Android Create a Custom RecyclerView.Adapter and Create Other Class from it

Question

Well people I have a RecyclerView which I populate from a WebService, and I have a DataProvider class that manage the async requests. So when the data is fetched I need this DataProvider to inform the RecyclerView.Adapter that there is new data. For this I need to add a method to RecyclerView.Adapter that allow this communication. But When I create a base class (which extends RecyclerView.Adapter) with this new method in it, and then create the custom adapter it won't let me Override RecyclerView.Adapter methods. What am I doing wrong?

This is the base class

public abstract class BaseRecyclerAdapter extends RecyclerView.Adapter<BaseRecyclerAdapter.ViewHolder>{

public static class ViewHolder extends RecyclerView.ViewHolder{

    public ViewHolder (View v){
        super(v);
    }
}

public BaseRecyclerAdapter(RecyclerView rv){

}

public void setDataSet( String data) {
   //This is the method i need to add
}

}

And this is the custom adapter which extends BaseRecyclerAdapter

public class PlacesAdapter extends BaseRecyclerAdapter<PlacesAdapter.ViewHolder> {

public static class ViewHolder extends RecyclerView.ViewHolder{
    public TextView mTextView;
    public ViewHolder(View v){
        super(v);
        mTextView= (TextView) v.findViewById(R.id.info_text);
    }
}

public PlacesAdapter(RecyclerView recyclerView){
    super(recyclerView);
}
@Override
public int getItemCount() {
    return 0;
}

@Override
public void setDataSet( String data) {

}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    //This says Method does not override method from its suplerclass
}

}

I guess it's something to do with type parameters, but I can't figure out what is going on

Answer 1

Check out this Gist from Pascal Welsch:

This helped me when I first started using the RecyclerView over the ListView.

import android.support.v7.widget.RecyclerView;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * Created by pascalwelsch on 04.07.14.
 */
public abstract class ArrayAdapter<T, VH extends RecyclerView.ViewHolder>
        extends RecyclerView.Adapter<VH> {

    private List<T> mObjects;

    public ArrayAdapter(final List<T> objects) {
        mObjects = objects;
    }

    /**
     * Adds the specified object at the end of the array.
     *
     * @param object The object to add at the end of the array.
     */
    public void add(final T object) {
        mObjects.add(object);
        notifyItemInserted(getItemCount() - 1);
    }

    /**
     * Remove all elements from the list.
     */
    public void clear() {
        final int size = getItemCount();
        mObjects.clear();
        notifyItemRangeRemoved(0, size);
    }

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

    public T getItem(final int position) {
        return mObjects.get(position);
    }

    public long getItemId(final int position) {
        return position;
    }

    /**
     * Returns the position of the specified item in the array.
     *
     * @param item The item to retrieve the position of.
     * @return The position of the specified item.
     */
    public int getPosition(final T item) {
        return mObjects.indexOf(item);
    }

    /**
     * Inserts the specified object at the specified index in the array.
     *
     * @param object The object to insert into the array.
     * @param index  The index at which the object must be inserted.
     */
    public void insert(final T object, int index) {
        mObjects.add(index, object);
        notifyItemInserted(index);

    }

    /**
     * Removes the specified object from the array.
     *
     * @param object The object to remove.
     */
    public void remove(T object) {
        final int position = getPosition(object);
        mObjects.remove(object);
        notifyItemRemoved(position);
    }

    /**
     * Sorts the content of this adapter using the specified comparator.
     *
     * @param comparator The comparator used to sort the objects contained in this adapter.
     */
    public void sort(Comparator<? super T> comparator) {
        Collections.sort(mObjects, comparator);
        notifyItemRangeChanged(0, getItemCount());
    }
}

Source: https://gist.github.com/passsy/f8eecc97c37e3de46176

Answer 2

Thanks Jared this helped me a lot

So finally the BaseRecyclerAdapter looks like this:

public abstract class BaseRecyclerAdapter<VH extends RecyclerView.ViewHolder>
    extends RecyclerView.Adapter<VH>{

public static class VH extends RecyclerView.ViewHolder{

    public VH (View v){
        super(v);
    }
}

public BaseRecyclerAdapter(RecyclerView rv){

}

public void setDataSet( String data) {
   //this is the special method added
}
}

And now you can override whatever method you like from RecyclerView.Adapter and implement the special method