Set selected item in Android BottomNavigationView

Question

I am using the new android.support.design.widget.BottomNavigationView from the support library. How can I set the current selection from code? I realized, that

Answer 1

IF YOU NEED TO DYNAMICALLY PASS FRAGMENT ARGUMENTS DO THIS

There are plenty of (mostly repeated or outdated) answers here but none of them handles a very common need: dynamically passing different arguments to the Fragment loaded into a tab.

You can't dynamically pass different arguments to the loaded Fragment by using setSelectedItemId(R.id.second_tab), which ends up calling the static OnNavigationItemSelectedListener. To overcome this limitation I've ended up doing this in my MainActivity that contains the tabs:

fun loadArticleTab(articleId: String) {
    bottomNavigationView.menu.findItem(R.id.tab_article).isChecked = true // use setChecked() in Java
    supportFragmentManager
        .beginTransaction()
        .replace(R.id.main_fragment_container, ArticleFragment.newInstance(articleId))
        .commit()
}

The ArticleFragment.newInstance() method is implemented as usual:

private const val ARG_ARTICLE_ID = "ARG_ARTICLE_ID"

class ArticleFragment : Fragment() {

    companion object {
        /**
         * @return An [ArticleFragment] that shows the article with the given ID.
         */
        fun newInstance(articleId: String): ArticleFragment {
            val args = Bundle()
            args.putString(ARG_ARTICLE_ID, day)
            val fragment = ArticleFragment()
            fragment.arguments = args
            return fragment
        }
    }

}