去年9月份发布了flutter_mall 的第一个版本到现在差不多有9个月了，到现在已经获得了1.2K star，好几个月没有写flutter了，最近回头看了下之前的代码，发现有很多地方可以进行优化，综合考虑以后决定用MVVM重构，并对bug进行修复。

对于什么是MVVM在这里我就不再说明，只给出如下图，自行体会

Provider是基于InheritedWidget实现的一套跨组件状态共享解决方案，这样就可以Model改变的时候刷新View显示的数据。

新建flutter_mvvm项目

文件夹	作用
constant	主要是放一些常量
models	后台返回的数据模型
views	页面
widgets	封装的自定义widget
utils	工具类
view_models	viewmodel

这里以获取商品列表为列

使用代码生成库序列化JSON采用框架json_serializable，没有使用过的可以看下具体的教程，非常方便的一个框架。

goods_model.dart

import 'package:json_annotation/json_annotation.dart';

part 'goods_model.g.dart';

class GoodListModel {
  List<GoodsModel> goodsEntitys;

  GoodListModel(this.goodsEntitys);

  factory GoodListModel.fromJson(List<dynamic> parseJson) {
    List<GoodsModel> goodsEntitys;
    goodsEntitys = parseJson.map((i) => GoodsModel.fromJson(i)).toList();
    return GoodListModel(goodsEntitys);
  }
}

@JsonSerializable()
class GoodsModel extends Object {
  @JsonKey(name: 'id')
  int id;

  @JsonKey(name: 'name')
  String name;

  @JsonKey(name: 'brief')
  String brief;

  @JsonKey(name: 'picUrl')
  String picUrl;

  @JsonKey(name: 'isNew')
  bool isNew;

  @JsonKey(name: 'isHot')
  bool isHot;

  @JsonKey(name: 'counterPrice')
  double counterPrice;

  @JsonKey(name: 'retailPrice')
  double retailPrice;

  GoodsModel(
    this.id,
    this.name,
    this.brief,
    this.picUrl,
    this.isNew,
    this.isHot,
    this.counterPrice,
    this.retailPrice,
  );

  factory GoodsModel.fromJson(Map<String, dynamic> srcJson) =>
      _$GoodsModelFromJson(srcJson);

  Map<String, dynamic> toJson() => _$GoodsModelToJson(this);
}

网络框架dio,并进行二次封装，用单例模式，并添加拦截器打印请求和返回的数据

import 'package:dio/dio.dart';

var dio;

class HttpUtil {
  // 工厂模式
  static HttpUtil get instance => _getInstance();

  static HttpUtil _httpUtil;

  static HttpUtil _getInstance() {
    if (_httpUtil == null) {
      _httpUtil = HttpUtil();
    }
    return _httpUtil;
  }

  HttpUtil() {
    BaseOptions options = BaseOptions(
      connectTimeout: 5000,
      receiveTimeout: 5000,
    );
    dio = new Dio(options);
    dio.interceptors
        .add(InterceptorsWrapper(onRequest: (RequestOptions options) {
      print("========================请求数据===================");
      print("url=${options.uri.toString()}");
      print("params=${options.data}");

      return options;
    }, onResponse: (Response response) {
      print("========================请求数据===================");
      print("code=${response.statusCode}");
      print("response=${response.data}");
    }, onError: (DioError error) {
      print("========================请求错误===================");
      print("message =${error.message}");
    }));
  }

  Future get(String url, {Map<String, dynamic> parameters, Options options}) async {
    Response response;
    if (parameters != null && options != null) {
      response = await dio.get(url, queryParameters: parameters, options: options);
    } else if (parameters != null && options == null) {
      response = await dio.get(url, queryParameters: parameters);
    } else if (parameters == null && options != null) {
      response = await dio.get(url, options: options);
    } else {
      response = await dio.get(url);
    }
    return response.data;
  }

  Future post(String url,
      {Map<String, dynamic> parameters,Options options}) async {
    Response response;
    if (parameters != null && options != null) {
      response = await dio.post(url, data: parameters, options: options);
    } else if (parameters != null && options == null) {
      response = await dio.post(url, data: parameters);
    } else if (parameters == null && options != null) {
      response = await dio.post(url, options: options);
    } else {
      response = await dio.post(url);
    }
    return response.data;
  }
}

定义网络请求返回处理结果的一些回调

typedef OnSuccessList<T>(List<T> banners);

typedef OnFail(String message);

typedef OnSuccess<T>(T onSuccess);

请求网络并处理返回数据

 Future getCategoryGoodsListData(
      Map<String, dynamic> parameters, OnSuccessList onSuccessList,
      {OnFail onFail}) async {
    try {
      var responseList = [];
      var response = await HttpUtil.instance
          .get(Api.GOODS_LIST_URL, parameters: parameters);
      if (response[Strings.HTTP_ERROR_NO] == 0) {
        responseList = response[Strings.HTTP_DATA][Strings.HTTP_LIST];
        GoodListModel goodListModel = GoodListModel.fromJson(responseList);
        onSuccessList(goodListModel.goodsEntitys);
      } else {
        onFail(response[Strings.HTTP_ERROR_MSG]);
      }
    } catch (e) {
      print(e);
      onFail(Strings.SERVER_EXCEPTION);
    }
  }

GoodsListModel中请求列表数据并在数据变化的时候通知view进行刷新

class GoodsListViewModel extends ChangeNotifier {
  GoodsService goodsService = GoodsService();
  List<GoodsModel> goodsData;
  bool hasData;
  void loadGoodsData(String categoryId, int page, int limit) async {
    var parameters = {"categoryId": categoryId, "page": page, "limit": limit};
    goodsService.getCategoryGoodsListData(parameters, (goodsList) {
      if (page == 1) {
        goodsData = goodsList;
        notifyListeners();
        return;
      }
      List<GoodsModel> data = goodsList;
      goodsData.addAll(data);
      notifyListeners();
    }, onFail: (message) {
     // ToastWidget.showToast(message);
      hasData = !(goodsData == null || goodsData.length == 0);
      notifyListeners();
    });
  }

}

在数据变化以后刷新列表

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  GoodsListViewModel model = GoodsListViewModel();
  AppThemeViewModel themeViewModel = AppThemeViewModel();

  @override
  void initState() {
    super.initState();
    model.loadGoodsData("1008002", 1, 100);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(Strings.MVVM),
        ),
        body: Center(
          child: ChangeNotifierProvider<GoodsListViewModel>(
            create: (context) => model,
            child:
                Consumer<GoodsListViewModel>(builder: (context, model, child) {
              return ListView.builder(
                  itemCount:
                      model.goodsData == null ? 0 : model.goodsData.length,
                  itemBuilder: (BuildContext context, int index) {
                    return InkWell(
                      child: Text(model.goodsData[index].name),
                      onTap: () {
                      Provider.of<AppThemeViewModel>(context,listen: false).changeTheme();
                      },
                    );
                  });
            }),
          ),
        ));
  }
}

到这里用mvvm实现一个简单商品列表页面就成功了。