问如何在颤振中自动扩展和关注应用程序中的搜索视图

EN

 @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
      title: Text("Search Product"),
      actions: <Widget>[
        IconButton(
          onPressed: () {
            showSearch(context: context, delegate: DataSearch());
          },
          icon: Icon(Icons.search),
        )
      ],
    ));
  }
}

class DataSearch extends SearchDelegate<String> {
  @override
  List<Widget>? buildActions(BuildContext context) {
    return [
      IconButton(
          onPressed: () {
            query = "";
          },
          icon: Icon(Icons.clear))
    ];
  }

  @override
  Widget? buildLeading(BuildContext context) {
    return IconButton(
        onPressed: () {
          close(context, "");
        },
        icon: Icon(Icons.arrow_back));
  }

  @override
  Widget buildResults(BuildContext context) {
    throw UnimplementedError();
  }

  @override
  Widget buildSuggestions(BuildContext context) {
    final suggestionList =
        productsController.products.where((p) => p.name!.toLowerCase().startsWith(query.toLowerCase())).toList();

    return ListView.builder(
      itemCount: query == "" ? 5 : suggestionList.length,
      itemBuilder: (BuildContext context, int index) {
        return ListTile(
            onTap: () {
              Navigator.pushNamed(context, ProductDetails.routeName,
                  arguments: ProductsDetailsArguments(product: suggestionList[index]));
            },
            leading: Icon(Icons.search),
            title: RichText(
                text: TextSpan(
                    text: suggestionList[index].name!.substring(0, query.length),
                    style: TextStyle(color: Colors.black, fontWeight: FontWeight.bold),
                    children: [
                  TextSpan(
                      text: suggestionList[index].name!.substring(query.length),
                      style: query == "" ? TextStyle(color: Colors.grey) : TextStyle(color: Colors.grey.shade600))
                ])));
      },
    );
  }
}