I created this very simple class extending SearchDelegate to use it as search bar:

class DataSearch extends SearchDelegate<String>{

  List<Widget>? buildActions(BuildContext context) {
    return [
          onPressed: () {query = '';},
          icon: const Icon(Icons.clear))

  Widget? buildLeading(BuildContext context) {
    return IconButton(
        onPressed: (){close(context, '');},
        icon: AnimatedIcon(
          progress: transitionAnimation,
          icon: AnimatedIcons.menu_arrow

  Widget buildResults(BuildContext context) {
    //TODO show some results based on the selection
    return Scaffold();

  Widget buildSuggestions(BuildContext context) {
    final namesList = [];
    final suggestionList = query.isEmpty ? [] : namesList;

    return ListView.builder(
      itemBuilder: (context, index) => ListTile(
        title: RichText(
          text: TextSpan(
              text: suggestionList[index].substring(0, query.length),
              style: const TextStyle(color: Colors.black, fontWeight: FontWeight.bold),
              children: [
                    text: suggestionList[index].substring(query.length),
                    style: const TextStyle(color: Colors.grey))
      itemCount: suggestionList.length,

and it works but to make it a bit better I'd like to make a new query to my database everytime the user inserts/removes a letter to the text input (similarly to the the onChanged attribute of the TextField) but I can't find a way to do it. What can I do?

Solution 1: THEODORE

You can drop the method anywhere inside the buildSuggestions Widget;