java - E/RecyclerView : No adapter attached; skipping layout -- when making a todo list app

Question

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

    Context context;
    ArrayList<ToDoItems> toDoItems;


    public ToDoAdapter(Context c, ArrayList<ToDoItems> p) {
        context = c;
        toDoItems = p;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.front_page_layout, viewGroup, false));
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder myViewHolder, int i) {
        myViewHolder.itemTitle.setText(toDoItems.get(i).getItemTitle());
        myViewHolder.itemSubject.setText(toDoItems.get(i).getItemSubject());
        myViewHolder.itemDueDate.setText(toDoItems.get(i).getItemDueDate());

    }

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

    class MyViewHolder extends RecyclerView.ViewHolder {
        TextView itemTitle;
        TextView itemSubject;
        TextView itemDueDate;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);

            itemTitle = itemView.findViewById(R.id.itemTitle);
            itemSubject = itemView.findViewById(R.id.itemSubject);
            itemDueDate = itemView.findViewById(R.id.itemDueDate);

        }
    }

}

我的Main.class文件

       //Working with data
            mainPageRecyclerView = findViewById(R.id.mainPageRecyclerView);
            mainPageRecyclerView.setLayoutManager(new LinearLayoutManager(this));
            list = new ArrayList<ToDoItems>();


            addNewTask.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent a = new Intent(MainActivity.this,NewTaskAct.class);
                    startActivity(a);
                }
            });

            //get data from firebase
            dbReference = FirebaseDatabase.getInstance().getReference().child("to-do-list");
            dbReference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    //set code to retrieve data and replace layout
                    for (DataSnapshot dataSnapshot1: dataSnapshot.getChildren())
                    {
                        ToDoItems p = dataSnapshot1.getValue(ToDoItems.class);
                        list.add(p);
                    }
                    toDoAdapter = new ToDoAdapter(MainActivity.this, list);
                    mainPageRecyclerView.setAdapter(toDoAdapter);
                    toDoAdapter.notifyDataSetChanged();
                }

我可以看到 Firebase 数据库中的数据，但它不会从数据库中提取信息，我只是在 android studio RUN 中收到以下错误 --> E/RecyclerView:没有附加适配器；跳过布局 作为学习的一部分，我正在编写一个简单的应用程序，我可以将信息写入 firebase，但当我的应用程序更改 View 并需要从数据库调用数据时，我不断收到上述错误

我在 YouTube 上浏览了其他堆栈溢出问题，但我无法理解适用于我的项目的解决方案

Answer 1

您的 Recyclerview 被跳过，因为在绘制布局时没有附加适配器。您当前正在通过事件回调设置适配器，该回调在布局已绘制且 Recyclerview 已被跳过后仍将返回。您需要调用setAdapter()直接在您的 Activity 的 onCreate 中然后更新适配器的数据，确保调用 notifydatasetchanged在您的事件回调中。

在您的 Activity 的 onCreate 中:

// Create an empty adapter since you don't have initial data
// (You may need to alter the constructor of your Adapter class 
//  to keep it from trying to process empty/null data so it doesn't break)
MyAdapter myAdapter = new MyAdapter(null);

// Set the Recyclerview's Adapter so it isn't skipped on the layout pass
myRecyclerView.setAdapter(myAdapter);

然后，在您的事件回调中:

// Update your Adapter with the new data using an update function you define in your Adapter
myAdapter.updateData(myNewData);

// Notify the Adapter that the data has changed
myAdapter.notifyDataSetChanged();