How to show active mark on RadioListTile?

How to show active mark on RadioListTile? I used selected and activeColor but it does not work.

RadioListTile(
  selected: true,
  activeColor: Theme.of(context).primaryColor, //
  title: Text(AppLocalizations.key(context, 'setDark')),
  value: ThemeMode.dark,
  groupValue: _themeMode,
  onChanged: (value) {},
),

>Solution :

Documentation

"groupValue → T?

The currently selected value for this group of radio buttons.

This radio button is considered selected if its value matches the groupValue.
"

The one selected is the one whose group value matches the value.

Therefore your radio buttons should have as groupValue Theme.Dark or Theme.Light and update it on onChanged.