Livrer un message à un fragment

Bonjour
Voici le code qui permet de livrer un message à un fragment sous Android:
public static class MainActivity extends Activity
implements HeadlinesFragment.OnHeadlineSelectedListener{
...

public void onArticleSelected(int position) {
// The user selected the headline of an article from the HeadlinesFragment
// Do something here to display that article

ArticleFragment articleFrag = (ArticleFragment)
getSupportFragmentManager().findFragmentById(R.id.article_fragment);

if (articleFrag != null) {
// If article frag is available, we're in two-pane layout...

// Call a method in the ArticleFragment to update its content
articleFrag.updateArticleView(position);
} else {
// Otherwise, we're in the one-pane layout and must swap frags...

// Create fragment and give it an argument for the selected article
ArticleFragment newFragment = new ArticleFragment();
Bundle args = new Bundle();
args.putInt(ArticleFragment.ARG_POSITION, position);
newFragment.setArguments(args);

FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();

// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);

// Commit the transaction
transaction.commit();
}
}
}