Null value passed in call to LayoutManager.LayoutParams.from()

[maoruibin]

I use this lib,and refer to example, but when get itemView's LayoutParam ,it values is null ,how to fix it, code like this, only for important code

/**
 * ViewHolderItem is a parent class for different item 
 */
 abstract static class ViewHolderItem extends RecyclerView.ViewHolder {

    public ViewHolderItem(View itemView) {
        super(itemView);
    }

    abstract void bindItem(Context context,Gank gank);
}

the method of onCreateViewHolder

@Override
public GankListAdapter.ViewHolderItem onCreateViewHolder(ViewGroup parent, int viewType) {
    //目前有三种类型 ==0 是妹子福利图片类型
    View view = null;
    if (viewType == GankType.福利.ordinal()) {
        view = LayoutInflater.from(parent.getContext()).inflate(R.layout.gank_item_girl, null);
        return new ViewHolderItemGirl(view);
    }else if(viewType == GankType.GANK_HEADER.ordinal()){
        view = LayoutInflater.from(parent.getContext()).inflate(R.layout.gank_item_header, null);
        return new ViewHolderItemHeader(view);
    } else {
        view = LayoutInflater.from(parent.getContext()).inflate(R.layout.gank_item_normal, null);
        return new ViewHolderItemNormal(view);
    }
}

error please

@Override
public void onBindViewHolder(final GankListAdapter.ViewHolderItem holder, int position) {
    final Gank gank = mGankList.get(position);
    holder.bindItem(mContext, gank);

    final View itemView = holder.itemView;

    ViewGroup.LayoutParams params = itemView.getLayoutParams();

    final GridSLM.LayoutParams lp = GridSLM.LayoutParams.from(params);
    // Overrides xml attrs, could use different layouts too.
    if (gank.isHeader) {
        lp.headerDisplay = LayoutManager.LayoutParams.HEADER_STICKY;
        if (lp.isHeaderInline() || (mMarginsFixed && !lp.isHeaderOverlay())) {
            lp.width = ViewGroup.LayoutParams.MATCH_PARENT;
        } else {
            lp.width = ViewGroup.LayoutParams.WRAP_CONTENT;
        }

        lp.headerEndMarginIsAuto = !mMarginsFixed;
        lp.headerStartMarginIsAuto = !mMarginsFixed;
    }
    lp.setSlm(LinearSLM.ID);
    lp.setColumnWidth(mContext.getResources().getDimensionPixelSize(R.dimen.grid_column_width));
    lp.setFirstPosition(gank.sectionFirstPosition);
    itemView.setLayoutParams(lp);
}

when execute GridSLM.LayoutParams.from(params); it will point params is null