как исправить "Попытка вызвать виртуальный метод"

Question

У меня есть эта плавающая кнопка действия, которая откроет диалоговое окно, где список предметов в программе recyclerView.но я получаю эту ошибку «Попытка вызвать виртуальный метод» void androidx.recyclerview.widget.RecyclerView.setLayoutManager (androidx.recyclerview.widget.RecyclerView $ LayoutManager) 'для ссылки на пустой объект "

Это мойадаптер:

public class UpdateListAdapter extends 
RecyclerView.Adapter<UpdateListAdapter.ViewHolder> {

public List<String> fileDoneList;
public List<String> fileNameList;

public UpdateListAdapter(List<String>fileNameList,List<String>fileDoneList){
    this.fileNameList = fileNameList;
    this.fileDoneList = fileDoneList;
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.popup_list_items,parent,false);
    return new ViewHolder(v);
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {

    String fileName = fileNameList.get(position);
    holder.fileNameView.setText(fileName);
}

@Override
public int getItemCount() {
    return fileNameList.size();
}

public class ViewHolder extends RecyclerView.ViewHolder{
    View mView;

    public TextView fileNameView;
    public ImageView fileDoneView;

    public ViewHolder(View itemView){
        super(itemView);

        mView = itemView;


        fileNameView = (TextView) mView.findViewById(R.id.post_fileType);
        fileDoneView = (ImageView) mView.findViewById(R.id.post_file_status);
       }
     } 
  }

это мои popup_list_items:

<RelativeLayout 
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_height="wrap_content"
   android:layout_width="match_parent">

<LinearLayout
   android:orientation="horizontal"
   android:padding="10dp"
   android:weightSum="10"
   android:layout_alignParentTop="true"
   android:layout_centerHorizontal="true"
   android:layout_width="match_parent"
   android:layout_height="wrap_content">

<ImageView
    android:id="@+id/post_file_icon"
    android:src="@mipmap/file_icon"
    android:layout_width="40dp"
    android:layout_height="40dp">
</ImageView>

<TextView
    android:id="@+id/post_fileType"
    android:layout_width="wrap_content"
    android:gravity="center_vertical"
    android:text="Filename.type"
    android:layout_weight="6"
    android:layout_height="match_parent">
</TextView>

<ImageView
    android:id="@+id/post_file_status"
    android:layout_width="20dp"
    android:layout_height="20dp"
    android:layout_gravity="center_vertical"
    android:layout_weight="2"
    android:src="@mipmap/progress">
</ImageView>

</LinearLayout>

</RelativeLayout>

это мой xml с recyclerView2

<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:orientation="vertical"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
 android:layout_width="wrap_content"
 android:layout_height="wrap_content">
<de.hdodenhof.circleimageview.CircleImageView
    android:id="@+id/post_userimg"
    android:layout_width="60dp"
    android:layout_height="60dp"
    android:layout_marginStart="28dp"
    android:layout_marginLeft="28dp"
    android:layout_marginTop="28dp"
    android:layout_marginEnd="51dp"
    android:layout_marginRight="51dp"
    android:src="@mipmap/user_profile"
    app:layout_constraintEnd_toStartOf="@+id/post_username"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

   <TextView
     android:id="@+id/post_username"
     android:layout_width="200dp"
     android:layout_height="45dp"
     android:textColor="@color/colorAccent"
     android:textAllCaps="true"
     android:textSize="18sp"
     android:layout_marginTop="40dp" />

  </LinearLayout>

  <EditText
    android:id="@+id/post_name"
    android:layout_width="200dp"
    android:layout_height="45dp"
    android:layout_marginTop="48dp"
    android:background="@drawable/round_post_txt"
    android:hint="Title"
    android:textColorHint="#000000"
    android:inputType="textPersonName" />

  <EditText
    android:id="@+id/post_tags"
    android:layout_width="200dp"
    android:layout_height="45dp"
    android:layout_marginTop="20dp"
    android:textColorHint="#000000"
    android:background="@drawable/round_post_txt"
    android:hint="Tags"
    android:inputType="textPersonName" />

  <EditText
    android:id="@+id/post_desc"
    android:layout_width="200dp"
    android:layout_height="45dp"
    android:layout_marginTop="20dp"
    android:textColorHint="#000000"
    android:background="@drawable/round_post_txt"
    android:hint="Description"
    android:inputType="textPersonName" />

  <ImageButton
    android:id="@+id/post_imgbtn"
    android:layout_width="200dp"
    android:layout_height="55dp"
    android:background="@android:color/transparent"
    android:scaleType="fitCenter"
    android:layout_gravity="center"
    android:layout_marginTop="28dp"
    android:src="@mipmap/upload_btn"/>

  <androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="10dp"
    android:layout_marginBottom="12dp">

  </androidx.recyclerview.widget.RecyclerView>

    <RelativeLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

     <Button
        android:id="@+id/post_button"
        android:layout_width="250dp"
        android:layout_height="45dp"
        android:layout_marginTop="54dp"
        android:background="@drawable/round"
        android:text="Submit"
        android:textAlignment="center"
        android:textColor="@color/colorAccent"
        android:textSize="18sp"
        android:layout_marginBottom="32dp"/>

     <ProgressBar
        android:id="@+id/post_progressBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/post_button"
        android:layout_alignLeft="@+id/post_button"
        android:layout_alignTop="@+id/post_button"
        android:layout_alignEnd="@+id/post_button"
        android:layout_alignRight="@+id/post_button"
        android:layout_alignBottom="@+id/post_button"
        android:layout_marginStart="97dp"
        android:layout_marginLeft="97dp"
        android:layout_marginTop="-2dp"
        android:layout_marginEnd="105dp"
        android:layout_marginRight="105dp"
        android:layout_marginBottom="0dp" />
   </RelativeLayout>


  </LinearLayout>

этоэто: где ошибка, я должен добавить снимок экрана также:

  @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home2);
    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    mAuth = FirebaseAuth.getInstance();
    currentUser = mAuth.getCurrentUser();
    mButton = (ImageButton) findViewById(R.id.post_imgbtn);
    mUploadList = (RecyclerView) findViewById(R.id.recyclerView2);

    fileNameList = new ArrayList<>();
    fileDoneList = new ArrayList<>();

    updateListAdapter = new UpdateListAdapter(fileNameList, fileDoneList);


    mUploadList.setLayoutManager(new LinearLayoutManager(this));
    mUploadList.setHasFixedSize(true);
    mUploadList.setAdapter(updateListAdapter);

    inipopup();



    mButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            CheckandRequestForPermission();


        }
    });

    FloatingActionButton fab = findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
           popupAddPost.show();
        }
    });
    DrawerLayout drawer = findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    getSupportFragmentManager().beginTransaction().replace(R.id.container,new HomeFragment()).commit();

    UpdateNavHeader();



}