2出现了这个错误

Question

我正在使用改造2和OkHttp3从服务器请求数据。我刚刚添加了脱机缓存代码，但它没有按预期工作。我得到了错误"无法解析主机"

当它试图从缓存中获取检索数据时（没有internet连接时），就会发生这种情况。下面是一段代码片段。

public static Interceptor provideCacheInterceptor() {
    return new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {
            Response response = chain.proceed(chain.request());

            // re-write response header to force use of cache
            CacheControl cacheControl = new CacheControl.Builder()
                    .maxAge(2, TimeUnit.MINUTES)
                    .build();

            return response.newBuilder()
                    .header(CACHE_CONTROL, cacheControl.toString())
                    .build();
        }
    };
}

public static Interceptor provideOfflineCacheInterceptor() {
    return new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {
            Request request = chain.request();

            if (!hasNetwork) {
                CacheControl cacheControl = new CacheControl.Builder()
                        .onlyIfCached()
                        .maxStale(7, TimeUnit.DAYS)
                        .build();

                request = request.newBuilder()
                        .removeHeader("Pragma")
                        .cacheControl(cacheControl)
                        .build();
            }

            return chain.proceed(request);
        }
    };
}

private static Cache provideCache() {
    Cache cache = null;
    try {
        cache = new Cache(new File(AdeptAndroid.getInstance().getCacheDir(), "http-cache"),
                10 * 1024 * 1024); // 10 MB
    } catch (Exception e) {
        Log.d("Test", "Could not create Cache!");
    }
    return cache;
}

最后，这里有一个结合了所有这些的方法。

private static OkHttpClient provideOkHttpClient() {
    return new OkHttpClient.Builder()
            .addInterceptor(provideHttpLoggingInterceptor())
            .addInterceptor(provideOfflineCacheInterceptor())
            .addNetworkInterceptor(provideCacheInterceptor())
            .cache(provideCache())
            .build();
}

Answer 1

请在模拟器上的清单文件权限关闭飞机模式中检查您的网络“打开”

Answer 2

您的服务器响应有一个“普拉格马：无缓存”标头。您应该在响应拦截器中删除这个标头，而不是请求拦截器。

在当前代码中，您已经将其从请求拦截器中删除。

您的provideCacheInterceptor（）应该如下所示：

public static Interceptor provideCacheInterceptor() {
    return new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {
            Response response = chain.proceed(chain.request());

            // re-write response header to force use of cache
            CacheControl cacheControl = new CacheControl.Builder()
                   .maxAge(2, TimeUnit.MINUTES)
                   .build();

           return response.newBuilder()
                    .header(CACHE_CONTROL, cacheControl.toString())
                    .removeHeader("Pragma")
                    .build();
        }
    };
}

Answer 3

我在kotlin的项目中也有同样的错误，我这样修复了它：

client.addInterceptor(provideOfflineCacheInterceptor(context))
client.addNetworkInterceptor(provideCacheInterceptor(context))

private fun provideOfflineCacheInterceptor(context: Context): Interceptor {
        return Interceptor { chain ->
            var request = chain.request()
            var cacheHeaderValue = if (!hasNetwork(context)!!){
                    "public, only-if-cached, max-stale=" + 60 * 60 * 24 * 1
                } else {
                    "public, max-age=" + 5
                }
            request = request.newBuilder().header("Cache-Control", cacheHeaderValue).build()
            chain.proceed(request)
        }
    }

    private fun provideCacheInterceptor(context: Context): Interceptor {
        return Interceptor { chain ->
            val request = chain.request()
            var cacheHeaderValue = if (!hasNetwork(context)!!){
                    "public, only-if-cached, max-stale=" + 60 * 60 * 24 * 1
                } else {
                    "public, max-age=" + 5
                }
            //request = request.newBuilder().build()
            val response = chain.proceed(request)
            response.newBuilder()
                    .removeHeader("Pragma")
                    .removeHeader("Cache-Control")
                    .header("Cache-Control", cacheHeaderValue)
                    .build()
        }
    }