RxJava 2.0与Retrofit 2.0 concat运算符

Question

我正在尝试使用concat运算符来返回来自领域的缓存数据和来自api调用的数据。我遇到一个问题，当api调用observable抛出异常它shorcut-cut进程并返回onError。我通过从此链接https://stackoverflow.com/a/32489728/6284609调用onErrorResumeNext找到了解决方案。现在我有另一个问题是我无法检查异常类型，我想检查它以便调用连接错误消息以及与我的api调用相关的其他自定义异常。欢迎任何解决方案。一般情况下，我想从缓存和api调用中读取数据，如果存在连接错误，我希望从缓存中获取数据，并且我希望api observable显示错误异常。谢谢。

这是我的函数加载缓存数据和api调用

   public static Observable<List<WorkoutWeekSessions>>
fetPackageWorkOutWeeksAndSessions(int traineeId, Realm realm, final Context context) {

    List<WorkoutWeekSessions> list = new ArrayList(realm.where(WorkoutWeekSessions.class).findAllAsync());

    Observable<List<WorkoutWeekSessions>> cachedWorkoutSessions = Observable.just(list)
            .subscribeOn(Schedulers.computation());


    WorkOutService requestService = ServiceGenerator.createService(WorkOutService.class);
    Observable<List<WorkoutWeekSessions>> apiWorkoutSessions= requestService.getPackageWorkOutWeeksAndSession(UrlManager.getTraineePackageWoroutsSessionsUrl(),
            traineeId)
            .flatMap(new Function<JsonElement, Observable<List<WorkoutWeekSessions>>>() {
                @Override
                public Observable<List<WorkoutWeekSessions>> apply(JsonElement jsonElement) throws Exception {
                    JsonObject asJsonObject = jsonElement.getAsJsonObject();
                    String result = asJsonObject.get(UrlManager.ResultTypes.RESULT).getAsString();

                    Timber.d(TAG, "result Tag" + result);

                    if (UrlManager.ResultTypes.isError(result) || UrlManager.ResultTypes.isFailure(result)) {
                        String errorMessage = asJsonObject.get(UrlManager.ResultTypes.RESULT_ERROR_MESSAGE).getAsString();
                        return Observable.error(new Exception(errorMessage));
                    }


                    if (UrlManager.ResultTypes.isSucess(result)) {


                        if (!GsonHelper.isNull(asJsonObject.get(UrlManager.ResultTypes.RESULT_DATA))
                                && asJsonObject.get(UrlManager.ResultTypes.RESULT_DATA).isJsonArray()) {
                            List<WorkoutWeekSessions> workoutWeekSessions = WorkoutWeekSessions
                                    .PackageWorkOutWeeksListParser
                                    .fromJsonElement(asJsonObject
                                            .getAsJsonArray(UrlManager
                                                    .ResultTypes
                                                    .RESULT_DATA));

                            return Observable.just(workoutWeekSessions);
                        } else {
                            return Observable.error(new Exception("Data is empty"));
                        }


                    }

                    if (UrlManager.ResultTypes.isLogin(result)) {
                        return Observable.error(new SessionTimeoutException());
                    }


                    return Observable.error(new Exception("Unkown Tag"));
                }
            })
            .subscribeOn(Schedulers.io());

    return Observable
            .concat(cachedWorkoutSessions, apiWorkoutSessions
                    .onErrorResumeNext(new Observable<List<WorkoutWeekSessions>>() {
                @Override
                protected void subscribeActual(Observer<? super List<WorkoutWeekSessions>> observer) {

                }
            }))
            .observeOn(AndroidSchedulers.mainThread());

}

这是我如何调用它并用于在使用concat之前处理异常

 private void retrievePackageWorkOutWeeksAndSessions() {

    if (!swipRefreshLayout_reLoad.isRefreshing()) {
        swipRefreshLayout_reLoad.setRefreshing(true);
    }

    WorkOuttNetworkCall.fetPackageWorkOutWeeksAndSessions(1, realmUI,getContext())
            .subscribe(new Observer<List<WorkoutWeekSessions>>() {
        @Override
        public void onSubscribe(Disposable d) {
            Timber.d(TAG, "onSubscribe() called with: d = [" + d + "]");
            compositeSubscription.add(d);
        }

        @Override
        public void onNext(List<WorkoutWeekSessions> list) {
            Timber.d(TAG, "onNext() called with: value = [" + list.size() + "]");
            swipRefreshLayout_reLoad.setRefreshing(false);


            if (list.size() == 0) {
                Toast.makeText(getContext(), R.string.noDietPackageAvailable, Toast.LENGTH_SHORT).show();
            }

            bindRecyclerData(list);


        }

        @Override
        public void onError(Throwable e) {
            e.printStackTrace();
            Timber.d(TAG, "onError() called with: e = [" + e + "]");

            swipRefreshLayout_reLoad.setRefreshing(false);
            if (e instanceof IOException) {
                Toast.makeText(getContext(), R.string.connectionError, Toast.LENGTH_SHORT).show();


            } else if (e instanceof NullPointerException) {

            } else if (e instanceof SessionTimeoutException) {
                AuthenticationManager.logOut();

            } else {
                Toast.makeText(getContext(),
                        e.getMessage(),
                        Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onComplete() {
            Log.d(TAG, "onComplete() called");
        }
    });


}