java - llenar - La vista de reciclador no llena ningún dato en mi pantalla

llenar un recyclerview con firebase

Question

Mi actividad principal muestra un RecyclerView vacío. Mi CardView no se muestra.

Los datos se almacenan en una base de datos de Firebase pero no se muestran por alguna razón.

También busqué en la web pero nada me ayudó. Probé todo lo que aparece en la web, así como en Stack Overflow.

MainActivity.java

public class MainActivity1 extends   AppCompatActivity {

private RecyclerView mQuestionList;

private CardView mCardVieww;

private DatabaseReference mDatabase;
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
private DatabaseReference mDatabaseUsers;
private LinearLayoutManager layoutManager;

private DatabaseReference mDatabaseCurrentUsers;

private  DatabaseReference mDatabaseLike;

private boolean mProcessLike = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main1);

    mAuth=FirebaseAuth.getInstance();

    mAuthListener=new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {

            if (firebaseAuth.getCurrentUser()== null){

                Intent loginIntent=new Intent(MainActivity1.this,LoginActivity.class);
                loginIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(loginIntent);
            }
        }
    };

    mDatabase= FirebaseDatabase.getInstance().getReference().child("Question");
    mDatabaseUsers=FirebaseDatabase.getInstance().getReference().child("Users");
    mDatabaseLike=FirebaseDatabase.getInstance().getReference().child("Likes");

    mDatabaseUsers.keepSynced(true);
    mDatabaseLike.keepSynced(true);
    mDatabase.keepSynced(true);


    mQuestionList=(RecyclerView) findViewById(R.id.question_list);
    layoutManager=new LinearLayoutManager(this);
    layoutManager.setReverseLayout(true);
    layoutManager.setStackFromEnd(true);

    mQuestionList.setHasFixedSize(true);
    mQuestionList.setLayoutManager(layoutManager);


    checkUserExist();
}

@Override
protected void onStart() {
    super.onStart();

    mAuth.addAuthStateListener(mAuthListener);


   FirebaseRecyclerAdapter <Question,QuestionViewHolder> fireRecyclerAdapter = new FirebaseRecyclerAdapter <Question,QuestionViewHolder>(
            Question.class,
           R.layout.question,
            QuestionViewHolder.class,

            mDatabase
    ){


        @Override
        protected void populateViewHolder(QuestionViewHolder viewHolder,Question model, int position){

            final String post_key = getRef(position).getKey()

            viewHolder.setTitle(model.getTitle());
            viewHolder.setDesc(model.getDesc());
            viewHolder.setImage(getApplicationContext(),model.getImage());
            viewHolder.setUsername(model.getUsername());

            viewHolder.setLikeBtn(post_key);

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

                   // Toast.makeText(MainActivity1.this,post_key,Toast.LENGTH_LONG).show();

                    Intent singleQuestionIntent=new Intent(MainActivity1.this,QuestionSingleActivity.class);
                    singleQuestionIntent.putExtra("question_id",post_key);
                    startActivity(singleQuestionIntent);
                }
            });

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

                    mProcessLike = true;

                        mDatabaseLike.addValueEventListener(new ValueEventListener() {

                            @Override
                                public void onDataChange(DataSnapshot dataSnapshot) {
                                    if (mProcessLike) {

                                    if (dataSnapshot.child(post_key).hasChild(mAuth.getCurrentUser().getUid())) {

                                        mDatabaseLike.child(post_key).child(mAuth.getCurrentUser().getUid()).removeValue();
                                        mProcessLike = false;

                                    } else {

                                        mDatabaseLike.child(post_key).child(mAuth.getCurrentUser().getUid()).setValue("RandomValue");
                                        mProcessLike = false;
                                    }
                                }
                            }

                            @Override
                            public void onCancelled(DatabaseError databaseError) {

                            }
                        });
                    }

            });
        }


    };

    mQuestionList.setHasFixedSize(true);
    mQuestionList.setLayoutManager(layoutManager);

    mQuestionList.setAdapter(fireRecyclerAdapter);

    }
   //cgeck user exist or not
    private void checkUserExist() {

    if (mAuth.getCurrentUser() != null) {

        final String user_id = mAuth.getCurrentUser().getUid();

        mDatabaseUsers.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                if (!dataSnapshot.hasChild(user_id)) {

                    Intent setupIntent = new Intent(MainActivity1.this, SetupActivity.class);
                    setupIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    startActivity(setupIntent);
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
     }
    }



    public  static class QuestionViewHolder extends RecyclerView.ViewHolder{

    View mView;

    ImageButton mLikeBtn;

    DatabaseReference mDatabaseLike;
    FirebaseAuth mAuth;

    public QuestionViewHolder(View itemView) {

        super(itemView);

        mView=itemView;

        mLikeBtn=(ImageButton) mView.findViewById(R.id.likeBtn);

        mDatabaseLike= FirebaseDatabase.getInstance().getReference().child("Likes");

        mAuth=FirebaseAuth.getInstance();
        mDatabaseLike.keepSynced(true);
    }

    public void setLikeBtn(final String post_key){

        mDatabaseLike.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                if (dataSnapshot.child(post_key).hasChild(mAuth.getCurrentUser().getUid())){

                    mLikeBtn.setImageResource(R.mipmap.thumb_grey);
                }else{
                    mLikeBtn.setImageResource(R.mipmap.thumb_grey);
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    }

    public void setTitle(String title){
        TextView post_title=(TextView) mView.findViewById(R.id.post_title);
        post_title.setText(title);

    }

    public void setDesc(String desc){
        TextView post_desc=(TextView) mView.findViewById(R.id.post_desc);
        post_desc.setText(desc);
    }

    public void setUsername(String username){
        TextView post_username=(TextView) mView.findViewById(R.id.post_username);
        post_username.setText(username);
    }

  public void setImage(final Context ctx, final String image){

        final ImageView post_image=(ImageView) mView.findViewById(R.id.post_image);
       //Picasso.with(ctx).load(image).into(post_image);

        Picasso.with(ctx).load(image).networkPolicy(NetworkPolicy.OFFLINE).into(post_image, new Callback() {
            @Override
            public void onSuccess() {

            }
            @Override
            public void onError() {
                Picasso.with(ctx).load(image).into(post_image);

            }
        });
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main_menu,menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if(item.getItemId()==R.id.action_add){

        startActivity(new Intent(MainActivity1.this,PostActivity.class));
    }

    if(item.getItemId()==R.id.action_logout){

        logout();
    }

    if(item.getItemId()==R.id.action_Qp){

        startActivity(new Intent(MainActivity1.this,MainActivity2.class));
    }

    return super.onOptionsItemSelected(item);
}

private void logout() {
    mAuth.signOut();
}
}

Question.java

 public class Question {

private CardView mCardView;
private  String title;
private  String desc;
private  String image;
private String username;


public Question(){
}

public Question(String title, String desc, String image,String username) {

    this.title = title;
    this.desc = desc;
    this.image = image;
    this.username = username;
}
public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

public String getDesc() {
    return desc;
}

public void setDesc(String desc) {
    this.desc = desc;
}

public String getImage() {
    return image;
}

public void setImage(String image) {
    this.image = image;
}

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}
}

activity_main1.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout 

xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.akhil.rtmnuforum.MainActivity1">

<android.support.v7.widget.RecyclerView

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

 </LinearLayout>

question.xml

    <?xml version="1.0" encoding="utf-8"?>

 <android.support.v7.widget.CardView

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:id="@+id/cardview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="20dp"
android:visibility="visible"
tools:context="com.example.akhil.rtmnuforum.MainActivity1">


 <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/post_image"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true"
        android:scaleType="centerCrop"
        android:src="@mipmap/add_btn" />

    <TextView
        android:id="@+id/post_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="15dp"
        android:text="Post Title Goes here"
        android:textSize="16dp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/post_desc"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="15dp"
        android:paddingLeft="15dp"
        android:paddingRight="15dp"
        android:text="Question Description Goes here" />

    <TextView
        android:id="@+id/post_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="15dp"
        android:paddingLeft="15dp"
        android:paddingRight="15dp"
        android:text="username"
        android:textSize="12dp"
        android:textStyle="bold" />

    <ImageButton
        android:id="@+id/likeBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:background="@color/cardview_light_background"
        app:srcCompat="@mipmap/ic_thumb_up_black_24dp" />
</LinearLayout>

</android.support.v7.widget.CardView>