android - 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. E.g.

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