Cant call a custom added method into my adapter (extends RecyclerView.Adapter<MyAdapter.ViewHolder>)

Question

Thank you in advance and dont be very hard with me, it is my first question.

I was trying to add a new item to my recyclerView through the adapter by declaring a method in my adapter called addItem(String newItem) Then I tried to call this method when the floating button is clikced and the problem is that the method does not even appear when i hit cntrl+space and if i write it down it gets on red. I have already tried to rebuild the project and nothing changes. ¿Any ideas about how to solve it?

MainActivity class

package com.example.sakur.recyclerviewapp;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

public class MainActivity extends AppCompatActivity {
    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    private FloatingActionButton mFloatingActionButton;
    private List<String> recyclerItems = Collections.emptyList();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        recyclerItems = new ArrayList<>();
        recyclerItems.add("First item");
        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
        mRecyclerView.setHasFixedSize(true);
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mAdapter = new MyAdapter(recyclerItems);
        mRecyclerView.setAdapter(mAdapter);
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.floating_action_button);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String itemNuevo = "New Card";
                mAdapter.addItem(itemNuevo);
                Snackbar.make(view, "Item added successfully", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();

            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

and the MyAdapter class

    package com.example.sakur.recyclerviewapp;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

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

/**
 * Created by Sakur on 19/12/2015.
 */
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    private List<String> mDataset= Collections.emptyList();

    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder



    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(List<String> myDataset) {
        mDataset = myDataset;
    }
    public void addItem(String newItem){
        mDataset.add(newItem);
        notifyDataSetChanged();
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                   int viewType) {
        // create a new view
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_card, parent, false);
        // set the view's size, margins, paddings and layout parameters
        //...
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element
        holder.mTextView.setText(mDataset.get(position));

    }

    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {

        return mDataset.size();
    }
    public static class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        public TextView mTextView;
        public ImageView mImageView;
        public ViewHolder(View v) {
            super(v);
            mTextView = (TextView) v.findViewById(R.id.text_card);
        }


    }
}

Answer 1

addItem(String) is not a method of RecyclerView.Adapter , but of your MyAdapter subclass. Obviously, RecyclerView.Adapter has no knowledge of the existence neither of your MyAdapter nor of your addItem(String) .

you can either change

private RecyclerView.Adapter mAdapter;

into

private MyAdapter mAdapter;

or cast mAdapter . Eg

 if (mAdater instanceof MyAdapter) {
     ((MyAdapter) mAdapter).addItem(...);
  }