android - Show PopupMenu for MenuItem which is not an Action

Question

how can I get the View Anchor for a PopupMenu if the corresponding MenuItem in ActionView is not shown as Action:

if (item.getItemId() == R.id.myMenu) {
        PopupMenu popupMenu = new PopupMenu (this, findViewById(R.id.myMenu));
        popupMenu.show();
        return true;
    }

    <item
        android:id="@+id/myMenu"
        appcompat:showAsAction="never"
        android:title="@string/sharePage"
        android:icon="@drawable/navigation_share"/>

appcompat:showAsAction="always"
すべてが 正常に機能するが
appcompat:showAsAction="never"、メソッドを使用するとfindViewById(R.id.myMenu)null が返されます。