class StaggeredGridLayoutManager extends RecyclerView.LayoutManager implements
        RecyclerView.SmoothScroller.ScrollVectorProvider {

    public int[] findFirstCompletelyVisibleItemPositions(int[] into) {
        if (into == null) {
            into = new int[mSpanCount];
        } else if (into.length < mSpanCount) {
            throw new IllegalArgumentException("Provided int[]'s size must be more than or equal"
                    + " to span count. Expected:" + mSpanCount + ", array size:" + into.length);
        }
        for (int i = 0; i < mSpanCount; i++) {
            into[i] = mSpans[i].findFirstCompletelyVisibleItemPosition();
        }
        return into;
    }

    @SuppressWarnings("unused") public  StaggeredGridLayoutManager(Context context, AttributeSet attrs, int defStyleAttr,
            int defStyleRes);
    public  StaggeredGridLayoutManager(int spanCount, int orientation);

}