Retrofit的使用

設置權限與添加依賴

定義請求接口

通過創建一個retrofit生成一個接口的實現類(動態代理)

調用接口請求數據

設置權限與添加依賴

權限：首先確保在AndroidManifest.xml中請求了網絡權限 ：

<uses-permission android:name="android.permission.INTERNET" />

（2）Studio用戶,在app/build.gradle文件中添加如下代碼：

dependencies {compile'com.squareup.retrofit2:retrofit:2.0.2'compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta3' }

定義請求接口

public interface GankioService {@GET("data/福利/10/{page}")Call<GirlData> getGirls(@Path("page") int page);@GET("data/Android/10/{page}")Call<AndroidData> getAndroidData(@Path("page") int page); }

請求的URL可以在函數中使用替換塊和參數進行動態更新，替換塊是{ and }包圍的字母數字組成的字符串，相應的參數必須使用相同的字符串被@Path進行注釋

然后創建一個retrofit

public static GankioService buildGankioService() {if (mGankioService == null) {Retrofit retfGank = new Retrofit.Builder().baseUrl("http://gank.io/api/").addConverterFactory(GsonConverterFactory.create()).build();mGankioService = retfGank.create(GankioService.class);}return mGankioService;}

retfGank.create(GankioService.class)用到了動態代理

大家一看就發現了 create方法返回了一個動態代理對象，那么動態代理是什么呢 ：
—在運行時， 動態代理類 實現了一個或者一組接口，目的是，其中任何一個接口的實例的方法調用將會被指派到統一的另一個接口的方法中。
InvocationHandler 中覆寫的 invoke() 方法，在進行原本的方法調用之前或者之后，可以做點事情。
所以當我們調用 httpStores.getUser(hashMap);的時候其實是走了動態代理的invoke方法，在這里Retrofit巧妙的理由注解把接口轉換成了一個HTTP請求

調用接口請求數據

private void loadFromInternet(int page) {start = page;final Call<GirlData> girlDataCall = mService.getGirls(page);girlDataCall.enqueue(new Callback<GirlData>() {@Overridepublic void onResponse(Call<GirlData> call, Response<GirlData> response) {mGirlData = response.body();List<Girl> newGirls = mGirlData.getGirls();// check if newGirls should be added into local girlsif (checkShouldAdded(newGirls)){addGirlsToDB(newGirls);}else{shouldLoadFromInternet = false;}mView.showMore(newGirls);mView.finishRefresh();}@Overridepublic void onFailure(Call<GirlData> call, Throwable t) {mView.finishRefresh();mView.showSnackBar();}});}

其中GirlData是由接口返回的json數據格式決定的

public class GirlData {/*** error : false* results : [{"_id":"56eb5db867765933d9b0a8fc","_ns":"ganhuo","createdAt":"2016-03-18T09:45:28.259Z","desc":"3.18","publishedAt":"2016-03-18T12:18:39.928Z","source":"chrome","type":"福利","url":"http://ww1.sinaimg.cn/large/7a8aed7bjw1f20ruz456sj20go0p0wi3.jpg","used":true,"who":"張涵宇"},{"_id":"56e8d0bb67765933d8be90be","_ns":"ganhuo","createdAt":"2016-03-16T11:19:23.692Z","desc":"3.16","publishedAt":"2016-03-17T11:14:16.306Z","source":"chrome","type":"福利","url":"http://ww4.sinaimg.cn/large/7a8aed7bjw1f1yjc38i9oj20hs0qoq6k.jpg","used":true,"who":"張涵宇"},{"_id":"56e8ce3967765933d8be90bd","_ns":"ganhuo","createdAt":"2016-03-16T11:08:41.957Z","desc":"3.16","publishedAt":"2016-03-16T11:24:01.505Z","source":"chrome","type":"福利","url":"http://ww3.sinaimg.cn/large/610dc034gw1f1yj0vc3ntj20e60jc0ua.jpg","used":true,"who":"代碼家"},{"_id":"56e764116776592d80511280","_ns":"ganhuo","createdAt":"2016-03-15T09:23:29.580Z","desc":"3.15","publishedAt":"2016-03-15T11:45:57.350Z","source":"chrome","type":"福利","url":"http://ww4.sinaimg.cn/large/7a8aed7bjw1f1xad7meu2j20dw0ku0vj.jpg","used":true,"who":"張涵宇"},{"_id":"56e619a46776591744cf05c0","_ns":"ganhuo","createdAt":"2016-03-14T09:53:40.126Z","desc":"3.14","publishedAt":"2016-03-14T11:55:19.66Z","source":"chrome","type":"福利","url":"http://ww1.sinaimg.cn/large/7a8aed7bjw1f1w5m7c9knj20go0p0ae4.jpg","used":true,"who":"張涵宇"},{"_id":"56e220ca67765966681b3a23","_ns":"ganhuo","createdAt":"2016-03-11T09:35:06.879Z","desc":"3.11--一周年快樂！！！","publishedAt":"2016-03-11T12:37:20.4Z","source":"chrome","type":"福利","url":"http://ww4.sinaimg.cn/large/7a8aed7bjw1f1so7l2u60j20zk1cy7g9.jpg","used":true,"who":"張涵宇"},{"_id":"56e0f0e86776596669cc2511","_ns":"ganhuo","createdAt":"2016-03-10T11:58:32.298Z","desc":"3.10","publishedAt":"2016-03-10T12:54:31.68Z","source":"chrome","type":"福利","url":"http://ww4.sinaimg.cn/large/7a8aed7bjw1f1rmqzruylj20hs0qon14.jpg","used":true,"who":"張涵宇"},{"_id":"56df891167765947765e2ad1","_ns":"ganhuo","createdAt":"2016-03-09T10:23:13.778Z","desc":"3.9","publishedAt":"2016-03-09T12:06:26.401Z","source":"chrome","type":"福利","url":"http://ww2.sinaimg.cn/large/7a8aed7bjw1f1qed6rs61j20ss0zkgrt.jpg","used":true,"who":"張涵宇"},{"_id":"56de2b1b6776592b6192bf46","_ns":"ganhuo","createdAt":"2016-03-08T09:30:03.578Z","desc":"3.8","publishedAt":"2016-03-08T12:55:59.161Z","source":"chrome","type":"福利","url":"http://ww3.sinaimg.cn/large/7a8aed7bjw1f1p77v97xpj20k00zkgpw.jpg","used":true,"who":"張涵宇"},{"_id":"56dd06b56776592b6246e979","_ns":"ganhuo","createdAt":"2016-03-07T12:42:29.664Z","desc":"3.7","publishedAt":"2016-03-07T12:49:24.470Z","source":"chrome","type":"福利","url":"http://ww1.sinaimg.cn/large/7a8aed7bjw1f1o75j517xj20u018iqnf.jpg","used":true,"who":"張涵宇"}]*/private boolean error;@SerializedName("results")private List<Girl> girls;public boolean isError() {return error;}public void setError(boolean error) {this.error = error;}public List<Girl> getGirls() {return girls;}public void setGirls(List<Girl> girls) {this.girls = girls;}}

是不是很簡單而且很優雅
當然Retrofit的內部實現更優雅使用了很多設計模式這里推薦一位大神的文章

Retrofit分析-經典設計模式案例 - 簡書

下面在說一下Okhttp的攔截器Interceptor 這真的是一個用起來非常爽的東西實現起來也非常簡單
上代碼

public class OkhttpInterceptor implements Interceptor { @Override public Response intercept(Interceptor.Chain chain) throws IOException { //取到當前請求的Requset Request oldRequest = chain.request(); //取到請求的URL ，對你的URL進行修改，比如拼接一個UID什么的 //也可以使用addQueryParameter拼接參數 String url = oldRequest.url().toString()+"?="+uid; Request newRequest = oldRequest.newBuilder() .method(oldRequest.method(), oldRequest.body()) .url(url) .build(); return chain.proceed(newRequest); } } 當然你也可以增加請求參數 HttpUrl.Builder urlBuilder = oldRequest.url()newBuilder() .scheme(oldRequest.url().scheme()) .addQueryParameter("key", "value") 只需要把url里的參數改為urlBuilder就行了

當然具體的業務需求也會遇到一些問題比如當我們的后臺用的是https的時候，需要用到自簽名證書，而OKhttp3已經沒有了setCertificates設置自簽名證書時怎么辦，沒關系我們還有萬能的反射呢，下面我們就利用反射把https給過濾掉

SSLContext sc = null; try { sc = SSLContext.getInstance("SSL"); sc.init(null, new TrustManager[]{new X509TrustManager() { @Override public void checkClientTrusted(java.security.cert.X509Certificate[] chain, String authType) throws java.security.cert.CertificateException { } @Override public void checkServerTrusted(java.security.cert.X509Certificate[] chain, String authType) throws java.security.cert.CertificateException { } @Override public java.security.cert.X509Certificate[] getAcceptedIssuers() { return null; } } }, new SecureRandom()); } catch (Exception e) { e.printStackTrace(); } HostnameVerifier hv1 = new HostnameVerifier() { @Override public boolean verify(String hostname, SSLSession session) { return true; }}; String workerClassName = "okhttp3.OkHttpClient"; try { sClient = new OkHttpClient.Builder().build(); Class workerClass = Class.forName(workerClassName); Field hostnameVerifier = workerClass.getDeclaredField("hostnameVerifier"); hostnameVerifier.setAccessible(true); hostnameVerifier.set(sClient, hv1); Field sslSocketFactory = workerClass.getDeclaredField("sslSocketFactory"); sslSocketFactory.setAccessible(true); sslSocketFactory.set(sClient, sc.getSocketFactory()); } catch (Exception e) { e.printStackTrace(); }

這個反射只是用在忽略https上，現在國內主流還是http，一般是用不上的，攔截器的話要debug看看清楚，你可以在http執行請求之前做一些操作，比如加一些請求參數或者是判斷什么的。

參考鏈接

30分鐘上手最火android網絡請求框架Retrofit - 簡書

Retrofit2.0使用 - OPEN 開發經驗庫

快速Android開發系列網絡篇之Retrofit - AngelDevil - 博客園

Retrofit分析-經典設計模式案例 - 簡書

Retrofit 解析 JSON 數據 - 簡書

Retrofit2.0

我在stackoverflow回答的關于Retrofit2.0的相關問題

使用RxJava與Retrofit2.0使用的實例：Retrofit 2.0 RxJava Sample

JW大神的文章

吳小龍Android Retrofit 2.0使用

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