记录RecyclerView的位置并进行恢复

//监听RecyclerView滚动状态
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
        if(recyclerView.getLayoutManager() != null) {
            getPositionAndOffset();
        }
    }
});

/**
 * 记录RecyclerView当前位置
 */
private void getPositionAndOffset() {
    LinearLayoutManager layoutManager = (LinearLayoutManager) mRecyclerView.getLayoutManager();
    //获取可视的第一个view
    View topView = layoutManager.getChildAt(0);
    if(topView != null) {
        //获取与该view的顶部的偏移量
        lastOffset = topView.getTop();
        //得到该View的数组位置
        lastPosition = layoutManager.getPosition(topView);
    }
}

/**
 * 让RecyclerView滚动到指定位置
 */
private void scrollToPosition() {
    if(mRecyclerView.getLayoutManager() != null && lastPosition >= 0) {
        ((LinearLayoutManager) mRecyclerView.getLayoutManager()).scrollToPositionWithOffset(lastPosition, lastOffset);
    }
}