如何从 Firebase 获取价值到 recyclerView

Question

this is a picture of firebase datathis is the image of log which i am getting in logcat

mDatabase=FirebaseDatabase.getInstance();
mRef=mDatabase.getReference("items").child("0").child("snippet");
mChildEventListner = new ChildEventListener() {

    @Override
    public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
        for (DataSnapshot Snapshot : dataSnapshot.getChildren()) {
            CategoriesModelClass user = dataSnapshot.getValue(CategoriesModelClass.class);
            Log.d("kkk", "" + user);
            title_description.add(user);
        }
        categoriesRecycleView.notifyDataSetChanged();
    }

这是我来自activitymain 的代码，我不知道我应该触发标题和描述的查询还是它会从 for 循环中获取它？

这是我的模型类的代码

public class CategoriesModelClass {
    String title,description;

    public CategoriesModelClass(){

    }

    public CategoriesModelClass(String title, String description) {
        this.title = title;
        this.description = description;
    }

    public String getTitle() {
        return title;
    }

    public String getDescription() {
        return description;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public void setDescription(String description) {
        this.description = description;
    }
}

我尝试在我的回收视图中设置这些数据，我只需要标题和描述

Answer 1

要获取description和title的值，请使用以下代码行：

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference snippetRef = rootRef.child("items").child("0").child("snippet");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        CategoriesModelClass user = dataSnapshot.getValue(CategoriesModelClass.class);
        Log.d("kkk", "" + user.getTitle());

        //Get the values out of the user object
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!
    }
};
snippetRef.addListenerForSingleValueEvent(valueEventListener);

看，没有必要循环snippet节点，这是因为我们需要根据存储的对象类型来获取数据。

如果0节点中有多个项目，请使用以下代码行：

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference zeroRef = rootRef.child("items").child("0");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            CategoriesModelClass user = ds.getValue(CategoriesModelClass.class);
            Log.d("kkk", "" + user.getTitle());
        }

        //Get the values out of the user object
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!
    }
};
zero.addListenerForSingleValueEvent(valueEventListener);