class SearchBarDemo extends StatefulWidget {
  @override
  _SearchBarDemoState createState() => _SearchBarDemoState();
}

class _SearchBarDemoState extends State<SearchBarDemo> {
  //String query="";
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar:AppBar(
            title:Text('点击放大镜搜索'),
            actions:<Widget>[
              IconButton(
                  icon:Icon(Icons.search),
                  onPressed: (){
                    showSearch(context:context,delegate: searchBarDelegate());
                  }
              ),
            ]
        )
    );
  }
}

const searchList = [
  "html",
  "css",
  "js",
  "flutter"
];

const recentSuggest = [
  "推荐-vue",
  "推荐-react",
  "推荐-angular",
  "推荐-dart"
];
class searchBarDelegate extends SearchDelegate<String>{
  //初始化加载
  @override
  List<Widget> buildActions(BuildContext context) {
    return [
      IconButton(
        icon: Icon(Icons.clear),
        onPressed: ()=>query="",
      )
    ];
  }
  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: AnimatedIcon(
          icon: AnimatedIcons.menu_arrow, progress: transitionAnimation),
      onPressed: ()=>close(context, null),
    );
  }
  @override
  Widget buildResults(BuildContext context) {
    return Container(
      width: 100.0,
      height: 100.0,
      child: Card(
        color: Colors.redAccent,
        child: Center(
          child: Text(query),
        ),
      ),
    );
  }
  @override
  Widget buildSuggestions(BuildContext context) {
    final suggestionList = query.isEmpty
        ? recentSuggest
        : searchList.where((input) => input.startsWith(query)).toList();
    return ListView.builder(
      itemCount: suggestionList.length,
      itemBuilder: (context,index) => ListTile(
        title: RichText(
            text: TextSpan(
                text: suggestionList[index].substring(0, query.length),
                style: TextStyle(
                    color: Colors.black, fontWeight: FontWeight.bold),
                children:[
                  TextSpan(
                      text: suggestionList[index].substring(query.length),
                      style: TextStyle(
                          color: Colors.grey
                      )
                  )
                ]
            )
        ),
      ),
    );
  }
}