Ошибка NPE, help

Question

12-20 16:51:39.672 6469-6469/com.evgeniy.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
                                                                         Process: com.evgeniy.myapplication, PID: 6469
                                                                         java.lang.NullPointerException
                                                                             at com.evgeniy.myapplication.MainActivity$1.onClick(MainActivity.java:51)
                                                                             at android.view.View.performClick(View.java:4438)
                                                                             at android.view.View$PerformClick.run(View.java:18422)
                                                                             at android.os.Handler.handleCallback(Handler.java:733)
                                                                             at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                             at android.os.Looper.loop(Looper.java:136)
                                                                             at android.app.ActivityThread.main(ActivityThread.java:5017)
                                                                             at java.lang.reflect.Method.invokeNative(Native Method)
                                                                             at java.lang.reflect.Method.invoke(Method.java:515)
                                                                             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
                                                                             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
                                                                             at dalvik.system.NativeStart.main(Native Method)

Помогите исправить, не кидайтесь сразу, я прочитал про эту ошибку и как исправить, ничего не вышло. Знаю что распространенная ошибка, помогите пожалуйста

UPD. MainActivity

package com.evgeniy.myapplication;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;


/**
 * Copyright (c) 2017.
 * All Rights Reserved.
 * <p>
 * Author: Pugachev Evgeniy <epygachovs26@mail.ru>
 * Date:   21.12.17
 */

public class MainActivity extends AppCompatActivity {
    static class Item {
        String name;
        int pricee;

        Item(String name, int pricee) {
            this.name = name;
            this.pricee = pricee;
        }
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final EditText name = (EditText) findViewById(R.id.name);
        final EditText pricee = (EditText) findViewById(R.id.pricee);
        final Button add = (Button) findViewById(R.id.add);
        final ListView items = (ListView) findViewById(R.id.items);
        final ItemsAdapter adapter = new ItemsAdapter();

        items.setAdapter(adapter);
        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                adapter.add(new Item(name.getText().toString(), Integer.valueOf(pricee.getText().toString())));
            }
        });
    }

    private class ItemsAdapter extends ArrayAdapter<Item> {
        ItemsAdapter() {
            super(MainActivity.this, R.layout.item);
        }

        @NonNull
        @Override
        public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
            final View view = getLayoutInflater().inflate(R.layout.item, null);
            final Item item = getItem(position);
            ((TextView) view.findViewById(R.id.name)).setText(item.name);
            ((TextView) view.findViewById(R.id.pricee)).setText(String.valueOf(item.pricee));
            return view;
        }
    }
}

Строка с ошибкой:

   adapter.add(new Item(name.getText().toString(), Integer.valueOf(pricee.getText().toString())));