RxAndroid 和 RxKotlin

implementation 'io.reactivex.rxjava2:rxandroid:2.0.2'

Observable.just(1,2)
    .subscribeOn(Schedulers.io())
    // 切换到 Android 的主线程
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(observerInt)

public static Scheduler mainThread() {
    return RxAndroidPlugins.onMainThreadScheduler(MAIN_THREAD);
}

private static final Scheduler MAIN_THREAD = RxAndroidPlugins.initMainThreadScheduler(
    new Callable<Scheduler>() {
        @Override public Scheduler call() throws Exception {
            return MainHolder.DEFAULT;
        }
    });
    
private static final class MainHolder {
    static final Scheduler DEFAULT = new HandlerScheduler(new Handler(Looper.getMainLooper()));
}

@Override
public Disposable schedule(Runnable run, long delay, TimeUnit unit) {
    ...

    run = RxJavaPlugins.onSchedule(run);

    ScheduledRunnable scheduled = new ScheduledRunnable(handler, run);

    Message message = Message.obtain(handler, scheduled);
    message.obj = this; // Used as token for batch disposal of this worker's runnables.

    handler.sendMessageDelayed(message, unit.toMillis(delay));

    // Re-check disposed state for removing in case we were racing a call to dispose().
    if (disposed) {
        handler.removeCallbacks(scheduled);
        return Disposables.disposed();
    }

    return scheduled;
}

Looper backgroundLooper = // ...
Observable.just("one", "two", "three", "four", "five")
        .observeOn(AndroidSchedulers.from(backgroundLooper))
        .subscribe(/* an Observer */)

public static Scheduler from(Looper looper) {
    if (looper == null) throw new NullPointerException("looper == null");
    return new HandlerScheduler(new Handler(looper));
}

implementation 'io.reactivex.rxjava2:rxkotlin:2.2.0'

Observable.fromArray("a","b","c").subscribe(observerStr)

arrayOf("a", "b", "c").toObservable().subscribe(observerStr)

fun <T : Any> Array<T>.toObservable(): Observable<T> = Observable.fromArray(*this)