Daten werden beim Laden von Firebase nicht in RecyclerView geladen

Question

Ich versuche, Daten aus der Firebase-Datenbank abzurufen, aber in meinem RecyclerView wird nichts geladen. Unten ist meine MainActivity.java. Ich weiß nicht, wo ich falsch gelaufen bin.

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 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<ModelClass> movies_; 
    public Context c; 
    private LinearLayoutManager linearLayoutManager; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     movies_ = new ArrayList<ModelClass>(); 

     recyclerView =(RecyclerView) findViewById(R.id.recyclerview); 

     linearLayoutManager = new LinearLayoutManager(this); 
     recyclerView.setLayoutManager(linearLayoutManager); 
     mRef = FirebaseDatabase.getInstance().getReferenceFromUrl("https://askdoctor-546bf.firebaseio.com/"); 




     mRef.child("Name").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); 



     } 

    } 

} 

Dann hier ist meine Adapter-Klasse.

package oerrride.we.huzykamz.testingappfirebase; 

import android.content.Context; 
import android.support.v7.widget.RecyclerView; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 

import java.util.ArrayList; 
import java.util.List; 

/** 
* Created by HUZY_KAMZ on 9/16/2016. 
*/ 
public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> { 


    protected Context c; 
    List<ModelClass> movies; 

    public MyAdapter(Context c, List<ModelClass> 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 null; 
    } 

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

     holder.name.setText(movies.get(position).getName()); 


    } 

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

Und hier ist meine POJO-Klasse.

[package oerrride.we.huzykamz.testingappfirebase; 

/** 
* Created by HUZY_KAMZ on 9/16/2016. 
*/ 
public class ModelClass { 

    private String name; 


    public ModelClass(){} 


    public ModelClass(String name) { 
     this.name = name; 
    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

Dies ist meine Konsole. Dies ist die Daten, die ich abrufen möchten:

Answer 1

in Ihrem Adapter Klasse Sie null zurückkehren;

Rückgabe Ihres Halterobjekts;

return holder; 

statt

return null; 

wie

@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; 
    }