尽管没有编译错误，但项目仍未显示在我的RecyclerView中

Question

我设法将内容的数据存储在Firebase数据库中。但是，这些项目根本没有显示在recyclerView上。我认为loadData()部分可能存在问题，因为我曾经遇到过一些关于适配器必须事先声明为抽象的问题。但是，我已经修改了代码。

DiaryActivity.java

package com.shiminu1521462c.fyp_2;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Context;
import android.content.Intent;
import android.content.res.Resources;
import android.os.Bundle;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.google.firebase.database.ValueEventListener;

public class DiaryActivity extends AppCompatActivity {

    private FirebaseAuth mAuth;
    private DatabaseReference fNotesDatabase;

    private RecyclerView mNotesList;
    private GridLayoutManager gridLayoutManager;
    private DatabaseReference noteRef;
    private Toolbar mToolbar;


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

        mToolbar = (Toolbar) findViewById(R.id.main_chat_toolbar);
        setSupportActionBar(mToolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setTitle("Diary");

        mNotesList = (RecyclerView) findViewById(R.id.notes_list);
        gridLayoutManager = new GridLayoutManager(this, 2, GridLayoutManager.VERTICAL, false);

        mNotesList.setHasFixedSize(true);
        mNotesList.setLayoutManager(gridLayoutManager);
        mNotesList.addItemDecoration(new GridSpacingDecoration(2, dpToPx(10), true));


        mAuth = FirebaseAuth.getInstance();
        if (mAuth.getCurrentUser() != null) {
            fNotesDatabase = FirebaseDatabase.getInstance().getReference().child("Notes").child(mAuth.getCurrentUser().getUid());
        }
        loadData();
    }

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

    }


    private void loadData() {
        FirebaseRecyclerOptions options =
                new FirebaseRecyclerOptions.Builder<NoteModel>()
                        .setQuery(fNotesDatabase, NoteModel.class)
                        .build();
        FirebaseRecyclerAdapter<NoteModel, NoteViewHolder> adapter
                = new FirebaseRecyclerAdapter<NoteModel, NoteViewHolder>(options) {

            @Override
            protected void onBindViewHolder(@NonNull final NoteViewHolder viewHolder, int position, @NonNull NoteModel model) {

                final String noteId = getRef(position).getKey();

                fNotesDatabase.child(noteId).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                        if (dataSnapshot.hasChild("title") && dataSnapshot.hasChild("timestamp")) {

                            String title = dataSnapshot.child("title").getValue().toString();
                            String timestamp = dataSnapshot.child("timestamp").getValue().toString();

                            viewHolder.setNoteTitle(title);
                            //viewHolder.setNoteTime(timestamp);

                            GetTimeAgo getTimeAgo = new GetTimeAgo();
                            viewHolder.setNoteTime(getTimeAgo.getTimeAgo(Long.parseLong(timestamp), getApplicationContext()));

                            viewHolder.noteCard.setOnClickListener(new View.OnClickListener() {
                                @Override
                                public void onClick(View view) {
                                    Intent intent = new Intent(DiaryActivity.this, DiaryNewNoteActivity.class);
                                    intent.putExtra("noteId", noteId);
                                    startActivity(intent);
                                }
                            });
                        }
                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {
                    }
                });
            }
            @NonNull
            @Override
            public NoteViewHolder onCreateViewHolder(@NonNull ViewGroup viewHolder, int i) {

                View view = LayoutInflater.from(viewHolder.getContext()).inflate(R.layout.activity_diary, viewHolder, false);
                NoteViewHolder viewHolder1 = new NoteViewHolder(view);
                return viewHolder1;
            }
        };
        mNotesList.setAdapter(adapter);
    }



            @Override
            public boolean onCreateOptionsMenu(Menu menu) {
                super.onCreateOptionsMenu(menu);

                getMenuInflater().inflate(R.menu.diary_menu, menu);

                return true;
            }

            @Override
            public boolean onOptionsItemSelected(MenuItem item) {
                super.onOptionsItemSelected(item);

                switch (item.getItemId()) {
                    case R.id.diary_new_note_btn:
                        Intent newIntent = new Intent(DiaryActivity.this, DiaryNewNoteActivity.class);
                        startActivity(newIntent);
                        break;

                    case android.R.id.home:
                        Intent myIntent = new Intent(DiaryActivity.this, DashboardActivity.class);
                        startActivity(myIntent);
                        break;
                }

                return true;
            }


            /**
             * Converting dp to pixel
             */
            private int dpToPx(int dp) {
                Resources r = getResources();
                return Math.round(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, r.getDisplayMetrics()));
            }
        }

Note.java

package com.shiminu1521462c.fyp_2;

import com.google.firebase.database.Exclude;

public class Note {
    private String documentId;
    private String title;
    private String description;
    private int priority;

    public Note(){
        //public no-arg constructor needed
    }

    public Note(String title, String description, int priority){
        this.title = title;
        this.description = description;
        this.priority = priority;
    }

    @Exclude
    public String getDocumentId() {
        return documentId;
    }

    public void setDocumentId(String documentId) {
        this.documentId = documentId;
    }

    public String getTitle(){
        return title;
    }

    public String getDescription(){
        return description;
    }

    public int getPriority() {
        return priority;
    }

    public void setPriority(int priority) {
        this.priority = priority;
    }
}

NoteModel.java

package com.shiminu1521462c.fyp_2;

public class NoteModel {
    public String noteTitle;
    public String noteTime;

    public NoteModel() {

    }

    public NoteModel(String noteTitle, String noteTime) {
        this.noteTitle = noteTitle;
        this.noteTime = noteTime;
    }

    public String getNoteTitle() {
        return noteTitle;
    }

    public void setNoteTitle(String noteTitle) {
        this.noteTitle = noteTitle;
    }

    public String getNoteTime() {
        return noteTime;
    }

    public void setNoteTime(String noteTime) {
        this.noteTime = noteTime;
    }
}

NoteViewHolder.java

package com.shiminu1521462c.fyp_2;

import android.view.View;
import android.widget.TextView;


import androidx.cardview.widget.CardView;
import androidx.recyclerview.widget.RecyclerView;

public class NoteViewHolder extends RecyclerView.ViewHolder {

    View mView;

    TextView textTitle, textTime;
    CardView noteCard;

    public NoteViewHolder(View itemView) {
        super(itemView);

        mView = itemView;

        textTitle = mView.findViewById(R.id.note_title);
        textTime = mView.findViewById(R.id.note_time);
        noteCard = mView.findViewById(R.id.note_card);

    }

    public void setNoteTitle(String title) {
        textTitle.setText(title);
    }

    public void setNoteTime(String time) {
        textTime.setText(time);
    }

}

activity_diary.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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:background="@drawable/background"
    tools:context=".DiaryActivity">

    <androidx.appcompat.widget.Toolbar
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/main_chat_toolbar"
        android:background="@color/colorPrimary"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
    </androidx.appcompat.widget.Toolbar>

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/notes_list"
        android:layout_below="@id/main_chat_toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    </androidx.recyclerview.widget.RecyclerView>


</RelativeLayout>

single_note_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="horizontal"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:minWidth="156dp">

    <androidx.cardview.widget.CardView
        android:id="@+id/note_card"
        android:layout_width="match_parent"
        android:layout_height="128dp"
        android:layout_margin="5dp"
        android:clickable="true"
        android:focusable="true"
        android:maxHeight="128dp"
        android:minHeight="128dp"
        app:contentPadding="5dp">

        <LinearLayout
            android:layout_width="156dp"
            android:layout_height="match_parent"
            android:minWidth="156dp"
            android:orientation="vertical">

            <TextView
                android:id="@+id/note_title"
                android:layout_width="156dp"
                android:layout_height="0dp"
                android:layout_marginBottom="10dp"
                android:layout_weight="1"
                android:ellipsize="end"
                android:maxLines="5"
                android:text="Note Title"
                />

            <TextView
                android:id="@+id/note_time"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:ellipsize="end"
                android:maxLines="1"
                android:text="Updated time"
                android:textSize="12sp" />
        </LinearLayout>

    </androidx.cardview.widget.CardView>

</LinearLayout>