lateinit var manager: ReviewManager
var reviewInfo: ReviewInfo? = null

// Call this method asap, for example in onCreate()
private fun initReviews() {
    manager = ReviewManagerFactory.create(this)
    manager.requestReviewFlow().addOnCompleteListener { request ->
        if (request.isSuccessful) {
            reviewInfo = request.result
        } else {
            // Log error
        }
    }
}

// Call this when you want to show the dialog
private fun askForReview() {
    if (reviewInfo != null) {
        manager.launchReviewFlow(this, reviewInfo).addOnFailureListener {
            // Log error and continue with the flow
        }.addOnCompleteListener { _ ->
            // Log success and continue with the flow
        }
    }
}