How to add child item to last item from RecyclerView?

Question

Actually i'm trying to make an app that take restaurant orders and i'm having some issues after adding child item to my order.

I have a recyclerView where i have different type's of food when i press on one of them i add it to recyclerView that work's something like a notebook, then i have an button that open an AlertDialog in which there is another recyclerView with variant's.

Example: i press on PIZZA from food recyclerView it's add it to the notebook after i press on variant's and i can add "WITH PEPERONI" or "LARGE" or both.

I have followed this guide ( here github project from the guide) for making the recyclerView with child item.

Now the issue is how can i add the child item to the last parent item?

like i'm adding parent item using this:

                dummyParentDataItem = new ItemPTERM();
                dummyParentDataItem.setButton_name(filteredList.get(position).getDeskS());
                dummyParentDataItem.setQuant( Integer.parseInt(filteredList.get(position).getQuant()));
                dummyChildDataItems = new ArrayList<>();

                dummyParentDataItem.setChildDataItems(dummyChildDataItems);
                itemCassas.add(dummyParentDataItem);

And this when i add a child from variant's recyclerView

                dummyChildDataItem = new DummyChildDataItem();
                dummyChildDataItem.setChildName(tipo.toString());
                dummyChildDataItems.add(dummyChildDataItem);

                dummyParentDataItem.setChildDataItems(dummyChildDataItems);
                itemCassas.add(dummyParentDataItem);

but obviously the app crash because that don't know which is the last paren't item to which add the child. When i try to put both parent and child when i'm adding food from recyclerView with:

                dummyParentDataItem = new ItemPTERM();
                dummyParentDataItem.setButton_name(filteredList.get(position).getDeskS());
                dummyParentDataItem.setQuant( Integer.parseInt(filteredList.get(position).getQuant()));
                dummyChildDataItems = new ArrayList<>();

                dummyChildDataItem = new DummyChildDataItem();
                dummyChildDataItem.setChildName("WITH PEPERONI");
                dummyChildDataItems.add(dummyChildDataItem);

                dummyParentDataItem.setChildDataItems(dummyChildDataItems);
                itemCassas.add(dummyParentDataItem);

that obviously works but i have to add the child in a separate method to the last parent.

How can i do it? any suggestion? Here is also my adapter code:

public class AdapterPTERM extends RecyclerView.Adapter<AdapterPTERM.ExampleViewHolder> {

    private ArrayList<ItemPTERM> mExampleList;


    @NonNull
    @Override
    public ExampleViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerview_pterm,parent,false);
        return new ExampleViewHolder(v);
    }

    AdapterPTERM(ArrayList<ItemPTERM> exampleList){
        mExampleList = exampleList;
    }

    @Override
    public void onBindViewHolder(@NonNull ExampleViewHolder holder, int position) {
        ItemPTERM item = mExampleList.get(position);

        holder.desc.setText(item.getBtnName());
        holder.qta.setText(String.valueOf(item.getQuant()));

        int noOfChildTextViews = holder.linearLayout_childItems.getChildCount();
        int noOfChild = item.getChildDataItems().size();

        if (noOfChild < noOfChildTextViews) {
            for (int index = noOfChild; index < noOfChildTextViews; index++) {
                TextView currentTextView = (TextView) holder.linearLayout_childItems.getChildAt(index);
                currentTextView.setVisibility(View.GONE);
            }
        }
        for (int textViewIndex = 0; textViewIndex < noOfChild; textViewIndex++) {
            TextView currentTextView = (TextView) holder.linearLayout_childItems.getChildAt(textViewIndex);
            currentTextView.setText(item.getChildDataItems().get(textViewIndex).getChildName());
        }

        if(position % 2 == 0 ){
            holder.itemView.setBackgroundColor(Color.parseColor("#C0C0C0"));

        }else if(position % 2 == 1){
            holder.itemView.setBackgroundColor(Color.parseColor("#D3D3D3"));
        }

    }

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

    public class ExampleViewHolder extends RecyclerView.ViewHolder {

        public TextView desc;
        public TextView qta;
        private LinearLayout linearLayout_childItems;
        private Context context;

        ExampleViewHolder(View itemView) {
            super(itemView);

            desc = itemView.findViewById(R.id.Desc);
            qta = itemView.findViewById(R.id.Qta);
            linearLayout_childItems = itemView.findViewById(R.id.ll_child_items);
            context = itemView.getContext();

            int intMaxNoOfChild = 0;
            for (int index = 0; index < mExampleList.size(); index++) {
                int intMaxSizeTemp = mExampleList.get(index).getChildDataItems().size();
                if (intMaxSizeTemp > intMaxNoOfChild) intMaxNoOfChild = intMaxSizeTemp;
            }
            for (int indexView = 0; indexView < intMaxNoOfChild; indexView++) {
                TextView textView = new TextView(context);
                textView.setId(indexView);
                textView.setPadding(0, 20, 0, 20);
                textView.setGravity(Gravity.CENTER);
                textView.setBackground(ContextCompat.getDrawable(context, R.drawable.background_sub_module_text));
                LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
                linearLayout_childItems.addView(textView, layoutParams);
            }

        }
    }

    public void removeItem(int position) {
        mExampleList.remove(position);
        notifyItemRemoved(position);
    }


}

Here is a screenshot of my activity

Answer 1

To display data in a RecylerView, you provide a list of items to its adapter.

To add a new element you just need to add the item to the list and call notifyDataSetChange() on the adapter.

For example you can create a new method in you adapter, like that:

public void addItem(ItemPTERM item){
   mExampleList.add(item);
   notifyDataSetChange();
}

EDIT

So what you can do is to allow your item to have a list of 'variants'.

For example if you select 'Pizza' and want to had 'big' and 'pepperoni', your item will be the pizza and 'big'and 'pepperoni' part of the variants list.

Food {
  String name;
  List<Variant> variants;
  //... Other attributes

  public void setVariant(Variant variant){
     if (variants == null) // We want to initialise the array only when necessary
        variants = new ArrayList<>();
     variants.add(variant);
  }

  @Nullable
  public List<Variant> getVariants(){
     return variants;
  }
}

Variant{
   String name;
  //... Other attributes
}

When you select a variant you add it to the appropriate Food object.

Approach 1

Then in your adapter, in the onBindViewHolder you can dynamically add the variants to the item;

This way is not the most optimised but should work:

Item layout

    <!-- Food Views-->
    ...

    <!-- Container for the variants -->
    <LinearLayout
        android:id="@+id/variants_list"
        android:layout_width="match_parent"
        android:orientation="vertical"
        android:layout_height="wrap_content"/>
</LinearLayout>

Variant layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/variant_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/variant_other_info"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

Adapter

final LayoutInflater mInflater;
List<Food> mFoods;

public FoodAdapter(Context context, ...){
   //...
   mInflater = LayoutInflater.from(context);
}

@Override
public void onBindViewHolder(@NonNull ExampleViewHolder holder, int position) {
   Food food = mFood.get(position);
   // Display food attributes
   //... 
   // Clear the container to set fresh info
   holder.variantsContainer.removeAllViews();

   List<Variant> variants = food.getVariants();
   if (variants != null && variants.size() > 0){
      // Display the variants when necessary
      for(Variant v : variants){
         View vView = mInflater.inflate(R.layout.variant_layout);
         TextView nameTV = vView.findViewById(R.id.variant_name);
         nameTV.setText(v.getName());
         // Set other fields values
         // ...
         holder.variantsContainer.addView(vView);
      }
   }
}

Approach 2

Another way to do it is to have a list of food object containing a list of variant as above, but to not use this list directly in the adapter.

Instead the adapter will use it's own list which will be both Food and Variant objects mix together. Your adapter should then be able to display 2 kinds of objects. This way is more flexible but you have to recreate the entire adapter list every time you change something.

For instance:

Let say you have 3 Food objects in the list. The first one has 1 variant, the second one none and the third one 2.

Then your adapter will get a list like that:

List<Object> items;

items will contain: {food1, variant1a, food2, food3, variant3a, variant3b}

And then your adapter will have to use two different layout to display either the Food or the Variant object.

@NonNull
@Override
public ExampleViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    if (viewType == 0) { // if food
        View vFood = mInflater.inflate(R.layout.food_layout, parent, false);
        return new FoodViewHolder(vFood);
    } else { // variant
        View vVariant = mInflater.inflate(R.layout.variant_layout, parent, false);
        return new VariantViewHolder(vVariant;
    }
}

@Override
public int getItemViewType(int position) {
    return (mItems.get(position) instanceof Food) ? 0 : 1;
}