我无法在android的主要活动中访问其他课程

Question

问题：我想在我的主要活动中实现RecyclerView，但是当我想为此设置适配器时，编译器向我提供红线错误。我无法在android的主要活动中访问另一个类：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">

<android.support.v7.widget.RecyclerView
    android:id="@+id/recycler"
 android:layout_width="match_parent"
    android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>

</LinearLayout>

MainActivity.java

package com.example.mypc.recyclerview;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import  android.widget.*;
public class MainActivity extends AppCompatActivity {
RecyclerView rv;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    rv=(RecyclerView)findViewById(R.id.recycler);
    rv.setLayoutManager(new LinearLayoutManager(this));
    String [] lang= 
   {"Hindi","English","Gujarati","Marathi","Punjabi","Tamil","Telgu"};
    rv.setAdapter(new ***RecyclerAdapter***(lang));      //Here comes the 
   //error
    }

}

layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:orientation="horizontal"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content">

<ImageView
    android:id="@+id/img"
    android:layout_width="82dp"
    android:layout_height="match_parent"
    android:src="@mipmap/ic_launcher"
    tools:layout_editor_absoluteY="35dp" />

<TextView
    android:id="@+id/tv"
    android:layout_width="627dp"
    android:layout_height="match_parent"
    android:text="@string/app_name" />
</LinearLayout>

RecyclerAdapter.java

import android.support.annotation.NonNull;
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 com.example.mypc.recyclerview.MainActivity;
import com.example.mypc.recyclerview.R;

import java.util.zip.Inflater;

public class RecyclerAdapter extends 
RecyclerView.Adapter<RecyclerAdapter.MyClass>{

String[] arr;
public RecyclerAdapter(String []arr) {
    this.arr=arr;
    }

@NonNull
@Override
public MyClass onCreateViewHolder( ViewGroup viewGroup, int i) {
    LayoutInflater inflater=LayoutInflater.from(viewGroup.getContext());
    View view=inflater.inflate(R.layout.list,viewGroup,false);
  return  new MyClass(view);


}


@Override
public void onBindViewHolder(@NonNull MyClass viewHolder, int i) {
    String title=arr[i];
    viewHolder.tv.setText(title);
}

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


public class MyClass extends RecyclerView.ViewHolder{

ImageView img;
 TextView tv;
    public MyClass(@NonNull View itemView) {
        super(itemView);
        img=(ImageView) itemView.findViewById(R.id.img);
        tv=(TextView) itemView.findViewById(R.id.tv);
    }
}
}