我正在嘗試從 android studio 的 recyclerview 中的 firestore 中檢索數據，但得到空白頁面並且沒有錯誤我嘗試了很多方法但沒有工作

Question

抱歉，在 adavaced bcz 我是第一次問關於堆棧流的問題所以如果需要任何其他請讓我知道我的 firestore Collestion 就像這些 collection("user").document(currentUserId).collection("AddBlog").document我需要 AddBlog 文檔，最后我的 firestore 字段名稱與 model.java 變量相同

活動名稱代碼 Trial.java

package com.example.talkvirtual;

import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.auth.FirebaseAuth;
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 TrialActivity extends AppCompatActivity {
    RecyclerView recyclerView;
    ArrayList<Model> dataList;

    FirebaseFirestore db;
    FirebaseAuth mAuth;

    MyAdapter myAdapter;

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

        recyclerView = findViewById(R.id.recyclerViewTrial);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        dataList = new ArrayList<>();
        recyclerView.setAdapter(myAdapter);

        myAdapter = new MyAdapter(dataList,this);
        db = FirebaseFirestore.getInstance();
        mAuth= FirebaseAuth.getInstance();
        String currentUserId = mAuth.getCurrentUser().getUid();
        db.collection("user").document(currentUserId).collection("AddBlog").get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
            @Override
            public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                List<DocumentSnapshot> list = queryDocumentSnapshots.getDocuments();
                for (DocumentSnapshot d : list) {
                    Model model = d.toObject(Model.class);
                    dataList.add(model);
                }
                myAdapter.notifyDataSetChanged();
            }
        });
    }
}

適配器代碼 class 名稱 MyAdapter.java

package com.example.talkvirtual;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {


    public MyAdapter(ArrayList<Model> listblogProfile, Context context) {
        this.ListblogProfile = listblogProfile;
        this.context = context;
    }

    private ArrayList<Model> ListblogProfile;
  private Context context;


  //  private ShowActivity activity;

    @NonNull
    @Override
    public MyAdapter.MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.container_blog, parent, false);
        return new MyViewHolder(view);

    }

    @Override
    public void onBindViewHolder(@NonNull MyAdapter.MyViewHolder holder, int position) {
        Model model = ListblogProfile.get(position);

        holder.blogTitleTv.setText(model.getBlogTitle());
        holder.blogContentTv.setText(model.getBlogContent());
    }

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


    }

    public static class MyViewHolder extends RecyclerView.ViewHolder {
        private TextView blogTitleTv, blogContentTv;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            blogContentTv = itemView.findViewById(R.id.blogContentContainer);
            blogTitleTv = itemView.findViewById(R.id.getTitleContainer);

        }
    }
}

我的卡的代碼查看 xml 文件

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/layoutNote"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:foreground="?attr/selectableItemBackgroundBorderless"
    app:cardElevation="8dp"
    android:layout_margin="10dp"
    android:background="@color/light_dark">

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

        <TextView
            android:id="@+id/getTitleContainer"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Title"
            android:textColor="@color/textColor"
            android:textSize="24dp"
            android:textStyle="bold"
            android:padding="10dp"
            />

        <TextView
            android:id="@+id/blogContentContainer"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:maxHeight="100dp"
            android:textColor="@color/textColor"
            android:hint="Blog Content"
            android:textColorHint="@color/gray"
            android:textSize="20dp"
            android:padding="10dp"/>
    </LinearLayout>

</androidx.cardview.widget.CardView>

代碼 model class

  package com.example.talkvirtual;

public class Model {
    String blogTitle;
    String blogContent;
    String id;
    public Model(){}//empty constructor is neccessary firebase

    public Model(String blogTitle, String blogContent, String id) {
        this.blogTitle = blogTitle;
        this.blogContent = blogContent;
        this.id = id;
    }
    public String getBlogTitle() {
        return blogTitle;
    }

    public void setBlogTitle(String blogTitle) {
        this.blogTitle = blogTitle;
    }

    public String getBlogContent() {
        return blogContent;
    }

    public void setBlogContent(String blogContent) {
        this.blogContent = blogContent;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }


}

Answer 1

我認為有兩個錯誤

1.當你為recyclerview設置適配器時，你的適配器沒有有效值

2.您的數據是 null 因為您沒有向它添加任何成員以及適配器。

 db.collection("user").document(currentUserId).collection("AddBlog").get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
        @Override
        public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
            List<DocumentSnapshot> list =     queryDocumentSnapshots.getDocuments();
            for (DocumentSnapshot d : list) {
                Model model = d.toObject(Model.class);
                dataList.add(model);
            }
            myAdapter.notifyDataSetChanged();
        }
    });
  myAdapter = new MyAdapter(dataList,this);
  recyclerView.setAdapter(myAdapter);

我想這應該是工作。