9. Flutter 网络请求

网络库

介绍

用于发送HTTP请求的可组合的、基于future的库。

包含一组高级函数和类，可以方便地使用HTTP资源。它是多平台的，支持移动、桌面和浏览器。

依赖库引入

dependencies:
  flutter:
    # 3.网络访问库
    http: 0.13.3

封装

一种思路基本步骤

1. 库 import
2. 核心方法
3. 转码为 utf8
4. 异常抛出

封装就是在使用时传入 成功、失败、完成的回调

另一种思路是使用 Future 的特性，完成后回调链

1. then()、catchError()、whenComplete()

import 'package:http/http.dart' as http;

class HttpManager {
  static Utf8Decoder utf8decoder = Utf8Decoder();

  static void getData(String url,
      {Map<String, String> headers, Function success, Function fail, Function complete}) async {
    try {
      var response = await http.get(Uri.parse(url), headers: headers);
      if (response.statusCode == 200) {
        // 解析 json 字符串，返回 Map<String，dynamic> 类型
        var result = json.decode(utf8decoder.convert(response.bodyBytes));
        success(result);
      } else {
        throw Exception('"Request failed with status: ${response.statusCode}"');
      }
    } catch (e) {
      fail(e);
    } finally {
      if (complete != null) {
        complete();
      }
    }
  }

  static Future requestData(String url, {Map<String, String> headers}) async {
    try {
      var response = await http.get(Uri.parse(url), headers: headers);
      if (response.statusCode == 200) {
        var result = json.decode(utf8decoder.convert(response.bodyBytes));
        return result;
      } else {
        throw Exception('"Request failed with status: ${response.statusCode}"');
      }
    }catch(e){
      Future.error(e);
    }
  }
}

使用

  // 下拉刷新
  void refresh() {
    HttpManager.getData(
      getUrl(),
      success: (json) {
        M model = getModel(json);
        removeUselessData(model.itemList);
        getData(model.itemList);
        viewState = ViewState.done;

        // 下一页数据的处理
        nextPageUrl = getNextUrl(model);
        refreshController.refreshCompleted();
        refreshController.footerMode.value = LoadStatus.canLoading;
        // 额外的操作：例如加载home的数据列表
        doExtraAfterRefresh();
      },
      fail: (e) {
        JinToast.showError(e.toString());
        refreshController.refreshFailed();
        viewState = ViewState.error;
      },
      complete: () => notifyListeners(),
    );
  }

  // 下拉刷新
  void refresh() {
    HttpManager.getData(
      getUrl(),
      success: (json) {
        M model = getModel(json);
        removeUselessData(model.itemList);
        getData(model.itemList);
        viewState = ViewState.done;

        // 下一页数据的处理
        nextPageUrl = getNextUrl(model);
        refreshController.refreshCompleted();
        refreshController.footerMode.value = LoadStatus.canLoading;
        // 额外的操作：例如加载home的数据列表
        doExtraAfterRefresh();
      },
      fail: (e) {
        JinToast.showError(e.toString());
        refreshController.refreshFailed();
        viewState = ViewState.error;
      },
      complete: () => notifyListeners(),
    );
  }