RxAssetsReader

import android.content.res.AssetManager;
import com.google.gson.Gson;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import rx.Observable;

public class AssetsReader {
  private final Gson gson;
  private final AssetManager assetManager;

  public AssetsReader(Gson gson, AssetManager assetManager) {
    this.gson = gson;
    this.assetManager = assetManager;
  }

  public <T> Observable<T> readJson(final String assetsFolderRelatedPath, Class<T> type) {
    return Observable.create(subscriber -> {
      try {
        InputStream stream = assetManager.open(assetsFolderRelatedPath);
        BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
        subscriber.onNext(gson.fromJson(reader, type));
        subscriber.onCompleted();
      } catch (Throwable e) {
        subscriber.onError(e);
      }
    });
  }
}