public class CheckOut extends AppCompatActivity {
    // Global Variables
    Vegetable_DataSource mDataSource_veg;
    Vegetable_DataItem veg_item;
    ShoppingCart_DataSource mDataSource_cart;
    List<ShoppingCart_DataItem> cart_ListFromDB;
    ShoppingCart_ItemAdaptor adapter;
    Float finalNet_sum;
    Float finalNet_price_value;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_checkout);
        // Using this, as I wished to use onResume()
        update_data();
        adapter = new ShoppingCart_ItemAdaptor(getApplicationContext(), cart_ListFromDB);

        ListView listView = (ListView) this.findViewById(R.id.shoppingList);
        listView.setAdapter(adapter);

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                // This function is updating cart_ListFromDB and calling adaptor.notifyDataSetChanged()
                show_itemSelector_dialog(position);
            }
        });
    }
    private void show_itemSelector_dialog(int position) {
        // Here, Entries in database are updated as per input from user.
        // Entries in database are updated
        // update_data fetches the updated cart_ListFromDB from database.
        update_data();
        adapter.notifyDataSetChanged();
    }

    private void update_data() {
        mDataSource_cart = new ShoppingCart_DataSource(getApplicationContext());
        mDataSource_cart.open();
        cart_ListFromDB = mDataSource_cart.GetAllItems_shopping_cart();
        mDataSource_cart.close();
    }
}

public class ShoppingCart_ItemAdaptor extends ArrayAdapter {
    private List<ShoppingCart_DataItem> mDataItems;
    private LayoutInflater mInflator;

    public ShoppingCart_ItemAdaptor(@NonNull Context context, List<ShoppingCart_DataItem> objects) {
        super(context, R.layout.item_checkout, objects);
        // mDataItems is being updated only when adaptor is created.
        mDataItems = objects;
        mInflator = LayoutInflater.from(context);
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        this.pref_login = this.getContext().getSharedPreferences(SESSION_SHARED_PREF, PRIVATE_MODE);
        if (convertView == null) {
            convertView = mInflator.inflate(R.layout.item_checkout, parent, false);
        }

        ShoppingCart_DataItem item = mDataItems.get(position);

        // Updating the view items as per "item"

        return convertView;
    }
}