BottomNavigationView - How to get selected menu item?

Get selected item at first and then getMenu().findItem(int itemId)

bottomNavigationView.getMenu().findItem(bottomNavigationView.getSelectedItemId())

Solution:

private int getSelectedItem(BottomNavigationView bottomNavigationView) {
    Menu menu = bottomNavigationView.getMenu();
    for (int i = 0; i < bottomNavigationView.getMenu().size(); i++) {
        MenuItem menuItem = menu.getItem(i);
        if (menuItem.isChecked()) {
            return menuItem.getItemId();
        }
    }
    return 0;
}

I think the simplest solution for checking if the previous item is the next item is this:

BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);

bottomNavigationView.setOnNavigationItemSelectedListener(
    new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            final int previousItem = bottomNavigationView.getSelectedItemId();
            final int nextItem = item.getItemId();
            if (previousItem != nextItem) {
                 switch (nextItem) {
                     case R.id.action_1:
                         // open fragment 1
                         break;
                     case R.id.action_2:
                         // open fragment 2
                         break;
                     case R.id.action_3:
                         // open fragment 3
                         break;
                 }
            }
            return true;
        }
    }
);

Note that there is no need for iterating, and that onNavigationItemSelected returns true, because the function consumes the event.

I hope it helps someone.

Get the currently selected menu item ID using getSelectedItemId:

int selectedItemId = bottomNavigationView.getSelectedItemId();
MenuItem selectedItem = bottomNavigationView.getMenu().findItem(selectedItemId);

This method started being available from Android Support Library 25.3.0.