方法已定义（Android 接口）但仍未找到？

Question

I am following Head first's guide to Android development as a reference and trying to implement a recyclerview with cardview for noodle dishes.

I am currently implementing the click functionality as an interface separate from the adapter as recommended in the book; though I am not using fragments at the moment. The one problem is that the method setListener i have defined is not being found by my MainActivity.

The error is "cannot find symbol method setListener()". So, my method is acting as if it is undefined. Do you know how to why and how to fix this issues? Here is the code for MainActivity

package com.justin.android.foodapp;

import androidx.appcompat.app.A

public class MainActivity extends AppCompatActivity {

    private Noodles[] noodlesDataset = Noodles.noodles;
    private RecyclerView recyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager layoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //Log.i("MainActivity", "Hello World");

        // get the recycler view
        recyclerView = (RecyclerView) findViewById(R.id.noodleRecycler);

        // use a linear layout manager
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        //specify an adapter
        mAdapter = new MyAdapter(noodlesDataset);
        recyclerView.setAdapter(mAdapter);
        LinearLayoutManager layoutManager = new LinearLayoutManager(MainActivity.this);
        recyclerView.setLayoutManager(layoutManager);

        mAdapter.setListener(new MyAdapter.Listener(){
            public void onClick(int position) {
                Intent intent = new Intent(MainActivity.this, NoodleDetailActivity.class);
                intent.putExtra(NoodleDetailActivity.EXTRA_NOODLE_ID, position);
                (MainActivity.this).startActivity(intent);
            }
        });

    }
}

Here is my adapter code, in which i try to define the setListener method

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    private Noodles[] mDataset;
    private Listener listener;

    interface Listener {
        void onClick(int position);
    }

    // set listener to the implementation of given interface
    public void setListener(Listener listener) {
        this.listener = listener;
    }

    public static class MyViewHolder extends RecyclerView.ViewHolder {
        public CardView cardView;
        public TextView textView;
        public ImageView imageView;
        public MyViewHolder(View v) {
            super(v);
            cardView = v.findViewById(R.id.card_view);
            textView = v.findViewById(R.id.textView);
            imageView = v.findViewById(R.id.food_image);
        }
    }
    // contructor; pass the data from Java class Noodles to MyAdapter
    public MyAdapter(Noodles[] noodlesDataset) {
        mDataset = noodlesDataset;
    }

    @Override
    public int getItemCount() {
        return mDataset.length;
    }

    // create a new ViewHolder and place the views in layout my_text_view inside.
    @Override
    public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
                                                     int viewType) {
        // create a new view
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.my_text_view, parent, false);

        MyViewHolder vh = new MyViewHolder(v);
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(MyViewHolder holder, final int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element
        final CardView cardView = holder.cardView;
        holder.textView.setText(mDataset[position].getName());
        holder.imageView.setImageResource(mDataset[position].getImageResourceId());

        // when clicked, send an intent from cardview
        cardView.setOnClickListener(new View.OnClickListener() {
            @Override
            // if listener is present, call the implementation of onClick set by the parent
            public void onClick(View v) {
                if (listener != null) {
                    listener.onClick(position);
                }
            }

        });
    }

}

Answer 1

replace this

private RecyclerView.Adapter mAdapter;

with

public MyAdapter mAdapter; 

and also remove extra things and update like below

   private RecyclerView recyclerView;
      public MyAdapter mAdapter;


        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            //Log.i("MainActivity", "Hello World");

            // get the recycler view
            recyclerView = (RecyclerView) findViewById(R.id.noodleRecycler);


            //specify an adapter
            mAdapter = new MyAdapter(noodlesDataset);
  LinearLayoutManager layoutManager = new LinearLayoutManager(MainActivity.this);
            recyclerView.setAdapter(mAdapter);

            recyclerView.setLayoutManager(layoutManager);