Retrofit + OkHttp + RxAndroid 缓存问题

@Override
public okhttp3.Response intercept(Chain chain) throws IOException {
Request request = chain.request();
//缓存
if(NetUtil.checkNetwork(mContext)==NetUtil.NO_NETWORK){
request = request.newBuilder()
.cacheControl(CacheControl.FORCE_CACHE)
.build();
Log.d("zgx","no network");
}

    okhttp3.Response response = chain.proceed(request);
    String requestUrl = response.request().url().uri().getPath();
    if(!TextUtils.isEmpty(requestUrl)){
        if(requestUrl.contains("LoginDataServlet")) {
            if (Looper.myLooper() == null) {
                Looper.prepare();
            }
            createObservable("现在请求的是登录接口");
        }
    }
    //缓存响应
    if(NetUtil.checkNetwork(mContext)!=NetUtil.NO_NETWORK){
        //有网的时候读接口上的@Headers里的配置，你可以在这里进行统一的设置
        String cacheControl = request.cacheControl().toString();
        Log.e("zgx","request====="+request);
        Log.e("zgx","request.toString()====="+request.header("body"));
        Log.e("zgx","request.cacheControl()====="+request.cacheControl());
        Log.e("zgx","cacheControl====="+cacheControl);
        return response.newBuilder()
                .header("Cache-Control", cacheControl)
                .removeHeader("Pragma")
                .build();
    }else{
        return response.newBuilder()
                .header("Cache-Control", "public, only-if-cached, max-stale=120")
                .removeHeader("Pragma")
                .build();
    }
}

    为什么String cacheControl = request.cacheControl().toString();获取不到值呢？

http://blog.csdn.net/iamzgx/article/details/51607387