項目一

項目中網絡請求偶有出現：

日志一

 D/libc-netbsd: [getaddrinfo]:  hostname=api1.51zhenghao.cn; servname=(null);   
app_uid=10332; ai_addrlen=0; ai_canonname=(null); ai_flags=1024; 
ai_family=0 from prox result 0

日志二

W/System.err: java.net.UnknownHostException: 
Unable to resolve host "api.51zhenghao.cn": No address associated with hostname

網絡框架使用的是

    // 聯網請求框架okgo
    compile 'com.lzy.net:okgo:3.0.3'

該網絡框架源碼地址
網絡框架說明

日志二問題解決辦法方案
一：Unable to resolve host "api.51zhenghao.cn": No address associated with hostname

搜索解決方案：如果將配置文件中的 android:required 設置為true 執行以上代碼的時候會報錯 ，目前原因未知

查看配置文件AndroidManifest.xml,定位到如下代碼，我也不清楚添加這個什么意義（不是我寫的）。

    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="false（true）" />

修改之后，基本沒有出現DNS解析不了的問題了。

二：

項目二

網絡請求框架Retrofit2.1.0

引入框架

    compile 'com.squareup.retrofit2:retrofit:2.1.0'
    compile 'com.squareup.retrofit2:converter-gson:2.1.0'
    compile 'com.squareup.retrofit2:adapter-rxjava:2.0.2'

有網無網絡先讀緩存中的數據

        //retrofit（非異步）網絡請求框架，與RxJava（異步框架）結合使用
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(baseUrl)
                .client(getOkHttpClient())
                .addConverterFactory(customGsonConverterFactory)
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())// 把 Retrofit 轉成 RxJava 可用的適配類。
                .build();

    private OkHttpClient getOkHttpClient() {
        Cache cache = new Cache(cacheFile, 1024 * 1024 * 50);//緩存文件為50MB
        httpClientBuilder.cache(cache);
        httpClientBuilder.addNetworkInterceptor(new Interceptor() {
          @Override
          public Response intercept(Chain chain) throws IOException {
              Request request = chain.request();

              request = request.newBuilder()
                     .addHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8")
                     .addHeader("Accept-Language", "zh-CN,zh;q=0.8")
                     .addHeader("Connection", "keep-alive")
                     .addHeader("Host", "api.51zhenghao.cn")
                     .build();
              Response response = chain.proceed(request);
              response = response.newBuilder()
                          .header("Cache-Control", "public, max-age=" + maxAge)//單位（秒）
                          .removeHeader("Pragma") //清除頭信息，因為服務器如果不支持，會返回一些干擾信息
                          .build();
            return response;
            }
        });
        okHttpClient = httpClientBuilder.build();
        return okHttpClient;
    }

有網絡從網絡獲取數據，無網絡從緩存中讀取數據

    private OkHttpClient getOkHttpClient() {
        Cache cache = new Cache(cacheFile, 1024 * 1024 * 50);//緩存文件為50MB
        OkHttpClient.Builder httpClientBuilder = new OkHttpClient.Builder();
        httpClientBuilder.cache(cache);
        //設置網絡請求緩存策略
        httpClientBuilder.addInterceptor(new Interceptor() {
            @Override
            public Response intercept(Chain chain) throws IOException {
                Request request = chain.request();
                if (NetUtil.isConnected(BaseApplication.getContext())) {
                    request = request.newBuilder()
                            .cacheControl(CacheControl.FORCE_NETWORK)//有網絡時只從網絡獲取
                            .build();
                } else {
                    request = request.newBuilder()
                            .cacheControl(CacheControl.FORCE_CACHE)//無網絡時只從緩存中讀取
                            .build();
                }
                Response response = chain.proceed(request);
                if (NetUtil.isConnected(BaseApplication.getContext())) {
                    response = response.newBuilder()
                            .build();
                } else {
                    response = response.newBuilder()
                            .removeHeader("Pragma")
                            .removeHeader("Cache-Control")//清楚響應體對Cache有影響的信息
                            .header("Cache-Control", "public, only-if-cached, max-stale=" + maxStale)//單位（秒）
                            .build();
                }
                return response;
            }
        });

        okHttpClient = httpClientBuilder.build();
        return okHttpClient;
}

拋出異常retrofit2.adapter.rxjava.HttpException:HTTP 504 Unsatisfiable Request (only-if-cached)