本文將圍繞Retrofit的組裝請求管理器、發起請求、請求響應的封裝進行介紹。
以獲取手機號碼歸屬地的整個流程為例：

Get請求

請求API類，這個類等待Retrofit通過動態代理的方式將這個接口的方法以及對應得注解生成一個http請求，在把這個http請求交給OkHttp處理。

public interface HttpService {
    @GET(GlobalVar.NetPorts.WEATHER)
    Observable <HttpResult<PhoneLocalBean>> queryWeather(@QueryMap Map<String, String> options);
}

請求管理器

創建一個請求管理器用來配置Retrofit與OkHttp的基本屬性。

public class HttpManager {

    public static final String SERVER = GlobalVar.SERVER; //服務器根地址
    private HttpService mHttpService;
    private Retrofit mAdapter;
    private static HttpManager instance;

    private HttpManager() {
        mAdapter = new Retrofit.Builder().baseUrl(SERVER).addConverterFactory(ScalarsConverterFactory.create()).addConverterFactory(GsonDConverterFactory.create()).addCallAdapterFactory(RxJavaCallAdapterFactory.create()).client(getBuilder().build()).build();
    }

    public static HttpManager getInstance() {
        if (instance == null) {
            instance = new HttpManager();
        }
        return instance;
    }

    public HttpService sendRequest() {
        if (mHttpService == null) {
            mHttpService = mAdapter.create(HttpService.class);
        }
        return mHttpService;
    }

    private OkHttpClient.Builder getBuilder() {
        //這里的存儲位置只是簡單獲取，根據實際需要修改
        File cacheFile = new File(BaseApplication.getContext().getCacheDir().getAbsolutePath(), "ShopHttpCache");
        Cache cache = new Cache(cacheFile, 1024 * 1024 * 100);

        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        builder.addInterceptor(new HttpCacheInterceptor());
        builder.cache(cache);
        builder.readTimeout(GlobalVar.READ_TIMEOUT, TimeUnit.SECONDS);
        builder.connectTimeout(GlobalVar.CONNECT_TIMEOUT, TimeUnit.SECONDS);
        builder.writeTimeout(GlobalVar.WRITE_TIMEOUT, TimeUnit.SECONDS);
        builder.retryOnConnectionFailure(true);
        return builder;
    }
}

請求攔截器

用于對請求的發起與響應的攔截，這里我們可以增加統一的Header，客戶端與服務端的加密驗證也可以放在這里，網絡緩存等等。

public class HttpCacheInterceptor implements Interceptor {

    private static final String TAG = "HttpManager";

    @Override public Response intercept(Chain chain) throws IOException {
        Request original = chain.request();
        Request.Builder requestBuilder = original.newBuilder().method(original.method(), original.body());

        Headers.Builder hb = new Headers.Builder();
        addHeader(hb);
        if (!NetUtils.isConnected(BaseApplication.getContext())) {
            //網絡不可用
            requestBuilder.cacheControl(CacheControl.FORCE_CACHE);
        } else { 
            requestBuilder.cacheControl(CacheControl.FORCE_NETWORK);
        }
        Request request = requestBuilder.headers(hb.build()).build();
        Log.d(TAG, "地址：" + request.url());

        try {
            Response response = chain.proceed(request);
            String cookie = response.headers().get("Set-Cookie");

            if (NetUtils.isConnected(BaseApplication.getContext())) { //如果網絡可用
                int maxAge = 60 * 3;
                response = response.newBuilder().removeHeader("Pragma").header("Cache-Control", "public, max-age=" + maxAge).build();
            } else {
                int maxStale = 60 * 60 * 24;
                response = response.newBuilder().removeHeader("Pragma").header("Cache-Control", "public, only-if-cached, max-stale=" + maxStale).build();
            }
            return response;
        } catch(Exception err) {
            Log.e("HttpManager", "http=============" + err.getLocalizedMessage());
        }
        return null;
    }

    private void addHeader(Headers.Builder header) {
        header.add("apikey", "8ca4b101096587f725ff69a07ff4d188");
    }
}

發起請求

這里的addMainSubscription用于簡化書寫并統一管理發起的訂閱，當Activity退出時統一取消訂閱。

@Override
public void queryWeather(String phone) {
    Map < String, String > options = new HashMap < >();
    options.put("phone", phone);
    addMainSubscription(HttpManager.getInstance().sendRequest().queryWeather(options), new HttpResultCallBack<PhoneLocalBean> () {

        @Override public void onResponse(PhoneLocalBean bean, int status) {
            if (bean != null) {
                mView.onUserLoadCompleted(bean);
            } else {
                mView.onUserLoadError();
            }
        }

        @Override public void onErr(String err, int status) {
            mView.showToast(err);
            mView.onUserLoadError();
        }
    });
}

自定義請求響應回調

對響應數據成功失敗的封裝，而一般的數據返回格式基本分為：
1、狀態碼
2、提示信息
3、具體數據內容
具體數據體可以是集合也可以是對象，所以使用了泛型HttpResult<M>統一處理。這里定義的M一方面是告訴GSON我的子數據格式是什么，另一方面用于回調方法中返回對應得數據類型。

public abstract class HttpResultCallBack<M> extends Subscriber <HttpResult<M>> {

    public abstract void onResponse(M m, int status);
    public abstract void onErr(String msg, int status);

    @Override public void onCompleted() {}

    @Override public void onError(Throwable e) {
        if (e != null) {
            if (e instanceof ResultException) {
                ResultException err = (ResultException) e;
                onErr(err.getErrMsg(), GlobalVar.RESULT_UNLOGIN);
            } else {
                onErr("網絡異常，請檢查網絡", GlobalVar.RESULT_UNLOGIN);
                Log.d("HttpManager", "解析失敗==：" + e.getMessage());
            }
        }
        onCompleted();
    }

    private void onHttpFail(String msg, int status) {
        onErr(msg, status);
    }

    @Override public void onNext(HttpResult < M > result) {
        String jsonResponse = new Gson().toJson(result);
        Log.d("HttpManager", "返回ok==：" + jsonResponse);
        if (result.getErrNum() == GlobalVar.RESULT_OK) {
            onResponse(result.getRetData(), GlobalVar.RESULT_OK);
        } else {
            onHttpFail(result.getErrMsg(), GlobalVar.RESULT_UNLOGIN);
        }
    }
}

結語

這里的代碼都是結合具體項目來寫的，雖然是抽出來的精簡版但更容易讀懂。我覺得直接看代碼更容易理解一段代碼的思想，所以大多都是以代碼為主注釋為輔。最后有哪些不足的地方也謝謝大家指出來^~。

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