How to update a texview in main screen by changing a value in an item inside a recycleview?

Question

I want to develop a screen that represents a store and in it you can find a list of products (presented by a recycleview) where you can find the price of each item and select your desired quantity.

when the user update the quantity of the product the price changes too.

I have a textview below the recycleview which display the total sum of prices of all selected products.

When the user want to change his required quantity of a specific product, it is simple to update the price represented in the item but how to update in the same time the one (the total one) in the main screen ?

Answer 1

Use Interface to listen to the change in the recycler view item and update the value on the user select the quantity. Create a interface class

public interface UpdateListener {
    void onQuantityUpdated();

}

In your adapter class

 private Context context;
private UpdateListener deleteListener;


public YourRVAdapter(Context context, List<ConsumedMaterialModel> list, 
    UpdateListener updateListener) {
    this.context = context;
    this.list = list;
    this.deleteListener = deleteListener;
}

on user select quantity inside adapter

updateListener.onQuantityUpdated();

Now implement this interface in your Activity

public class MainActivity extends AppCompatActivity implements UpdateListener


 @Override
public void onQuantityUpdated() {
    //update your textview by calculating amount here
}