Retrofit 与 annotation Processor ，EventBus结合使用的一个简单示例

Retrofit 与 annotation Processor ，EventBus结合使用的一个简单示例

代码地址：https://github.com/baofei/RetrofitAnnotation

用annotation processor 把Retrofit的接口生成Manager，网络请求成功的数据将会使用EventBus post出去

简单介绍下(Annotation Processing )，在Java中有一个apt的命令行工具（也包含了javac命令的功能，即编译功能），它的作用是在编译源文件(.java)之前，通过一个自定义的注解处理器(AnnotationProcessor)解释并处理源文件中的注解，由注解处理器生成一些新的源文件，字节码文件(.class)，或其他的文本文件，APT也会对新生成源文件进行编译，直到没有新的文件生成。具体的Google下就有了。

APT需要实现AbstractProcessor，可以看看大神们写的文章。

部分代码
RetrofitManager , 实现Retrofit的单例

public class RetrofitManager {
 public static RetrofitManager mManager = new RetrofitManager();
 public static OkHttpClient mClient;
 private Retrofit retrofit;
 public String mBaseUrl;
 public HashMap mHeader;
 private int mRetrofitCode;
 private Context mContext;
 private RetrofitManager() {
 }
 public static RetrofitManager getInstance() {
 return mManager;
 }
 public void init(Context context, String url) {
 mBaseUrl = url;
 mClient = createClient();
 mContext = context.getApplicationContext();
 createRetrofit();
 }
 private OkHttpClient createClient() {
 return new OkHttpClient.Builder().build();
 }
 private void createRetrofit() {
 retrofit = new Retrofit.Builder()
 .baseUrl(mBaseUrl)
 .addConverterFactory(GsonConverterFactory.create())
 .client(mClient)
 .build();
 mRetrofitCode = retrofit.hashCode();
 }
 public synchronized Retrofit getRetrofit() {
 return retrofit;
 }
 public int getRetrofitCode() {
 return mRetrofitCode;
 }
 public synchronized void resetRetrofit(String url) {
 mBaseUrl = url;
 mClient = null;
 mClient = createClient();
 retrofit = null;
 createRetrofit();
 }

}

实现Callback，请求完成后用EventBus post出数据

 public class ApCallBack implements Callback {
 T body;
 private Object extra;
 public ApCallBack(Class body) {
 this(body, null);
 }
 public ApCallBack(Class body, Object extra) {
 this.extra = extra;
 try {
 this.body = (T) body.newInstance();
 } catch (InstantiationException e) {
 e.printStackTrace();
 } catch (IllegalAccessException e) {
 e.printStackTrace();
 }
 }
 @Override
 public void onResponse(Call call, Response response) {
 if (response.isSuccessful()) {
 BaseResponse bean = response.body();
 if (extra != null) {
 bean.extra = extra;
 }
 EventBus.getDefault().post(bean);
 } else {
 onFailure(call, new Throwable("HTTP STATUS CODE " + response.code()));
 }
 }
 @Override
 public void onFailure(Call call, Throwable t) {
 if (body == null) {
 body = (T) new BaseResponse();
 }
 if (extra != null) {
 body.extra = extra;
 }
 body.code = Http.ERROR_CODE_FAILURE;
 body.desc = getFailureDesc();
 EventBus.getDefault().post(body);
 }
 protected String getFailureDesc() {
 return "network error";
 }

}

Manager的一个基类， annotation processor 把Retrofit的接口生成Manager的基类

/**
 * 基类，用于创建接口相关service
 * Created by baofei on 2016/9/22.
 */
public class BaseManager {
    private int mRetrofitCode;
    private T service;
    public BaseManager() {
      create();
    }
    private void create() {
    mRetrofitCode = RetrofitManager.getInstance().getRetrofitCode();
     service =  (T) RetrofitManager.getInstance().getRetrofit().create(getT());
    }
    private Class getT() {
            Type genType = getClass().getGenericSuperclass();
            Type[] params = ((ParameterizedType) genType).getActualTypeArguments();
return (Class) params[0];
    }

    /**
     * 获取T相关接口service类
     *
     * @return T的具体实现
     */
    public T getService() {
        if(mRetrofitCode != RetrofitManager.getInstance().getRetrofitCode()){
            resetService();
        }
        return service;
    }

    /**
     * 切换环境重置service
     */
    public void resetService() {
        create();
    }
}```
http请求接口
``` @Manager
public interface ApiService {

    @POST("/api/addr/getDefaultAddr")
    Call getDefaultAddr();
}```

 运行编译时，annotation processor根据ApiService 和BaseManager生成如下代码,代码生成位置为build/generated/source/apt里

public final class ApiServiceManager extends BaseManager {
private static ApiServiceManager sApiServiceManager;

public static synchronized ApiServiceManager getInstance() {
if (sApiServiceManager == null) {
sApiServiceManager = new ApiServiceManager();
}
return sApiServiceManager;
}

public Call getDefaultAddr() {
Call call = getService().getDefaultAddr();
call.enqueue(new ApCallBack(ResultBean.class));
return call;
}
}

代码中就可以使用 ApiServiceManager.getInstance().getDefaultAddr();