RecyclerView Android Studio不显示来自Firebase数据库的数据

// 1. 添加Firebase到Android项目中
// ...

// 2. 创建RecyclerView布局
// activity_main.xml
<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

// 3. 创建RecyclerView适配器
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    private List<String> mData;

    public MyAdapter(List<String> data) {
        mData = data;
    }

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

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        String item = mData.get(position);
        holder.textView.setText(item);
    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView textView;

        public ViewHolder(View itemView) {
            super(itemView);
            textView = itemView.findViewById(R.id.textView);
        }
    }
}

// 4. 获取Firebase数据库引用
DatabaseReference databaseRef = FirebaseDatabase.getInstance().getReference();

// 5. 监听数据变化
databaseRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        List<String> data = new ArrayList<>();
        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
            String item = snapshot.getValue(String.class);
            data.add(item);
        }
        // 6. 更新RecyclerView数据
        MyAdapter adapter = new MyAdapter(data);
        recyclerView.setAdapter(adapter);
        adapter.notifyDataSetChanged();
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        // 处理取消监听事件
    }
});