RxUtils

RxUtils.java

import rx.Observable;
import rx.Subscription;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;
import rx.subscriptions.CompositeSubscription;

public class RxUtils {

    /**
     * {@link rx.Observable.Transformer} that transforms the source observable to subscribe in the
     * io thread and observe on the Android's UI thread.
     */
    private static Observable.Transformer ioToMainThreadSchedulerTransformer;

    static {
        ioToMainThreadSchedulerTransformer = createIOToMainThreadScheduler();
    }

    /**
     * Get {@link rx.Observable.Transformer} that transforms the source observable to subscribe in
     * the io thread and observe on the Android's UI thread.
     *
     * Because it doesn't interact with the emitted items it's safe ignore the unchecked casts.
     *
     * @return {@link rx.Observable.Transformer}
     */
    @SuppressWarnings("unchecked")
    private static <T> Observable.Transformer<T, T> createIOToMainThreadScheduler() {
        return tObservable -> tObservable.subscribeOn(Schedulers.io())
                .unsubscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread());
    }

    @SuppressWarnings("unchecked")
    public static <T> Observable.Transformer<T, T> applyIOToMainThreadSchedulers() {
        return ioToMainThreadSchedulerTransformer;
    }

    public static void unsubscribeIfNotNull(Subscription subscription) {
        if (subscription != null) {
            subscription.unsubscribe();
        }
    }

    public static CompositeSubscription getNewCompositeSubIfUnsubscribed(CompositeSubscription subscription) {
        if (subscription == null || subscription.isUnsubscribed()) {
            return new CompositeSubscription();
        }

        return subscription;
    }
}

UseExample.java

ApiService.getInstance().apiCall(parameter)
                    .compose(RxUtil.applyIOToMainThreadSchedulers())
                    .subscribe(data -> {});