An RxJava-friendly AlertDialog

RxAlertDialog.kt

package com.meetup.rx

import android.content.Context
import android.support.annotation.StringRes
import android.support.v7.app.AlertDialog
import rx.Emitter
import rx.Observable

/**
 *
 * A lightweight version of (and inspired by) https://github.com/xavierlepretre/rx-alert-dialog
 *
 * Usage:
 *  observable
 *      .observeOn(AndroidSchedulers.mainThread())
 *      .flatMap({ event ->
 *          RxAlertDialog.show(context, R.string.title, R.string.message, android.R.string.ok)
 *      })
 *      .subscribe({ button ->
 *          when (button) {
 *              RxAlertDialog.BUTTON_POSITIVE -> Log.v("OK")
 *              RxAlertDialog.BUTTON_NEGATIVE-> Log.v("Cancel")
 *              RxAlertDialog.DISMISS_ALERT-> Log.v("Dismissed")
 *          }
 *     })
 *
 */
class RxAlertDialog {
    companion object {
        const val DISMISS_ALERT = 0
        const val BUTTON_POSITIVE = 1
        const val BUTTON_NEGATIVE = 2

        @JvmStatic @JvmOverloads
        fun show(
            context: Context,
            @StringRes title: Int? = null,
            @StringRes message: Int? = null,
            @StringRes positiveButton: Int? = null,
            @StringRes negativeButton: Int? = null): Observable<Int> {

            return Observable.create<Int>({ emitter ->
                val builder = AlertDialog.Builder(context)
                    .setOnDismissListener { emitter.onNext(DISMISS_ALERT) }

                title?.let { builder.setTitle(it)}
                message?.let { builder.setMessage(it)}
                positiveButton?.let { builder.setPositiveButton(positiveButton, { _, _ -> emitter.onNext(BUTTON_POSITIVE)})}
                negativeButton?.let { builder.setNegativeButton(negativeButton, { _, _ -> emitter.onNext(BUTTON_NEGATIVE)})}

                val dialog = builder.show()
                emitter.setCancellation { dialog.dismiss() }
            }, Emitter.BackpressureMode.NONE)
        }
    }
}

You could use Single instead of Observable btw