Creating a list of and registering channels for notifications reliably.

ChannelIds.kt

package com.aniketkadam.premail.base.notifications

import android.app.NotificationManager
import androidx.annotation.StringRes
import com.aniketkadam.premail.R

enum class ChannelIds(
    @StringRes val channelNameRes: Int, @StringRes val channelDescriptionRes: Int,
    val importance: Int
) {
    REMINDERS(
        R.string.reminders_channel_name,
        R.string.reminders_channel_description,
        NotificationManager.IMPORTANCE_HIGH
    )
}

ChannelRegistration.kt

package com.aniketkadam.premail.base.notifications

import android.app.NotificationChannel
import android.app.NotificationManager
import android.content.Context
import android.content.Context.NOTIFICATION_SERVICE
import android.os.Build

class ChannelRegistration {

    /**
     * Register every notification channel defined in the enum [ChannelIds]
     */
    fun registerChannels(c: Context) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {

            val notificationManager = c.getSystemService(NOTIFICATION_SERVICE) as NotificationManager

            ChannelIds.values().forEach {
                val name = c.getString(it.channelNameRes)
                val descriptionText = c.getString(it.channelDescriptionRes)
                val importance = it.importance

                val mChannel = NotificationChannel(it.name, name, importance)
                mChannel.description = descriptionText

                // Register the channel with the system; you can't change the importance
                // or other notification behaviors after this
                notificationManager.createNotificationChannel(mChannel)
            }
        }
    }
}