这里有很多关于Retrofit缓存的复杂答案,但似乎都没有帮助我.

如何缓存来自Retrofit响应的代码响应？

我的应用程序可以正常下载下面的JSON,但我需要为它做一个缓存,我从来没有在Android上进行缓存.

我需要离线打开应用程序并从我的Retrofit调用中获取结果,就好像我在线一样.

public class APIClient {

public static final String BASE_URL = "https://raw.githubusercontent.com/";
private static Retrofit retrofit = null;

public static Retrofit getClient() {
    if (retrofit==null) {
        OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
        httpClient.addInterceptor(new Interceptor() {
            @Override
            public Response intercept(Interceptor.Chain chain) throws IOException {
                Request original = chain.request();

                Request request = original.newBuilder()
                        .method(original.method(), original.body())
                        .build();
                return chain.proceed(request);
            }
        });

        OkHttpClient client = httpClient.build();
        retrofit = new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .client(client)
                .build();
    }
    return retrofit;
}}

json响应非常简单：

{  
   "fruits":[  
      {  
         "name":"Apple",
         "image":"https://upload.wikimedia.org/wikipedia/commons/thumb/1/15/Red_Apple.jpg/265px-Red_Apple.jpg",
         "price":35
      },
      {  
         "name":"Banana",
         "image":"https://upload.wikimedia.org/wikipedia/commons/thumb/4/44/Bananas_white_background_DS.jpg/320px-Bananas_white_background_DS.jpg",
         "price":12
      },
      {  
         "name":"Grapes",
         "image":"https://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Table_grapes_on_white.jpg/320px-Table_grapes_on_white.jpg",
         "price":45
      },
      {  
         "name":"Pineapple",
         "image":"https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Pineapple_and_cross_section.jpg/286px-Pineapple_and_cross_section.jpg",
         "price":200
      },
      {  
         "name":"cherry",
         "image":"http://www.desicomments.com/wp-content/uploads/2017/05/Cherry-Image-600x570.jpg",
         "price":13
      },
      {  
         "name":"clementine",
         "image":"http://www.icecreamnation.org/wp-content/uploads/2013/04/Clementine_orange.jpg",
         "price":12.4
      },
      {  
         "name":"olive",
         "image":"https://www.homenaturalcures.com/wp-content/uploads/olive.jpg",
         "price":9.5
      },
      {  
         "name":"tomato",
         "image":"http://cdn2.stylecraze.com/wp-content/uploads/2013/05/tomato-hair-benefits1.jpg",
         "price":8.75
      },
      {  
         "name":"huckleberry",
         "image":"http://farm3.static.flickr.com/2131/2082287810_47339fc93e.jpg",
         "price":11.75
      },
      {  
         "name":"papaya",
         "image":"http://media.mercola.com/assets/images/foodfacts/papaya-nutrition-facts.jpg",
         "price":2.75
      },
      {  
         "name":"lime",
         "image":"https://www.florihana.com/images/stories/virtuemart/product/FLE019%20-%20LIME.jpg",
         "price":5.75
      },
      {  
         "name":"pear",
         "image":"https://www.organicfacts.net/wp-content/uploads/pear.jpg",
         "price":4.75
      }
   ]
}

解决方法:

假设服务器遵循Cache-Control / If-Modified-Since标头,那么您所要做的就是创建一个Cache对象并将其设置为OkHttpClient.改造将照顾其余部分.

    int cacheSize = 10 * 1024 * 1024; // 10 MB  
    Cache cache = new Cache(getCacheDir(), cacheSize);

    OkHttpClient okHttpClient = new OkHttpClient.Builder()  
            .cache(cache)
            .build();

    Retrofit.Builder builder = new Retrofit.Builder()  
            .baseUrl("http://10.0.2.2:3000/")
            .client(okHttpClient)
            .addConverterFactory(GsonConverterFactory.create());

    Retrofit retrofit = builder.build();

资料来源：futurestud.io