Firestore数据未显示在回收器视图中

Question

我正试图添加数据在我的回收视图从火炉。我有带名字的文件（级别级别编号）但没有显示我的活动这是代码：

主要活动水平：

公共类级别活动扩展AppCompat活动{

// Recycler View object
RecyclerView recyclerView;

// Array list for recycler view data source
public static List<String> levelList = new ArrayList<>();

// Layout Manager
RecyclerView.LayoutManager RecyclerViewLayoutManager;

// adapter class object
LevelAdapter adapter;

// Linear Layout Manager
LinearLayoutManager HorizontalLayout;

FirebaseFirestore firebaseFirestore;

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


    // initialisation with id's
    recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
    RecyclerViewLayoutManager = new LinearLayoutManager(getApplicationContext());

    // Set LayoutManager on Recycler View
    recyclerView.setLayoutManager(RecyclerViewLayoutManager);

    firebaseFirestore = FirebaseFirestore.getInstance();

    loadLevel();
    // calling constructor of adapter
    // with source list as a parameter
    adapter = new LevelAdapter(levelList);

    // Set Horizontal Layout Manager
    // for Recycler view
    HorizontalLayout = new LinearLayoutManager(LevelActivity.this, LinearLayoutManager.HORIZONTAL, false);
    recyclerView.setLayoutManager(HorizontalLayout);

    // Set adapter on recycler view
    recyclerView.setAdapter(adapter);
}

private void loadLevel(){
    levelList.clear();

    firebaseFirestore.collection("QUIZ LEVELS")
            .document("TOTAL_LEVELS").get()
            .addOnCompleteListener(task -> {
                if (task.isSuccessful()) {
                    DocumentSnapshot doc = task.getResult();
                    if (doc.exists()) {
                        long levelCount = (long) doc.get("count");

                        for (int i = 1; i <= levelCount; i++) {
                            String levelName = doc.getString("LEVEL" + i);
                            levelList.add(levelName);
                        }

                    }else{
                        Toast.makeText(LevelActivity.this, "no level", Toast.LENGTH_SHORT).show();
                    }

                }else{

                    Toast.makeText(LevelActivity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                }
            });
}

}

水平调整器

公共类级别适配器扩展了RecyclerView。适配器

// List with String type
private final List<String> levelList;

// View Holder class which
// extends RecyclerView.ViewHolder
public class MyView extends RecyclerView.ViewHolder {
    // Text View
    TextView textView;

    // parameterised constructor for View Holder class
    // which takes the view as a parameter
    public MyView(View view) {
        super(view);
        // initialise TextView with id
        textView = (TextView) view.findViewById(R.id.textview);
    }
}

// Constructor for adapter class
// which takes a list of String type
public LevelAdapter(List<String> horizontalList) {
    this.levelList = horizontalList;
}

// Override onCreateViewHolder which deals
// with the inflation of the card layout
// as an item for the RecyclerView.
@Override
public MyView onCreateViewHolder(ViewGroup parent, int viewType) {
    // Inflate item.xml using LayoutInflator
    View itemView
            = LayoutInflater
            .from(parent.getContext())
            .inflate(R.layout.recycler_view_item,
                    parent, false);

    // return itemView
    return new MyView(itemView);
}

// Override onBindViewHolder which deals
// with the setting of different data
// and methods related to clicks on
// particular items of the RecyclerView.
@Override
public void onBindViewHolder(final MyView holder, final int position) {
    // Set the text of each item of
    // Recycler view with the list items
    holder.textView.setText(levelList.get(position));
}

// Override getItemCount which Returns
// the length of the RecyclerView.
@Override
public int getItemCount() {
    return levelList.size();
}

}

Answer 1

从firestore/firebase加载数据需要一段时间。在收到文档的响应后，应该在加载级别内调用set adapter

 RecyclerView recyclerView;

 // Array list for recycler view data source
 public static List<String> levelList = new ArrayList<>();

// Layout Manager
RecyclerView.LayoutManager RecyclerViewLayoutManager;

// adapter class object
LevelAdapter adapter;

// Linear Layout Manager
LinearLayoutManager HorizontalLayout;

FirebaseFirestore firebaseFirestore;

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


// initialisation with id's
recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
RecyclerViewLayoutManager = new 
LinearLayoutManager(getApplicationContext());

// Set LayoutManager on Recycler View
recyclerView.setLayoutManager(RecyclerViewLayoutManager);

firebaseFirestore = FirebaseFirestore.getInstance();

 HorizontalLayout = new LinearLayoutManager(LevelActivity.this, 
LinearLayoutManager.HORIZONTAL, false);
recyclerView.setLayoutManager(HorizontalLayout);

 loadLevel();




 }

private void loadLevel(){
levelList.clear();

     firebaseFirestore.collection("QUIZ LEVELS")
        .document("TOTAL_LEVELS").get()
        .addOnCompleteListener(task -> {
            if (task.isSuccessful()) {
                DocumentSnapshot doc = task.getResult();
                if (doc.exists()) {
                    long levelCount = (long) doc.get("count");

                    for (int i = 1; i <= levelCount; i++) {
                        String levelName = doc.getString("LEVEL" + i);
                        levelList.add(levelName);
                    }
                  //Set Adapter here
                  adapter = new LevelAdapter(levelList);




                 // Set adapter on recycler view
                 recyclerView.setAdapter(adapter);

                }else{
                    Toast.makeText(LevelActivity.this, "no level", 
 Toast.LENGTH_SHORT).show();
                }

            }else{

                Toast.makeText(LevelActivity.this, 
 task.getException().getMessage(), Toast.LENGTH_SHORT).show();
            }
        });
}