making shopping app but cart count from mainactivity does not carry over to details activity page

In my app, the displayed cart count does not carry over from mainactivity to detailsactivity. For eg if I add 3 items and it shows 3 in textview over cart in mainactivity page, when i go to details page the textview becomes 0. have been at this for days and need help. thank you.

its an issue with the onCreateOptionsMenu setting the textview to 0 again after it is called on second activity

public class MenuActivity extends AppCompatActivity {
public static TextView tv;
public static List<GeneralFood> cartFoods = new ArrayList<>();
public Toolbar toolbar;


@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}

@Override
public boolean onPrepareOptionsMenu(Menu menu) {
    return true;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    if (tv == null) {
        MenuItem item = menu.findItem(R.id.action_addcart);
        MenuItemCompat.setActionView(item, R.layout.cart_count_layout);
        RelativeLayout notifCount = (RelativeLayout) MenuItemCompat.getActionView(item);
        tv = notifCount.findViewById(R.id.hotlist_hot);
        View view = notifCount.findViewById(R.id.hotlist_bell);

        cartUpdate();

        view.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent myIntent = new Intent(MenuActivity.this, CartActivity.class);
                startActivity(myIntent);

            }
        });

    }else {
        cartUpdate();
    }
    return true;
}

public static void cartUpdate() {
    if (tv != null && cartFoods != null)
        tv.setText(Integer.toString(cartFoods.size()));
}

@Override
protected void onResume() {
    super.onResume();
    cartUpdate();
}

}

Details:

public class Details extends MenuActivity {


TextView foodTitle, foodPrice, foodCalories, foodDescription, foodFat, foodSodium, foodProtein;
ImageView foodImage;
ImageButton foodDetailsPlus;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_details);
    toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    getSupportActionBar().setTitle("Details");
    toolbar.setTitleTextColor(0xFFFFFFFF);
    toolbar.setNavigationIcon(R.drawable.ic_arrow_back_black_24dp);

    toolbar.setNavigationOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Details.super.onBackPressed();
        }
    });


    foodTitle = findViewById(R.id.food_title);
    foodPrice = findViewById(R.id.food_price);
    foodCalories = findViewById(R.id.food_calories);
    foodDescription = findViewById(R.id.food_description);
    foodFat = findViewById(R.id.food_fat);
    foodSodium = findViewById(R.id.food_sodium);
    foodProtein = findViewById(R.id.food_protein);
    foodImage = findViewById(R.id.food_image);
    foodDetailsPlus = findViewById(R.id.regular_food_plus_details);

    foodTitle.setText(getIntent().getStringExtra("foodTitle"));
    foodPrice.setText(Double.toString(getIntent().getDoubleExtra("foodPrice", 0)));
    foodCalories.setText(Integer.toString(getIntent().getIntExtra("foodCalories", 0)));
    foodDescription.setText(getIntent().getStringExtra("foodDescription"));
    Picasso.get().load(getIntent().getStringExtra("foodImage")).fit().into(foodImage);
    foodFat.setText(Integer.toString(getIntent().getIntExtra("foodFat", 0)));
    foodSodium.setText(Integer.toString(getIntent().getIntExtra("foodSodium", 0)));
    foodProtein.setText(Integer.toString(getIntent().getIntExtra("foodProtein", 0)));

}

}

MainActivity:

public class MainActivity extends MenuActivity {

RecyclerView recyclerViewHorizontal;
RecyclerView recyclerViewVertical;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    getSupportActionBar().setTitle("Foodish");
    toolbar.setTitleTextColor(0xFFFFFFFF);

    recyclerViewHorizontal = findViewById(R.id.horizontal_recyclerview);
    LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
    recyclerViewHorizontal.setLayoutManager(linearLayoutManager);

    recyclerViewVertical = findViewById(R.id.vertical_recyclerview);
    LinearLayoutManager linearLayoutManager2 = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
    recyclerViewVertical.setLayoutManager(linearLayoutManager2);

    RetrofitInterface retrofitService = RetrofitClient.getClient().create(RetrofitInterface.class);

    Call<Food> call = retrofitService.getFoods();
    call.enqueue(new Callback<Food>() {
        @Override
        public void onResponse(Call<Food> call, Response<Food> response) {
            List<GeneralFood> popularFoods = response.body().getPopularFood();
            recyclerViewHorizontal.setAdapter(new HorizontalAdapter(popularFoods, R.layout.recyclerview_horizontal, MainActivity.this));

            List<GeneralFood> regularFoods = response.body().getRegularFood();
            recyclerViewVertical.setNestedScrollingEnabled(false);
            recyclerViewVertical.setAdapter(new VerticalAdapter(regularFoods, R.layout.recyclerview_vertical, getApplicationContext()));
        }

        @Override
        public void onFailure(Call<Food> call, Throwable t) {

        }
    });
}

}