dart – 如何在flutter中创建工具栏搜索视图

class SearchAppBar extends StatefulWidget {
  @override
  _SearchAppBarState createState() => new _SearchAppBarState();
}

class _SearchAppBarState extends State<SearchAppBar> {
  Widget appBartitle = new Text("AppBar title");
  Icon actionIcon = new Icon(Icons.search);
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        centertitle: true,title:appBartitle,actions: <Widget>[
          new IconButton(icon: actionIcon,onPressed:(){
          setState(() {
                     if ( this.actionIcon.icon == Icons.search){
                      this.actionIcon = new Icon(Icons.closE);
                      this.appBartitle = new TextField(
                        style: new TextStyle(
                          color: Colors.white,),decoration: new InputDecoration(
                          prefixIcon: new Icon(Icons.search,color: Colors.whitE),hintText: "Search...",hintStyle: new TextStyle(color: Colors.whitE)
                        ),);}
                      else {
                        this.actionIcon = new Icon(Icons.search);
                        this.appBartitle = new Text("AppBar title");
                      }


                    });
        },]
      ),);
  }
}