Flutter，具有许多api异步调用的渲染小部件

Question

我是dev和flutter的新手。我刚刚用TextField构建了一个测试窗口小部件，当我完成输入文本时，它将调用api来连续获取并显示数据，并清除TextField中的文本，之后可以再次通过此textfield调用另一个api，在我调用的数据的Listbuilder中的新行中显示新数据。这是我的代码。

class MyApp4 extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _MyApp4State();
  }
}

class _MyApp4State extends State<MyApp4> {
  String url = 'http://test.local:8000/test/url=';
  Future sap ;
  TextEditingController eCtrl = TextEditingController();
  List<String> _testlist = [];


  @override
  void initState() {
    super.initState();
    sap = fetchPost(url);
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: AppBar(title: Text('Long List App')),
      body: new  Container(
          margin: EdgeInsets.only(top: 30.0),
          child: new Column(
            children: <Widget>[
              Row(
                children: <Widget>[
                  SizedBox(width: 20,),
                  Text('Barcode :   ', style: TextStyle(
                    fontSize: 18.0,
                    fontWeight: FontWeight.bold,
                  ),),
                  SizedBox(width: 20,),
                  new Flexible(child: new TextFormField(
                    //   autofocus: true,
                    controller: eCtrl,
                    //   textInputAction: TextInputAction.done,
                    onFieldSubmitted: (text){
                      _testlist.add(text);
                      setState(() {
                        url = ( 'http://test.local:8000/test/url='+ eCtrl.text);
                        sap = handCheckfetch(url);
                      });
                      print(sap.toString());
                      print(_testlist.length.toString());
                      print(_testlist.asMap().toString());
                      print(url);

                      eCtrl.clear();
                    },
                  ),
                  ),
                  SizedBox(width: 20,),
//                  new Icon(Icons.check_box_outline_blank ),
//                  SizedBox(width: 20,),
                ],
              ),
              SizedBox(height: 30,),
              new Expanded(
                child: ListView.builder(
                    itemCount: _testlist == null ? 0 : _testlist.length,
                    itemBuilder: (context, index) {
                      return FutureBuilder (future: sap, builder: (context, snapshot){
                        if (snapshot.hasData) {
                          return  Container(
                            child: snapshot.data,
                          );
                        } return CircularProgressIndicator();
                      },);
                    }
                ),

              )
            ],
          )
      ),
    );

  }
}

 Future handCheckfetch(String url) async {
    String username = '*******';
    String password = '*******';
    String basicAuth =
        'Basic ' + base64Encode(utf8.encode('$username:$password'));
    var response = await http.get((url),
        headers: <String, String>{'authorization': basicAuth}
    );
    var sap = Sap.fromJson(json.decode(response.body));
    if (response.statusCode == 200) {

      print(response.statusCode);
      // If the call to the server was successful, parse the JSON.
      return
        Container(
            child: Row(
              children: <Widget>[
                SizedBox(width: 15,),
                Text('Barcode : ', style: TextStyle(
                  fontSize: 18.0,
                  fontWeight: FontWeight.bold,
                ),),
                SizedBox(width: 15,),
                new Text(
                  sap.results[0].barcode.toString(),
                  style: TextStyle(fontSize: 18),),
                SizedBox(width: 15),
                new Icon(
                  sap.results[0].handCheck
                      ? Icons.check_box
                      : Icons.check_box_outline_blank,
                  size: 20,
                ),
                SizedBox(width: 15,),
              ],
            )
        );
    }
    else if (response.statusCode == 500) {}
    else {
      // If that call was not successful, throw an error.
      throw Exception('Failed to load post');
    }
  }

当我在行中输入文本时，我想显示列表提示，其中包含来自差异api调用的许多数据，但是当我更改文本时，它总是在最后输入之后更改。对不起，糟糕的礼物:(