Implement multiple ViewHolder types in RecycleView adapter

Question

It\'s maybe a discussion not a question.

Normal way to implement multiple types

As you know, if we want to implement multiple types in RecyclerView

Answer 1

Here you can use Dynamic method dispatch. Below i share my idea. //Activity Code

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    ArrayList<Object> dataList = new ArrayList<>();
    dataList.add("Apple");
    dataList.add("Orange");
    dataList.add("Cherry");
    dataList.add("Papaya");
    dataList.add("Grapes");
    dataList.add(100);
    dataList.add(200);
    dataList.add(300);
    dataList.add(400);
    ViewAdapter viewAdapter = new ViewAdapter(dataList);
    recyclerView.setAdapter(viewAdapter);

}

}

//Adapter code

public class ViewAdapter extends RecyclerView.Adapter<BaseViewHolder> {
private ArrayList<Object> dataList;
public ViewAdapter(ArrayList<Object> dataList) {
    this.dataList = dataList;
}

@Override
public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    BaseViewHolder baseViewHolder;

    if(viewType == 0) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_one,parent,false);
        baseViewHolder  = new ViewHolderOne(view);
    }else  {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_two,parent,false);
        baseViewHolder  = new ViewHolderSecond(view);
    }
    return baseViewHolder;
}

@Override
public void onBindViewHolder(BaseViewHolder holder, int position) {
    holder.bindData(dataList.get(position));
}

@Override
public int getItemViewType(int position) {
    Object obj = dataList.get(position);
    int type = 0;
    if(obj instanceof Integer) {
        type = 0;
    }else if(obj instanceof String) {
        type = 1;
    }
    return type;
}

@Override
public int getItemCount() {
    return dataList != null ? dataList.size() : 0;
}

}

//Base View Holder Code.

public abstract class BaseViewHolder<T> extends RecyclerView.ViewHolder {
public BaseViewHolder(View itemView) {
    super(itemView);
}

public abstract void bindData(T data);

}

//View Holder One Source Code.

public class ViewHolderOne extends BaseViewHolder<Integer> {

private TextView txtView;
public ViewHolderOne(View itemView) {
    super(itemView);
    txtView = itemView.findViewById(R.id.txt_number);
}

@Override
public void bindData(Integer data) {
    txtView.setText("Number:" + data);
}

}

//View Holder Two

public class ViewHolderSecond extends BaseViewHolder<String> {

private TextView textView;
public ViewHolderSecond(View itemView) {
    super(itemView);
    textView = itemView.findViewById(R.id.txt_string);
}

@Override
public void bindData(String data) {
    textView.setText("Text:" + data);
}

}

For project Source: enter link description here

Answer 2

It might not be the answer you're expecting but here is an example using Epoxy, which really makes your life easier:

First you define your models:

@EpoxyModelClass(layout = R.layout.header_view_model)
public abstract class HeaderViewModel extends EpoxyModel<TextView> {

    @EpoxyAttribute
    String title;

    @Override
    public void bind(TextView view) {
        super.bind(view);
        view.setText(title);
    }

}

@EpoxyModelClass(layout = R.layout.drink_view_model)
public abstract class DrinkViewModel extends EpoxyModel<View> {

    @EpoxyAttribute
    Drink drink;

    @EpoxyAttribute
    Presenter presenter;

    @Override
    public void bind(View view) {
        super.bind(view);

        final TextView title = view.findViewById(R.id.title);
        final TextView description = view.findViewById(R.id.description);

        title.setText(drink.getTitle());
        description.setText(drink.getDescription());
        view.setOnClickListener(v -> presenter.drinkClicked(drink));
    }

    @Override
    public void unbind(View view) {
        view.setOnClickListener(null);
        super.unbind(view);
    }

}

@EpoxyModelClass(layout = R.layout.food_view_model)
public abstract class FoodViewModel extends EpoxyModel<View> {

    @EpoxyAttribute
    Food food;

    @EpoxyAttribute
    Presenter presenter;

    @Override
    public void bind(View view) {
        super.bind(view);

        final TextView title = view.findViewById(R.id.title);
        final TextView description = view.findViewById(R.id.description);
        final TextView calories = view.findViewById(R.id.calories);

        title.setText(food.getTitle());
        description.setText(food.getDescription());
        calories.setText(food.getCalories());
        view.setOnClickListener(v -> presenter.foodClicked(food));
    }

    @Override
    public void unbind(View view) {
        view.setOnClickListener(null);
        super.unbind(view);
    }

}

Then you define your Controller:

public class DrinkAndFoodController extends Typed2EpoxyController<List<Drink>, List<Food>> {

    @AutoModel
    HeaderViewModel_ drinkTitle;

    @AutoModel
    HeaderViewModel_ foodTitle;

    private final Presenter mPresenter;

    public DrinkAndFoodController(Presenter presenter) {
        mPresenter = presenter;
    }

    @Override
    protected void buildModels(List<Drink> drinks, List<Food> foods) {
        if (!drinks.isEmpty()) {
            drinkTitle
                    .title("Drinks")
                    .addTo(this);
            for (Drink drink : drinks) {
                new DrinkViewModel_()
                        .id(drink.getId())
                        .drink(drink)
                        .presenter(mPresenter)
                        .addTo(this);
            }
        }

        if (!foods.isEmpty()) {
            foodTitle
                    .title("Foods")
                    .addTo(this);
            for (Food food : foods) {
                new FoodViewModel_()
                        .id(food.getId())
                        .food(food)
                        .presenter(mPresenter)
                        .addTo(this);
            }
        }
    }
}

Initialize your Controller:

DrinkAndFodController mController = new DrinkAndFoodController(mPresenter);
mController.setSpanCount(1);

final GridLayoutManager layoutManager = new GridLayoutManager(getContext(), 1);
layoutManager.setSpanSizeLookup(mController.getSpanSizeLookup());
mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setAdapter(mController.getAdapter());

And finally you can add your data as easily as this:

final List<Drink> drinks = mManager.getDrinks();
final List<Food> foods = mManager.getFoods();
mController.setData(drinks, foods);

You'll have a list thats looks like:

Drinks
Drink 1
Drink 2
Drink 3
...
Foods
Food1
Food2
Food3
Food4
...

For more informations you can check the wiki.

Answer 3

Second one is buggy because when ViewHolders get recycled it produces unexpected behavior. I considered changing visibility during binding but it isn't performant enough for large amount of Views. Recycler inside RecyclerView stores ViewHolders per type so first way is more performant.