Observable<List<City>> getHotCityList(Observable<Response<List<City>>> hotCitys, EvictProvider evictProvider);

 Observable<List<City>> getHotCityList(Observable<String> hotCitys, EvictProvider evictProvider);

apiServiceCache.getHotCityList(stringObservable, new EvictProvider(false))
            .compose(ComposeString2List.newCompose(new TypeToken<Response<List<City>>>(){}))

 public class ComposeString2List<T> implements Observable.Transformer<String, List<T>> {

     public TypeToken<Response<List<T>>> typeToken;

     public static ComposeString2List newCompose(TypeToken typeToken) {
        return new ComposeString2List(typeToken);
    }

    public ComposeString2List(TypeToken<Response<List<T>>> typeToken) {
        this.typeToken = typeToken;
    }

    @Override
     public Observable<List<T>> call(Observable<String> responseObservable) {
         return NetworkUtils.isNetworkAvailableObservable()
                 .flatMap(aBoolean -> responseObservable)
                 .flatMap(new ReadListFunc(typeToken))
                 .onErrorResumeNext(ResponseErrorHandle.errorResumeFunc())
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread());
     }

     // 读取列表数据
     private static class ReadListFunc<E> implements Func1<String, Observable<List<E>>> {

         private TypeToken<Response<List<E>>> typeToken;

         public ReadListFunc(TypeToken<Response<List<E>>> typeToken) {
             this.typeToken = typeToken;
         }

        @Override
         public Observable<List<E>> call(String responseReply) {
             Response<List<E>> response = new Gson().fromJson(responseReply, typeToken.getType());
             if (response != null && response.code == ReturnCode.CODE_SUCCESS) {
                 return Observable.just(response.data);
             } else {
                 return Observable.error(new Throwable());
             }
         }
     }

 }

public class BaseResponse<T> {
    public int code;
    public List<T> results;
}

public class ApiResponse extends BaseResponse<ApiResponse.FocusListItem> {

    public static class FocusListItem {
        。。。
    }
}

Observable<Reply<ApiResponse>> getFocusList(Observable<ApiResponse> observable, EvictProvider evictProvider);