Flutter从入门到入土（三）网络请求Dio

1、网络请求

  Dio _dio = new Dio();

  Future getInformationJson(User user) async {

    var url = 'http://xxx/xxx/xxx?username=' + user._username +
        '&password=' + user._password;

    Response response = await _dio.get(url);
    if (response.statusCode == HttpStatus.ok) {
      var data = jsonDecode(response.toString());　　//JSON数据的解析
      try{
        data['payload']['scores'].forEach((v) {
//          print(v['className']);
          Scores score = new Scores(
              v['term'], v['className'], v['credit'].toString(), v['score'],
              v['gpa'].toString());
          user._scores.add(score);
        });

        user._avggpa = data['payload']['gpa'].toString();
        user._avgscore = data['payload']['avg'].toString();
        user._size = data['payload']['size'].toString();
      }catch(e){
        print(e);
      }
    }
    return user;
  }

2、异步请求(在执行界面渲染的类当中)

  void initState() {
    super.initState();
    user = new User();

    information.getInformationJson(user).then((val){
      user = val;
      build(context);
    });
  }

使用setState(() {});

  @override
  Widget build(BuildContext context){
    // TODO: implement build

    if(user._scores == null || user._scores.length == 0){
      return loadingWidget();
    }else{
      print('main');
      setState(() {});
      return mainWidget();
    }
  }

当user获得到数据后就会重新渲染页面（loadingWidget ==> mainWidget）