How to add submenu items to NavigationView program

Question

I'm trying to add submenu items to NavigationView programmatically . I'm able to add items into menu but not into submenu

Adding items to menu works

Menu menu = mNavigationView.getMenu();
menu.add(Menu.NONE, Menu.NONE, index, "Menu Item1");

But adding items to sub menu doesn't work

Menu menu = mNavigationView.getMenu();
SubMenu subMenu = menu.addSubMenu("Sub menu title");
subMenu.add(Menu.NONE, Menu.NONE, index, "SubMenu Item1");

Answer 1

The trick to call BaseAdapter.notifyDataSetChanged on the underlying Adapter that contains the menu items. You could use reflection to grab the ListView or just loop over the NavigationView children until you reach it.

This isn't the most up-to-date code, as fas as I know Google hasn't pushed the most recent changes to the Support Library, but essentially NavigationMenuPresenter.prepareMenuItems is called when you call BaseAdpater.notifyDataSetChanged.

But if you want to see the most recent source, you can download it through the SDK Manager. Choose Sources for Android MNC. Then navigate to

yourAndroidSDK/sources/android-MNC/android/support/design/internal/NavigationMenuPresenter.java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...
    final Menu menu = mNavigationView.getMenu();
    for (int i = 0; i < 4; i++) {
        menu.add("Menu Item " + (i + 1));
    }
    final SubMenu subMenu = menu.addSubMenu("SubMenu Title");
    for (int i = 0; i < 2; i++) {
        subMenu.add("SubMenu Item " + (i + 1));
    }
    for (int i = 0, count = mNavigationView.getChildCount(); i < count; i++) {
        final View child = mNavigationView.getChildAt(i);
        if (child != null && child instanceof ListView) {
            final ListView menuView = (ListView) child;
            final HeaderViewListAdapter adapter = (HeaderViewListAdapter) menuView.getAdapter();
            final BaseAdapter wrapped = (BaseAdapter) adapter.getWrappedAdapter();
            wrapped.notifyDataSetChanged();
        }
    }

}

Results

Answer 2

Somebody figured out a way to do it via reflection and accessing a private field. It's not pretty, but it'll work, for the moment. https://stackoverflow.com/a/30604299/4232051