title: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.database
body: <p>I am trying to retrieve data into a RecyclerView from Firebase Database but am experiencing this error  java.lang.NullPointerException: Attempt to invoke virtual method. <code>'com.google.firebase.database.DatabaseReference com.google.firebase.database.DatabaseReference.child(java.lang.String)' on a null object reference</code></p>
  
  <p>Below is my main activity class .</p>
  
  <pre><code>    package oerrride.we.huzykamz.testingappfirebase;
  
      import android.app.Dialog;
      import android.content.Context;
      import android.support.v7.app.AppCompatActivity;
      import android.os.Bundle;
      import android.support.v7.widget.LinearLayoutManager;
      import android.support.v7.widget.RecyclerView;
      import android.view.View;
      import android.widget.Button;
  
      import com.google.android.gms.common.GoogleApiAvailability;
      import com.google.android.gms.tasks.Task;
      import com.google.firebase.database.ChildEventListener;
      import com.google.firebase.database.DataSnapshot;
      import com.google.firebase.database.DatabaseError;
      import com.google.firebase.database.DatabaseReference;
      import com.google.firebase.database.FirebaseDatabase;
      import com.google.firebase.database.ValueEventListener;
  
      import java.util.ArrayList;
      import java.util.List;
  
  
      public class MainActivity extends AppCompatActivity {
  
          private Button but;
          private DatabaseReference mRef;
          private MyAdapter adapter;
          public RecyclerView recyclerView;
  
          public List&lt;ModelClass&gt; movies_;
          public Context c;
          private LinearLayoutManager linearLayoutManager;
  
          private DatabaseReference mMovieRef =mRef.child("Name");
  
          @Override
          protected void onCreate(Bundle savedInstanceState) {
              super.onCreate(savedInstanceState);
              setContentView(R.layout.activity_main);
              movies_ = new ArrayList&lt;ModelClass&gt;();
  
              recyclerView =(RecyclerView) findViewById(R.id.recyclerview);
  
              linearLayoutManager = new LinearLayoutManager(this);
              recyclerView.setLayoutManager(linearLayoutManager);
              recyclerView.setHasFixedSize(true);
              mRef =  FirebaseDatabase.getInstance().getReferenceFromUrl("xxxxxxxxxxxxxxxxxxxxxx");
  
  
              mRef.addChildEventListener(new ChildEventListener() {
                  @Override
                  public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                      LoadData(dataSnapshot);
                  }
  
                  @Override
                  public void onChildChanged(DataSnapshot dataSnapshot, String s) {
                      LoadData(dataSnapshot);
                  }
  
                  @Override
                  public void onChildRemoved(DataSnapshot dataSnapshot) {
  
                  }
  
                  @Override
                  public void onChildMoved(DataSnapshot dataSnapshot, String s) {
  
                  }
  
                  @Override
                  public void onCancelled(DatabaseError databaseError) {
  
                  }
              });
  
  
  
  
          }
  
  
  
          public void LoadData (DataSnapshot dataSnapshot){
              for(DataSnapshot singlesnapshot :dataSnapshot.getChildren()){
                String taskTitle =singlesnapshot.getValue(String.class);
  
                  movies_.add(new ModelClass(taskTitle));
  
                  adapter = new MyAdapter(MainActivity.this, movies_);
                  recyclerView.setAdapter(adapter);
  
  
  
              }
  
          }
  
      }
  
  
  And this is my Adapter class .
  
  
  
  
  
  
  
  public class MyAdapter extends RecyclerView.Adapter&lt;MyViewHolder&gt; {
  
  
  
  
   protected   Context c;
      List&lt;ModelClass&gt; movies;
  
  public MyAdapter(Context c, List&lt;ModelClass&gt; movies) {
      this.c = c;
      this.movies = movies;
  }
  
  @Override
  public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
  
      View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_activity,parent,false);
      MyViewHolder holder = new MyViewHolder(v);
      return holder;
  }
  
  @Override
  public void onBindViewHolder(MyViewHolder holder, int position) {
  
      holder.name.setText(movies.get(position).getName());
    // PicassoClient.downloadImage(c,movies.get(position).getUrl(),holder.img);
  
  }
  
  @Override
  public int getItemCount() {
      return movies.size();
  }
  </code></pre>
  
  <p>}</p>
  
  <p>Below is my Console of Firebase database</p>
  
  <p><a href="http://i.stack.imgur.com/I4M0K.png" rel="nofollow">Firebase Console data am trying to fetch</a></p>