最近事比较多，距离上次写文章已经过去了一个月了。上一篇文章Retrofit全攻略——基础篇 介绍了Retrofit的基础用法，这篇文章介绍点进阶的用法。

打印网络日志

在开发阶段，为了方便调试，我们需要查看网络日志。因为Retrofit2.0+底层是采用的OKHttp请求的。可以给OKHttp设置拦截器，用来打印日志。 首先可以在app/build.gradle中添加依赖，这是官方的日志拦截器。

compile 'com.squareup.okhttp3:logging-interceptor:3.3.0'
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然后在代码中设置：

    public static Retrofit getRetrofit() {//如果mRetrofit为空  或者服务器地址改变 重新创建if (mRetrofit == null) {OkHttpClient httpClient;OkHttpClient.Builder builder=new OkHttpClient.Builder();//阶段分为开发和发布阶段，当前为开发阶段设置拦截器if (BuildConfig.DEBUG) {HttpLoggingInterceptor logging = new HttpLoggingInterceptor();//设置拦截器级别logging.setLevel(HttpLoggingInterceptor.Level.BODY);builder.addInterceptor(logging);}httpClient=builder.build();//构建RetrofitmRetrofit = new Retrofit.Builder()//配置服务器路径.baseUrl(mServerUrl)//返回的数据通过Gson解析.addConverterFactory(GsonConverterFactory.create())//配置回调库，采用RxJava.addCallAdapterFactory(RxJavaCallAdapterFactory.create())//设置OKHttp模板.client(httpClient).build();}return mRetrofit;}
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当处于开发阶段的时候，设置监听日志的拦截器。拦截有4个级别，分别是

1. BODY
2. HEADERS
3. BASIC
4. NONE

其中BODY输出的日志是最全的。

#添加相同的请求参数 为了更好的管理迭代版本，一般每次发起请求的时候都传输当前程序的版本号到服务器。 有些项目我们每次还会传用户id，token令牌等相同的参数。 如果在每个请求的接口都添加这些参数太繁琐。Retrofit可以通过拦截器添加相同的请求参数，无需再每个接口添加了。

步骤一，自己拦截器

public class CommonInterceptor implements Interceptor {@Overridepublic Response intercept(Interceptor.Chain chain) throws IOException {Request oldRequest = chain.request();// 添加新的参数HttpUrl.Builder authorizedUrlBuilder = oldRequest.url().newBuilder().scheme(oldRequest.url().scheme()).host(oldRequest.url().host()).addQueryParameter("device_type", "1").addQueryParameter("version", BuildConfig.VERSION_NAME).addQueryParameter("token", PreUtils.getString(R.string.token)).addQueryParameter("userid", PreUtils.getString(R.string.user_id));// 新的请求Request newRequest = oldRequest.newBuilder().method(oldRequest.method(), oldRequest.body()).url(authorizedUrlBuilder.build()).build();return chain.proceed(newRequest);}
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实现原理就是拦截之前的请求，添加完参数，再传递新的请求。这个位置我添加了四个公共的参数。 然后再Retrofit初始化的时候配置。

        if (mRetrofit == null) {OkHttpClient httpClient;OkHttpClient.Builder builder=new OkHttpClient.Builder();//添加公共参数builder.addInterceptor(new CommonInterceptor());httpClient=builder.build();//构建RetrofitmRetrofit = new Retrofit.Builder()//.....client(httpClient).build();}
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处理约定错误

除了常见的404，500等异常，网络请求中我们往往还会约定些异常，比如token失效，账号异常等等。

以token失效为例，每次请求我们都需要验证是否失效，如果在每个接口都处理一遍错误就有点太繁琐了。

我们可以统一处理下错误。

步骤一，Retrofit初始化时添加自定义转化器

mRetrofit = new Retrofit.Builder()//配置服务器路径baseUrl(mServerUrl)//配置回调库，采用RxJava.addCallAdapterFactory(RxJavaCallAdapterFactory.create())//配置转化库，默认是Gson，这里修改了。.addConverterFactory(ResponseConverterFactory.create()).client(httpClient).build();
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步骤二 创建ResponseConverterFactory

步骤一 ResponseConverterFactory这个类是需要我们自己创建的。

public class ResponseConverterFactory extends Converter.Factory {/*** Create an instance using a default {@link Gson} instance for conversion. Encoding to JSON and* decoding from JSON (when no charset is specified by a header) will use UTF-8.*/public static ResponseConverterFactory create() {return create(new Gson());}/*** Create an instance using {@code gson} for conversion. Encoding to JSON and* decoding from JSON (when no charset is specified by a header) will use UTF-8.*/public static ResponseConverterFactory create(Gson gson) {return new ResponseConverterFactory(gson);}private final Gson gson;private ResponseConverterFactory(Gson gson) {if (gson == null) throw new NullPointerException("gson == null");this.gson = gson;}@Overridepublic Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,Retrofit retrofit) {//  TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(type));return new GsonResponseBodyConverter<>(gson, type);}@Overridepublic Converter<?, RequestBody> requestBodyConverter(Type type,Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(type));return new GsonRequestBodyConverter<>(gson, adapter);}
}复制代码

这里面我们自定义了请求和响应时解析JSON的转换器——GsonRequestBodyConverter和GsonResponseBodyConverter。

其中GsonRequestBodyConverter 负责处理请求时传递JSON对象的格式，不需要额外处理任何事，直接使用默认的GSON解析。代码我直接贴出来：

final class GsonRequestBodyConverter<T> implements Converter<T, RequestBody> {private static final MediaType MEDIA_TYPE = MediaType.parse("application/json; charset=UTF-8");private static final Charset UTF_8 = Charset.forName("UTF-8");private final Gson gson;private final TypeAdapter<T> adapter;GsonRequestBodyConverter(Gson gson, TypeAdapter<T> adapter) {this.gson = gson;this.adapter = adapter;}@Override public RequestBody convert(T value) throws IOException {Buffer buffer = new Buffer();Writer writer = new OutputStreamWriter(buffer.outputStream(), UTF_8);JsonWriter jsonWriter = gson.newJsonWriter(writer);adapter.write(jsonWriter, value);jsonWriter.close();return RequestBody.create(MEDIA_TYPE, buffer.readByteString());}
}
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GsonResponseBodyConverter负责把响应的数据转换成JSON格式，这个我们需要处理一下。

public class GsonResponseBodyConverter<T> implements Converter<ResponseBody, T> {private final Gson gson;private final Type type;GsonResponseBodyConverter(Gson gson, Type type) {this.gson = gson;this.type = type;}@Overridepublic T convert(ResponseBody value) throws IOException {String response = value.string();try {Log.i("YLlibrary", "response>>> "+response);//ResultResponse 只解析result字段BaseInfo baseInfo = gson.fromJson(response, BaseInfo.class);if (baseInfo.getHeader().getCode().equals("1")) {//正确return gson.fromJson(response, type);} else {//ErrResponse 将msg解析为异常消息文本 错误码可以自己指定.throw new ResultException(-1024, baseInfo,response);}} finally {}}}复制代码

这种情况只是应用于后台接口数据统一的情况。比如我们项目的格式是这样的

      {header : {"message":"token失效","code":"99"}data : {}}
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当code值是1的时候，表示正确，其它数字表示错误。只有正确的时候data才会有内容。

这里我用BaseInfo解析这个JSON：

public class BaseInfo {/*** header : {"message":"用户名或密码错误","code":"0"}* data : {}*/private HeaderBean header;public HeaderBean getHeader() {return header;}public void setHeader(HeaderBean header) {this.header = header;}public static class HeaderBean {/*** message : 用户名或密码错误* code : 0*/private String message;private String code;public String getMessage() {return message;}public void setMessage(String message) {this.message = message;}public String getCode() {return code;}public void setCode(String code) {this.code = code;}}
}
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服务器返回的数据实体对象全部继承BaseInfo 只是data内容不一样。

ResultException这个类用于捕获服务器约定的错误类型

/*** 这个类用于捕获服务器约定的错误类型*/
public class ResultException extends RuntimeException {private int errCode = 0;private BaseInfo info;private String response;public ResultException(int errCode, BaseInfo info,String response) {super(info.getHeader().getMessage());this.info=info;this.errCode = errCode;this.response=response;}public String getResponse() {return response;}public void setResponse(String response) {this.response = response;}public int getErrCode() {return errCode;}public BaseInfo getBaseInfo(){return info;}
}
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最后定义Retrofit处理异常的代码

public abstract class AbsAPICallback<T> extends Subscriber<T> {//对应HTTP的状态码private static final int UNAUTHORIZED = 401;private static final int FORBIDDEN = 403;private static final int NOT_FOUND = 404;private static final int REQUEST_TIMEOUT = 408;private static final int INTERNAL_SERVER_ERROR = 500;private static final int BAD_GATEWAY = 502;private static final int SERVICE_UNAVAILABLE = 503;private static final int GATEWAY_TIMEOUT = 504;//出错提示private final String networkMsg;private final String parseMsg;private final String unknownMsg;protected AbsAPICallback(String networkMsg, String parseMsg, String unknownMsg) {this.networkMsg = networkMsg;this.parseMsg = parseMsg;this.unknownMsg = unknownMsg;}public  AbsAPICallback(){networkMsg="net error(联网失败)";parseMsg="json parser error(JSON解析失败)";unknownMsg="unknown error(未知错误)";}ProgressBar progressBar;public  AbsAPICallback(ProgressBar progressBar){this();this.progressBar=progressBar;}@Overridepublic void onError(Throwable e) {Throwable throwable = e;//获取最根源的异常while(throwable.getCause() != null){e = throwable;throwable = throwable.getCause();}ApiException ex;if (e instanceof HttpException){             //HTTP错误HttpException httpException = (HttpException) e;ex = new ApiException(e, httpException.code());switch(httpException.code()){case UNAUTHORIZED:case FORBIDDEN://  onPermissionError(ex);          //权限错误，需要实现// break;case NOT_FOUND:case REQUEST_TIMEOUT:case GATEWAY_TIMEOUT:case INTERNAL_SERVER_ERROR:case BAD_GATEWAY:case SERVICE_UNAVAILABLE:default:ex.setDisplayMessage(networkMsg);  //均视为网络错误onNetError(ex);break;}} else if (e instanceof ResultException){    //服务器返回的错误ResultException resultException = (ResultException) e;onResultError(resultException);} else if (e instanceof JsonParseException|| e instanceof JSONException|| e instanceof ParseException){ex = new ApiException(e, ApiException.PARSE_ERROR);ex.setDisplayMessage(parseMsg);            //均视为解析错误onNetError(ex);} else {ex = new ApiException(e, ApiException.UNKNOWN);ex.setDisplayMessage(unknownMsg);          //未知错误onNetError(ex);}}static long time;protected  void onNetError(ApiException e){long currentTime=System.currentTimeMillis();if(currentTime-time>3000){  //防止连续反馈time=currentTime;UIUtils.showToast("网络加载失败");}e.printStackTrace();onApiError(e);}/*** 错误回调*/protected  void onApiError(ApiException ex){Log.i("YLLibrary","onApiError");if(progressBar!=null)UIUtils.runOnUiThread(new Runnable() {@Overridepublic void run() {progressBar.setVisibility(View.GONE);progressBar=null;}});}//    /**
//     * 权限错误，需要实现重新登录操作
//     */
//    protected void  onPermissionError(ApiException ex){
//        ex.printStackTrace();
//    }/*** 服务器返回的错误*/protected  synchronized  void onResultError(ResultException ex){
//        if(ex.getErrCode()== XApplication.API_ERROR){
//            UIUtils.getContext().onApiError(); //可以用来处理Token失效
//            return ;
//        }if(ConstantValue.TOKEN_ERROR.equals(ex.getBaseInfo().getHeader().getCode())&&!TextUtils.isEmpty(PreUtils.getString(R.string.token))){ //验证token是否为空是为了防止连续两次请求PreUtils.putString(R.string.user_id,null);PreUtils.putString(R.string.token,null);PreUtils.putString(R.string.orgDistrict,null);if(BaseActivity.runActivity!=null){Intent intent = new Intent(UIUtils.getContext(), LoginActivity.class);if(BaseActivity.runActivity instanceof MainActivity){MainActivity activity= (MainActivity) BaseActivity.runActivity;int tabIndex=activity.getCurrentTab();//activity.switchCurrentTab(0);activity.startActivityForResult(intent,tabIndex+10);}else {BaseActivity.runActivity.startActivity(intent);}}}Log.i("YLLibrary","resultError");if(ex.getBaseInfo()!=null&&!TextUtils.isEmpty(ex.getBaseInfo().getHeader().getMessage()))UIUtils.showToast(ex.getBaseInfo().getHeader().getMessage());ApiException apiException = new ApiException(ex, ex.getErrCode());onApiError(apiException);}@Overridepublic void onCompleted() {Log.i("YLLibrary","onCompleted");if(progressBar!=null)UIUtils.runOnUiThread(new Runnable() {@Overridepublic void run() {progressBar.setVisibility(View.GONE);progressBar=null;}});}}
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实际接口请求的代码，使用自定义异常回调的类——AbsAPICallback就可以统一处理异常:

        ApiRequestManager.createApi().problemDetail(dataBean.getId()).compose(ApiRequestManager.<QuestionDetailInfo>applySchedulers()).subscribe(new AbsAPICallback<QuestionDetailInfo>() {@Overridepublic void onNext(QuestionDetailInfo baseInfo) {fillData(baseInfo);}});
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