ActivityResult.kt

import android.app.Activity
import android.content.Intent
import android.os.Bundle
import kotlinx.coroutines.experimental.suspendCancellableCoroutine

typealias RequestCode = Int
typealias ResultCode = Int

data class ActivityResult(
    val requestCode: RequestCode,
    val resultCode: ResultCode,
    val data: Intent?
)

object MutableRelay {
    var request: Intent? = null
    var result: ((ActivityResult) -> Unit)? = null
}

val REQUEST_CODE = 1337

class ResultActivity : Activity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        MutableRelay.request
            ?.let { startActivityForResult(it, REQUEST_CODE) }
            ?: finish()
    }

    override fun onActivityResult(requestCode: RequestCode, resultCode: ResultCode, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)

        finish()

        if (requestCode == REQUEST_CODE) {
            MutableRelay.result?.let {
                it(ActivityResult(requestCode = requestCode,
                                  resultCode = resultCode,
                                  data = data))
            }
        }
    }
}

suspend fun Activity.awaitActivityForResult(intent: Intent): ActivityResult =
    suspendCancellableCoroutine { cont ->
        cont.invokeOnCompletion {
            MutableRelay.request = null
            MutableRelay.result = null
        }

        MutableRelay.request = intent
        MutableRelay.result = { cont.resume(it) }

        startActivity(Intent(this, ResultActivity::class.java))
    }

styles.xml

<style name="Theme.Transparent" parent="android:Theme">
    <item name="android:windowIsTranslucent">true</item>
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:windowContentOverlay">@null</item>
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowIsFloating">true</item>
    <item name="android:backgroundDimEnabled">false</item>
</style>