FirelerView的Firebase数据仅显示一个项目

我正在从firebase检索数据并尝试在回收站视图中显示，每件事情都很好，但它只显示列表中的一个项目（共有14项）

如果您不理解这个问题，请发表评论

这是我从firebase获取数据快照的主要活动

public class cakes_activity extends AppCompatActivity {
RecyclerView recyclerView;
ArrayList<Data> listdata;
private DatabaseReference mref;
private  NorthAdaptor north;
private final Context context = this;


public int counter = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_cakes);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    EditText editText = (EditText) findViewById(R.id.editText) ;
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    //FIREBASE
    recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    mref= FirebaseDatabase.getInstance().getReference("Cakes");
    mref.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            Data data = dataSnapshot.getValue(Data.class);
            listdata = new ArrayList<>();
            listdata.add(data);
            north = new NorthAdaptor(context,listdata);
            recyclerView.setLayoutManager(new LinearLayoutManager(context));
            recyclerView.hasFixedSize();
            recyclerView.setAdapter(north);

        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {



        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {



        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {



        }

        @Override
        public void onCancelled(DatabaseError databaseError) {



        }
    });

}

以下代码是我的适配器类：

public class NorthAdaptor extends RecyclerView.Adapter<NorthAdaptor.NorthHolder> {
    private LayoutInflater inflater;
    ArrayList<Data> northy;

    public NorthAdaptor(Context context,ArrayList<Data> northy)
    {
        inflater=LayoutInflater.from(context);
        this.northy=northy;

    }
    public NorthHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.each_item,parent,false);
        NorthHolder holder = new NorthHolder(view);
        return holder;

    }

    @Override
    public void onBindViewHolder(NorthHolder holder, int position) {
        holder.text2.setText(northy.get(position).getName());
        holder.text3.setText("₹."+northy.get(position).getRS());

    }

    @Override
    public int getItemCount() {

        return northy.size();
    }
    class NorthHolder extends RecyclerView.ViewHolder implements View.OnClickListener
    {

        TextView text,text2,text3;
        ImageView img;
        private final Context context;
        public NorthHolder(View itemview)
        {
            super(itemview);
            context = itemView.getContext();
            CardView card = (CardView) itemView.findViewById(R.id.card);
            text3=(TextView)itemView.findViewById(R.id.Rs);
            text2 = (TextView) itemView.findViewById(R.id.itemtext2);
            img = (ImageView) itemView.findViewById(R.id.itemimage);
            card.setOnClickListener(this);

        }
        @Override
        public void onClick(View view){
            Toast.makeText(
                    cakes_activity.this,
                    "Your message here",
                    Toast.LENGTH_SHORT
            ).show();

        }
    }
}

这是我的java类来存储从firebase收到的数据

public class Data {
private String ID,Name,image,RS;
public Data(){

}

public Data(String ID, String Name, String image, String RS) {
    this.ID = ID;
    this.Name = Name;
    this.image= image;
    this.RS = RS;
}

public String getId() {
    return ID;
}
public String getRS() {
    return RS;
}

public void setId(String id) {

    this.ID = id;
}

public String getName() {
    return Name;
}

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

public String getimage() {
    return image;
}

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

}