Passing Data to RecyclerView Adapter

Question

I make a call to retrofit, and the size of the response is what I want to pass as the primary data set for my RecyclerView adapter. I can confirm I am successfully calling to Retrofit.

I am curious how I would pass the size of the data set to MyAdapter class. Below is my code:

In my Main Activity:

call.enqueue(new Callback<List<Recipe>>() {
        @Override
        public void onResponse(Call<List<Recipe>> call, Response<List<Recipe>> response) {
            Log.v("TAG", String.valueOf(response.isSuccessful()));
            mRecipeListResponse = response.body();
            for (Recipe recipe : mRecipeListResponse){
                Log.v("ID", recipe.getId().toString());
            }

            mAdapter.setDataSet(mRecipeListResponse);
            mRecipeList.setAdapter(mAdapter);
  ;            }

        @Override
        public void onFailure(Call<List<Recipe>> call, Throwable t) {
            Log.v("TAG", t.getMessage());
        }
    });

MyAdapter:

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

private List<Recipe> mRecipeDataSet;

public class ViewHolder extends RecyclerView.ViewHolder{


    protected CardView mCardView;
    protected TextView mTextView;

    public ViewHolder(View itemView) {
        super(itemView);

        mCardView = itemView.findViewById(R.id.recipe_cardview);
        mTextView = itemView.findViewById(R.id.id_of_recipe_item);
    }
}
@NonNull
@Override
public MyAdapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.recipe_item, parent,false);
    return new ViewHolder(v);
}

@Override
public void onBindViewHolder(@NonNull MyAdapter.ViewHolder holder, int position) {
        String id = mRecipeDataSet.get(position).getId();
        holder.mTextView.setText(id);

}

@Override
public int getItemCount() {
    return mRecipeDataSet.size();
}

public List<Recipe> setDataSet(List<Recipe> recipeList){
    return mRecipeDataSet;
}

public List<Recipe> getmRecipeDataSet() {
    return mRecipeDataSet;
}
}

Answer 1

My guess is you initiate the MyAdapter with null mRecipeDataSet . Try the following code.

private List<Recipe> mRecipeDataSet = new ArrayList<Recipe>();

and replace your code

//this is wrong, it doesn't do the right thing as the function name suggests.
public List<Recipe> setDataSet(List<Recipe> recipeList){
    return mRecipeDataSet;
}

to

public void setDataSet(List<Recipe> recipeList){
    mRecipeDataSet = recipeList;
}