Flutter remote data acquisition interface UI refresh

Import 'Package: Flutter / material.dart' ;
 Import 'Package: HTTP / http.dart' AS HTTP; 

void main () => RunApp (the MyApp ()); 

class the MyApp the extends StatelessWidget { 
  @override 
  the Widget Build (BuildContext context) { 
    // the TODO: Implement build
     // need to build a component material 
    return MaterialApp ( 
      title: 'remote data acquisition and analyzing the model' , 
      Home: MyPage (), 
    ); 
  } 
} 

class MyPage the extends StatefulWidget {
   // must be rewritten the method returns to State 
  @override 
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return MyState();
  }
}

class MyState extends State<MyPage> {
  String ddddd = "ffffffff";

//  @override
//  void setState(fn) {
//    // TODO: implement setState
//    super.setState(fn);
//
//  }

  //必须重写build方法 - 返回一个部件
  @override
  Widget build(BuildContext context) {
    // TODO: implement build

    return Scaffold(
      appbar: the AppBar ( 
        title: the Text ( 'data transfer model' ), 
      ), 
      body: the Column ( 
        Children: <the Widget> [ 

          Container ( 
              Child: GestureDetector ( 
            Child: the Text (ddddd), 
//                 onTap in: fetchPost,
             // refresh interface
 //             onTap in: fetchPost, // there is a need for a method, rather than a return value of the method 
              onTap in: () { 
                 fetchPost () the then ((value) {. 
                    the setState (() { 
                      ddddd = value; 
                    }); 
                 } );
              },  
          ))
        ], 
      ), 
    ); 
  } 
} 

// Returns String, text displayed on the text member
 // call interface data acquisition server 
Future <String> fetchPost () {the async
   Final Response = 
      the await http.get ( "HTTPS: / /wanandroid.com/wxarticle/chapters/json " );
   Final Result = response.body; 
  Print (Result); 
  return Result; 
}

A simple demo