使用按钮 onClick 在片段之间切换，但底部导航图标不会改变

Question

I have an app which has food menu and cart in the bottom navigation and used fragments for those. There is a button in the cart fragment which will show when the cart is empty. This is a 'Add Food' button because the cart is empty. This button takes the user to the menu fragment. That part of the code works, but my issue is that the icon in the bottom navigation bar is not changing from cart icon to menu icon.

public class CartFragment extends Fragment {

private LinearLayout emptyCartInfo;
private Button addFoodButton;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_cart, container, false);
    setHasOptionsMenu(true);
    //return inflater.inflate(R.layout.fragment_cart, container, false);

    emptyCartInfo = view.findViewById(R.id.cart_empty_layout);
    addFoodButton = view.findViewById(R.id.add_food_button);
    addFoodButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            Fragment menu = new MenuFragment();
            FragmentTransaction ft = getFragmentManager().beginTransaction();
            ft.replace(R.id.fragment_container, menu);
            ft.commit();


        }
    });

    return view;
}

}

The code above works fine on click of the button which takes me to menu fragment, however, the icon shown in the bottom navigation remains selected as cart and I need help as how to change this from within the fragment. When fragment switches from cart to menu, icon in the bottom navigation should also change which in my case does not. Need to do this from within the cart fragment under the onClick method.

Answer 1

In your onClick function, you should add a statement that turns off the focus from one MenuItem by changing the colour: (In case that menu is already defined)

menu.findItem(R.id.main_page).setIconColor(Color.WHITE);

And the same thing in the second Fragment, while resuming it, change the colour to your "focused" colour.

Also, I'd like to suggest, just because I think it would be a better UX, changing the bottom navigation to a tabbed menu (TabbedLayout). Then, just remove the button and you'll be able to swipe between Fragments.