无法从数据库中检索Post键和值。这是我第一次尝试使用FirebaseRecyclerAdapter从Firebase数据库中检索数据。但我不知道问题出在哪里。我也尝试调试，但编译器不会进入onCreateViewHolder或onBindViewHolder函数。但我完全按照FirebaseUI进行实时数据库参考。

NEWSFEEDBANK.JAVA

private FirebaseRecyclerAdapter<NewsFeed, NewsFeedViewHolder> adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_news_feed_bank);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    SharedPreferences sharedPreferences = getSharedPreferences("BankData", Context.MODE_PRIVATE);
    username = sharedPreferences.getString("UserName", "UserName");

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

    mDatabase = FirebaseDatabase.getInstance().getReference().child("Posts");
    mAuth = FirebaseAuth.getInstance();

    mAuthListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            if (mAuth.getCurrentUser() == null) {
                Intent loginIntent = new Intent(NewsFeedBank.this, Login.class);
                loginIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
                startActivity(loginIntent);
            }
        }
    };

    DisplayPosts();
}

private void DisplayPosts() {

    FirebaseRecyclerOptions<NewsFeed> options = new FirebaseRecyclerOptions.Builder<NewsFeed>().setQuery(mDatabase, NewsFeed.class).build();

    adapter = new FirebaseRecyclerAdapter<NewsFeed, NewsFeedViewHolder>(options) {
        @Override
        protected void onBindViewHolder(@NonNull NewsFeedViewHolder holder, int position, @NonNull NewsFeed model) {

          //  holder.title.setText(model.getTitle());
        //    holder.des.setText(model.getDesc());
            holder.usern.setText(model.getUsername());

        }

        @NonNull
        @Override
        public NewsFeedViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
            View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.card_items, viewGroup, false);
            NewsFeedViewHolder holder = new NewsFeedViewHolder(view);
            return holder;
        }
    };
    recyclerView.setAdapter(adapter);


}

@Override
protected void onStart() {
    super.onStart();
    adapter.startListening();
}

@Override
protected void onStop() {
    super.onStop();
    adapter.stopListening();
}

public static class NewsFeedViewHolder extends RecyclerView.ViewHolder {
    TextView title, des, usern;
    View mView;

    public NewsFeedViewHolder(@NonNull View itemView) {
        super(itemView);
        usern = (TextView) mView.findViewById(R.id.view_poster_username);
    }

}}

NEWSFEED.JAVA

导入com.google.firebase.storage。存储参考；

公共类NewsFeed{

private String Title, Description ,UserName;
private StorageReference imageUrl;

public NewsFeed(String UserName, String Title, String Description) {
    this.Title = Title;
    this.Description = Description;
    this.UserName = UserName;
}
public NewsFeed() {
}

public void setUsername(String UserName) {
    this.UserName = UserName;
}
public void setTitle(String Title) {
    this.Title = Title;
}
public void setDesc(String Description) {
    this.Description = Description;
}

public String getTitle() {
    return Title;
}
public String getDesc() {
    return Description;
}
public String getUsername() {
    return UserName;
}}