Make a Android TextView (EditText) observable in RxJava

RxTextView.kt

/**
 * Adapted (and translated in Kotlin) from https://gist.github.com/FrantisekGazo/d1a62fcddd0c97453ee6d57efef17916
 * Nice usage scenario https://www.novatec-gmbh.de/en/blog/building-android-components/
 */
object RxTextView {
    private val textViewObservables = HashMap<TextView, Observable<CharSequence>>()

    @JvmStatic
    fun textChanges(view: TextView): Observable<CharSequence> {
        val observable = textViewObservables[view]
        if (observable != null) {
            return observable
        }
        return Observable.create(TextViewTextOnSubscribe(view))
    }
}

private class TextViewTextOnSubscribe(val view: TextView): ObservableOnSubscribe<CharSequence> {

    override fun subscribe(emitter: ObservableEmitter<CharSequence>) {
        MainThreadDisposable.verifyMainThread()

        val watcher = object: TextWatcher {
            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
            }

            override fun afterTextChanged(s: Editable?) {
            }

            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
                if (!emitter.isDisposed)
                    emitter.onNext(s!!)
            }

        }

        view.addTextChangedListener(watcher)

        emitter.setCancellable { view.removeTextChangedListener(watcher) }

        emitter.onNext(view.text)
    }
}