Future，FutureBuilder

Future，FutureBuilder

Future：代表网络请求的一个未来结果，包含成功和失败，以及其他的状态；
FutureBuilder：异步UI的编程，接受一个Future作为异步对象，然后根据Future的结果，来渲染UI。

class _MyHomePageState extends State<MyHomePage> {
  String showResult = '';

  Future<CommonModel> fetchPost() async {
    var url = 'http://www.devio.org/io/flutter_app/json/test_common_model.json';
    final response = await http.get(Uri.parse(url));
    Utf8Decoder utf8decoder = Utf8Decoder(); // fix:中文乱码问题
    final result = json.decode(utf8decoder.convert(response.bodyBytes));
    return CommonModel.fromJson(result);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('网络请求测试|Future|FutureBuilder使用技巧'),
      ),
      body: FutureBuilder<CommonModel>(
          future: fetchPost(), // 指定future
          builder: (BuildContext context, AsyncSnapshot<CommonModel> snapshot) {
            switch (snapshot.connectionState) {
              case ConnectionState.none:
                return Center(child: Text('Input a url to start'));
              case ConnectionState.waiting:
                return Center(child: CircularProgressIndicator());
              case ConnectionState.active:
                return Text('data');
              case ConnectionState.done:
                if (snapshot.hasError) {
                  return Text('${snapshot.error}',
                      style: TextStyle(color: Colors.red));
                } else {
                  return Text('item:${snapshot.data.toString()}');
                }
            }
          }),
    );
  }
}

/// 工厂模式，创建对象。
class CommonModel {
  final String icon;
  final String title;
  final String url;
  final String statusBarColor;
  final bool hideAppBar;

  CommonModel({
    required this.icon,
    required this.title,
    required this.url,
    required this.statusBarColor,
    required this.hideAppBar,
  });

  factory CommonModel.fromJson(Map<String, dynamic> json) {
    return CommonModel(
      icon: json['icon'],
      title: json['title'],
      url: json['url'],
      statusBarColor: json['statusBarColor'],
      hideAppBar: json['hideAppBar'],
    );
  }
  @override
  String toString() {
    return 'CommonModel{icon: $icon, title: $title, url: $url, statusBarColor: $statusBarColor, hideAppBar: $hideAppBar}';
  }
}

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