From API 25.3.0 it was introduced the method setSelectedItemId(int id)
which lets you mark an item as selected as if it was tapped.
From docs:
Set the selected menu item ID. This behaves the same as tapping on an item.
Code example:
BottomNavigationView bottomNavigationView;
bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottomNavigationView);
bottomNavigationView.setOnNavigationItemSelectedListener(myNavigationItemListener);
bottomNavigationView.setSelectedItemId(R.id.my_menu_item_id);
IMPORTANT
You MUST have already added all items to the menu (in case you do this programmatically) and set the Listener before calling setSelectedItemId(I believe you want the code in your listener to run when you call this method). If you call setSelectedItemId before adding the menu items and setting the listener nothing will happen.
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