Force RecyclerView to call onCreateViewHolder

What you need to do is:

1. Modify your Adapter:

• Specify two types of Views that your Adapter can inflate:

private static final int LARGE_GRID_ITEM = -1;
private static final int SMALL_GRID_ITEM = -2;

• Create a field that can store current type mCurrentType

• Use your Adapter's getItemViewType. For example like this:

@Override
public int getItemViewType (int position) {
    return mCurrentType;
}

• In your createViewHolder use the viewType to decide what type of ViewHolder you need to create.

public final RecyclerView.ViewHolder createViewHolder (ViewGroup parent, int viewType){
    if (viewType == LARGE_GRID_ITEM) {
        //return large grid view holder
    } else {
        //return small grid view holder
    }
}

• Additionally you can create methods:

public void toggleItemViewType () {
    if (mCurrentType == LARGE_GRID_ITEM){
        mCurrentType = SMALL_GRID_ITEM;
    } else {
        mCurrentType = LARGE_GRID_ITEM;
    }
}

public boolean displaysLargeGrid(){
    return mCurrentType == LARGE_GRID_ITEM;
}

2. Modify the code you posted:

layoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
        @Override
        public int getSpanSize(int position) {
            if (adapter.displaysLargeGrid()) {
                return 1;
            } else {
                return columnCount; //show one item per row
            }
        }
    });

@Override
public void onClick(View v) {
    adapter.toggleItemViewType();
    adapter.notifyDataSetChanged();
}

Its not the optimal choice but it's better to create a new Adapter, which will call onCreateViewHolder(). This way you can avoid your troubles, by the cost of very tiny performance issues.