用PagerSnapHelper+RecyclerView模仿ViewPager行为，比ViewPager更加流畅

用法很简单，只需要new一个PagerSnapHelper对象attach到RecyclerView对象上，就能实现了Viewpager的粘性滑动,以下代码呢是我在网上搜的一个模仿抖音滑动并且需要播放视频特意封装的一个类，使用这个布局管理器直接就能实现和ViewPager类似的布局，但是还是需要动态的去设置他的宽度（通常情况下是屏幕的宽度，根据需求计算），里面包含的当前item的position的获取以及item离开界面时候的销毁监听，感觉很有用，特意贴出来给大家分享一下，类里面有大佬的github地址，博客地址我也是找不到了就没做成链接

 /**
     * Created by 钉某人
     * github: https://github.com/DingMouRen
     * email: [email protected]
     * edit by yc
     */
    
    public class ViewPagerLayoutManager extends LinearLayoutManager {
        private static final String TAG = "ViewPagerLayoutManager";
        private PagerSnapHelper mPagerSnapHelper;
        private OnViewPagerListener mOnViewPagerListener;
        private RecyclerView mRecyclerView;
        private int mDrift;//位移，用来判断移动方向
    
        public ViewPagerLayoutManager(Context context, int orientation) {
            super(context, orientation, false);
            init();
        }
    
        public ViewPagerLayoutManager(Context context, int orientation, boolean reverseLayout) {
            super(context, orientation, reverseLayout);
            init();
        }
    
        private void init() {
            mPagerSnapHelper = new PagerSnapHelper();
        }
    
        @Override
        public void onAttachedToWindow(RecyclerView view) {
            super.onAttachedToWindow(view);
    
            mPagerSnapHelper.attachToRecyclerView(view);
            this.mRecyclerView = view;
            mRecyclerView.addOnChildAttachStateChangeListener(mChildAttachStateChangeListener);
        }
    
    
        /**
         * 滑动状态的改变
         * 缓慢拖拽-> SCROLL_STATE_DRAGGING
         * 快速滚动-> SCROLL_STATE_SETTLING
         * 空闲状态-> SCROLL_STATE_IDLE
         *
         * @param state
         */
        @Override
        public void onScrollStateChanged(int state) {
            switch (state) {
                case RecyclerView.SCROLL_STATE_IDLE:
                    View viewIdle = mPagerSnapHelper.findSnapView(this);
                    if (viewIdle != null) {
                        int positionIdle = getPosition(viewIdle);
                        int childCount = getChildCount();
                        if (mOnViewPagerListener != null && getChildCount() <= 2) {
                            mOnViewPagerListener.onPageSelected(positionIdle, positionIdle == getItemCount() - 1);
                        }
                    }
                    break;
                case RecyclerView.SCROLL_STATE_DRAGGING:
                    break;
                case RecyclerView.SCROLL_STATE_SETTLING:
                    break;
                default:
                    break;
            }
        }
    
    
        /**
         * 监听竖直方向的相对偏移量
         *
         * @param dy
         * @param recycler
         * @param state
         * @return
         */
        @Override
        public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
            this.mDrift = dy;
            return super.scrollVerticallyBy(dy, recycler, state);
        }
    
    
        /**
         * 监听水平方向的相对偏移量
         *
         * @param dx
         * @param recycler
         * @param state
         * @return
         */
        @Override
        public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
            this.mDrift = dx;
            return super.scrollHorizontallyBy(dx, recycler, state);
        }
    
        /**
         * if return >= 0 snap is exist
         * if return < 0 snap is not exist
         *
         * @return
         */
        public int findSnapPosition() {
            View viewIdle = mPagerSnapHelper.findSnapView(this);
            if (viewIdle != null) {
                return getPosition(viewIdle);
            } else {
                return -1;
            }
        }
    
        /**
         * 设置监听
         *
         * @param listener
         */
        public void setOnViewPagerListener(OnViewPagerListener listener) {
            this.mOnViewPagerListener = listener;
        }
    
        private RecyclerView.OnChildAttachStateChangeListener mChildAttachStateChangeListener = new RecyclerView.OnChildAttachStateChangeListener() {
            @Override
            public void onChildViewAttachedToWindow(View view) {
                if (mOnViewPagerListener != null && getChildCount() == 1) {
                    mOnViewPagerListener.onInitComplete();
                }
            }
    
            @Override
            public void onChildViewDetachedFromWindow(View view) {
                if (mOnViewPagerListener != null) {
                    if (mDrift >= 0) {
                        mOnViewPagerListener.onPageRelease(true, getPosition(view));
                    } else {
                        mOnViewPagerListener.onPageRelease(false, getPosition(view));
                    }
                }
    
            }
        };
    }



/**
 * Created by 钉某人
 * github: https://github.com/DingMouRen
 * email: [email protected]
 * 用于ViewPagerLayoutManager的监听
 *
 * @author yc
 */

public interface OnViewPagerListener {


    /**
     * 初始化第一个View
     */
    void onInitComplete();


    /**
     * 选中的监听以及判断是否滑动到底部
     *
     * @param position
     * @param isBottom
     */
    void onPageSelected(int position, boolean isBottom);


    /**
     * 释放的监听
     *
     * @param isNext
     * @param position
     */
    void onPageRelease(boolean isNext, int position);
}