Recyclerview 一次滚动一个item距离

//snapHelper是为了过滤掉item显示一半的情况，这样点击会导致只移动了半个Item距离
LinearSnapHelper snapHelper=new LinearSnapHelper();
snapHelper.attachToRecyclerView(mRecyclerView);
findViewById(R.id.btnUp).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int firstCompletelyVisible =linearLayoutManager.
findFirstCompletelyVisibleItemPosition();
linearLayoutManager.scrollToPositionWithOffset(Math.max(0,firstCompletelyVisible-1), 0);
}
});
findViewById(R.id.btnDown).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int firstCompletelyVisible = linearLayoutManager.
findFirstCompletelyVisibleItemPosition();
linearLayoutManager.scrollToPositionWithOffset(Math.min(data.size(),firstCompletelyVisible+1), 0);
}
});