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I want to get all child of child items one by one in firebase database

here is model class :

I want that I get all food items from all categories one by one and than show every single food item data in recycler view

and after getting list of all items I want that I add only those items in a list which pin value is TRUE

public class Items {
    String name, desc,image, category;
    int price;
    boolean pin;


    public Items(String name, String desc, String image, String category, int price, boolean pin) {
        this.name = name;
        this.desc = desc;
        this.image = image;
        this.category = category;
        this.price = price;
        this.pin = pin;
    }

    public Items() {
    }

    public boolean isPin() {
        return pin;
    }

    public void setPin(boolean pin) {
        this.pin = pin;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }
}

here is the java class file code : when I check snapshot using snapshot.getValue() in log it gives me all categories also items, but it is not adding in a list…why ???

DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("admin");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                list.getClass();
                for (DataSnapshot dataSnapshot : snapshot.getChildren()){
                    Items items = dataSnapshot.getValue(Items.class);
                    list.add(items);
                }
                adapter.notifyDataSetChanged();

            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        });

this is my database :

I want all food item from all category one by one

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Answer

Your for (DataSnapshot dataSnapshot : snapshot.getChildren()){ loop only loops over one level in the database, so your dataSnapshot points to BBQ and then Chines, not to the individual food items.

Since you want to loop over two nested node levels, you need two nested loops in your code:

DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("admin");
reference.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot snapshot) {
        list.getClass();
        for (DataSnapshot categorySnapshot : snapshot.getChildren()){ // 👈
            for (DataSnapshot itemSnapshot : categorySnapshot.getChildren()){ // 👈
                Items items = itemSnapshot.getValue(Items.class); // 👈
                list.add(items);
            }
        }
        adapter.notifyDataSetChanged();

    }

    @Override
    public void onCancelled(@NonNull DatabaseError error) {
        throw error.toException(); // 👈 Never ignore errors
    }
});

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