上篇Retrofit初探 中已初步使用了Retrofit，简单介绍了Retrofit的使用步骤。本篇继续深入分析一下Retrofit流程。
Retrofit创建 先看一下Retrofit的创建1 2 3 4 5 6 7 Retrofit retrofit = new Retrofit.Builder() .baseUrl(URL) .addConverterFactory(FastjsonConverterFactory.create()) .addCallAdapterFactory(RxJavaCallAdapterFactory.create()) .build();
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 public Retrofit build () okhttp3.Call.Factory callFactory = this .callFactory; if (callFactory == null ) { callFactory = new OkHttpClient(); } Executor callbackExecutor = this .callbackExecutor; if (callbackExecutor == null ) { callbackExecutor = platform.defaultCallbackExecutor(); } List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this .adapterFactories); adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor)); List<Converter.Factory> converterFactories = new ArrayList<>(this .converterFactories); return new Retrofit(callFactory, baseUrl, converterFactories, adapterFactories, callbackExecutor, validateEagerly); }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 private static final Platform PLATFORM = findPlatform();static Platform get () return PLATFORM; } private static Platform findPlatform () try { Class.forName("android.os.Build" ); if (Build.VERSION.SDK_INT != 0 ) { return new Android(); } } catch (ClassNotFoundException ignored) { } return new Platform(); }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 static class Android extends Platform @Override public Executor defaultCallbackExecutor () return new MainThreadExecutor(); } @Override CallAdapter.Factory defaultCallAdapterFactory (Executor callbackExecutor) { return new ExecutorCallAdapterFactory(callbackExecutor); } static class MainThreadExecutor implements Executor private final Handler handler = new Handler(Looper.getMainLooper()); @Override public void execute (Runnable r) handler.post(r); } } }
Retrofit请求的创建 在Volley中描述一个HTTP请求是需要创建一个Request对象，然后把这个请求对象放到一个队列中，让网络线程去处理。那Retrofit是怎么做的呢？1 2 3 4 5 6 7 interface Api @GET ("/repos/{owner}/{repo}/contributors" ) Call<List<Contributor>> repoContributors( @Path ("owner" ) String owner, @Path ("repo" ) String repo); } Api api = retrofit.create(Api.class);
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 public <T> T create (final Class<T> service) { Utils.validateServiceInterface(service); if (validateEagerly) { eagerlyValidateMethods(service); } return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class<?>[] { service }, new InvocationHandler() { private final Platform platform = Platform.get(); @Override public Object invoke (Object proxy, Method method, Object... args) throws Throwable { if (method.getDeclaringClass() == Object.class) { return method.invoke(this , args); } if (platform.isDefaultMethod(method)) { return platform.invokeDefaultMethod(method, service, proxy, args); } ServiceMethod serviceMethod = loadServiceMethod(method); OkHttpCall okHttpCall = new OkHttpCall<>(serviceMethod, args); return serviceMethod.callAdapter.adapt(okHttpCall); } }); }
service)方法使用了 动态代理 来生成接口实现类。通过该函数，我们可以拿到一个前面自定义的Api的一个代理类，其功能就相当于一个Api对象，
1 2 3 ServiceMethod serviceMethod = loadServiceMethod(method); OkHttpCall okHttpCall = new OkHttpCall<>(serviceMethod, args); return serviceMethod.callAdapter.adapt(okHttpCall);
