bottomNavigationBar.setTabSelectedListener(new BottomNavigationBar.OnTabSelectedListener(){
@Override
public void onTabSelected(int position) { }
@Override
public void onTabUnselected(int position) { }
@Override
public void onTabReselected(int position) { }
});
根据position来判断选定的哪个。使用bottomNavigationBar的TabSelectedListener监听来判断