Creating a generic PagedListAdapter using android paging library

Question

My app has more than 4 lists of different data models.
I want to create a more generic CommonAdapter that extends PagedListAdapter
Here is my current code

public abstract class CommonPagedListAdapter<T, VH extends RecyclerView.ViewHolder>
        extends PagedListAdapter<T, VH> {

    private Context mContext;
    private ArrayList<T> mArrayList;

    public abstract void onItemClick(T model, int position);
    public abstract int getLayoutResId();

    protected CommonPagedListAdapter(Context context, ArrayList<T> arrayList,
                                     @NonNull DiffUtil.ItemCallback<T> diffCallback) {
        super(diffCallback);
        this.mContext  = context;
        this.mArrayList = arrayList;
    }

    @NonNull
    @Override
    public VH onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        //what should i return here?
        View view = LayoutInflater.from(mContext).inflate(getLayoutResId(),parent,false);
        return (VH) new ItemViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull VH holder, int position) {
        //what should i do here?
//        holder
    }

    class ItemViewHolder extends RecyclerView.ViewHolder {

        public ItemViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }
}

I'm using PagelListAdapter from the Android Paging Library
I would like to know a few things:
- What should be set in the onCreateViewHolder as I'll be having different ViewHolders?
- What should be set in onBindViewHolder?
- Is this really the right way that makes the CommonPagedListAdapter extensible and maintainable?

Answer 1

I had a similar issue where I tried to create a single adapter to use for multiple different list types. I ultimately came to the conclusion that it is best to use a separate adapter for each list type solely because it avoids having to make a very big "common" adapter class which goes against the "single-responsibility" principle. That way, each adapter is a lot smaller, more maintainable, and flexible.

However, if you really want to use a single adapter for similar items, the way I usually do it is by creating unique ViewHolders for each item type and then binding them accordingly in onBindViewHolder using a switch statement or something similar. In order to do this, you would need to override an additional method called getItemViewType in your adapter.

There's a really good guide that goes over how to create an adapter that can handle different view types on Codepath: https://guides.codepath.com/android/Heterogenous-Layouts-inside-RecyclerView