RecyclerView match_parent不起作用的问题

以前的备注，今天翻出来写个博客记录一下, RecyclerView的item布局设置match_parent经常不起作用，可以在代码中填充布局时这样写：

    @Override
    public Main2ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new Main2ViewHolder(LayoutInflater.from(mContext).inflate(R.layout.item,parent,false));
    }

因为源码中有如下内容

                    if (root != null) {
                        if (DEBUG) {
                            System.out.println("Creating params from root: " +
                                    root);
                        }
                        // Create layout params that match root, if supplied
                        params = root.generateLayoutParams(attrs);
                        if (!attachToRoot) {
                            // Set the layout params for temp if we are not
                            // attaching. (If we are, we use addView, below)
                            temp.setLayoutParams(params);
                        }
                    }