如何与OKHttp使用缓存中的数据时，离线改造 [英] How Retrofit with OKHttp use cache data when offline

问题描述

我要改造与OkHttp使用缓存的时候没有互联网。

I want to Retrofit with OkHttp uses cache when is no Internet.

我prepare OkHttpClient是这样的：

I prepare OkHttpClient like this:

    RestAdapter.Builder builder= new RestAdapter.Builder()
       .setRequestInterceptor(new RequestInterceptor() {
            @Override
            public void intercept(RequestFacade request) {
                request.addHeader("Accept", "application/json;versions=1");
                if (MyApplicationUtils.isNetworkAvaliable(context)) {
                    int maxAge = 60; // read from cache for 1 minute
                    request.addHeader("Cache-Control", "public, max-age=" + maxAge);
                } else {
                    int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale
                    request.addHeader("Cache-Control", 
                        "public, only-if-cached, max-stale=" + maxStale);
                }
            }
    });

和这样的设置缓存：

   Cache cache = null;
    try {
        cache = new Cache(httpCacheDirectory, 10 * 1024 * 1024);
    } catch (IOException e) {
        Log.e("OKHttp", "Could not create http cache", e);
    }

    OkHttpClient okHttpClient = new OkHttpClient();
    if (cache != null) {
        okHttpClient.setCache(cache);
    }

和我查了根深蒂固的设备，在高速缓存目录中保存文件的响应头和gzip文件。

and I checked on rooted device, that in cache directory are saving files with the "Response headers" and Gzip files.

但我不明白的离线改造缓存正确的答案，虽然在gzip文件是codeD我正确的答案。所以，我怎样才能使改造可以读取GZIP文件，他怎么能知道哪些文件应该是（因为我有几个文件有与其他反应）？

But I don't get the correct answer from retrofit cache in offline, although in GZip file is coded my correct answer. So how can I make Retrofit can read GZip file and how can he know which file it should be (because I have a few files there with other responses) ?

推荐答案

我在公司simlar问题：）

I have simlar problem in my company :)

问题是在服务器端。在serwer回应，我有：

The problem was on server side. In serwer response i have:

Pragma: no-cache

所以，当我删除了这一切开始工作。之前，我删除它，我得到的所有的时间这样的例外： 504不可满足要求（只-IF-缓存）

好了，所以如何实现在我身边的样子。

Ok so how implementation on my side looks.

    OkHttpClient okHttpClient = new OkHttpClient();

    File httpCacheDirectory = new File(appContext.getCacheDir(), "responses");

    Cache cache = new Cache(httpCacheDirectory, maxSizeInBytes);
    okHttpClient.setCache(cache);

    OkClient okClient = new OkClient(okHttpClient);

    RestAdapter.Builder builder = new RestAdapter.Builder();
    builder.setEndpoint(endpoint);
    builder.setClient(okClient);

如果您在测试问题，哪一方是问题（服务器或应用程序）。你可以用这样的feauture设置从服务器接收的头。

If you have problems in testing on which side is problem (server or app). You can use such feauture to set headers received from server.

private static final Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
    @Override
    public Response intercept(Chain chain) throws IOException {
        Response originalResponse = chain.proceed(chain.request());
        return originalResponse.newBuilder()
                               .removeHeader("Pragma")
                               .header("Cache-Control",
                                       String.format("max-age=%d", 60))
                               .build();
    }
};

和简单地添加：

okHttpClient.networkInterceptors().add(REWRITE_CACHE_CONTROL_INTERCEPTOR);

由于是，你可以看到我能够删除杂注：无缓存头测试时间

此外，我建议你阅读有关的Cache-Control 标题：

Also i suggest you to read about Cache-Control header:

最大年龄，的max-stale

其他有用的链接：

HTTP头字段列表

缓存控制研究

另一个示例code

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