Implementing different layouts for RecyclerView but getting class cast erro on onBindViewHolder

问题

I'm following this tutorial but I'm getting the following cast error:

java.lang.ClassCastException: com.banshai.appetit.controllers.home.OpenRestaurantsViewHolder cannot be cast to com.banshai.appetit.controllers.home.FirstOpenRestaurantVHolder at com.banshai.appetit.controllers.home.RestaurantAdapter.onBindViewHolder

The error is being called at onBindViewHolder when trying to cast: FirstOpenRestaurantVHolder firstVH = (FirstOpenRestaurantVHolder) viewholder; . What Am I missing?

This is my complete adapter:

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

    private List<Restaurant> restaurants;
    private Context context;
    private SharedData sharedData;

    private final int FIRST_OPEN_RESTAURANT = 0;
    private final int OPEN_RESTAURANT = 1;

    public RestaurantAdapter(List<Restaurant> restaurantsList) {
        restaurants = restaurantsList;
        sharedData = SharedData.getInstance();
    }

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

    @Override
    public int getItemViewType(int position) {

        //If position is 0 this means we need to use FirstOpenRestaurantVHolder
        if (position == 0) {
            return FIRST_OPEN_RESTAURANT;

        } else if (position > 0) {
            return OPEN_RESTAURANT;
        }


        return OPEN_RESTAURANT; //TODO ojo con este default
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {

        RecyclerView.ViewHolder viewHolder;
        LayoutInflater inflater = LayoutInflater.from(viewGroup.getContext());

        switch (viewType) {
            case FIRST_OPEN_RESTAURANT:

                View firstOpenRest = inflater.inflate(R.layout.intro_home_restaurant_first_card, viewGroup, false);
                viewHolder = new OpenRestaurantsViewHolder(firstOpenRest);
                break;

            case OPEN_RESTAURANT: //TODO ojo este no va ser el default
                View openRest = inflater.inflate(R.layout.intro_home_resturant_card_row, viewGroup, false);
                viewHolder = new FirstOpenRestaurantVHolder(openRest);
                break;

            default:
                View openRestaurant = inflater.inflate(R.layout.intro_home_resturant_card_row, viewGroup, false);
                viewHolder = new FirstOpenRestaurantVHolder(openRestaurant);
                break;

        }

        return viewHolder;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewholder, int position) {
        switch (viewholder.getItemViewType()) {

            case FIRST_OPEN_RESTAURANT:
                FirstOpenRestaurantVHolder firstVH = (FirstOpenRestaurantVHolder) viewholder;
                firstVH.franchiseName.setText("FIRST!!!");


                break;

            default:
                OpenRestaurantsViewHolder openVH = (OpenRestaurantsViewHolder) viewholder;
                openVH.franchiseName.setText("OPEN BUT NOT FIRST");
                break;
        }
    }

    public class OpenRestaurantsViewHolder extends RecyclerView.ViewHolder {

        protected TextView franchiseName;
        protected TextView homeCategory;
        protected ImageView restaurantPhoto;
        protected ImageView franchiseLogo;


        public OpenRestaurantsViewHolder(View view) {
            super(view);

            franchiseName = (TextView) view.findViewById(R.id.home_franchise_name);
            restaurantPhoto = (ImageView) view.findViewById(R.id.home_resturant_pic);
            franchiseLogo = (ImageView) view.findViewById(R.id.home_franchise_logo);
            homeCategory = (TextView) view.findViewById(R.id.home_category);


        }
    }

    public class FirstOpenRestaurantVHolder extends RecyclerView.ViewHolder {

        protected TextView franchiseName;
        protected TextView homeCategory;
        protected ImageView restaurantPhoto;
        protected ImageView franchiseLogo;


        public FirstOpenRestaurantVHolder(View view) {
            super(view);

            franchiseName = (TextView) view.findViewById(R.id.home_first_franchise_name);
            restaurantPhoto = (ImageView) view.findViewById(R.id.home_first_resturant_pic);
            franchiseLogo = (ImageView) view.findViewById(R.id.home_first_franchise_logo);
            homeCategory = (TextView) view.findViewById(R.id.home_first_category);
        }


    }
}

回答1:

Had to change your code for if instead of switch to make it clearer (this is just personal preference), added some console logs to see what was happening but this should work:

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

    private List<Restaurant> restaurants;
    private Context context;
    private SharedData sharedData;

    private final int FIRST_OPEN_RESTAURANT = 0;
    private final int OPEN_RESTAURANT = 1;

    public RestaurantAdapter(List<Restaurant> restaurantsList) {
        restaurants = restaurantsList;
        sharedData = SharedData.getInstance();
    }

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

    @Override
    public int getItemViewType(int position) {
        Log.i("getItemVi(position)", "position=" + position);
        //If position is 0 this means we need to use FirstOpenRestaurantVHolder
        if (position == 0) {
            return 0;

        } else if (position > 0) {
            return 1;
        }


        return 1; //TODO ojo con este default
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
        Log.i("onCreateVewHo(viewType)", "viewType=" + viewType);

        RecyclerView.ViewHolder viewHolder;
        LayoutInflater inflater = LayoutInflater.from(viewGroup.getContext());

        if (viewType == 0) {
            View firstOpenRest = inflater.inflate(R.layout.intro_home_restaurant_first_card, viewGroup, false);
            viewHolder = new FirstOpenRestaurantVHolder(firstOpenRest);

        } else {
            View openRestaurant = inflater.inflate(R.layout.intro_home_resturant_card_row, viewGroup, false);
            viewHolder = new OpenRestaurantsViewHolder(openRestaurant);
        }

        return viewHolder;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewholder, int position) {
        Log.i("onBindViewHolder", "viewholder.getItemViewType()=" + viewholder.getItemViewType());

        if (viewholder.getItemViewType() == 0) {
            FirstOpenRestaurantVHolder firstVH = (FirstOpenRestaurantVHolder) viewholder;
            firstVH.franchiseName.setText("FIRST!!!");

        } else {
            OpenRestaurantsViewHolder openVH = (OpenRestaurantsViewHolder) viewholder;
            openVH.franchiseName.setText("OPEN BUT NOT FIRST");

        }
    }

    public class OpenRestaurantsViewHolder extends RecyclerView.ViewHolder {

        protected TextView franchiseName;
        protected TextView homeCategory;
        protected ImageView restaurantPhoto;
        protected ImageView franchiseLogo;


        public OpenRestaurantsViewHolder(View view) {
            super(view);
            franchiseName = (TextView) view.findViewById(R.id.home_franchise_name);
            restaurantPhoto = (ImageView) view.findViewById(R.id.home_resturant_pic);
            franchiseLogo = (ImageView) view.findViewById(R.id.home_franchise_logo);
            homeCategory = (TextView) view.findViewById(R.id.home_category);

        }
    }

    public class FirstOpenRestaurantVHolder extends RecyclerView.ViewHolder {

        protected TextView franchiseName;
        protected TextView homeCategory;
        protected ImageView restaurantPhoto;
        protected ImageView franchiseLogo;


        public FirstOpenRestaurantVHolder(View view) {
            super(view);

            franchiseName = (TextView) view.findViewById(R.id.home_first_franchise_name);
            restaurantPhoto = (ImageView) view.findViewById(R.id.home_first_resturant_pic);
            franchiseLogo = (ImageView) view.findViewById(R.id.home_first_franchise_logo);
            homeCategory = (TextView) view.findViewById(R.id.home_first_category);
        }


    }
}

回答2:

Problem is Here:

case FIRST_OPEN_RESTAURANT:
  FirstOpenRestaurantVHolder firstVH = (FirstOpenRestaurantVHolder) viewholder; 

in onCreateViewHolder setting OpenRestaurantsViewHolder in case of FIRST_OPEN_RESTAURANT but in onBindViewHolder casting getTag value to FirstOpenRestaurantVHolder :

case FIRST_OPEN_RESTAURANT:
      OpenRestaurantsViewHolder firstVH = (OpenRestaurantsViewHolder) viewholder;

来源：https://stackoverflow.com/questions/33378489/implementing-different-layouts-for-recyclerview-but-getting-class-cast-erro-on-o