Android 轮播图的实现自动+手动滑动+指示+点击事件

Bertha 。 2023-10-17 11:56 115阅读 0赞

1.图片加载框架

compile 'com.github.bumptech.glide:glide:3.5.2'

2.一个先写一个布局

<?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="180dp"
 >
 
 <com.hzq.xiaoqiang.widget.banner.loopviewpager.AutoLoopViewPager
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 
 android:id="@+id/alvp_viewpager" />
 
 
 <com.hzq.xiaoqiang.widget.banner.indicator.AnimatorCircleIndicator
 
 android:layout_marginTop="160dp"
 android:layout_width="match_parent"
 android:layout_height="24dp"
 android:id="@+id/anim_indicator" />
 
 </RelativeLayout>

3.创建一个 Activity

public class MainActivity extends AppCompatActivity {
        //模拟数据
        private String[] mViewList = {"http://img2.imgtn.bdimg.com/it/u=3093785514,1341050958&fm=21&gp=0.jpg", "http://img2.3lian.com/2014/f2/37/d/40.jpg",  "http://img2.3lian.com/2014/f2/37/d/39.jpg", "http://www.8kmm.com/UploadFiles/2012/8/201208140920132659.jpg", "http://f.hiphotos.baidu.com/image/h%3D200/sign=1478eb74d5a20cf45990f9df460b4b0c/d058ccbf6c81800a5422e5fdb43533fa838b4779.jpg", "http://f.hiphotos.baidu.com/image/pic/item/09fa513d269759ee50f1971ab6fb43166c22dfba.jpg"};
    
        private AutoLoopViewPager mViewPager;
        private AnimatorCircleIndicator animindicator;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            this.animindicator = (AnimatorCircleIndicator) findViewById(anim_indicator);
            this.mViewPager = (AutoLoopViewPager) findViewById(R.id.alvp_viewpager);
            //创建一个适配器 把模拟数据传过去
            BannerAdapter mAdapter = new BannerAdapter(this, mViewList);
    
            //在adapter中必须要复写getItemPosition方法,使用Fragment的话必须使用FragmentStatePagerAdapter
            mViewPager.setAdapter(mAdapter);
    
            //设置滚动间隔时间
            mViewPager.setInterval(2000);
            //开始滚动
            mViewPager.startAutoScroll();
    
            //indicator与viewpager关联
            animindicator.setViewPager(mViewPager);
    
            //轮播图的点击事件
            mViewPager.setOnTouchListener(new View.OnTouchListener() {
                int flage = 0 ;
                @Override
                public boolean onTouch(View v, MotionEvent event) {
                    switch (event.getAction()){
                        case MotionEvent.ACTION_DOWN:
                            flage = 0 ;
                            break ;
                        case MotionEvent.ACTION_MOVE:
                            flage = 1 ;
                            break ;
                        case  MotionEvent.ACTION_UP :
                            if (flage == 0) {
                                int item = mViewPager.getCurrentItem();
                                if (item == 0) {
                                    Intent intent = new Intent(this, LoginActivity.class);
                                    startActivity(intent);
                                } else if (item == 1) {
                                    Intent intent = new Intent(this, LoginActivity.class);
                                    startActivity(intent);
                                } else if (item == 2) {
                                    Intent intent = new Intent(this, LoginActivity.class);
                                    startActivity(intent);
                                }else if (item == 3) {
                                    Intent intent = new Intent(this, LoginActivity.class);
                                    startActivity(intent);
                                }
                            }
                            break ;
                    }
                    return false;
                }
            });
        }
    }

4.创建一个Adapter

public class BannerAdapter extends PagerAdapter {
        private Context context;    String[] mViewList;
    
        public BannerAdapter(Context context, String[] viewList) {
            this.context = context;
            this.mViewList = viewList;
    
        }
    
        @Override
        public int getCount() {
            return mViewList == null? 0 : mViewList.length;
        }
    
        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }
    
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            View view = View.inflate(context, R.layout.item_banner_image, null);
            ImageView iv = (ImageView) view.findViewById(R.id.iv_image);
            Glide.with(context).load(mViewList[position]).error(R.mipmap.ic_launcher).into(iv);
            container.addView(view);
            return view;
        }
    
        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View) object);
        }
    
    
        //这一步必须有！直接照抄
        @Override
        public int getItemPosition(Object object) {
            return POSITION_NONE;
        }
    }

5.Adapter布局 item\_banner\_image

<?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="match_parent"
 android:layout_height="match_parent">
 
 <ImageView
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:id="@+id/iv_image"
 android:scaleType="centerCrop"
 />
 
 </LinearLayout>

6.在res文件下的values下的attrs.xml添加一下代码

<declare-styleable name="LoopViewPager">
 <attr format="float|reference" name="scale"/>
 </declare-styleable>
 
 <declare-styleable name="SimpleCircleIndicator">
 <attr name="dot_interval" format="dimension|reference"/>
 <attr name="selected_radius" format="dimension|reference"/>
 <attr name="unselected_radius" format="dimension|reference"/>
 <attr name="selected_color" format="color|reference"/>
 <attr name="unselected_color" format="color|reference"/>
 <attr name="selected_strokeWidth" format="dimension|reference"/>
 <attr name="unselected_strokeWidth" format="dimension|reference"/>
 <attr name="selectedStroke" format="boolean"/>
 <attr name="unselectedStroke" format="boolean"/>
 </declare-styleable>
 
 <declare-styleable name="LinePageIndicator">
 
 <attr format="boolean" name="centered"/>
 
 <attr format="color|reference" name="unselectedColor"/>
 
 <attr format="color|reference" name="selectedColor"/>
 
 <attr format="dimension" name="lineWidth"/>
 
 <attr format="dimension|reference" name="strokeWidth"/>
 
 <attr format="dimension|reference" name="gapWidth"/>
 
 <attr name="android:background"/>
 </declare-styleable>
 
 
 <declare-styleable name="AnotherCircleIndicator">
 <attr format="dimension" name="another_ci_radius"/>
 <attr format="dimension" name="another_ci_margin"/>
 <attr format="color|integer" name="another_ci_background"/>
 <attr format="color|integer" name="another_ci_selected_background"/>
 <attr name="another_ci_gravity">
 <enum name="left" value="0"/>
 <enum name="center" value="1"/>
 <enum name="right" value="2"/>
 </attr>
 <attr name="another_ci_mode">
 <enum name="inside" value="0"/>
 <enum name="outside" value="1"/>
 <enum name="solo" value="2"/>
 </attr>
 </declare-styleable>
 
 
 <declare-styleable name="CircleIndicator">
 <attr format="dimension" name="ci_width"/>
 <attr format="dimension" name="ci_height"/>
 <attr format="dimension" name="ci_margin"/>
 <attr format="reference" name="ci_animator"/>
 <attr format="reference" name="ci_animator_reverse"/>
 <attr format="reference" name="ci_drawable"/>
 <attr format="reference" name="ci_drawable_unselected"/>
 </declare-styleable>

7.创建一个文件夹( indicator)复制以下俩个类的代码

AnimatorCircleIndicator类

public class AnimatorCircleIndicator extends LinearLayout implements IPageIndicator {
 
 private final static int DEFAULT_INDICATOR_WIDTH = 5;
 private AutoLoopViewPager mViewPager;
 private int mIndicatorMargin = -1;
 private int mIndicatorWidth = -1;
 private int mIndicatorHeight = -1;
 private int mAnimatorResId = R.animator.scale_with_alpha;
 private int mAnimatorReverseResId = 0;
 private int mIndicatorBackgroundResId = R.drawable.white_radius;
 private int mIndicatorUnselectedBackgroundResId = R.drawable.white_radius;
 private Animator mAnimatorOut;
 private Animator mAnimatorIn;
 private Animator mImmediateAnimatorOut;
 private Animator mImmediateAnimatorIn;
 
 private int mLastPosition = -1;
 
 public AnimatorCircleIndicator(Context context) {
 super(context);
 init(context, null);
 }
 
 public AnimatorCircleIndicator(Context context, AttributeSet attrs) {
 super(context, attrs);
 init(context, attrs);
 }
 
 private void init(Context context, AttributeSet attrs) {
 setOrientation(LinearLayout.HORIZONTAL);
 setGravity(Gravity.CENTER);
 handleTypedArray(context, attrs);
 checkIndicatorConfig(context);
 }
 
 private void handleTypedArray(Context context, AttributeSet attrs) {
 if (attrs == null) {
 return;
 }
 
 TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.CircleIndicator);
 mIndicatorWidth = typedArray.getDimensionPixelSize(R.styleable.CircleIndicator_ci_width, -1);
 mIndicatorHeight = typedArray.getDimensionPixelSize(R.styleable.CircleIndicator_ci_height, -1);
 mIndicatorMargin = typedArray.getDimensionPixelSize(R.styleable.CircleIndicator_ci_margin, -1);
 
 mAnimatorResId = typedArray.getResourceId(R.styleable.CircleIndicator_ci_animator,
 R.animator.scale_with_alpha);
 mAnimatorReverseResId =
 typedArray.getResourceId(R.styleable.CircleIndicator_ci_animator_reverse, 0);
 mIndicatorBackgroundResId =
 typedArray.getResourceId(R.styleable.CircleIndicator_ci_drawable, R.drawable.white_radius);
 mIndicatorUnselectedBackgroundResId =
 typedArray.getResourceId(R.styleable.CircleIndicator_ci_drawable_unselected,
 mIndicatorBackgroundResId);
 typedArray.recycle();
 }
 
 /**
 * Create and configure Indicator in Java code.
 */
 public void configureIndicator(int indicatorWidth, int indicatorHeight, int indicatorMargin) {
 configureIndicator(indicatorWidth, indicatorHeight, indicatorMargin, R.animator.scale_with_alpha, 0,
 R.drawable.white_radius, R.drawable.white_radius);
 }
 
 public void configureIndicator(int indicatorWidth, int indicatorHeight, int indicatorMargin,
 int animatorId, int animatorReverseId,
 int indicatorBackgroundId, int indicatorUnselectedBackgroundId) {
 
 mIndicatorWidth = indicatorWidth;
 mIndicatorHeight = indicatorHeight;
 mIndicatorMargin = indicatorMargin;
 
 mAnimatorResId = animatorId;
 mAnimatorReverseResId = animatorReverseId;
 mIndicatorBackgroundResId = indicatorBackgroundId;
 mIndicatorUnselectedBackgroundResId = indicatorUnselectedBackgroundId;
 
 checkIndicatorConfig(getContext());
 }
 
 private void checkIndicatorConfig(Context context) {
 mIndicatorWidth = (mIndicatorWidth < 0) ? dip2px(DEFAULT_INDICATOR_WIDTH) : mIndicatorWidth;
 mIndicatorHeight = (mIndicatorHeight < 0) ? dip2px(DEFAULT_INDICATOR_WIDTH) : mIndicatorHeight;
 mIndicatorMargin = (mIndicatorMargin < 0) ? dip2px(DEFAULT_INDICATOR_WIDTH) : mIndicatorMargin;
 
 mAnimatorResId = (mAnimatorResId == 0) ? R.animator.scale_with_alpha : mAnimatorResId;
 
 mAnimatorOut = createAnimatorOut(context);
 mImmediateAnimatorOut = createAnimatorOut(context);
 mImmediateAnimatorOut.setDuration(0);
 
 mAnimatorIn = createAnimatorIn(context);
 mImmediateAnimatorIn = createAnimatorIn(context);
 mImmediateAnimatorIn.setDuration(0);
 
 mIndicatorBackgroundResId =
 (mIndicatorBackgroundResId == 0) ? R.drawable.white_radius : mIndicatorBackgroundResId;
 mIndicatorUnselectedBackgroundResId =
 (mIndicatorUnselectedBackgroundResId == 0) ? mIndicatorBackgroundResId
 : mIndicatorUnselectedBackgroundResId;
 }
 
 private Animator createAnimatorOut(Context context) {
 return AnimatorInflater.loadAnimator(context, mAnimatorResId);
 }
 
 private Animator createAnimatorIn(Context context) {
 Animator animatorIn;
 if (mAnimatorReverseResId == 0) {
 animatorIn = AnimatorInflater.loadAnimator(context, mAnimatorResId);
 animatorIn.setInterpolator(new ReverseInterpolator());
 } else {
 animatorIn = AnimatorInflater.loadAnimator(context, mAnimatorReverseResId);
 }
 return animatorIn;
 }
 
 @Override public void setViewPager(AutoLoopViewPager viewPager) {
 if (viewPager == null || viewPager.getAdapter() == null) {
 throw new IllegalStateException("you must initial the viewpager with adapter");
 }
 
 int initialPosition;
 
 viewPager.removeOnPageChangeListener(this);
 viewPager.addOnPageChangeListener(this);
 initialPosition = viewPager.getCurrentItem();
 
 this.mViewPager = viewPager;
 
 createIndicators(initialPosition);
 setCurrentItem(initialPosition);
 }
 
 @Override public void setCurrentItem(int item) {
 onPageSelected(item);
 }
 
 @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 }
 
 @Override public void onPageSelected(int position) {
 
 if (mViewPager.getAdapter() == null
 || mViewPager.getAdapter()
 .getCount() <= 0) {
 return;
 }
 
 position = position % getRealCount();
 
 if (mAnimatorIn.isRunning()) {
 mAnimatorIn.end();
 mAnimatorIn.cancel();
 }
 
 if (mAnimatorOut.isRunning()) {
 mAnimatorOut.end();
 mAnimatorOut.cancel();
 }
 
 if (mLastPosition >= 0) {
 View currentIndicator = getChildAt(mLastPosition);
 if (currentIndicator != null) {
 currentIndicator.setBackgroundResource(mIndicatorUnselectedBackgroundResId);
 mAnimatorIn.setTarget(currentIndicator);
 mAnimatorIn.start();
 }
 }
 
 View selectedIndicator = getChildAt(position);
 if (selectedIndicator != null) {
 selectedIndicator.setBackgroundResource(mIndicatorBackgroundResId);
 mAnimatorOut.setTarget(selectedIndicator);
 mAnimatorOut.start();
 }
 
 mLastPosition = position;
 }
 
 @Override public void onPageScrollStateChanged(int state) {
 }
 
 private void createIndicators(int initialPosition) {
 removeAllViews();
 
 int count = getRealCount();
 
 for (int i = 0; i < count; i++) {
 if (initialPosition == i) {
 addIndicator(mIndicatorBackgroundResId, mImmediateAnimatorOut);
 } else {
 addIndicator(mIndicatorUnselectedBackgroundResId, mImmediateAnimatorIn);
 }
 }
 }
 
 private void addIndicator(@DrawableRes int backgroundDrawableId, Animator animator) {
 if (animator.isRunning()) {
 animator.end();
 animator.cancel();
 }
 
 View Indicator = new View(getContext());
 Indicator.setBackgroundResource(backgroundDrawableId);
 addView(Indicator, mIndicatorWidth, mIndicatorHeight);
 LayoutParams lp = (LayoutParams) Indicator.getLayoutParams();
 lp.leftMargin = mIndicatorMargin;
 lp.rightMargin = mIndicatorMargin;
 Indicator.setLayoutParams(lp);
 
 animator.setTarget(Indicator);
 animator.start();
 }
 
 private class ReverseInterpolator implements Interpolator {
 @Override public float getInterpolation(float value) {
 return Math.abs(1.0f - value);
 }
 }
 
 public int dip2px(float dpValue) {
 final float scale = getResources().getDisplayMetrics().density;
 return (int) (dpValue * scale + 0.5f);
 }
 
 private int getRealCount() {
 if (mViewPager == null) {
 return 0;
 }
 
 try {
 PagerAdapter adapter = mViewPager.getAdapter();
 if (adapter instanceof IRealAdapter) {
 return ((IRealAdapter) adapter).getRealCount();
 }
 
 return adapter.getCount();
 } catch (Exception e) {
 return 0;
 }
 }
 
 public void notifyDataSetChanged() {
 
 int newCount = getRealCount();
 int currentCount = getChildCount();
 
 if (newCount == currentCount) { // No change
 return;
 } else if (mLastPosition < newCount) {
 mLastPosition = mViewPager.getCurrentItem();
 } else {
 mLastPosition = -1;
 }
 
 createIndicators(mLastPosition);
 }
 }

IPageIndicator接口:

/**
     * auther: 小强
     * time: 17/3/24 27 17:12
     * description: indicator接口,可实现该接口写自己的indicator
     */
    public interface IPageIndicator extends LoopViewPager.OnPageChangeListener {
    
        void setViewPager(AutoLoopViewPager viewPager);
    
        void setCurrentItem(int item);
    
        void notifyDataSetChanged();
    }

8.创建loopviewpager文件夹复制一下几个类的代码

AutoLoopViewPager类

/**
 * auther: 小强
 * time: 17/3/24 27 17:13
 * description: indicator接口,可实现该接口写自己的indicator
 * 
 * 1. 添加自定义属性,可以控制宽高
 * 2. to be continued
 */
 public class AutoLoopViewPager extends AutoScrollViewPager {
 
 /**
 * 默认的宽高比,用于宽高都是wrap_content时
 */
 private static final float DEFAULT_SCALE = 0.5F;
 
 private float mScale = DEFAULT_SCALE;
 
 public AutoLoopViewPager(Context context) {
 this(context, null);
 }
 
 public AutoLoopViewPager(Context context, AttributeSet attrs) {
 super(context, attrs);
 
 TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.LoopViewPager);
 mScale = typedArray.getFloat(R.styleable.LoopViewPager_scale, DEFAULT_SCALE);
 typedArray.recycle();
 }
 
 
 @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 //super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 
 int width_mode = View.MeasureSpec.getMode(widthMeasureSpec);
 int width_size = View.MeasureSpec.getSize(widthMeasureSpec);
 
 int height_mode = View.MeasureSpec.getMode(heightMeasureSpec);
 int height_size = View.MeasureSpec.getSize(heightMeasureSpec);
 
 
 int width_result = width_size;
 int height_result = height_size;
 
 width_result = width_size;//宽度wrap_content时,size由父控件决定.总是等于parent_size,即屏幕宽度.
 
 if (height_mode == View.MeasureSpec.EXACTLY) {
 height_result = height_size;
 } else {
 height_result = (int) (width_result * mScale + 0.5);
 }
 
 int measureSpecWidth = View.MeasureSpec.makeMeasureSpec(width_result, View.MeasureSpec.EXACTLY);
 int measureSpecHeight = View.MeasureSpec.makeMeasureSpec(height_result, View.MeasureSpec.EXACTLY);
 
 super.onMeasure(measureSpecWidth, measureSpecHeight);
 }
 
 }

AutoScrollViewPager类

public class AutoScrollViewPager extends LoopViewPager {
 
 public static final int DEFAULT_INTERVAL = 1500;
 
 public static final int LEFT = 0;
 public static final int RIGHT = 1;
 
 /**
 * do nothing when sliding at the last or first item
 **/
 public static final int SLIDE_BORDER_MODE_NONE = 0;
 /**
 * cycle when sliding at the last or first item
 **/
 public static final int SLIDE_BORDER_MODE_CYCLE = 1;
 /**
 * deliver event to parent when sliding at the last or first item
 **/
 public static final int SLIDE_BORDER_MODE_TO_PARENT = 2;
 
 /**
 * auto scroll time in milliseconds, default is {@link #DEFAULT_INTERVAL}
 **/
 private long interval = DEFAULT_INTERVAL;
 /**
 * auto scroll direction, default is {@link #RIGHT}
 **/
 private int direction = RIGHT;
 /**
 * whether automatic cycle when auto scroll reaching the last or first item, default is true.
 * 设置是否轮播
 **/
 private boolean isCycle = true;
 /**
 * whether stop auto scroll when touching, default is true
 **/
 private boolean stopScrollWhenTouch = true;
 /**
 * how to process when sliding at the last or first item, default is {@link #SLIDE_BORDER_MODE_NONE}
 **/
 private int slideBorderMode = SLIDE_BORDER_MODE_NONE;
 /**
 * whether animating when auto scroll at the last or first item
 **/
 private boolean isBorderAnimation = true;
 /**
 * scroll factor for auto scroll animation, default is 1.0
 **/
 private double autoScrollFactor = 1.0;
 /**
 * scroll factor for swipe scroll animation, default is 1.0
 **/
 private double swipeScrollFactor = 1.0;
 
 private Handler handler;
 private boolean isAutoScroll = false;
 private boolean isStopByTouch = false;
 private float touchX = 0f, downX = 0f;
 private CustomDurationScroller scroller = null;
 
 public static final int SCROLL_WHAT = 0;
 
 public AutoScrollViewPager(Context paramContext) {
 super(paramContext);
 init();
 }
 
 public AutoScrollViewPager(Context paramContext, AttributeSet paramAttributeSet) {
 super(paramContext, paramAttributeSet);
 init();
 }
 
 private void init() {
 handler = new MyHandler(this);
 setViewPagerScroller();
 }
 
 /**
 * start auto scroll, first scroll delay time is {@link #getInterval()}
 * 开始滑动
 */
 public void startAutoScroll() {
 isAutoScroll = true;
 sendScrollMessage((long) (interval + scroller.getDuration() / autoScrollFactor * swipeScrollFactor));
 }
 
 /**
 * start auto scroll
 *
 * @param delayTimeInMills first scroll delay time
 */
 public void startAutoScroll(int delayTimeInMills) {
 isAutoScroll = true;
 sendScrollMessage(delayTimeInMills);
 }
 
 /**
 * stop auto scroll
 */
 public void stopAutoScroll() {
 isAutoScroll = false;
 handler.removeMessages(SCROLL_WHAT);
 }
 
 /**
 * set the factor by which the duration of sliding animation will change while swiping
 */
 public void setSwipeScrollDurationFactor(double scrollFactor) {
 swipeScrollFactor = scrollFactor;
 }
 
 /**
 * set the factor by which the duration of sliding animation will change while auto scrolling.
 * the bigger the slower.
 */
 public void setAutoScrollDurationFactor(double scrollFactor) {
 autoScrollFactor = scrollFactor;
 }
 
 private void sendScrollMessage(long delayTimeInMills) {
 /** remove messages before, keeps one message is running at most **/
 handler.removeMessages(SCROLL_WHAT);
 handler.sendEmptyMessageDelayed(SCROLL_WHAT, delayTimeInMills);
 }
 
 /**
 * set ViewPager scroller to change animation duration when sliding
 */
 private void setViewPagerScroller() {
 try {
 Field scrollerField = ViewPager.class.getDeclaredField("mScroller");
 scrollerField.setAccessible(true);
 Field interpolatorField = ViewPager.class.getDeclaredField("sInterpolator");
 interpolatorField.setAccessible(true);
 
 scroller = new CustomDurationScroller(getContext(), (Interpolator) interpolatorField.get(null));
 scrollerField.set(this, scroller);
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
 
 /**
 * scroll only once
 */
 public void scrollOnce() {
 PagerAdapter adapter = getAdapter();
 int currentItem = getCurrentItem();
 int totalCount;
 if (adapter == null || (totalCount = adapter.getCount()) <= 1) {
 return;
 }
 
 int nextItem = (direction == LEFT) ? --currentItem : ++currentItem;
 if (nextItem < 0) {
 if (isCycle) {
 setCurrentItem(totalCount - 1, isBorderAnimation);
 }
 } else if (nextItem == totalCount) {
 if (isCycle) {
 setCurrentItem(0, isBorderAnimation);
 }
 } else {
 setCurrentItem(nextItem, true);
 }
 }
 
 /**
 * <ul>
 * if stopScrollWhenTouch is true
 * <li>if event is down, stop auto scroll.</li>
 * <li>if event is up, start auto scroll again.</li>
 * </ul>
 */
 @Override
 public boolean dispatchTouchEvent(MotionEvent ev) {
 int action = MotionEventCompat.getActionMasked(ev);
 
 if (stopScrollWhenTouch) {
 if ((action == MotionEvent.ACTION_DOWN) && isAutoScroll) {
 isStopByTouch = true;
 stopAutoScroll();
 } else if (ev.getAction() == MotionEvent.ACTION_UP && isStopByTouch) {
 //action_up时,直接开始滚动.
 startAutoScroll();
 }
 }
 
 if (slideBorderMode == SLIDE_BORDER_MODE_TO_PARENT || slideBorderMode == SLIDE_BORDER_MODE_CYCLE) {
 touchX = ev.getX();
 if (ev.getAction() == MotionEvent.ACTION_DOWN) {
 downX = touchX;
 }
 int currentItem = getCurrentItem();
 PagerAdapter adapter = getAdapter();
 int pageCount = adapter == null ? 0 : adapter.getCount();
 /**
 * current index is first one and slide to right or current index is last one and slide to left. 
 * if slide border mode is to parent, then requestDisallowInterceptTouchEvent false. 
 * else scroll to last one when current item is first one, scroll to first one when current item is last
 * one.
 */
 if ((currentItem == 0 && downX <= touchX) || (currentItem == pageCount - 1 && downX >= touchX)) {
 if (slideBorderMode == SLIDE_BORDER_MODE_TO_PARENT) {
 getParent().requestDisallowInterceptTouchEvent(false);
 } else {
 if (pageCount > 1) {
 setCurrentItem(pageCount - currentItem - 1, isBorderAnimation);
 }
 getParent().requestDisallowInterceptTouchEvent(true);
 }
 return super.dispatchTouchEvent(ev);
 }
 }
 getParent().requestDisallowInterceptTouchEvent(true);
 
 return super.dispatchTouchEvent(ev);
 }
 
 private static class MyHandler extends Handler {
 
 private final WeakReference<AutoScrollViewPager> autoScrollViewPager;
 
 public MyHandler(AutoScrollViewPager autoScrollViewPager) {
 this.autoScrollViewPager = new WeakReference<AutoScrollViewPager>(autoScrollViewPager);
 }
 
 @Override
 public void handleMessage(Message msg) {
 super.handleMessage(msg);
 
 switch (msg.what) {
 case SCROLL_WHAT:
 AutoScrollViewPager pager = this.autoScrollViewPager.get();
 if (pager != null) {
 pager.scroller.setScrollDurationFactor(pager.autoScrollFactor);
 pager.scrollOnce();
 pager.scroller.setScrollDurationFactor(pager.swipeScrollFactor);
 pager.sendScrollMessage(pager.interval + pager.scroller.getDuration());
 }
 break;
 default:
 break;
 }
 }
 }
 
 /**
 * get auto scroll time in milliseconds, default is {@link #DEFAULT_INTERVAL}
 *
 * @return the interval
 */
 public long getInterval() {
 return interval;
 }
 
 /**
 * set auto scroll time in milliseconds, default is {@link #DEFAULT_INTERVAL}
 * 多久触发自动滑动.
 *
 * @param interval the interval to set
 */
 public void setInterval(long interval) {
 this.interval = interval;
 }
 
 /**
 * get auto scroll direction
 *
 * @return {@link #LEFT} or {@link #RIGHT}, default is {@link #RIGHT}
 */
 public int getDirection() {
 return (direction == LEFT) ? LEFT : RIGHT;
 }
 
 /**
 * set auto scroll direction
 * 设置滑动方法,从左到右还是从右到左
 *
 * @param direction {@link #LEFT} or {@link #RIGHT}, default is {@link #RIGHT}
 */
 public void setDirection(int direction) {
 this.direction = direction;
 }
 
 /**
 * whether automatic cycle when auto scroll reaching the last or first item, default is true
 *
 * @return the isCycle
 */
 public boolean isCycle() {
 return isCycle;
 }
 
 /**
 * set whether automatic cycle when auto scroll reaching the last or first item, default is true
 *
 * @param isCycle the isCycle to set
 */
 public void setCycle(boolean isCycle) {
 this.isCycle = isCycle;
 }
 
 /**
 * whether stop auto scroll when touching, default is true
 *
 * @return the stopScrollWhenTouch
 */
 public boolean isStopScrollWhenTouch() {
 return stopScrollWhenTouch;
 }
 
 /**
 * set whether stop auto scroll when touching, default is true
 *
 * @param stopScrollWhenTouch
 */
 public void setStopScrollWhenTouch(boolean stopScrollWhenTouch) {
 this.stopScrollWhenTouch = stopScrollWhenTouch;
 }
 
 /**
 * get how to process when sliding at the last or first item
 *
 * @return the slideBorderMode {@link #SLIDE_BORDER_MODE_NONE}, {@link #SLIDE_BORDER_MODE_TO_PARENT},
 * {@link #SLIDE_BORDER_MODE_CYCLE}, default is {@link #SLIDE_BORDER_MODE_NONE}
 */
 public int getSlideBorderMode() {
 return slideBorderMode;
 }
 
 /**
 * set how to process when sliding at the last or first item
 *
 * @param slideBorderMode {@link #SLIDE_BORDER_MODE_NONE}, {@link #SLIDE_BORDER_MODE_TO_PARENT},
 * {@link #SLIDE_BORDER_MODE_CYCLE}, default is {@link #SLIDE_BORDER_MODE_NONE}
 */
 public void setSlideBorderMode(int slideBorderMode) {
 this.slideBorderMode = slideBorderMode;
 }
 
 /**
 * whether animating when auto scroll at the last or first item, default is true
 *
 * @return
 */
 public boolean isBorderAnimation() {
 return isBorderAnimation;
 }
 
 /**
 * set whether animating when auto scroll at the last or first item, default is true
 * 设置滑动到最后一页时是否显示回到第一页的动画,默认显示,即会经过中间页.
 */
 public void setBorderAnimation(boolean isBorderAnimation) {
 this.isBorderAnimation = isBorderAnimation;
 }
 
 @Override
 protected void onDetachedFromWindow() {
 if (handler != null) {
 handler.removeCallbacksAndMessages(null);
 }
 super.onDetachedFromWindow();
 }
 }

CustomDurationScroller类

public class CustomDurationScroller extends Scroller {
    
        /**
         * 影响滑动速度的因子
         */
        private double scrollFactor = 1;
    
        public CustomDurationScroller(Context context) {
            super(context);
        }
    
        public CustomDurationScroller(Context context, Interpolator interpolator) {
            super(context, interpolator);
        }
    
        /**
         * Set the factor by which the duration will change
         */
        public void setScrollDurationFactor(double scrollFactor) {
            this.scrollFactor = scrollFactor;
        }
    
        @Override
        public void startScroll(int startX, int startY, int dx, int dy, int duration) {
            //修改duration来控制速度.一定的路程内,时间越长,滑的越慢
            super.startScroll(startX, startY, dx, dy, (int) (duration * scrollFactor));
        }
    }

IRealAdapter接口

/**
     * author: 小强
     * date: on 17/3/24 17:17
     * description:
     */
    public interface IRealAdapter {
        int getRealCount();
    }

LoopViewPager类

public class LoopViewPager extends ViewGroup {
 private static final String TAG = "LoopViewPager";
 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[] LAYOUT_ATTRS = new int[] { android.R.attr.layout_gravity };
 
 static class ItemInfo {
 Object object;
 int position;
 boolean scrolling;
 float widthFactor;
 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 mTopPageBounds;
 private int mBottomPageBounds;
 
 // 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;
 private float mInitialMotionX;
 /**
 * Position of the last motion event.
 */
 private float mLastMotionX;
 private float mLastMotionY;
 /**
 * 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 mLeftEdge;
 private EdgeEffectCompat mRightEdge;
 
 private boolean mFirstLayout = true;
 private boolean mNeedCalculatePageOffsets = false;
 private boolean mCalledSuper;
 private int mDecorChildCount;
 
 private List<OnPageChangeListener> mOnPageChangeListeners;
 private OnPageChangeListener mOnPageChangeListener;
 private OnPageChangeListener mInternalPageChangeListener;
 private OnAdapterChangeListener mAdapterChangeListener;
 
 /**
 * 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 int mScrollState = SCROLL_STATE_IDLE;
 
 /**
 * Callback interface for responding to changing state of the selected page.
 */
 public interface OnPageChangeListener {
 
 /**
 * 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.
 * 
 * @param position
 * Position index of the first page currently being
 * displayed. Page position+1 will be visible if
 * positionOffset is nonzero.
 * @param positionOffset
 * Value from [0, 1) indicating the offset from the page at
 * position.
 * @param positionOffsetPixels
 * Value in pixels indicating the offset from position.
 */
 public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels);
 
 /**
 * This method will be invoked when a new page becomes selected.
 * Animation is not necessarily complete.
 * 
 * @param position
 * Position index of the new selected page.
 */
 public void onPageSelected(int position);
 
 /**
 * Called when the scroll state changes. Useful for discovering when the
 * user begins dragging, when the pager is automatically settling to the
 * current page, or when it is fully stopped/idle.
 * 
 * @param state
 * The new scroll state.
 * @see LoopViewPager#SCROLL_STATE_IDLE
 * @see LoopViewPager#SCROLL_STATE_DRAGGING
 * @see LoopViewPager#SCROLL_STATE_SETTLING
 */
 public void onPageScrollStateChanged(int state);
 }
 
 /**
 * Simple implementation of the {@link OnPageChangeListener} interface with
 * stub implementations of each method. Extend this if you do not intend to
 * override every method of {@link OnPageChangeListener}.
 */
 public static class SimpleOnPageChangeListener implements OnPageChangeListener {
 @Override
 public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 // This space for rent
 }
 
 @Override
 public void onPageSelected(int position) {
 // This space for rent
 }
 
 @Override
 public void onPageScrollStateChanged(int state) {
 // This space for rent
 }
 }
 
 /**
 * 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 LoopViewPager(Context context) {
 super(context);
 initViewPager();
 }
 
 public LoopViewPager(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);
 mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);
 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
 mLeftEdge = new EdgeEffectCompat(context);
 mRightEdge = new EdgeEffectCompat(context);
 
 final float density = context.getResources().getDisplayMetrics().density;
 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);
 }
 }
 
 private void setScrollState(int newState) {
 if (mScrollState == newState) {
 return;
 }
 
 mScrollState = newState;
 if (mOnPageChangeListener != null) {
 mOnPageChangeListener.onPageScrollStateChanged(newState);
 }
 
 if (mOnPageChangeListeners != null) {
 for (int i = 0, z = mOnPageChangeListeners.size(); i < z; i++) {
 OnPageChangeListener listener = mOnPageChangeListeners.get(i);
 if (listener != null) {
 listener.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);
 if (ii.position < 0 && ii.object == null) {
 // 左側のダミーページ
 continue;
 }
 mAdapter.destroyItem(this, ii.position, ii.object);
 }
 // 左側のダミーページを削除
 if (mAdapter.getCount() == 2) {
 for (int i = 0; i < getChildCount(); i++) {
 View child = getChildAt(i);
 if (isDummy(child)) {
 removeView(child);
 }
 }
 }
 
 mAdapter.finishUpdate(this);
 mItems.clear();
 removeNonDecorViews();
 mCurItem = 0;
 scrollTo(0, 0);
 }
 
 final PagerAdapter oldAdapter = mAdapter;
 mAdapter = adapter;
 
 if (mAdapter != null) {
 if (mObserver == null) {
 mObserver = new PagerObserver();
 }
 mAdapter.registerDataSetObserver(mObserver);
 mPopulatePending = false;
 mFirstLayout = true;
 if (mRestoredCurItem >= 0) {
 mAdapter.restoreState(mRestoredAdapterState, mRestoredClassLoader);
 setCurrentItemInternal(mRestoredCurItem, false, true);
 mRestoredCurItem = -1;
 mRestoredAdapterState = null;
 mRestoredClassLoader = null;
 } else {
 populate();
 }
 }
 
 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;
 }
 
 /**
 * 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;
 }
 
 final int pageLimit = mOffscreenPageLimit;
 
 final int N = mAdapter.getCount();
 if (N != 2) {
 if (item < 0) {
 item = 0;
 } else if (item >= N) {
 item = N - 1;
 }
 
 // TODO CHANGE
 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;
 // CHANGE
 int orgItem = item;
 if (N == 2) {
 if (item < 0) {
 item = mCurItem == 0 ? 1 : 0;
 } else if (item >= N) {
 item = N - 1;
 }
 }
 
 // CHANGE
 int oldPosition = mCurItem;
 populate(item);
 // CHANGE
 final ItemInfo curInfo = infoForPosition(orgItem);
 int destX = 0;
 if (curInfo != null) {
 final int width = getWidth();
 destX = (int) (width * Math.max(mFirstOffset, Math.min(curInfo.offset, mLastOffset)));
 }
 
 // CHANGE
 if (mPopulatePending == false && oldPosition != item) {
 if (N == 2 && item == 1) {
 oldPosition = -1;
 }
 final ItemInfo oldInfo = infoForPosition(oldPosition);
 if (oldInfo != null) {
 final int width = getWidth();
 int x = (int) (width * Math.max(mFirstOffset, Math.min(oldInfo.offset, mLastOffset)));
 scrollTo(x, 0);
 }
 }
 
 if (smoothScroll) {
 smoothScrollTo(destX, 0, velocity);
 if (dispatchSelected && mOnPageChangeListener != null) {
 mOnPageChangeListener.onPageSelected(item);
 }
 
 if (mOnPageChangeListeners != null) {
 for (int i = 0, z = mOnPageChangeListeners.size(); i < z; i++) {
 OnPageChangeListener listener = mOnPageChangeListeners.get(i);
 if (listener != null) {
 listener.onPageSelected(item);
 }
 }
 }
 
 if (dispatchSelected && mInternalPageChangeListener != null) {
 mInternalPageChangeListener.onPageSelected(item);
 }
 } else {
 if (dispatchSelected && mOnPageChangeListener != null) {
 mOnPageChangeListener.onPageSelected(item);
 }
 
 if (mOnPageChangeListeners != null) {
 for (int i = 0, z = mOnPageChangeListeners.size(); i < z; i++) {
 OnPageChangeListener listener = mOnPageChangeListeners.get(i);
 if (listener != null) {
 listener.onPageSelected(item);
 }
 }
 }
 
 if (dispatchSelected && mInternalPageChangeListener != null) {
 mInternalPageChangeListener.onPageSelected(item);
 }
 completeScroll();
 scrollTo(destX, 0);
 }
 }
 
 
 /**
 * Set a listener that will be invoked whenever the page changes or is incrementally
 * scrolled. See {@link OnPageChangeListener}.
 *
 * @param listener Listener to set
 *
 * @deprecated Use {@link #addOnPageChangeListener(OnPageChangeListener)}
 * and {@link #removeOnPageChangeListener(OnPageChangeListener)} instead.
 */
 @Deprecated
 public void setOnPageChangeListener(OnPageChangeListener listener) {
 mOnPageChangeListener = listener;
 }
 
 /**
 * Add a listener that will be invoked whenever the page changes or is incrementally
 * scrolled. See {@link OnPageChangeListener}.
 *
 * Components that add a listener should take care to remove it when finished.
 * Other components that take ownership of a view may call {@link #clearOnPageChangeListeners()}
 * to remove all attached listeners.
 *
 * @param listener listener to add
 */
 public void addOnPageChangeListener(OnPageChangeListener listener) {
 if (mOnPageChangeListeners == null) {
 mOnPageChangeListeners = new ArrayList<>();
 }
 mOnPageChangeListeners.add(listener);
 }
 
 /**
 * Remove a listener that was previously added via
 * {@link #addOnPageChangeListener(OnPageChangeListener)}.
 *
 * @param listener listener to remove
 */
 public void removeOnPageChangeListener(OnPageChangeListener listener) {
 if (mOnPageChangeListeners != null) {
 mOnPageChangeListeners.remove(listener);
 }
 }
 
 /**
 * Remove all listeners that are notified of any changes in scroll state or position.
 */
 public void clearOnPageChangeListeners() {
 if (mOnPageChangeListeners != null) {
 mOnPageChangeListeners.clear();
 }
 }
 
 /**
 * 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.
 */
 OnPageChangeListener setInternalPageChangeListener(OnPageChangeListener listener) {
 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.
 * 
 * 
 * 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.
 * 
 * 
 * 
 * You should keep this limit low, especially if your pages have complex
 * layouts. This setting defaults to 1.
 * 
 * 
 * @param limit
 * How many pages will be kept offscreen in an idle state.
 */
 public void setOffscreenPageLimit(int limit) {
 if (limit < 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 width = getWidth();
 recomputeScrollPosition(width, width, 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();
 populate();
 setScrollState(SCROLL_STATE_IDLE);
 return;
 }
 
 setScrollingCacheEnabled(true);
 setScrollState(SCROLL_STATE_SETTLING);
 
 final int width = getWidth();
 final int halfWidth = width / 2;
 final float distanceRatio = Math.min(1f, 1.0f * Math.abs(dx) / width);
 final float distance = halfWidth + halfWidth * distanceInfluenceForSnapDuration(distanceRatio);
 
 int duration = 0;
 velocity = Math.abs(velocity);
 if (velocity > 0) {
 duration = 4 * Math.round(1000 * Math.abs(distance / velocity));
 } else {
 final float pageWidth = width * mAdapter.getPageWidth(mCurItem);
 final float pageDelta = (float) Math.abs(dx) / (pageWidth + 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.widthFactor = mAdapter.getPageWidth(position);
 if (index < 0 || index >= mItems.size()) {
 // CHANGE
 if (index < 0) {
 mItems.add(0, ii);
 } else {
 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.
 
 boolean needPopulate = mItems.size() < mOffscreenPageLimit * 2 + 1 && mItems.size() < mAdapter.getCount();
 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;
 }
 
 if (ii.position < 0 && ii.object == null) {
 // 左側のダミーページを
 } else {
 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, mAdapter.getCount() - 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);
 
 // 左側のダミーページを削除
 if (isDummy(child)) {
 removeView(child);
 continue;
 }
 
 final LayoutParams lp = (LayoutParams) child.getLayoutParams();
 if (!lp.isDecor) {
 lp.widthFactor = 0.f;
 }
 }
 
 setCurrentItemInternal(newCurrItem, false, true);
 requestLayout();
 }
 }
 
 void populate() {
 populate(mCurItem);
 }
 
 // CHANGE
 boolean mRequestLayoutNeed = false;
 
 void populate(int newCurrentItem) {
 
 // CHANGE
 int oldCurrentItem = mCurItem;
 int oldItemsSize = mItems.size();
 
 ItemInfo oldCurInfo = null;
 if (mCurItem != newCurrentItem) {
 oldCurInfo = infoForPosition(mCurItem);
 mCurItem = newCurrentItem;
 mRequestLayoutNeed = true;
 }
 
 if (mAdapter == null) {
 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) {
 
 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 N = mAdapter.getCount();
 
 final int pageLimit = mOffscreenPageLimit;
 // CHANGE
 final int startPos = (mCurItem + N - pageLimit) % N;
 // final int startPos = Math.max(0, mCurItem - pageLimit);
 final int endPos = (mCurItem + pageLimit) % N;
 // final int endPos = Math.min(N - 1, mCurItem + pageLimit);
 
 // 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);
 // CHANGE
 if (ii.position == mCurItem) {
 curItem = ii;
 break;
 }
 }
 
 // CHANGE
 if (curIndex >= mItems.size() && mItems.size() > 0 && oldCurInfo != null) {
 int oldPosition = oldCurInfo.position;
 int f = oldPosition < mCurItem ? oldPosition + N : oldPosition;
 int l = oldPosition > mCurItem ? oldPosition - N : oldPosition;
 int fDiff = f - mCurItem;
 int lDiff = mCurItem - l;
 if (fDiff < lDiff) {
 curIndex = 0;
 } else if (lDiff < fDiff) {
 curIndex = mItems.size();
 } else {
 curIndex = mCurItem < oldPosition ? 0 : mItems.size();
 }
 }
 
 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) {
 
 if (N > 1) {
 // ANALYZE 左側のページ
 float extraWidthLeft = 0.f;
 int itemIndex = curIndex - 1;
 ItemInfo ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
 final float leftWidthNeeded = 2.f - curItem.widthFactor;
 
 for (int i = 0; i < N; i++) {
 final int pos = ((mCurItem - 1 - i) + N) % N;
 
 // CHANGE
 ItemInfo firstInfo = mItems.get(0);
 if (pos == firstInfo.position && firstInfo.scrolling) {
 break;
 }
 
 // CHANGE
 if (extraWidthLeft >= leftWidthNeeded && (pos < startPos || pos > endPos || itemIndex < 0)) {
 if (ii == null) {
 break;
 }
 // ANALYZE 右にスクロールして、左側のページを削除
 if (pos == ii.position && !ii.scrolling && N > 3) {
 mItems.remove(itemIndex);
 mAdapter.destroyItem(this, pos, ii.object);
 itemIndex--;
 curIndex--;
 ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
 }
 } else if (ii != null && pos == ii.position) {
 extraWidthLeft += ii.widthFactor;
 itemIndex--;
 ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
 } else {
 // CHANGE
 ItemInfo lastInfo = mItems.get(mItems.size() - 1);
 if (pos == lastInfo.position) {
 ii = lastInfo;
 mItems.remove(lastInfo);
 mItems.add(itemIndex + 1, lastInfo);
 } else {
 // 左側のページを追加
 ii = addNewItem(pos, itemIndex + 1);
 }
 curIndex++;
 extraWidthLeft += ii.widthFactor;
 ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
 }
 }
 
 // ANALYZE 右側のページ
 float extraWidthRight = curItem.widthFactor;
 itemIndex = curIndex + 1;
 if (extraWidthRight < 2.f) {
 ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
 for (int i = 0; i < N; i++) {
 final int pos = ((mCurItem + 1 + i) + N) % N;
 // CHANGE
 if (extraWidthRight >= 2.f && (pos > endPos || pos < startPos || itemIndex >= mItems.size())) {
 if (ii == null) {
 break;
 }
 
 // ANALYZE 左にスクロールして、右側のページを削除
 // CHANGE
 if (pos == ii.position) {
 if (!ii.scrolling) {
 mItems.remove(itemIndex);
 mAdapter.destroyItem(this, pos, ii.object);
 ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
 } else {
 itemIndex++;
 ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
 }
 }
 } else if (ii != null && pos == ii.position) {
 extraWidthRight += ii.widthFactor;
 itemIndex++;
 ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
 } else {
 // CHANGE
 ItemInfo firstInfo = mItems.get(0);
 if (firstInfo.position == -1 && mItems.size() > 1) {
 firstInfo = mItems.get(1);
 }
 if (pos == firstInfo.position && N > 1) {
 ii = firstInfo;
 mItems.remove(firstInfo);
 mItems.add(itemIndex - 1, firstInfo);
 curIndex--;
 } else {
 // 右側のページを追加
 ii = addNewItem(pos, itemIndex);
 itemIndex++;
 }
 extraWidthRight += ii.widthFactor;
 ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
 }
 }
 }
 }
 
 // CHANGE
 if (N == 2) {
 if (mItems.size() < 3) {
 ItemInfo lastInfo = mItems.get(mItems.size() - 1);
 // 左側のダミーページを追加
 ItemInfo ii = new ItemInfo();
 ii.position = -1;
 ii.object = null;
 ii.widthFactor = lastInfo.widthFactor;
 ImageView dummyView = new ImageView(getContext());
 dummyView.setTag(-1);
 this.addView(dummyView);
 mItems.add(0, ii);
 curIndex++;
 }
 }
 
 calculatePageOffsets(curItem, curIndex, oldCurInfo);
 
 if (N > 3) {
 if (oldItemsSize > 3) {
 if (mItems.size() > 3) {
 if (mRequestLayoutNeed) {
 requestLayout();
 mRequestLayoutNeed = false;
 }
 }
 }
 }
 }
 
 if (DEBUG) {
 for (int i = 0; i < mItems.size(); i++) {
 }
 }
 
 mAdapter.setPrimaryItem(this, mCurItem, curItem != null ? curItem.object : null);
 
 mAdapter.finishUpdate(this);
 
 // Check width measurement of current pages. 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();
 if (!lp.isDecor && lp.widthFactor == 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.widthFactor = ii.widthFactor;
 }
 }
 }
 
 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(FOCUS_FORWARD)) {
 break;
 }
 }
 }
 }
 }
 }
 
 private void calculatePageOffsets(ItemInfo curItem, int curIndex, ItemInfo oldCurInfo) {
 final int N = mAdapter.getCount();
 final int width = getWidth();
 final float marginOffset = width > 0 ? (float) mPageMargin / width : 0;
 // Fix up offsets for later layout.
 if (oldCurInfo != null) {
 final int oldCurPosition = oldCurInfo.position;
 // Base offsets off of oldCurInfo.
 if (oldCurPosition < curItem.position) {
 // ANALYZE 右に移動した。以前のページ + 1から新しいページまでの各ページのオフセットを計算
 int itemIndex = 0;
 ItemInfo ii = null;
 float offset = oldCurInfo.offset + oldCurInfo.widthFactor + marginOffset;
 for (int pos = oldCurPosition + 1; pos <= curItem.position && itemIndex < mItems.size(); pos++) {
 ii = mItems.get(itemIndex);
 // ANALYZE position が pos より大きくなる ItemInfo を mItems を下から探す
 while (pos > ii.position && itemIndex < mItems.size() - 1) {
 itemIndex++;
 ii = mItems.get(itemIndex);
 }
 // ANALYZE position が pos より大きい = position が pos と同じになる
 // ItemInfo がなかった
 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.widthFactor + marginOffset;
 }
 } else if (oldCurPosition > curItem.position) {
 // ANALYZE 左に移動した。以前のページ - 1 から新しいページまでの各ページのオフセットを計算
 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.widthFactor + marginOffset;
 ii.offset = offset;
 }
 }
 }
 
 // Base all offsets off of curItem.
 final int itemCount = mItems.size();
 // CHANGE
 curItem.offset = 0;
 mFirstOffset = /* curItem.position == 0 ? curItem.offset : */-Float.MAX_VALUE;
 mLastOffset = /*
 * curItem.position == N - 1 ? curItem.offset +
 * curItem.widthFactor - 1 :
 */Float.MAX_VALUE;
 
 float offset = curItem.offset;
 int pos = curItem.position - 1;
 // Previous pages
 for (int i = curIndex - 1; i >= 0; i--, pos--) {
 final ItemInfo ii = mItems.get(i);
 // CHANGE
 while (pos > ii.position && N != 2) {
 offset -= mAdapter.getPageWidth(pos--) + marginOffset;
 }
 offset -= ii.widthFactor + marginOffset;
 ii.offset = offset;
 if (ii.position == 0)
 mFirstOffset = offset;
 }
 
 offset = curItem.offset + curItem.widthFactor + 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.widthFactor - 1;
 }
 ii.offset = offset;
 offset += ii.widthFactor + marginOffset;
 }
 
 // CHANGE
 if (N <= 3) {
 requestLayout();
 }
 
 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 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);
 }
 }
 }
 
 private boolean isDummy(View child) {
 if (!(child instanceof ImageView)) {
 return false;
 }
 
 Object tag = child.getTag();
 
 if (tag == null) {
 return false;
 }
 
 if (!(tag instanceof Integer)) {
 return false;
 }
 
 int index = (Integer) tag;
 return index == -1;
 }
 
 ItemInfo infoForChild(View child) {
 // CHANGE
 final int N = mAdapter.getCount();
 boolean isDummy = isDummy(child);
 
 for (int i = 0; i < mItems.size(); i++) {
 ItemInfo ii = mItems.get(i);
 // CHANGE
 if (isDummy && ii.position == -1) {
 return ii;
 }
 if (ii.position != -1 && 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, or 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 measuredWidth = getMeasuredWidth();
 final int maxGutterSize = measuredWidth / 10;
 mGutterSize = Math.min(maxGutterSize, mDefaultGutterSize);
 
 // Children are just made to fill our space.
 int childWidthSize = measuredWidth - getPaddingLeft() - getPaddingRight();
 int childHeightSize = getMeasuredHeight() - 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) {
 
 final LayoutParams lp = (LayoutParams) child.getLayoutParams();
 if (lp == null || !lp.isDecor) {
 final int widthSpec = MeasureSpec.makeMeasureSpec((int) (childWidthSize * lp.widthFactor),
 MeasureSpec.EXACTLY);
 child.measure(widthSpec, mChildHeightMeasureSpec);
 }
 }
 }
 }
 
 @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 (w != oldw) {
 recomputeScrollPosition(w, oldw, mPageMargin, mPageMargin);
 }
 }
 
 private void recomputeScrollPosition(int width, int oldWidth, int margin, int oldMargin) {
 if (oldWidth > 0 && !mItems.isEmpty()) {
 final int widthWithMargin = width + margin;
 final int oldWidthWithMargin = oldWidth + oldMargin;
 final int xpos = getScrollX();
 final float pageOffset = (float) xpos / oldWidthWithMargin;
 final int newOffsetPixels = (int) (pageOffset * widthWithMargin);
 
 scrollTo(newOffsetPixels, getScrollY());
 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(newOffsetPixels, 0, (int) (targetInfo.offset * width), 0, newDuration);
 }
 } else {
 final ItemInfo ii = infoForPosition(mCurItem);
 final float scrollOffset = ii != null ? Math.min(ii.offset, mLastOffset) : 0;
 final int scrollPos = (int) (scrollOffset * width);
 if (scrollPos != getScrollX()) {
 completeScroll();
 scrollTo(scrollPos, getScrollY());
 }
 }
 }
 
 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
 mInLayout = true;
 populate();
 mInLayout = false;
 
 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 scrollX = getScrollX();
 
 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;
 }
 childLeft += scrollX;
 child.layout(childLeft, childTop, childLeft + child.getMeasuredWidth(),
 childTop + child.getMeasuredHeight());
 decorCount++;
 }
 }
 }
 
 // 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 loff = (int) (width * ii.offset);
 
 int childLeft = paddingLeft + loff;
 int childTop = paddingTop;
 
 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) * lp.widthFactor), MeasureSpec.EXACTLY);
 final int heightSpec = MeasureSpec.makeMeasureSpec((int) (height - paddingTop - paddingBottom),
 MeasureSpec.EXACTLY);
 child.measure(widthSpec, heightSpec);
 }
 
 child.layout(childLeft, childTop, childLeft + child.getMeasuredWidth(),
 childTop + child.getMeasuredHeight());
 }
 }
 }
 
 // CHANGE
 scrollTo(0, 0);
 
 mTopPageBounds = paddingTop;
 mBottomPageBounds = height - paddingBottom;
 mDecorChildCount = decorCount;
 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(x)) {
 mScroller.abortAnimation();
 scrollTo(0, y);
 }
 }
 
 // Keep on drawing until the animation has finished.
 ViewCompat.postInvalidateOnAnimation(this);
 return;
 }
 
 // Done with scroll, clean up state.
 completeScroll();
 }
 
 private boolean pageScrolled(int xpos) {
 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 width = getWidth();
 final int widthWithMargin = width + mPageMargin;
 final float marginOffset = (float) mPageMargin / width;
 final int currentPage = ii.position;
 final float pageOffset = (((float) xpos / width) - ii.offset) / (ii.widthFactor + marginOffset);
 final int offsetPixels = (int) (pageOffset * widthWithMargin);
 
 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 scrollX = getScrollX();
 int paddingLeft = getPaddingLeft();
 int paddingRight = getPaddingRight();
 final int width = getWidth();
 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 hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
 int childLeft = 0;
 switch (hgrav) {
 default:
 childLeft = paddingLeft;
 break;
 case Gravity.LEFT:
 childLeft = paddingLeft;
 paddingLeft += child.getWidth();
 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;
 }
 childLeft += scrollX;
 
 final int childOffset = childLeft - child.getLeft();
 if (childOffset != 0) {
 child.offsetLeftAndRight(childOffset);
 }
 }
 }
 
 if (mOnPageChangeListener != null) {
 mOnPageChangeListener.onPageScrolled(position, offset, offsetPixels);
 }
 
 if (mOnPageChangeListeners != null) {
 for (int i = 0, z = mOnPageChangeListeners.size(); i < z; i++) {
 OnPageChangeListener listener = mOnPageChangeListeners.get(i);
 if (listener != null) {
 listener.onPageScrolled(position, offset, offsetPixels);
 }
 }
 }
 
 if (mInternalPageChangeListener != null) {
 mInternalPageChangeListener.onPageScrolled(position, offset, offsetPixels);
 }
 mCalledSuper = true;
 }
 
 private void completeScroll() {
 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);
 }
 setScrollState(SCROLL_STATE_IDLE);
 }
 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) {
 populate();
 }
 }
 
 private boolean isGutterDrag(float x, float dx) {
 return (x < mGutterSize && dx > 0) || (x > getWidth() - mGutterSize && dx < 0);
 }
 
 @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.
 
 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) {
 
 return true;
 }
 if (mIsUnableToDrag) {
 
 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 x = MotionEventCompat.getX(ev, pointerIndex);
 final float dx = x - mLastMotionX;
 final float xDiff = Math.abs(dx);
 final float y = MotionEventCompat.getY(ev, pointerIndex);
 final float yDiff = Math.abs(y - mLastMotionY);
 
 
 if (dx != 0 && !isGutterDrag(mLastMotionX, dx) && canScroll(this, false, (int) dx, (int) x, (int) y)) {
 // Nested view has scrollable area under this point. Let it
 // be handled there.
 mInitialMotionX = mLastMotionX = x;
 mLastMotionY = y;
 mIsUnableToDrag = true;
 return false;
 }
 if (xDiff > mTouchSlop && xDiff > yDiff) {
 
 mIsBeingDragged = true;
 setScrollState(SCROLL_STATE_DRAGGING);
 
 // CHANGE
 if (mAdapter.getCount() == 2) {
 setupDummyView();
 }
 
 mLastMotionX = dx > 0 ? mInitialMotionX + mTouchSlop : mInitialMotionX - mTouchSlop;
 setScrollingCacheEnabled(true);
 } else {
 if (yDiff > 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.
 
 mIsUnableToDrag = true;
 }
 }
 if (mIsBeingDragged) {
 // Scroll to follow the motion event
 if (performDrag(x)) {
 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 = ev.getY();
 mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
 mIsUnableToDrag = false;
 
 mScroller.computeScrollOffset();
 if (mScrollState == SCROLL_STATE_SETTLING
 && Math.abs(mScroller.getFinalX() - mScroller.getCurrX()) > mCloseEnough) {
 // Let the user 'catch' the pager as it animates.
 mScroller.abortAnimation();
 mPopulatePending = false;
 populate();
 mIsBeingDragged = true;
 setScrollState(SCROLL_STATE_DRAGGING);
 } else {
 completeScroll();
 mIsBeingDragged = false;
 }
 
 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;
 }
 
 private void setupDummyView() {
 int childCount = getChildCount();
 ImageView dummyView = null;
 View targetView = null;
 ItemInfo targetInfo = mItems.get(2);
 for (int i = 0; i < childCount; i++) {
 View child = getChildAt(i);
 if (child instanceof ImageView) {
 Object tag = child.getTag();
 if (tag != null && tag instanceof Integer) {
 int index = (Integer) tag;
 if (index == -1) {
 dummyView = (ImageView) child;
 continue;
 }
 }
 }
 
 if (mAdapter.isViewFromObject(child, targetInfo.object)) {
 targetView = child;
 }
 }
 
 if (targetView != null && dummyView != null) {
 Bitmap bitmap = getViewBitmap(targetView);
 dummyView.setImageBitmap(bitmap);
 }
 }
 
 @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();
 mIsBeingDragged = true;
 setScrollState(SCROLL_STATE_DRAGGING);
 
 // CHANGE
 if (mAdapter.getCount() == 2) {
 setupDummyView();
 }
 
 // Remember where the motion event started
 mLastMotionX = mInitialMotionX = ev.getX();
 mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
 break;
 }
 case MotionEvent.ACTION_MOVE:
 if (!mIsBeingDragged) {
 final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
 final float x = MotionEventCompat.getX(ev, pointerIndex);
 final float xDiff = Math.abs(x - mLastMotionX);
 final float y = MotionEventCompat.getY(ev, pointerIndex);
 final float yDiff = Math.abs(y - mLastMotionY);
 
 if (xDiff > mTouchSlop && xDiff > yDiff) {
 
 mIsBeingDragged = true;
 mLastMotionX = x - mInitialMotionX > 0 ? mInitialMotionX + mTouchSlop : mInitialMotionX
 - mTouchSlop;
 setScrollState(SCROLL_STATE_DRAGGING);
 setScrollingCacheEnabled(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 x = MotionEventCompat.getX(ev, activePointerIndex);
 needsInvalidate |= performDrag(x);
 }
 break;
 case MotionEvent.ACTION_UP:
 if (mIsBeingDragged) {
 final VelocityTracker velocityTracker = mVelocityTracker;
 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
 int initialVelocity = (int) VelocityTrackerCompat.getXVelocity(velocityTracker, mActivePointerId);
 mPopulatePending = true;
 final int width = getWidth();
 final int scrollX = getScrollX();
 final ItemInfo ii = infoForCurrentScrollPosition();
 final int currentPage = ii.position;
 final float pageOffset = (((float) scrollX / width) - ii.offset) / ii.widthFactor;
 final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
 final float x = MotionEventCompat.getX(ev, activePointerIndex);
 final int totalDelta = (int) (x - mInitialMotionX);
 int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity, totalDelta);
 setCurrentItemInternal(nextPage, true, true, initialVelocity);
 
 mActivePointerId = INVALID_POINTER;
 endDrag();
 needsInvalidate = mLeftEdge.onRelease() | mRightEdge.onRelease();
 }
 break;
 case MotionEvent.ACTION_CANCEL:
 if (mIsBeingDragged) {
 setCurrentItemInternal(mCurItem, true, true);
 mActivePointerId = INVALID_POINTER;
 endDrag();
 needsInvalidate = mLeftEdge.onRelease() | mRightEdge.onRelease();
 }
 break;
 case MotionEventCompat.ACTION_POINTER_DOWN: {
 final int index = MotionEventCompat.getActionIndex(ev);
 final float x = MotionEventCompat.getX(ev, index);
 mLastMotionX = x;
 mActivePointerId = MotionEventCompat.getPointerId(ev, index);
 break;
 }
 case MotionEventCompat.ACTION_POINTER_UP:
 onSecondaryPointerUp(ev);
 mLastMotionX = MotionEventCompat.getX(ev, MotionEventCompat.findPointerIndex(ev, mActivePointerId));
 break;
 }
 if (needsInvalidate) {
 ViewCompat.postInvalidateOnAnimation(this);
 }
 return true;
 }
 
 private boolean performDrag(float x) {
 boolean needsInvalidate = false;
 
 final float deltaX = mLastMotionX - x;
 mLastMotionX = x;
 
 float oldScrollX = getScrollX();
 float scrollX = oldScrollX + deltaX;
 final int width = getWidth();
 
 float leftBound = width * mFirstOffset;
 float rightBound = width * mLastOffset;
 boolean leftAbsolute = true;
 boolean rightAbsolute = true;
 
 final ItemInfo firstItem = mItems.get(0);
 final ItemInfo lastItem = mItems.get(mItems.size() - 1);
 if (firstItem.position != 0) {
 leftAbsolute = false;
 leftBound = firstItem.offset * width;
 }
 if (lastItem.position != mAdapter.getCount() - 1) {
 rightAbsolute = false;
 rightBound = lastItem.offset * width;
 }
 
 if (scrollX < leftBound) {
 if (leftAbsolute) {
 float over = leftBound - scrollX;
 needsInvalidate = mLeftEdge.onPull(Math.abs(over) / width);
 }
 scrollX = leftBound;
 } else if (scrollX > rightBound) {
 if (rightAbsolute) {
 float over = scrollX - rightBound;
 needsInvalidate = mRightEdge.onPull(Math.abs(over) / width);
 }
 scrollX = rightBound;
 }
 // Don't lose the rounded component
 mLastMotionX += scrollX - (int) scrollX;
 scrollTo((int) scrollX, getScrollY());
 pageScrolled((int) scrollX);
 
 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 width = getWidth();
 final float scrollOffset = width > 0 ? (float) getScrollX() / width : 0;
 final float marginOffset = width > 0 ? (float) mPageMargin / width : 0;
 int lastPos = -1;
 float lastOffset = 0.f;
 float lastWidth = 0.f;
 boolean first = true;
 
 ItemInfo lastItem = null;
 for (int i = 0; i < mItems.size(); i++) {
 ItemInfo ii = mItems.get(i);
 float offset;
 // CHANGE
 if (!first && ii.position != lastPos + 1 && mAdapter.getCount() != 2) {
 // Create a synthetic item for a missing page.
 ii = mTempItem;
 ii.offset = lastOffset + lastWidth + marginOffset;
 ii.position = lastPos + 1;
 ii.widthFactor = mAdapter.getPageWidth(ii.position);
 i--;
 }
 offset = ii.offset;
 
 final float leftBound = offset;
 final float rightBound = offset + ii.widthFactor + marginOffset;
 if (first || scrollOffset >= leftBound) {
 if (scrollOffset < rightBound || i == mItems.size() - 1) {
 return ii;
 }
 } else {
 return lastItem;
 }
 first = false;
 lastPos = ii.position;
 lastOffset = offset;
 lastWidth = ii.widthFactor;
 lastItem = ii;
 }
 
 return lastItem;
 }
 
 private int determineTargetPage(int currentPage, float pageOffset, int velocity, int deltaX) {
 int targetPage;
 if (Math.abs(deltaX) > mFlingDistance && Math.abs(velocity) > mMinimumVelocity) {
 targetPage = velocity > 0 ? currentPage : currentPage + 1;
 } else {
 if (currentPage + pageOffset + 0.5f >= 0f) {
 targetPage = (int) (currentPage + pageOffset + 0.5f);
 } else {
 targetPage = (int) (currentPage + pageOffset + 0.5f - 1f);
 }
 }
 
 final int N = mAdapter.getCount();
 
 // CHANGE
 if (N == 2) {
 // ページ数2
 if (mCurItem == 1) {
 // -1 1 0
 if (currentPage == -1 && targetPage == 0) {
 targetPage = 1;
 }
 if (targetPage == 2) {
 targetPage = 0;
 }
 }
 
 } else if (mItems.size() > 0) {
 final ItemInfo firstItem = mItems.get(0);
 final ItemInfo lastItem = mItems.get(mItems.size() - 1);
 
 // CHANGE
 if (firstItem.position > lastItem.position) {
 // 端にいる
 if (targetPage >= N) {
 targetPage = targetPage % N;
 }
 }
 }
 
 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 (!mLeftEdge.isFinished()) {
 final int restoreCount = canvas.save();
 final int height = getHeight() - getPaddingTop() - getPaddingBottom();
 final int width = getWidth();
 
 canvas.rotate(270);
 canvas.translate(-height + getPaddingTop(), mFirstOffset * width);
 mLeftEdge.setSize(height, width);
 needsInvalidate |= mLeftEdge.draw(canvas);
 canvas.restoreToCount(restoreCount);
 }
 if (!mRightEdge.isFinished()) {
 final int restoreCount = canvas.save();
 final int width = getWidth();
 final int height = getHeight() - getPaddingTop() - getPaddingBottom();
 
 canvas.rotate(90);
 canvas.translate(-getPaddingTop(), -(mLastOffset + 1) * width);
 mRightEdge.setSize(height, width);
 needsInvalidate |= mRightEdge.draw(canvas);
 canvas.restoreToCount(restoreCount);
 }
 } else {
 mLeftEdge.finish();
 mRightEdge.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 scrollX = getScrollX();
 final int width = getWidth();
 
 final float marginOffset = (float) mPageMargin / width;
 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.widthFactor) * width;
 offset = ii.offset + ii.widthFactor + marginOffset;
 } else {
 float widthFactor = mAdapter.getPageWidth(pos);
 drawAt = (offset + widthFactor) * width;
 offset += widthFactor + marginOffset;
 }
 
 if (drawAt + mPageMargin > scrollX) {
 mMarginDrawable.setBounds((int) drawAt, mTopPageBounds, (int) (drawAt + mPageMargin + 0.5f),
 mBottomPageBounds);
 mMarginDrawable.draw(canvas);
 }
 
 if (drawAt > scrollX + width) {
 break; // No more visible, no sense in continuing
 }
 }
 }
 }
 
 // CHANGE
 Bitmap getViewBitmap(View v) {
 v.clearFocus();
 v.setPressed(false);
 
 // もともとの設定値を保持しておく
 boolean willNotCache = v.willNotCacheDrawing();
 int color = v.getDrawingCacheBackgroundColor();
 
 // 描画をキャッシュしないようにセット
 v.setWillNotCacheDrawing(false);
 
 // 描画キャッシュをクリアして、背景を透明にセット
 v.setDrawingCacheBackgroundColor(0);
 
 // 以前の描画キャッシュを破棄
 if (color != 0) {
 v.destroyDrawingCache();
 }
 
 // 新しく描画キャッシュを作成
 v.buildDrawingCache();
 
 // キャッシュ用の Bitmap を取得
 Bitmap cacheBitmap = v.getDrawingCache();
 if (cacheBitmap == null) {
 
 return null;
 }
 
 // キャッシュ用の Bitmap からドラッグ中の画像に使うための Bitmap を作成
 Bitmap bitmap = Bitmap.createBitmap(cacheBitmap);
 
 // もともとセットされていた描画キャッシュに戻す
 v.destroyDrawingCache();
 v.setWillNotCacheDrawing(willNotCache);
 v.setDrawingCacheBackgroundColor(color);
 
 return bitmap;
 }
 
 /**
 * Start a fake drag of the pager.
 * 
 * 
 * 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.
 * 
 * 
 * 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);
 mInitialMotionX = mLastMotionX = 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.getXVelocity(velocityTracker, mActivePointerId);
 mPopulatePending = true;
 final int width = getWidth();
 final int scrollX = getScrollX();
 final ItemInfo ii = infoForCurrentScrollPosition();
 final int currentPage = ii.position;
 final float pageOffset = (((float) scrollX / width) - ii.offset) / ii.widthFactor;
 final int totalDelta = (int) (mLastMotionX - mInitialMotionX);
 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 xOffset
 * Offset in pixels to drag by.
 * @see #beginFakeDrag()
 * @see #endFakeDrag()
 */
 public void fakeDragBy(float xOffset) {
 if (!mFakeDragging) {
 throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");
 }
 
 mLastMotionX += xOffset;
 
 float oldScrollX = getScrollX();
 float scrollX = oldScrollX - xOffset;
 final int width = getWidth();
 
 float leftBound = width * mFirstOffset;
 float rightBound = width * mLastOffset;
 
 final ItemInfo firstItem = mItems.get(0);
 final ItemInfo lastItem = mItems.get(mItems.size() - 1);
 if (firstItem.position != 0) {
 leftBound = firstItem.offset * width;
 }
 if (lastItem.position != mAdapter.getCount() - 1) {
 rightBound = lastItem.offset * width;
 }
 
 if (scrollX < leftBound) {
 scrollX = leftBound;
 } else if (scrollX > rightBound) {
 scrollX = rightBound;
 }
 // Don't lose the rounded component
 mLastMotionX += scrollX - (int) scrollX;
 scrollTo((int) scrollX, getScrollY());
 pageScrolled((int) scrollX);
 
 // Synthesize an event for the VelocityTracker.
 final long time = SystemClock.uptimeMillis();
 final MotionEvent ev = MotionEvent
 .obtain(mFakeDragBeginTime, time, MotionEvent.ACTION_MOVE, mLastMotionX, 0, 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;
 mLastMotionX = MotionEventCompat.getX(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);
 }
 }
 }
 }
 }
 
 /**
 * 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 dx
 * 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 dx, 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 (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() && y + scrollY >= child.getTop()
 && y + scrollY < child.getBottom()
 && canScroll(child, true, dx, x + scrollX - child.getLeft(), y + scrollY - child.getTop())) {
 return true;
 }
 }
 }
 
 return checkV && ViewCompat.canScrollHorizontally(v, -dx);
 }
 
 @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;
 
 boolean handled = false;
 
 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);
 if (nextFocused != null && nextFocused != currentFocused) {
 if (direction == View.FOCUS_LEFT) {
 // 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 nextLeft = getChildRectInPagerCoordinates(mTempRect, nextFocused).left;
 final int currLeft = getChildRectInPagerCoordinates(mTempRect, currentFocused).left;
 if (currentFocused != null && nextLeft >= currLeft) {
 handled = pageLeft();
 } else {
 handled = nextFocused.requestFocus();
 }
 } else if (direction == View.FOCUS_RIGHT) {
 // 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 nextLeft = getChildRectInPagerCoordinates(mTempRect, nextFocused).left;
 final int currLeft = getChildRectInPagerCoordinates(mTempRect, currentFocused).left;
 if (currentFocused != null && nextLeft <= currLeft) {
 handled = pageRight();
 } else {
 handled = nextFocused.requestFocus();
 }
 }
 } else if (direction == FOCUS_LEFT || direction == FOCUS_BACKWARD) {
 // Trying to move left and nothing there; try to page.
 handled = pageLeft();
 } else if (direction == FOCUS_RIGHT || direction == FOCUS_FORWARD) {
 // Trying to move right and nothing there; try to page.
 handled = pageRight();
 }
 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 pageLeft() {
 if (mCurItem > 0) {
 setCurrentItem(mCurItem - 1, true);
 return true;
 }
 return false;
 }
 
 boolean pageRight() {
 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) {
 // ViewPagers should only report accessibility info for the current
 // page,
 // otherwise things get very confusing.
 
 // TODO: Should this note something about the paging container?
 
 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(LoopViewPager.class.getName());
 }
 
 @Override
 public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat info) {
 super.onInitializeAccessibilityNodeInfo(host, info);
 info.setClassName(LoopViewPager.class.getName());
 info.setScrollable(mAdapter != null && mAdapter.getCount() > 1);
 if (mAdapter != null && mCurItem >= 0 && mCurItem < mAdapter.getCount() - 1) {
 info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD);
 }
 if (mAdapter != null && mCurItem > 0 && mCurItem < mAdapter.getCount()) {
 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 (mAdapter != null && mCurItem >= 0 && mCurItem < mAdapter.getCount() - 1) {
 setCurrentItem(mCurItem + 1);
 return true;
 }
 }
 return false;
 case AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD: {
 if (mAdapter != null && mCurItem > 0 && mCurItem < mAdapter.getCount()) {
 setCurrentItem(mCurItem - 1);
 return true;
 }
 }
 return false;
 }
 return false;
 }
 }
 
 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 Gravity}.
 */
 public int gravity;
 
 /**
 * Width as a 0-1 multiplier of the measured pager width
 */
 public float widthFactor = 0.f;
 
 /**
 * true if this view was added during layout and needs to be measured
 * before being positioned.
 */
 public boolean needsMeasure;
 
 public LayoutParams() {
 super(MATCH_PARENT, MATCH_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();
 }
 }
 }