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SmartCache for Retrofit2

SmartCache - preloaded responses for Retrofit 2 Build Status

This library calls your callback twice: first cached, then fresh data

Instead of showing an empty screen while waiting for a network response, why not load the latest successful response from storage?

  • Responses are saved in device storage & RAM
  • No extra logic, only Call<T> becomes SmartCall<T>
  • Extend your own adapters for other caching strategies

Install and use

  1. Add SmartCache to Gradle dependencies, and JitPack to repos:
repositories {
    maven { url "https://jitpack.io" }
//               ^^^^^^^^^^^^^^^^^^^ Add this!
}

dependencies {
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'
    implementation 'com.github.fikisipi:SmartCache:2.9.0'
//                  ^^^^^^^^^^^^^^^^^^^ Add this!
}
  1. Add SmartCallFactory to your Retrofit Builder (where this is an Activity/Context):
Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://your-api.org")
        .addConverterFactory(GsonConverterFactory.create())
        .addCallAdapterFactory(SmartCallFactory.createBasic(this))
//                             ^^^^^^^^^^^^^^^^ Add this!
        .build();
  1. Replace Call<T> with SmartCall<T> and you are done ✔️.
public interface GitHubService {
   @GET("/users/{user}/repos")
   SmartCall<List<Repo>> listRepos(@Path("user") String user);
// ^^^^^^^^^  Rename `Call` to `SmartCall`
}

Checking if the callback data is preloaded

Every enqueue() callback is fired with preloaded data before the network invokes the callback. You can check which is which using SmartCache.isResponseFromNetwork(response):

new Callback<YourModel>() {
  @Override
  public void onResponse(Call<YourModel> call, Response<YourModel> response) {
    if(SmartCache.isResponseFromNetwork(response)) {

Clearing cache and choosing which requests should be cached

Most apps shouldn't cache stateful routes like POST/PUT so by default only GET routes are cached. You can change this by supplying filter: (Request) -> bool when creating the factory SmartCallFactory.createBasic(this, filter).

Each interface CachingSystem now has void clearCache() to delete the cache. By default, SmartCache uses BasicCaching as a LRU system, so clearing can be done like this:

BasicCaching.buildFromContext(getApplicationContext()).clearCache();

💻 Check the demo app for these examples.

Demo app

For a complete example check demoapp/.

...

How it works

...

One request corresponds to two responses: a cache response and a network response. Loading content from your phone is faster than loading from network; therefore your app will show stale content while waiting for a fresh network response. (Note: If the network response comes first, cache won't happen.)

Help needed from contributors:

  • Make it work with RxJava
  • Implement a pool of threads

License

Copyright 2015-2021 Filip Dimitrovski

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.