RxAlertDialog.kt

import android.content.Context
import android.support.annotation.MainThread
import android.support.v7.app.AlertDialog
import io.reactivex.Observable

enum class RxDialogActionStyle {
    POSITIVE, NEGATIVE, NEUTRAL
}

data class RxDialogAction(val title: CharSequence, val style: RxDialogActionStyle)

enum class RxDialogResult {
    POSITIVE, NEGATIVE, NEUTRAL, CANCEL
}

@MainThread
fun showAlertDialog(context: Context, title: CharSequence?, message: CharSequence, actions: Iterable<RxDialogAction>, cancellable: Boolean = true): Observable<RxDialogResult> {
    return Observable.create<RxDialogResult> { emitter ->
        val builder = AlertDialog.Builder(context)
        builder.setTitle(title)
        builder.setMessage(message)
        builder.setCancelable(cancellable)
        if (cancellable) {
            builder.setOnCancelListener {
                emitter.onNext(RxDialogResult.CANCEL)
                emitter.onComplete()
            }
        }
        actions.forEach { action ->
            when (action.style) {
                RxDialogActionStyle.POSITIVE -> {
                    builder.setPositiveButton(action.title, { _, _ ->
                        emitter.onNext(RxDialogResult.POSITIVE)
                        emitter.onComplete()
                    })
                }
                RxDialogActionStyle.NEGATIVE -> {
                    builder.setNegativeButton(action.title, { _, _ ->
                        emitter.onNext(RxDialogResult.NEGATIVE)
                        emitter.onComplete()
                    })
                }
                RxDialogActionStyle.NEUTRAL -> {
                    builder.setNeutralButton(action.title, { _, _ ->
                        emitter.onNext(RxDialogResult.NEUTRAL)
                        emitter.onComplete()
                    })
                }
            }
        }

        val dialog = builder.create()
        dialog.show()

        emitter.setCancellable {
            dialog.dismiss()
        }
    }
}

SampleActivity.kt

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.widget.Toast
import com.jakewharton.rxbinding2.view.RxView
import io.reactivex.disposables.CompositeDisposable
import io.reactivex.disposables.Disposable

class SampleActivity : AppCompatActivity() {

    private val compositeDisposable = CompositeDisposable()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        RxView.clicks(findViewById(R.id.button))
                .flatMap {
                    val positive = RxDialogAction("OK", RxDialogActionStyle.POSITIVE)
                    val negative = RxDialogAction("Cancel", RxDialogActionStyle.NEGATIVE)
                    showAlertDialog(this@SampleActivity, "title", "message", listOf(positive, negative))
                }.subscribe { result ->
                    when (result) {
                        RxDialogResult.POSITIVE -> Toast.makeText(this@SampleActivity, "Positive", Toast.LENGTH_SHORT).show()
                        RxDialogResult.NEGATIVE -> Toast.makeText(this@SampleActivity, "Negative", Toast.LENGTH_SHORT).show()
                        RxDialogResult.CANCEL -> Toast.makeText(this@SampleActivity, "Cancel", Toast.LENGTH_SHORT).show()
                        else -> throw IllegalStateException()
                    }
                }.addTo(compositeDisposable)
    }

    override fun onDestroy() {
        super.onDestroy()
        compositeDisposable.clear()
    }

    private fun Disposable.addTo(compositeDisposable: CompositeDisposable) =
            compositeDisposable.add(this)
}