thing1.js

private fun startAnimate() {
    RxJavaPlugins.setErrorHandler { /*Catch InterruptedException*/ }
    compositeDisposable.add(Observable
        .create<Int> { emitter ->
            while (true) {
                if (control == 1) {
                    for (x in 0 until image.size) {
                        emitter.onNext(x)
                        Thread.sleep(100)
                    }
                } else {
                    for (x in (image.size - 1) downTo 0) {
                        emitter.onNext(x)
                        Thread.sleep(100)
                    }
                }
                control *= -1
                Thread.sleep(300)
            }
        }
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe { showImage(it) })
}