java - Recycler View不显示从Firestore数据库获取的数据

我正在从Firestore数据库中获取一些数据，并将其显示在RecyclerView中。我可以通过Log.d()语句将数据提取到应用程序中。但是，数据不会出现在RecyclerView中。

我的MainActivity.java：

public class MainActivity extends AppCompatActivity {

FirebaseFirestore db;
List<MenuItem> foodList;
RecyclerView menulist;
MenuAdapter madap;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    CollectionReference foodRef= db.collection("Food");

    foodList = new ArrayList<>();
    madap = new MenuAdapter(foodList);
    menulist = (RecyclerView)findViewById(R.id.listview);
    menulist.setHasFixedSize(true);
    menulist.setLayoutManager(new LinearLayoutManager(this));
    menulist.setAdapter(madap);

    db.collection("Food").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) {
            if (task.isSuccessful()){
                for (QueryDocumentSnapshot doc : task.getResult())
                {
                   MenuItem mi = doc.toObject(MenuItem.class);
                   foodList.add(mi);

                }
                madap.notifyDataSetChanged();
            }
        }
    });


}

我的activity_main.xml：

 <?xml version="1.0" encoding="utf-8"?>
 <androidx.constraintlayout.widget.ConstraintLayout
 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:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="#f0ead6"
 tools:context=".MainActivity">

<TextView
    android:id="@+id/textView9"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="28dp"
    android:layout_marginTop="132dp"
    android:text="Please select what you would like to eat"
    android:textSize="20sp"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<TextView
    android:id="@+id/textView6"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="172dp"
    android:layout_marginTop="70dp"
    android:text="Menu."
    android:textColor="#000"
    android:textSize="24sp"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/listview"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="16dp"
    android:layout_marginTop="186dp"
    android:layout_marginEnd="355dp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

我的MenuAdapter.java：

 public class MenuAdapter extends RecyclerView.Adapter<MenuAdapter.ViewHolder> {
 public List<MenuItem> foodList;
 public MenuAdapter(List<MenuItem> foodList){
        this.foodList= foodList;
 }

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

 }

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

     holder.mdof.setText(foodList.get(position).getDescof());
     holder.mnof.setText(foodList.get(position).getNameof());
     holder.mpof.setText(foodList.get(position).getPriceof());

 }

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

 public  class ViewHolder extends RecyclerView.ViewHolder{
     View mView;
     public TextView mnof, mpof, mdof;

     public ViewHolder (View itemView){
         super(itemView);
         mView=itemView;
         mnof= mView.findViewById(R.id.nof);
         mpof= mView.findViewById(R.id.pof);
         mdof= mView.findViewById(R.id.dof);
     }}}

最后是MenuItem.java类：

public class MenuItem {

public MenuItem(){}
public MenuItem(String nameof, String priceof, String descof) {
    this.nameof = nameof;
    this.priceof = priceof;
    this.descof = descof;
}

public String getNameof() {
    return nameof;
}

public void setNameof(String nameof) {
    this.nameof = nameof;
}

public String getPriceof() {
    return priceof;
}

public void setPriceof(String priceof) {
    this.priceof = priceof;
}

public String getDescof() {
    return descof;
}

public void setDescof(String descof) {
    this.descof = descof;
}

String nameof, priceof,descof;

}

关于此的任何评论将是有帮助的。没有错误，任何崩溃或异常。

最佳答案

您需要告诉适配器，您已经使用以下命令在列表中添加了数据


yourAdapter.notifyDataSetChanged（）


在您的情况下，调用是从firestore异步的，因此在添加项循环完成后添加notify

db.collection("Food").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) {
            if (task.isSuccessful()){
                for (QueryDocumentSnapshot doc : task.getResult())
                {
                   MenuItem mi = doc.toObject(MenuItem.class);
                   foodList.add(mi);

                }
                madap.notifyDataSetChanged()
                Log.d("Firelog","The XML file has issues.");
            }
        }
    });