如何使用FirebaseFirestore在安卓中创建动态水平回收视图？


<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />


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"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:text="Dynamic Horizontal Recycler View"
        android:textAlignment="center"
        android:textColor="@color/purple_500"
        android:textSize="15sp" />
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/idRVItems"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="40dp"
        android:background="@color/purple_500" />
LinearLayout>


public class DataModal {
    // variables for storing our image and name.
    private String name;
    private String imgUrl;
    public DataModal() {
        // empty constructor required for firebase.
    }
    // constructor for our object class.
    public DataModal(String name, String imgUrl) {
        this.name = name;
        this.imgUrl = imgUrl;
    }
    // getter and setter methods
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getImgUrl() {
        return imgUrl;
    }
    public void setImgUrl(String imgUrl) {
        this.imgUrl = imgUrl;
    }
}


xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:gravity="center"
    android:orientation="vertical">
    
    <ImageView
        android:id="@+id/idIVimage"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_margin="4dp"
        android:background="@color/white"
        android:backgroundTint="@color/white"
        android:padding="3dp" />
    
    <TextView
        android:id="@+id/idTVtext"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="2dp"
        android:padding="3dp"
        android:text="Category Text"
        android:textAlignment="center"
        android:textColor="@color/white" />
LinearLayout>


import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
public class DataRVAdapter extends RecyclerView.Adapter<DataRVAdapter.ViewHolder> {
    private ArrayList<DataModal> dataModalArrayList;
    private Context context;
    // constructor class for our Adapter
    public DataRVAdapter(ArrayList<DataModal> dataModalArrayList, Context context) {
        this.dataModalArrayList = dataModalArrayList;
        this.context = context;
    }
    @NonNull
    @Override
    public DataRVAdapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // passing our layout file for displaying our card item
        return new DataRVAdapter.ViewHolder(LayoutInflater.from(context).inflate(R.layout.image_rv_item, parent, false));
    }
    @Override
    public void onBindViewHolder(@NonNull DataRVAdapter.ViewHolder holder, int position) {
        // setting data to our views in Recycler view items.
        DataModal modal = dataModalArrayList.get(position);
        holder.courseNameTV.setText(modal.getName());
        // we are using Picasso to load images
        // from URL inside our image view.
        Picasso.get().load(modal.getImgUrl()).into(holder.courseIV);
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // setting on click listener
                // for our items of recycler items.
                Toast.makeText(context, "Clicked item is " + modal.getName(), Toast.LENGTH_SHORT).show();
            }
        });
    }
    @Override
    public int getItemCount() {
        // returning the size of array list.
        return dataModalArrayList.size();
    }
    public class ViewHolder extends RecyclerView.ViewHolder {
        // creating variables for our 
        // views of recycler items.
        private TextView courseNameTV;
        private ImageView courseIV;
        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            // initializing the views of recycler views.
            courseNameTV = itemView.findViewById(R.id.idTVtext);
            courseIV = itemView.findViewById(R.id.idIVimage);
        }
    }
}


import android.os.Bundle;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.QuerySnapshot;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
    private RecyclerView courseRV;
    private ArrayList<DataModal> dataModalArrayList;
    private DataRVAdapter dataRVAdapter;
    private FirebaseFirestore db;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // initializing our variables.
        courseRV = findViewById(R.id.idRVItems);
        // initializing our variable for firebase 
        // firestore and getting its instance.
        db = FirebaseFirestore.getInstance();
        // creating our new array list
        dataModalArrayList = new ArrayList<>();
        courseRV.setHasFixedSize(true);
        // adding horizontal layout manager for our recycler view.
        courseRV.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
        // adding our array list to our recycler view adapter class.
        dataRVAdapter = new DataRVAdapter(dataModalArrayList, this);
        // setting adapter to our recycler view.
        courseRV.setAdapter(dataRVAdapter);
        loadrecyclerViewData();
    }
    private void loadrecyclerViewData() {
        db.collection("Data").get()
                .addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                    @Override
                    public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                        // after getting the data we are calling on success method
                        // and inside this method we are checking if the received 
                        // query snapshot is empty or not.
                        if (!queryDocumentSnapshots.isEmpty()) {
                            // if the snapshot is not empty we are hiding our
                            // progress bar and adding our data in a list.
                            List<DocumentSnapshot> list = queryDocumentSnapshots.getDocuments();
                            for (DocumentSnapshot d : list) {
                                // after getting this list we are passing that 
                                // list to our object class.
                                DataModal dataModal = d.toObject(DataModal.class);
                                // and we will pass this object class
                                // inside our arraylist which we have
                                // created for recycler view.
                                dataModalArrayList.add(dataModal);
                            }
                            // after adding the data to recycler view.
                            // we are calling recycler view notifyDataSetChanged
                            // method to notify that data has been changed in recycler view.
                            dataRVAdapter.notifyDataSetChanged();
                        } else {
                            // if the snapshot is empty we are 
                            // displaying a toast message.
                            Toast.makeText(MainActivity.this, "No data found in Database", Toast.LENGTH_SHORT).show();
                        }
                    }
                }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                // if we do not get any data or any error we are displaying 
                // a toast message that we do not get any data
                Toast.makeText(MainActivity.this, "Fail to get the data.", Toast.LENGTH_SHORT).show();
            }
        });
    }
}