas.translate(-width - getPaddingLeft(), -(mLastOffset + 1) * height);                mBottomEdge.setSize(width, height);                needsInvalidate |= mBottomEdge.draw(canvas);                canvas.restoreToCount(restoreCount);            }        } else {            mTopEdge.finish();            mBottomEdge.finish();        }        if (needsInvalidate) {            // Keep animating            ViewCompat.postInvalidateOnAnimation(this);        }    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        // Draw the margin drawable between pages if needed.        if (mPageMargin > 0 && mMarginDrawable != null && mItems.size() > 0 && mAdapter != null) {            final int scrollY = getScrollY();            final int height = getHeight();            final float marginOffset = (float) mPageMargin / height;            int itemIndex = 0;            ItemInfo ii = mItems.get(0);            float offset = ii.offset;            final int itemCount = mItems.size();            final int firstPos = ii.position;            final int lastPos = mItems.get(itemCount - 1).position;            for (int pos = firstPos; pos < lastPos; pos++) {                while (pos > ii.position && itemIndex < itemCount) {                    ii = mItems.get(++itemIndex);                }                float drawAt;                if (pos == ii.position) {                    drawAt = (ii.offset + ii.heightFactor) * height;                    offset = ii.offset + ii.heightFactor + marginOffset;                } else {                    float heightFactor = mAdapter.getPageWidth(pos);                    drawAt = (offset + heightFactor) * height;                    offset += heightFactor + marginOffset;                }                if (drawAt + mPageMargin > scrollY) {                    mMarginDrawable.setBounds(mLeftPageBounds, (int) drawAt, mRightPageBounds, (int) (drawAt + mPageMargin + 0.5f));                    mMarginDrawable.draw(canvas);                }                if (drawAt > scrollY + height) {                    break; // No more visible, no sense in continuing                }            }        }    }    /**     * Start a fake drag of the pager.     * <p/>     * <p>     * A fake drag can be useful if you want to synchronize the motion of the     * ViewPager with the touch scrolling of another view, while still letting     * the ViewPager control the snapping motion and fling behavior. (e.g.     * parallax-scrolling tabs.) Call {@link #fakeDragBy(float)} to simulate the     * actual drag motion. Call {@link #endFakeDrag()} to complete the fake drag     * and fling as necessary.     * <p/>     * <p>     * During a fake drag the ViewPager will ignore all touch events. If a real     * drag is already in progress, this method will return false.     *     * @return true if the fake drag began successfully, false if it could not     *         be started.     * @see #fakeDragBy(float)     * @see #endFakeDrag()     */    public boolean beginFakeDrag() {        if (mIsBeingDragged) {            return false;        }        mFakeDragging = true;        setScrollState(SCROLL_STATE_DRAGGING);        mInitialMotionY = mLastMotionY = 0;        if (mVelocityTracker == null) {            mVelocityTracker = VelocityTracker.obtain();        } else {            mVelocityTracker.clear();        }        final long time = SystemClock.uptimeMillis();        final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);        mVelocityTracker.addMovement(ev);        ev.recycle();        mFakeDragBeginTime = time;        return true;    }    /**     * End a fake drag of the pager.     *     * @see #beginFakeDrag()     * @see #fakeDragBy(float)     */    public void endFakeDrag() {        if (!mFakeDragging) {            throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");        }        final VelocityTracker velocityTracker = mVelocityTracker;        velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);        int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker, mActivePointerId);        mPopulatePending = true;        final int height = getClientHeight();        final int scrollY = getScrollY();        final ItemInfo ii = infoForCurrentScrollPosition();        final int currentPage = ii.position;        final float pageOffset = (((float) scrollY / height) - ii.offset) / ii.heightFactor;        final int totalDelta = (int) (mLastMotionY - mInitialMotionY);        int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity, totalDelta);        setCurrentItemInternal(nextPage, true, true, initialVelocity);        endDrag();        mFakeDragging = false;    }    /**     * Fake drag by an offset in pixels. You must have called     * {@link #beginFakeDrag()} first.     *     * @param yOffset     *            Offset in pixels to drag by.     * @see #beginFakeDrag()     * @see #endFakeDrag()     */    public void fakeDragBy(float yOffset) {        if (!mFakeDragging) {            throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");        }        mLastMotionY += yOffset;        float oldScrollY = getScrollY();        float scrollY = oldScrollY - yOffset;        final int height = getClientHeight();        float topBound = height * mFirstOffset;        float bottomBound = height * mLastOffset;        final ItemInfo firstItem = mItems.get(0);        final ItemInfo lastItem = mItems.get(mItems.size() - 1);        if (firstItem.position != 0) {            topBound = firstItem.offset * height;        }        if (lastItem.position != mAdapter.getCount() - 1) {            bottomBound = lastItem.offset * height;        }        if (scrollY < topBound) {            scrollY = topBound;        } else if (scrollY > bottomBound) {            scrollY = bottomBound;        }        // Don't lose the rounded component        mLastMotionY += scrollY - (int) scrollY;        scrollTo(getScrollX(), (int) scrollY);        pageScrolled((int) scrollY);        // Synthesize an event for the VelocityTracker.        final long time = SystemClock.uptimeMillis();        final MotionEvent ev = MotionEvent.obtain(mFakeDragBeginTime, time, MotionEvent.ACTION_MOVE, 0, mLastMotionY, 0);        mVelocityTracker.addMovement(ev);        ev.recycle();    }    /**     * Returns true if a fake drag is in progress.     *     * @return true if currently in a fake drag, false otherwise.     * @see #beginFakeDrag()     * @see #fakeDragBy(float)     * @see #endFakeDrag()     */    public boolean isFakeDragging() {        return mFakeDragging;    }    private void onSecondaryPointerUp(MotionEvent ev) {        final int pointerIndex = MotionEventCompat.getActionIndex(ev);        final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex);        if (pointerId == mActivePointerId) {            // This was our active pointer going up. Choose a new            // active pointer and adjust accordingly.            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;            mLastMotionY = MotionEventCompat.getY(ev, newPointerIndex);            mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex);            if (mVelocityTracker != null) {                mVelocityTracker.clear();            }        }    }    private void endDrag() {        mIsBeingDragged = false;        mIsUnableToDrag = false;        if (mVelocityTracker != null) {            mVelocityTracker.recycle();            mVelocityTracker = null;        }    }    private void setScrollingCacheEnabled(boolean enabled) {        if (mScrollingCacheEnabled != enabled) {            mScrollingCacheEnabled = enabled;            if (USE_CACHE) {                final int size = getChildCount();                for (int i = 0; i < size; ++i) {                    final View child = getChildAt(i);                    if (child.getVisibility() != GONE) {                        child.setDrawingCacheEnabled(enabled);                    }                }            }        }    }    public boolean internalCanScrollVertically(int direction) {        if (mAdapter == null) {            return false;        }        final int height = getClientHeight();        final int scrollY = getScrollY();        if (direction < 0) {            return (scrollY > (int) (height * mFirstOffset));        } else if (direction > 0) {            return (scrollY < (int) (height * mLastOffset));        } else {            return false;        }    }    /**     * Tests scrollability within child views of v given a delta of dx.     *     * @param v     *            View to test for horizontal scrollability     * @param checkV     *            Whether the view v passed should itself be checked for     *            scrollability (true), or just its children (false).     * @param dy     *            Delta scrolled in pixels     * @param x     *            X coordinate of the active touch point     * @param y     *            Y coordinate of the active touch point     * @return true if child views of v can be scrolled by delta of dx.     */    protected boolean canScroll(View v, boolean checkV, int dy, int x, int y) {        if (v instanceof ViewGroup) {            final ViewGroup group = (ViewGroup) v;            final int scrollX = v.getScrollX();            final int scrollY = v.getScrollY();            final int count = group.getChildCount();            // Count backwards - let topmost views consume scroll distance            // first.            for (int i = count - 1; i >= 0; i--) {                // TODO: Add versioned support here for transformed views.                // This will not work for transformed views in Honeycomb+                final View child = group.getChildAt(i);                if (y + scrollY >= child.getTop() && y + scrollY < child.getBottom() && x + scrollX >= child.getLeft() && x + scrollX < child.getRight() && canScroll(child, true, dy, x + scrollX - child.getLeft(), y + scrollY - child.getTop())) {                    return true;                }            }        }        return checkV && ViewCompat.canScrollVertically(v, -dy);    }    @Override    public boolean dispatchKeyEvent(KeyEvent event) {        // Let the focused view and/or our descendants get the key first        return super.dispatchKeyEvent(event) || executeKeyEvent(event);    }    /**     * You can call this function yourself to have the scroll view perform     * scrolling from a key event, just as if the event had been dispatched to     * it by the view hierarchy.     *     * @param event     *            The key event to execute.     * @return Return true if the event was handled, else false.     */    public boolean executeKeyEvent(KeyEvent event) {        boolean handled = false;        if (event.getAction() == KeyEvent.ACTION_DOWN) {            switch (event.getKeyCode()) {            case KeyEvent.KEYCODE_DPAD_LEFT:                handled = arrowScroll(FOCUS_LEFT);                break;            case KeyEvent.KEYCODE_DPAD_RIGHT:                handled = arrowScroll(FOCUS_RIGHT);                break;            case KeyEvent.KEYCODE_TAB:                if (Build.VERSION.SDK_INT >= 11) {                    // The focus finder had a bug handling FOCUS_FORWARD and                    // FOCUS_BACKWARD                    // before Android 3.0. Ignore the tab key on those devices.                    if (KeyEventCompat.hasNoModifiers(event)) {                        handled = arrowScroll(FOCUS_FORWARD);                    } else if (KeyEventCompat.hasModifiers(event, KeyEvent.META_SHIFT_ON)) {                        handled = arrowScroll(FOCUS_BACKWARD);                    }                }                break;            }        }        return handled;    }    public boolean arrowScroll(int direction) {        View currentFocused = findFocus();        if (currentFocused == this) {            currentFocused = null;        } else if (currentFocused != null) {            boolean isChild = false;            for (ViewParent parent = currentFocused.getParent(); parent instanceof ViewGroup; parent = parent.getParent()) {                if (parent == this) {                    isChild = true;                    break;                }            }            if (!isChild) {                // This would cause the focus search down below to fail in fun                // ways.                final StringBuilder sb = new StringBuilder();                sb.append(currentFocused.getClass().getSimpleName());                for (ViewParent parent = currentFocused.getParent(); parent instanceof ViewGroup; parent = parent.getParent()) {                    sb.append(" => ").append(parent.getClass().getSimpleName());                }                Log.e(TAG, "arrowScroll tried to find focus based on non-child " + "current focused view " + sb.toString());                currentFocused = null;            }        }        boolean handled = false;        View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);        if (nextFocused != null && nextFocused != currentFocused) {            if (direction == View.FOCUS_UP) {                // If there is nothing to the left, or this is causing us to                // jump to the right, then what we really want to do is page                // left.                final int nextTop = getChildRectInPagerCoordinates(mTempRect, nextFocused).top;                final int currTop = getChildRectInPagerCoordinates(mTempRect, currentFocused).top;                if (currentFocused != null && nextTop >= currTop) {                    handled = pageUp();                } else {                    handled = nextFocused.requestFocus();                }            } else if (direction == View.FOCUS_DOWN) {                // If there is nothing to the right, or this is causing us to                // jump to the left, then what we really want to do is page                // right.                final int nextDown = getChildRectInPagerCoordinates(mTempRect, nextFocused).bottom;                final int currDown = getChildRectInPagerCoordinates(mTempRect, currentFocused).bottom;                if (currentFocused != null && nextDown <= currDown) {                    handled = pageDown();                } else {                    handled = nextFocused.requestFocus();                }            }        } else if (direction == FOCUS_UP || direction == FOCUS_BACKWARD) {            // Trying to move left and nothing there; try to page.            handled = pageUp();        } else if (direction == FOCUS_DOWN || direction == FOCUS_FORWARD) {            // Trying to move right and nothing there; try to page.            handled = pageDown();        }        if (handled) {            playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));        }        return handled;    }    private Rect getChildRectInPagerCoordinates(Rect outRect, View child) {        if (outRect == null) {            outRect = new Rect();        }        if (child == null) {            outRect.set(0, 0, 0, 0);            return outRect;        }        outRect.left = child.getLeft();        outRect.right = child.getRight();        outRect.top = child.getTop();        outRect.bottom = child.getBottom();        ViewParent parent = child.getParent();        while (parent instanceof ViewGroup && parent != this) {            final ViewGroup group = (ViewGroup) parent;            outRect.left += group.getLeft();            outRect.right += group.getRight();            outRect.top += group.getTop();            outRect.bottom += group.getBottom();            parent = group.getParent();        }        return outRect;    }    boolean pageUp() {        if (mCurItem > 0) {            setCurrentItem(mCurItem - 1, true);            return true;        }        return false;    }    boolean pageDown() {        if (mAdapter != null && mCurItem < (mAdapter.getCount() - 1)) {            setCurrentItem(mCurItem + 1, true);            return true;        }        return false;    }    /**     * We only want the current page that is being shown to be focusable.     */    @Override    public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {        final int focusableCount = views.size();        final int descendantFocusability = getDescendantFocusability();        if (descendantFocusability != FOCUS_BLOCK_DESCENDANTS) {            for (int i = 0; i < getChildCount(); i++) {                final View child = getChildAt(i);                if (child.getVisibility() == VISIBLE) {                    ItemInfo ii = infoForChild(child);                    if (ii != null && ii.position == mCurItem) {                        child.addFocusables(views, direction, focusableMode);                    }                }            }        }        // we add ourselves (if focusable) in all cases except for when we are        // FOCUS_AFTER_DESCENDANTS and there are some descendants focusable.        // this is        // to avoid the focus search finding layouts when a more precise search        // among the focusable children would be more interesting.        if (descendantFocusability != FOCUS_AFTER_DESCENDANTS ||        // No focusable descendants                (focusableCount == views.size())) {            // Note that we can't call the superclass here, because it will            // add all views in. So we need to do the same thing View does.            if (!isFocusable()) {                return;            }            if ((focusableMode & FOCUSABLES_TOUCH_MODE) == FOCUSABLES_TOUCH_MODE && isInTouchMode() && !isFocusableInTouchMode()) {                return;            }            if (views != null) {                views.add(this);            }        }    }    /**     * We only want the current page that is being shown to be touchable.     */    @Override    public void addTouchables(ArrayList<View> views) {        // Note that we don't call super.addTouchables(), which means that        // we don't call View.addTouchables(). This is okay because a ViewPager        // is itself not touchable.        for (int i = 0; i < getChildCount(); i++) {            final View child = getChildAt(i);            if (child.getVisibility() == VISIBLE) {                ItemInfo ii = infoForChild(child);                if (ii != null && ii.position == mCurItem) {                    child.addTouchables(views);                }            }        }    }    /**     * We only want the current page that is being shown to be focusable.     */    @Override    protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect) {        int index;        int increment;        int end;        int count = getChildCount();        if ((direction & FOCUS_FORWARD) != 0) {            index = 0;            increment = 1;            end = count;        } else {            index = count - 1;            increment = -1;            end = -1;        }        for (int i = index; i != end; i += increment) {            View child = getChildAt(i);            if (child.getVisibility() == VISIBLE) {                ItemInfo ii = infoForChild(child);                if (ii != null && ii.position == mCurItem) {                    if (child.requestFocus(direction, previouslyFocusedRect)) {                        return true;                    }                }            }        }        return false;    }    @Override    public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {        // Dispatch scroll events from this ViewPager.        if (event.getEventType() == AccessibilityEventCompat.TYPE_VIEW_SCROLLED) {            return super.dispatchPopulateAccessibilityEvent(event);        }        // Dispatch all other accessibility events from the current page.        final int childCount = getChildCount();        for (int i = 0; i < childCount; i++) {            final View child = getChildAt(i);            if (child.getVisibility() == VISIBLE) {                final ItemInfo ii = infoForChild(child);                if (ii != null && ii.position == mCurItem && child.dispatchPopulateAccessibilityEvent(event)) {                    return true;                }            }        }        return false;    }    @Override    protected ViewGroup.LayoutParams generateDefaultLayoutParams() {        return new LayoutParams();    }    @Override    protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {        return generateDefaultLayoutParams();    }    @Override    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {        return p instanceof LayoutParams && super.checkLayoutParams(p);    }    @Override    public ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs) {        return new LayoutParams(getContext(), attrs);    }    class MyAccessibilityDelegate extends AccessibilityDelegateCompat {        @Override        public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) {            super.onInitializeAccessibilityEvent(host, event);            event.setClassName(ViewPager.class.getName());            final AccessibilityRecordCompat recordCompat = AccessibilityRecordCompat.obtain();            recordCompat.setScrollable(canScroll());            if (event.getEventType() == AccessibilityEventCompat.TYPE_VIEW_SCROLLED && mAdapter != null) {                recordCompat.setItemCount(mAdapter.getCount());                recordCompat.setFromIndex(mCurItem);                recordCompat.setToIndex(mCurItem);            }        }        @Override        public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat info) {            super.onInitializeAccessibilityNodeInfo(host, info);            info.setClassName(ViewPager.class.getName());            info.setScrollable(canScroll());            if (internalCanScrollVertically(1)) {                info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD);            }            if (internalCanScrollVertically(-1)) {                info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD);            }        }        @Override        public boolean performAccessibilityAction(View host, int action, Bundle args) {            if (super.performAccessibilityAction(host, action, args)) {                return true;            }            switch (action) {            case AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD: {                if (internalCanScrollVertically(1)) {                    setCurrentItem(mCurItem + 1);                    return true;                }            }                return false;            case AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD: {                if (internalCanScrollVertically(-1)) {                    setCurrentItem(mCurItem - 1);                    return true;                }            }                return false;            }            return false;        }        private boolean canScroll() {            return (mAdapter != null) && (mAdapter.getCount() > 1);        }    }    private class PagerObserver extends DataSetObserver {        @Override        public void onChanged() {            dataSetChanged();        }        @Override        public void onInvalidated() {            dataSetChanged();        }    }    /**     * Layout parameters that should be supplied for views added to a ViewPager.     */    public static class LayoutParams extends ViewGroup.LayoutParams {        /**         * true if this view is a decoration on the pager itself and not a view         * supplied by the adapter.         */        public boolean isDecor;        /**         * Gravity setting for use on decor views only: Where to position the         * view page within the overall ViewPager container; constants are         * defined in {@link android.view.Gravity}.         */        public int gravity;        /**         * Width as a 0-1 multiplier of the measured pager width         */        float heightFactor = 0.f;        /**         * true if this view was added during layout and needs to be measured         * before being positioned.         */        boolean needsMeasure;        /**         * Adapter position this view is for if !isDecor         */        int position;        /**         * Current child index within the ViewPager that this view occupies         */        int childIndex;        public LayoutParams() {            super(FILL_PARENT, FILL_PARENT);        }        public LayoutParams(Context context, AttributeSet attrs) {            super(context, attrs);            final TypedArray a = context.obtainStyledAttributes(attrs, LAYOUT_ATTRS);            gravity = a.getInteger(0, Gravity.TOP);            a.recycle();        }    }    static class ViewPositionComparator implements Comparator<View> {        @Override        public int compare(View lhs, View rhs) {            final LayoutParams llp = (LayoutParams) lhs.getLayoutParams();            final LayoutParams rlp = (LayoutParams) rhs.getLayoutParams();            if (llp.isDecor != rlp.isDecor) {                return llp.isDecor ? 1 : -1;            }            return llp.position - rlp.position;        }    }}

然后在自己的Activity中的处理

 

package com.example.test;import java.util.Locale;import android.app.Activity;import android.app.FragmentManager;import android.graphics.drawable.ColorDrawable;import android.os.Bundle;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentActivity;import android.support.v4.app.FragmentPagerAdapter;import android.support.v4.view.ViewPager;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.TextView;public class MainActivity extends FragmentActivity {    private static final float MIN_SCALE = 0.75f;    private static final float MIN_ALPHA = 0.75f;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        VerticalViewPager verticalViewPager = (VerticalViewPager) findViewById(R.id.verticalviewpager);        verticalViewPager.setAdapter(new DummyAdapter(getSupportFragmentManager()));        verticalViewPager.setPageMargin(getResources().getDimensionPixelSize(R.dimen.pagemargin));        verticalViewPager.setPageMarginDrawable(new ColorDrawable(getResources().getColor(android.R.color.holo_green_dark)));        verticalViewPager.setPageTransformer(true, new ViewPager.PageTransformer() {            @Override            public void transformPage(View view, float position) {                int pageWidth = view.getWidth();                int pageHeight = view.getHeight();                if (position < -1) { // [-Infinity,-1)                    // This page is way off-screen to the left.                    view.setAlpha(0);                } else if (position <= 1) { // [-1,1]                    // Modify the default slide transition to shrink the page as                    // well                    float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));                    float vertMargin = pageHeight * (1 - scaleFactor) / 2;                    float horzMargin = pageWidth * (1 - scaleFactor) / 2;                    if (position < 0) {                        view.setTranslationY(vertMargin - horzMargin / 2);                    } else {                        view.setTranslationY(-vertMargin + horzMargin / 2);                    }                    // Scale the page down (between MIN_SCALE and 1)                    view.setScaleX(scaleFactor);                    view.setScaleY(scaleFactor);                    // Fade the page relative to its size.                    view.setAlpha(MIN_ALPHA + (scaleFactor - MIN_SCALE) / (1 - MIN_SCALE) * (1 - MIN_ALPHA));                } else { // (1,+Infinity]                    // This page is way off-screen to the right.                    view.setAlpha(0);                }            }        });    }    public class DummyAdapter extends FragmentPagerAdapter {        public DummyAdapter(android.support.v4.app.FragmentManager fm) {            super(fm);        }        @Override        public Fragment getItem(int position) {            // getItem is called to instantiate the fragment for the given page.            // Return a PlaceholderFragment (defined as a static inner class            // below).            return PlaceholderFragment.newInstance(position + 1);        }        @Override        public int getCount() {            // Show 3 total pages.            return 3;        }        @Override        public CharSequence getPageTitle(int position) {//            Locale l = Locale.getDefault();            switch (position) {            case 0:                return "PAGE 1";            case 1:                return "PAGE 2";            case 2:                return "PAGE 3";            }            return null;        }    }    /**     * A placeholder fragment containing a simple view.     */    public static class PlaceholderFragment extends Fragment {        /**         * The fragment argument representing the section number for this         * fragment.         */        private static final String ARG_SECTION_NUMBER = "section_number";        /**         * Returns a new instance of this fragment for the given section number.         */        public static PlaceholderFragment newInstance(int sectionNumber) {            PlaceholderFragment fragment = new PlaceholderFragment();            Bundle args = new Bundle();            args.putInt(ARG_SECTION_NUMBER, sectionNumber);            fragment.setArguments(args);            return fragment;        }        public PlaceholderFragment() {        }        @Override        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {            View rootView = inflater.inflate(R.layout.fragment_layout, container, false);            TextView textView = (TextView) rootView.findViewById(R.id.textview);            textView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));            return rootView;        }    }}

其中有些动画的效果 ，github上也有人实现这样的效果，但是对v4包的依赖，不适用于在一些新的V4包；但是上面的方式经测试完美兼容；

相关的Demo如下：

   http://files.cnblogs.com/kingfly13/Test.zip