Can Retrofit with OKHttp Use Cache Data When Offline?
This question explores the use of Retrofit and OKHttp to cache HTTP responses for offline access. The code provided in the question follows a common approach, but the inability to retrieve cached responses offline suggests some additional configurations are needed.
Edit for Retrofit 2.x
For Retrofit 2.x, the preferred method for offline caching involves using an OkHttp Interceptor.
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Create an Interceptor:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | <code class = "java" > private static final Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
@Override public Response intercept(Chain chain) throws IOException {
Response originalResponse = chain.proceed(chain.request());
if (Utils.isNetworkAvailable(context)) {
int maxAge = 60;
return originalResponse.newBuilder()
.header( "Cache-Control" , "public, max-age=" + maxAge)
.build();
} else {
int maxStale = 60 * 60 * 24 * 28;
return originalResponse.newBuilder()
.header( "Cache-Control" , "public, only-if-cached, max-stale=" + maxStale)
.build();
}
}
};</code>
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Setup client:
1 2 3 4 5 6 7 8 9 10 | <code class = "java" >OkHttpClient client = new OkHttpClient();
client.networkInterceptors().add(REWRITE_CACHE_CONTROL_INTERCEPTOR);
File httpCacheDirectory = new File(context.getCacheDir(), "responses" );
int cacheSize = 10 * 1024 * 1024;
Cache cache = new Cache(httpCacheDirectory, cacheSize);
client.setCache(cache);</code>
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Add client to retrofit
1 2 3 4 5 | <code class = "java" >Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(client)
.addConverterFactory(GsonConverterFactory.create())
.build();</code>
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OKHttp 2.0.x (Original Answer)
In OKHttp 2.0.x, the setResponseCache method is now setCache:
1 2 3 4 5 6 7 8 9 10 11 12 13 | <code class = "java" >File httpCacheDirectory = new File(context.getCacheDir(), "responses" );
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);
}</code>
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Original Answer
The original answer emphasizes the need for a Cache-Control: public header in the server response for OkClient to access cached data offline.
Additionally, parameterized header configuration can be achieved using a RequestInterceptor:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | <code class = "java" >RestAdapter.Builder builder= new RestAdapter.Builder()
.setRequestInterceptor( new RequestInterceptor() {
@Override
public void intercept(RequestFacade request) {
request.addHeader( "Accept" , "application/json;versions=1" );
if (MyApplicationUtils.isNetworkAvailable(context)) {
int maxAge = 60;
request.addHeader( "Cache-Control" , "public, max-age=" + maxAge);
} else {
int maxStale = 60 * 60 * 24 * 28;
request.addHeader( "Cache-Control" ,
"public, only-if-cached, max-stale=" + maxStale);
}
}
});</code>
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